forked from OSchip/llvm-project
7099 lines
261 KiB
C++
7099 lines
261 KiB
C++
//===- ValueTracking.cpp - Walk computations to compute properties --------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains routines that help analyze properties that chains of
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// computations have.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/ADT/APFloat.h"
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/None.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/AssumeBundleQueries.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/GuardUtils.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/Loads.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/OptimizationRemarkEmitter.h"
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#include "llvm/Analysis/TargetLibraryInfo.h"
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#include "llvm/IR/Argument.h"
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#include "llvm/IR/Attributes.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Constant.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/DiagnosticInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/IntrinsicsAArch64.h"
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#include "llvm/IR/IntrinsicsRISCV.h"
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#include "llvm/IR/IntrinsicsX86.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Metadata.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/IR/Type.h"
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#include "llvm/IR/User.h"
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#include "llvm/IR/Value.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/KnownBits.h"
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#include "llvm/Support/MathExtras.h"
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#include <algorithm>
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#include <array>
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#include <cassert>
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#include <cstdint>
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#include <iterator>
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#include <utility>
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using namespace llvm;
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using namespace llvm::PatternMatch;
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// Controls the number of uses of the value searched for possible
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// dominating comparisons.
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static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses",
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cl::Hidden, cl::init(20));
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/// Returns the bitwidth of the given scalar or pointer type. For vector types,
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/// returns the element type's bitwidth.
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static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
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if (unsigned BitWidth = Ty->getScalarSizeInBits())
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return BitWidth;
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return DL.getPointerTypeSizeInBits(Ty);
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}
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namespace {
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// Simplifying using an assume can only be done in a particular control-flow
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// context (the context instruction provides that context). If an assume and
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// the context instruction are not in the same block then the DT helps in
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// figuring out if we can use it.
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struct Query {
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const DataLayout &DL;
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AssumptionCache *AC;
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const Instruction *CxtI;
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const DominatorTree *DT;
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// Unlike the other analyses, this may be a nullptr because not all clients
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// provide it currently.
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OptimizationRemarkEmitter *ORE;
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/// If true, it is safe to use metadata during simplification.
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InstrInfoQuery IIQ;
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Query(const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo,
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OptimizationRemarkEmitter *ORE = nullptr)
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: DL(DL), AC(AC), CxtI(CxtI), DT(DT), ORE(ORE), IIQ(UseInstrInfo) {}
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};
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} // end anonymous namespace
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// Given the provided Value and, potentially, a context instruction, return
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// the preferred context instruction (if any).
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static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
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// If we've been provided with a context instruction, then use that (provided
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// it has been inserted).
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if (CxtI && CxtI->getParent())
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return CxtI;
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// If the value is really an already-inserted instruction, then use that.
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CxtI = dyn_cast<Instruction>(V);
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if (CxtI && CxtI->getParent())
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return CxtI;
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return nullptr;
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}
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static const Instruction *safeCxtI(const Value *V1, const Value *V2, const Instruction *CxtI) {
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// If we've been provided with a context instruction, then use that (provided
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// it has been inserted).
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if (CxtI && CxtI->getParent())
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return CxtI;
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// If the value is really an already-inserted instruction, then use that.
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CxtI = dyn_cast<Instruction>(V1);
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if (CxtI && CxtI->getParent())
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return CxtI;
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CxtI = dyn_cast<Instruction>(V2);
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if (CxtI && CxtI->getParent())
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return CxtI;
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return nullptr;
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}
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static bool getShuffleDemandedElts(const ShuffleVectorInst *Shuf,
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const APInt &DemandedElts,
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APInt &DemandedLHS, APInt &DemandedRHS) {
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// The length of scalable vectors is unknown at compile time, thus we
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// cannot check their values
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if (isa<ScalableVectorType>(Shuf->getType()))
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return false;
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int NumElts =
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cast<FixedVectorType>(Shuf->getOperand(0)->getType())->getNumElements();
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int NumMaskElts = cast<FixedVectorType>(Shuf->getType())->getNumElements();
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DemandedLHS = DemandedRHS = APInt::getNullValue(NumElts);
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if (DemandedElts.isNullValue())
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return true;
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// Simple case of a shuffle with zeroinitializer.
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if (all_of(Shuf->getShuffleMask(), [](int Elt) { return Elt == 0; })) {
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DemandedLHS.setBit(0);
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return true;
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}
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for (int i = 0; i != NumMaskElts; ++i) {
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if (!DemandedElts[i])
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continue;
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int M = Shuf->getMaskValue(i);
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assert(M < (NumElts * 2) && "Invalid shuffle mask constant");
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// For undef elements, we don't know anything about the common state of
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// the shuffle result.
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if (M == -1)
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return false;
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if (M < NumElts)
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DemandedLHS.setBit(M % NumElts);
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else
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DemandedRHS.setBit(M % NumElts);
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}
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return true;
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}
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static void computeKnownBits(const Value *V, const APInt &DemandedElts,
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KnownBits &Known, unsigned Depth, const Query &Q);
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static void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
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const Query &Q) {
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// FIXME: We currently have no way to represent the DemandedElts of a scalable
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// vector
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if (isa<ScalableVectorType>(V->getType())) {
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Known.resetAll();
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return;
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}
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auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
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APInt DemandedElts =
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FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
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computeKnownBits(V, DemandedElts, Known, Depth, Q);
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}
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void llvm::computeKnownBits(const Value *V, KnownBits &Known,
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const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT,
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OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
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::computeKnownBits(V, Known, Depth,
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Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
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}
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void llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
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KnownBits &Known, const DataLayout &DL,
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unsigned Depth, AssumptionCache *AC,
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const Instruction *CxtI, const DominatorTree *DT,
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OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
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::computeKnownBits(V, DemandedElts, Known, Depth,
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Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
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}
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static KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
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unsigned Depth, const Query &Q);
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static KnownBits computeKnownBits(const Value *V, unsigned Depth,
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const Query &Q);
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KnownBits llvm::computeKnownBits(const Value *V, const DataLayout &DL,
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unsigned Depth, AssumptionCache *AC,
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const Instruction *CxtI,
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const DominatorTree *DT,
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OptimizationRemarkEmitter *ORE,
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bool UseInstrInfo) {
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return ::computeKnownBits(
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V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
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}
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KnownBits llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
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const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT,
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OptimizationRemarkEmitter *ORE,
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bool UseInstrInfo) {
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return ::computeKnownBits(
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V, DemandedElts, Depth,
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Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
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}
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bool llvm::haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
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const DataLayout &DL, AssumptionCache *AC,
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const Instruction *CxtI, const DominatorTree *DT,
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bool UseInstrInfo) {
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assert(LHS->getType() == RHS->getType() &&
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"LHS and RHS should have the same type");
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assert(LHS->getType()->isIntOrIntVectorTy() &&
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"LHS and RHS should be integers");
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// Look for an inverted mask: (X & ~M) op (Y & M).
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Value *M;
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if (match(LHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
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match(RHS, m_c_And(m_Specific(M), m_Value())))
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return true;
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if (match(RHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
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match(LHS, m_c_And(m_Specific(M), m_Value())))
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return true;
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IntegerType *IT = cast<IntegerType>(LHS->getType()->getScalarType());
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KnownBits LHSKnown(IT->getBitWidth());
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KnownBits RHSKnown(IT->getBitWidth());
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computeKnownBits(LHS, LHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
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computeKnownBits(RHS, RHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
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return KnownBits::haveNoCommonBitsSet(LHSKnown, RHSKnown);
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}
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bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI) {
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for (const User *U : CxtI->users()) {
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if (const ICmpInst *IC = dyn_cast<ICmpInst>(U))
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if (IC->isEquality())
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if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
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if (C->isNullValue())
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continue;
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return false;
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}
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return true;
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}
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static bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
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const Query &Q);
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bool llvm::isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
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bool OrZero, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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return ::isKnownToBeAPowerOfTwo(
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V, OrZero, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
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}
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static bool isKnownNonZero(const Value *V, const APInt &DemandedElts,
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unsigned Depth, const Query &Q);
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static bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q);
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bool llvm::isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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return ::isKnownNonZero(V, Depth,
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Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
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}
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bool llvm::isKnownNonNegative(const Value *V, const DataLayout &DL,
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unsigned Depth, AssumptionCache *AC,
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const Instruction *CxtI, const DominatorTree *DT,
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bool UseInstrInfo) {
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KnownBits Known =
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computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
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return Known.isNonNegative();
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}
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bool llvm::isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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if (auto *CI = dyn_cast<ConstantInt>(V))
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return CI->getValue().isStrictlyPositive();
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// TODO: We'd doing two recursive queries here. We should factor this such
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// that only a single query is needed.
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return isKnownNonNegative(V, DL, Depth, AC, CxtI, DT, UseInstrInfo) &&
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isKnownNonZero(V, DL, Depth, AC, CxtI, DT, UseInstrInfo);
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}
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bool llvm::isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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KnownBits Known =
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computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
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return Known.isNegative();
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}
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static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
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const Query &Q);
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bool llvm::isKnownNonEqual(const Value *V1, const Value *V2,
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const DataLayout &DL, AssumptionCache *AC,
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const Instruction *CxtI, const DominatorTree *DT,
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bool UseInstrInfo) {
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return ::isKnownNonEqual(V1, V2, 0,
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Query(DL, AC, safeCxtI(V2, V1, CxtI), DT,
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UseInstrInfo, /*ORE=*/nullptr));
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}
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static bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
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const Query &Q);
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bool llvm::MaskedValueIsZero(const Value *V, const APInt &Mask,
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const DataLayout &DL, unsigned Depth,
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AssumptionCache *AC, const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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return ::MaskedValueIsZero(
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V, Mask, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
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}
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static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
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unsigned Depth, const Query &Q);
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static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
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const Query &Q) {
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// FIXME: We currently have no way to represent the DemandedElts of a scalable
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// vector
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if (isa<ScalableVectorType>(V->getType()))
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return 1;
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auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
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APInt DemandedElts =
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FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
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return ComputeNumSignBits(V, DemandedElts, Depth, Q);
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}
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unsigned llvm::ComputeNumSignBits(const Value *V, const DataLayout &DL,
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unsigned Depth, AssumptionCache *AC,
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const Instruction *CxtI,
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const DominatorTree *DT, bool UseInstrInfo) {
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return ::ComputeNumSignBits(
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V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
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}
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static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
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bool NSW, const APInt &DemandedElts,
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KnownBits &KnownOut, KnownBits &Known2,
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unsigned Depth, const Query &Q) {
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computeKnownBits(Op1, DemandedElts, KnownOut, Depth + 1, Q);
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// If one operand is unknown and we have no nowrap information,
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// the result will be unknown independently of the second operand.
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if (KnownOut.isUnknown() && !NSW)
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return;
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computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
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KnownOut = KnownBits::computeForAddSub(Add, NSW, Known2, KnownOut);
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}
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static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
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const APInt &DemandedElts, KnownBits &Known,
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KnownBits &Known2, unsigned Depth,
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const Query &Q) {
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computeKnownBits(Op1, DemandedElts, Known, Depth + 1, Q);
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computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
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bool isKnownNegative = false;
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bool isKnownNonNegative = false;
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// If the multiplication is known not to overflow, compute the sign bit.
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if (NSW) {
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if (Op0 == Op1) {
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// The product of a number with itself is non-negative.
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isKnownNonNegative = true;
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} else {
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bool isKnownNonNegativeOp1 = Known.isNonNegative();
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bool isKnownNonNegativeOp0 = Known2.isNonNegative();
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bool isKnownNegativeOp1 = Known.isNegative();
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bool isKnownNegativeOp0 = Known2.isNegative();
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// The product of two numbers with the same sign is non-negative.
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isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
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(isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
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// The product of a negative number and a non-negative number is either
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// negative or zero.
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if (!isKnownNonNegative)
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isKnownNegative =
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(isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
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Known2.isNonZero()) ||
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(isKnownNegativeOp0 && isKnownNonNegativeOp1 && Known.isNonZero());
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}
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}
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Known = KnownBits::mul(Known, Known2);
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// Only make use of no-wrap flags if we failed to compute the sign bit
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// directly. This matters if the multiplication always overflows, in
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// which case we prefer to follow the result of the direct computation,
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// though as the program is invoking undefined behaviour we can choose
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// whatever we like here.
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if (isKnownNonNegative && !Known.isNegative())
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Known.makeNonNegative();
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else if (isKnownNegative && !Known.isNonNegative())
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Known.makeNegative();
|
|
}
|
|
|
|
void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
|
|
KnownBits &Known) {
|
|
unsigned BitWidth = Known.getBitWidth();
|
|
unsigned NumRanges = Ranges.getNumOperands() / 2;
|
|
assert(NumRanges >= 1);
|
|
|
|
Known.Zero.setAllBits();
|
|
Known.One.setAllBits();
|
|
|
|
for (unsigned i = 0; i < NumRanges; ++i) {
|
|
ConstantInt *Lower =
|
|
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
|
|
ConstantInt *Upper =
|
|
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
|
|
ConstantRange Range(Lower->getValue(), Upper->getValue());
|
|
|
|
// The first CommonPrefixBits of all values in Range are equal.
|
|
unsigned CommonPrefixBits =
|
|
(Range.getUnsignedMax() ^ Range.getUnsignedMin()).countLeadingZeros();
|
|
APInt Mask = APInt::getHighBitsSet(BitWidth, CommonPrefixBits);
|
|
APInt UnsignedMax = Range.getUnsignedMax().zextOrTrunc(BitWidth);
|
|
Known.One &= UnsignedMax & Mask;
|
|
Known.Zero &= ~UnsignedMax & Mask;
|
|
}
|
|
}
|
|
|
|
static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
|
|
SmallVector<const Value *, 16> WorkSet(1, I);
|
|
SmallPtrSet<const Value *, 32> Visited;
|
|
SmallPtrSet<const Value *, 16> EphValues;
|
|
|
|
// The instruction defining an assumption's condition itself is always
|
|
// considered ephemeral to that assumption (even if it has other
|
|
// non-ephemeral users). See r246696's test case for an example.
|
|
if (is_contained(I->operands(), E))
|
|
return true;
|
|
|
|
while (!WorkSet.empty()) {
|
|
const Value *V = WorkSet.pop_back_val();
|
|
if (!Visited.insert(V).second)
|
|
continue;
|
|
|
|
// If all uses of this value are ephemeral, then so is this value.
|
|
if (llvm::all_of(V->users(), [&](const User *U) {
|
|
return EphValues.count(U);
|
|
})) {
|
|
if (V == E)
|
|
return true;
|
|
|
|
if (V == I || isSafeToSpeculativelyExecute(V)) {
|
|
EphValues.insert(V);
|
|
if (const User *U = dyn_cast<User>(V))
|
|
append_range(WorkSet, U->operands());
|
|
}
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
// Is this an intrinsic that cannot be speculated but also cannot trap?
|
|
bool llvm::isAssumeLikeIntrinsic(const Instruction *I) {
|
|
if (const IntrinsicInst *CI = dyn_cast<IntrinsicInst>(I))
|
|
return CI->isAssumeLikeIntrinsic();
|
|
|
|
return false;
|
|
}
|
|
|
|
bool llvm::isValidAssumeForContext(const Instruction *Inv,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
// There are two restrictions on the use of an assume:
|
|
// 1. The assume must dominate the context (or the control flow must
|
|
// reach the assume whenever it reaches the context).
|
|
// 2. The context must not be in the assume's set of ephemeral values
|
|
// (otherwise we will use the assume to prove that the condition
|
|
// feeding the assume is trivially true, thus causing the removal of
|
|
// the assume).
|
|
|
|
if (Inv->getParent() == CxtI->getParent()) {
|
|
// If Inv and CtxI are in the same block, check if the assume (Inv) is first
|
|
// in the BB.
|
|
if (Inv->comesBefore(CxtI))
|
|
return true;
|
|
|
|
// Don't let an assume affect itself - this would cause the problems
|
|
// `isEphemeralValueOf` is trying to prevent, and it would also make
|
|
// the loop below go out of bounds.
|
|
if (Inv == CxtI)
|
|
return false;
|
|
|
|
// The context comes first, but they're both in the same block.
|
|
// Make sure there is nothing in between that might interrupt
|
|
// the control flow, not even CxtI itself.
|
|
// We limit the scan distance between the assume and its context instruction
|
|
// to avoid a compile-time explosion. This limit is chosen arbitrarily, so
|
|
// it can be adjusted if needed (could be turned into a cl::opt).
|
|
unsigned ScanLimit = 15;
|
|
for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
|
|
if (!isGuaranteedToTransferExecutionToSuccessor(&*I) || --ScanLimit == 0)
|
|
return false;
|
|
|
|
return !isEphemeralValueOf(Inv, CxtI);
|
|
}
|
|
|
|
// Inv and CxtI are in different blocks.
|
|
if (DT) {
|
|
if (DT->dominates(Inv, CxtI))
|
|
return true;
|
|
} else if (Inv->getParent() == CxtI->getParent()->getSinglePredecessor()) {
|
|
// We don't have a DT, but this trivially dominates.
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool cmpExcludesZero(CmpInst::Predicate Pred, const Value *RHS) {
|
|
// v u> y implies v != 0.
|
|
if (Pred == ICmpInst::ICMP_UGT)
|
|
return true;
|
|
|
|
// Special-case v != 0 to also handle v != null.
|
|
if (Pred == ICmpInst::ICMP_NE)
|
|
return match(RHS, m_Zero());
|
|
|
|
// All other predicates - rely on generic ConstantRange handling.
|
|
const APInt *C;
|
|
if (!match(RHS, m_APInt(C)))
|
|
return false;
|
|
|
|
ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(Pred, *C);
|
|
return !TrueValues.contains(APInt::getNullValue(C->getBitWidth()));
|
|
}
|
|
|
|
static bool isKnownNonZeroFromAssume(const Value *V, const Query &Q) {
|
|
// Use of assumptions is context-sensitive. If we don't have a context, we
|
|
// cannot use them!
|
|
if (!Q.AC || !Q.CxtI)
|
|
return false;
|
|
|
|
if (Q.CxtI && V->getType()->isPointerTy()) {
|
|
SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NonNull};
|
|
if (!NullPointerIsDefined(Q.CxtI->getFunction(),
|
|
V->getType()->getPointerAddressSpace()))
|
|
AttrKinds.push_back(Attribute::Dereferenceable);
|
|
|
|
if (getKnowledgeValidInContext(V, AttrKinds, Q.CxtI, Q.DT, Q.AC))
|
|
return true;
|
|
}
|
|
|
|
for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
|
|
if (!AssumeVH)
|
|
continue;
|
|
CallInst *I = cast<CallInst>(AssumeVH);
|
|
assert(I->getFunction() == Q.CxtI->getFunction() &&
|
|
"Got assumption for the wrong function!");
|
|
|
|
// Warning: This loop can end up being somewhat performance sensitive.
|
|
// We're running this loop for once for each value queried resulting in a
|
|
// runtime of ~O(#assumes * #values).
|
|
|
|
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
|
|
"must be an assume intrinsic");
|
|
|
|
Value *RHS;
|
|
CmpInst::Predicate Pred;
|
|
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
|
|
if (!match(I->getArgOperand(0), m_c_ICmp(Pred, m_V, m_Value(RHS))))
|
|
return false;
|
|
|
|
if (cmpExcludesZero(Pred, RHS) && isValidAssumeForContext(I, Q.CxtI, Q.DT))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
|
|
unsigned Depth, const Query &Q) {
|
|
// Use of assumptions is context-sensitive. If we don't have a context, we
|
|
// cannot use them!
|
|
if (!Q.AC || !Q.CxtI)
|
|
return;
|
|
|
|
unsigned BitWidth = Known.getBitWidth();
|
|
|
|
// Refine Known set if the pointer alignment is set by assume bundles.
|
|
if (V->getType()->isPointerTy()) {
|
|
if (RetainedKnowledge RK = getKnowledgeValidInContext(
|
|
V, {Attribute::Alignment}, Q.CxtI, Q.DT, Q.AC)) {
|
|
Known.Zero.setLowBits(Log2_32(RK.ArgValue));
|
|
}
|
|
}
|
|
|
|
// Note that the patterns below need to be kept in sync with the code
|
|
// in AssumptionCache::updateAffectedValues.
|
|
|
|
for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
|
|
if (!AssumeVH)
|
|
continue;
|
|
CallInst *I = cast<CallInst>(AssumeVH);
|
|
assert(I->getParent()->getParent() == Q.CxtI->getParent()->getParent() &&
|
|
"Got assumption for the wrong function!");
|
|
|
|
// Warning: This loop can end up being somewhat performance sensitive.
|
|
// We're running this loop for once for each value queried resulting in a
|
|
// runtime of ~O(#assumes * #values).
|
|
|
|
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
|
|
"must be an assume intrinsic");
|
|
|
|
Value *Arg = I->getArgOperand(0);
|
|
|
|
if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
assert(BitWidth == 1 && "assume operand is not i1?");
|
|
Known.setAllOnes();
|
|
return;
|
|
}
|
|
if (match(Arg, m_Not(m_Specific(V))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
assert(BitWidth == 1 && "assume operand is not i1?");
|
|
Known.setAllZero();
|
|
return;
|
|
}
|
|
|
|
// The remaining tests are all recursive, so bail out if we hit the limit.
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
continue;
|
|
|
|
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
|
|
if (!Cmp)
|
|
continue;
|
|
|
|
// We are attempting to compute known bits for the operands of an assume.
|
|
// Do not try to use other assumptions for those recursive calls because
|
|
// that can lead to mutual recursion and a compile-time explosion.
|
|
// An example of the mutual recursion: computeKnownBits can call
|
|
// isKnownNonZero which calls computeKnownBitsFromAssume (this function)
|
|
// and so on.
|
|
Query QueryNoAC = Q;
|
|
QueryNoAC.AC = nullptr;
|
|
|
|
// Note that ptrtoint may change the bitwidth.
|
|
Value *A, *B;
|
|
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
|
|
|
|
CmpInst::Predicate Pred;
|
|
uint64_t C;
|
|
switch (Cmp->getPredicate()) {
|
|
default:
|
|
break;
|
|
case ICmpInst::ICMP_EQ:
|
|
// assume(v = a)
|
|
if (match(Cmp, m_c_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
Known.Zero |= RHSKnown.Zero;
|
|
Known.One |= RHSKnown.One;
|
|
// assume(v & b = a)
|
|
} else if (match(Cmp,
|
|
m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)), m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits MaskKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in the mask that are known to be one, we can propagate
|
|
// known bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.Zero & MaskKnown.One;
|
|
Known.One |= RHSKnown.One & MaskKnown.One;
|
|
// assume(~(v & b) = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits MaskKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in the mask that are known to be one, we can propagate
|
|
// inverted known bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.One & MaskKnown.One;
|
|
Known.One |= RHSKnown.Zero & MaskKnown.One;
|
|
// assume(v | b = a)
|
|
} else if (match(Cmp,
|
|
m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)), m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits BKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in B that are known to be zero, we can propagate known
|
|
// bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.Zero & BKnown.Zero;
|
|
Known.One |= RHSKnown.One & BKnown.Zero;
|
|
// assume(~(v | b) = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits BKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in B that are known to be zero, we can propagate
|
|
// inverted known bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.One & BKnown.Zero;
|
|
Known.One |= RHSKnown.Zero & BKnown.Zero;
|
|
// assume(v ^ b = a)
|
|
} else if (match(Cmp,
|
|
m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)), m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits BKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in B that are known to be zero, we can propagate known
|
|
// bits from the RHS to V. For those bits in B that are known to be one,
|
|
// we can propagate inverted known bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.Zero & BKnown.Zero;
|
|
Known.One |= RHSKnown.One & BKnown.Zero;
|
|
Known.Zero |= RHSKnown.One & BKnown.One;
|
|
Known.One |= RHSKnown.Zero & BKnown.One;
|
|
// assume(~(v ^ b) = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
KnownBits BKnown =
|
|
computeKnownBits(B, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in B that are known to be zero, we can propagate
|
|
// inverted known bits from the RHS to V. For those bits in B that are
|
|
// known to be one, we can propagate known bits from the RHS to V.
|
|
Known.Zero |= RHSKnown.One & BKnown.Zero;
|
|
Known.One |= RHSKnown.Zero & BKnown.Zero;
|
|
Known.Zero |= RHSKnown.Zero & BKnown.One;
|
|
Known.One |= RHSKnown.One & BKnown.One;
|
|
// assume(v << c = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// For those bits in RHS that are known, we can propagate them to known
|
|
// bits in V shifted to the right by C.
|
|
RHSKnown.Zero.lshrInPlace(C);
|
|
Known.Zero |= RHSKnown.Zero;
|
|
RHSKnown.One.lshrInPlace(C);
|
|
Known.One |= RHSKnown.One;
|
|
// assume(~(v << c) = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
// For those bits in RHS that are known, we can propagate them inverted
|
|
// to known bits in V shifted to the right by C.
|
|
RHSKnown.One.lshrInPlace(C);
|
|
Known.Zero |= RHSKnown.One;
|
|
RHSKnown.Zero.lshrInPlace(C);
|
|
Known.One |= RHSKnown.Zero;
|
|
// assume(v >> c = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
// For those bits in RHS that are known, we can propagate them to known
|
|
// bits in V shifted to the right by C.
|
|
Known.Zero |= RHSKnown.Zero << C;
|
|
Known.One |= RHSKnown.One << C;
|
|
// assume(~(v >> c) = a)
|
|
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
|
|
m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
// For those bits in RHS that are known, we can propagate them inverted
|
|
// to known bits in V shifted to the right by C.
|
|
Known.Zero |= RHSKnown.One << C;
|
|
Known.One |= RHSKnown.Zero << C;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
// assume(v >=_s c) where c is non-negative
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth + 1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
if (RHSKnown.isNonNegative()) {
|
|
// We know that the sign bit is zero.
|
|
Known.makeNonNegative();
|
|
}
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SGT:
|
|
// assume(v >_s c) where c is at least -1.
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth + 1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
if (RHSKnown.isAllOnes() || RHSKnown.isNonNegative()) {
|
|
// We know that the sign bit is zero.
|
|
Known.makeNonNegative();
|
|
}
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
// assume(v <=_s c) where c is negative
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth + 1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
if (RHSKnown.isNegative()) {
|
|
// We know that the sign bit is one.
|
|
Known.makeNegative();
|
|
}
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SLT:
|
|
// assume(v <_s c) where c is non-positive
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
if (RHSKnown.isZero() || RHSKnown.isNegative()) {
|
|
// We know that the sign bit is one.
|
|
Known.makeNegative();
|
|
}
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_ULE:
|
|
// assume(v <=_u c)
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// Whatever high bits in c are zero are known to be zero.
|
|
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
// assume(v <_u c)
|
|
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
|
|
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
|
|
KnownBits RHSKnown =
|
|
computeKnownBits(A, Depth+1, QueryNoAC).anyextOrTrunc(BitWidth);
|
|
|
|
// If the RHS is known zero, then this assumption must be wrong (nothing
|
|
// is unsigned less than zero). Signal a conflict and get out of here.
|
|
if (RHSKnown.isZero()) {
|
|
Known.Zero.setAllBits();
|
|
Known.One.setAllBits();
|
|
break;
|
|
}
|
|
|
|
// Whatever high bits in c are zero are known to be zero (if c is a power
|
|
// of 2, then one more).
|
|
if (isKnownToBeAPowerOfTwo(A, false, Depth + 1, QueryNoAC))
|
|
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros() + 1);
|
|
else
|
|
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
|
|
// If assumptions conflict with each other or previous known bits, then we
|
|
// have a logical fallacy. It's possible that the assumption is not reachable,
|
|
// so this isn't a real bug. On the other hand, the program may have undefined
|
|
// behavior, or we might have a bug in the compiler. We can't assert/crash, so
|
|
// clear out the known bits, try to warn the user, and hope for the best.
|
|
if (Known.Zero.intersects(Known.One)) {
|
|
Known.resetAll();
|
|
|
|
if (Q.ORE)
|
|
Q.ORE->emit([&]() {
|
|
auto *CxtI = const_cast<Instruction *>(Q.CxtI);
|
|
return OptimizationRemarkAnalysis("value-tracking", "BadAssumption",
|
|
CxtI)
|
|
<< "Detected conflicting code assumptions. Program may "
|
|
"have undefined behavior, or compiler may have "
|
|
"internal error.";
|
|
});
|
|
}
|
|
}
|
|
|
|
/// Compute known bits from a shift operator, including those with a
|
|
/// non-constant shift amount. Known is the output of this function. Known2 is a
|
|
/// pre-allocated temporary with the same bit width as Known and on return
|
|
/// contains the known bit of the shift value source. KF is an
|
|
/// operator-specific function that, given the known-bits and a shift amount,
|
|
/// compute the implied known-bits of the shift operator's result respectively
|
|
/// for that shift amount. The results from calling KF are conservatively
|
|
/// combined for all permitted shift amounts.
|
|
static void computeKnownBitsFromShiftOperator(
|
|
const Operator *I, const APInt &DemandedElts, KnownBits &Known,
|
|
KnownBits &Known2, unsigned Depth, const Query &Q,
|
|
function_ref<KnownBits(const KnownBits &, const KnownBits &)> KF) {
|
|
unsigned BitWidth = Known.getBitWidth();
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
|
|
|
|
// Note: We cannot use Known.Zero.getLimitedValue() here, because if
|
|
// BitWidth > 64 and any upper bits are known, we'll end up returning the
|
|
// limit value (which implies all bits are known).
|
|
uint64_t ShiftAmtKZ = Known.Zero.zextOrTrunc(64).getZExtValue();
|
|
uint64_t ShiftAmtKO = Known.One.zextOrTrunc(64).getZExtValue();
|
|
bool ShiftAmtIsConstant = Known.isConstant();
|
|
bool MaxShiftAmtIsOutOfRange = Known.getMaxValue().uge(BitWidth);
|
|
|
|
if (ShiftAmtIsConstant) {
|
|
Known = KF(Known2, Known);
|
|
|
|
// If the known bits conflict, this must be an overflowing left shift, so
|
|
// the shift result is poison. We can return anything we want. Choose 0 for
|
|
// the best folding opportunity.
|
|
if (Known.hasConflict())
|
|
Known.setAllZero();
|
|
|
|
return;
|
|
}
|
|
|
|
// If the shift amount could be greater than or equal to the bit-width of the
|
|
// LHS, the value could be poison, but bail out because the check below is
|
|
// expensive.
|
|
// TODO: Should we just carry on?
|
|
if (MaxShiftAmtIsOutOfRange) {
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
|
|
// It would be more-clearly correct to use the two temporaries for this
|
|
// calculation. Reusing the APInts here to prevent unnecessary allocations.
|
|
Known.resetAll();
|
|
|
|
// If we know the shifter operand is nonzero, we can sometimes infer more
|
|
// known bits. However this is expensive to compute, so be lazy about it and
|
|
// only compute it when absolutely necessary.
|
|
Optional<bool> ShifterOperandIsNonZero;
|
|
|
|
// Early exit if we can't constrain any well-defined shift amount.
|
|
if (!(ShiftAmtKZ & (PowerOf2Ceil(BitWidth) - 1)) &&
|
|
!(ShiftAmtKO & (PowerOf2Ceil(BitWidth) - 1))) {
|
|
ShifterOperandIsNonZero =
|
|
isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
|
|
if (!*ShifterOperandIsNonZero)
|
|
return;
|
|
}
|
|
|
|
Known.Zero.setAllBits();
|
|
Known.One.setAllBits();
|
|
for (unsigned ShiftAmt = 0; ShiftAmt < BitWidth; ++ShiftAmt) {
|
|
// Combine the shifted known input bits only for those shift amounts
|
|
// compatible with its known constraints.
|
|
if ((ShiftAmt & ~ShiftAmtKZ) != ShiftAmt)
|
|
continue;
|
|
if ((ShiftAmt | ShiftAmtKO) != ShiftAmt)
|
|
continue;
|
|
// If we know the shifter is nonzero, we may be able to infer more known
|
|
// bits. This check is sunk down as far as possible to avoid the expensive
|
|
// call to isKnownNonZero if the cheaper checks above fail.
|
|
if (ShiftAmt == 0) {
|
|
if (!ShifterOperandIsNonZero.hasValue())
|
|
ShifterOperandIsNonZero =
|
|
isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
|
|
if (*ShifterOperandIsNonZero)
|
|
continue;
|
|
}
|
|
|
|
Known = KnownBits::commonBits(
|
|
Known, KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt))));
|
|
}
|
|
|
|
// If the known bits conflict, the result is poison. Return a 0 and hope the
|
|
// caller can further optimize that.
|
|
if (Known.hasConflict())
|
|
Known.setAllZero();
|
|
}
|
|
|
|
static void computeKnownBitsFromOperator(const Operator *I,
|
|
const APInt &DemandedElts,
|
|
KnownBits &Known, unsigned Depth,
|
|
const Query &Q) {
|
|
unsigned BitWidth = Known.getBitWidth();
|
|
|
|
KnownBits Known2(BitWidth);
|
|
switch (I->getOpcode()) {
|
|
default: break;
|
|
case Instruction::Load:
|
|
if (MDNode *MD =
|
|
Q.IIQ.getMetadata(cast<LoadInst>(I), LLVMContext::MD_range))
|
|
computeKnownBitsFromRangeMetadata(*MD, Known);
|
|
break;
|
|
case Instruction::And: {
|
|
// If either the LHS or the RHS are Zero, the result is zero.
|
|
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
|
|
Known &= Known2;
|
|
|
|
// and(x, add (x, -1)) is a common idiom that always clears the low bit;
|
|
// here we handle the more general case of adding any odd number by
|
|
// matching the form add(x, add(x, y)) where y is odd.
|
|
// TODO: This could be generalized to clearing any bit set in y where the
|
|
// following bit is known to be unset in y.
|
|
Value *X = nullptr, *Y = nullptr;
|
|
if (!Known.Zero[0] && !Known.One[0] &&
|
|
match(I, m_c_BinOp(m_Value(X), m_Add(m_Deferred(X), m_Value(Y))))) {
|
|
Known2.resetAll();
|
|
computeKnownBits(Y, DemandedElts, Known2, Depth + 1, Q);
|
|
if (Known2.countMinTrailingOnes() > 0)
|
|
Known.Zero.setBit(0);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Or:
|
|
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
|
|
Known |= Known2;
|
|
break;
|
|
case Instruction::Xor:
|
|
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
|
|
Known ^= Known2;
|
|
break;
|
|
case Instruction::Mul: {
|
|
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
|
|
computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, DemandedElts,
|
|
Known, Known2, Depth, Q);
|
|
break;
|
|
}
|
|
case Instruction::UDiv: {
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::udiv(Known, Known2);
|
|
break;
|
|
}
|
|
case Instruction::Select: {
|
|
const Value *LHS = nullptr, *RHS = nullptr;
|
|
SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor;
|
|
if (SelectPatternResult::isMinOrMax(SPF)) {
|
|
computeKnownBits(RHS, Known, Depth + 1, Q);
|
|
computeKnownBits(LHS, Known2, Depth + 1, Q);
|
|
switch (SPF) {
|
|
default:
|
|
llvm_unreachable("Unhandled select pattern flavor!");
|
|
case SPF_SMAX:
|
|
Known = KnownBits::smax(Known, Known2);
|
|
break;
|
|
case SPF_SMIN:
|
|
Known = KnownBits::smin(Known, Known2);
|
|
break;
|
|
case SPF_UMAX:
|
|
Known = KnownBits::umax(Known, Known2);
|
|
break;
|
|
case SPF_UMIN:
|
|
Known = KnownBits::umin(Known, Known2);
|
|
break;
|
|
}
|
|
break;
|
|
}
|
|
|
|
computeKnownBits(I->getOperand(2), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
|
|
// Only known if known in both the LHS and RHS.
|
|
Known = KnownBits::commonBits(Known, Known2);
|
|
|
|
if (SPF == SPF_ABS) {
|
|
// RHS from matchSelectPattern returns the negation part of abs pattern.
|
|
// If the negate has an NSW flag we can assume the sign bit of the result
|
|
// will be 0 because that makes abs(INT_MIN) undefined.
|
|
if (match(RHS, m_Neg(m_Specific(LHS))) &&
|
|
Q.IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
|
|
Known.Zero.setSignBit();
|
|
}
|
|
|
|
break;
|
|
}
|
|
case Instruction::FPTrunc:
|
|
case Instruction::FPExt:
|
|
case Instruction::FPToUI:
|
|
case Instruction::FPToSI:
|
|
case Instruction::SIToFP:
|
|
case Instruction::UIToFP:
|
|
break; // Can't work with floating point.
|
|
case Instruction::PtrToInt:
|
|
case Instruction::IntToPtr:
|
|
// Fall through and handle them the same as zext/trunc.
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::ZExt:
|
|
case Instruction::Trunc: {
|
|
Type *SrcTy = I->getOperand(0)->getType();
|
|
|
|
unsigned SrcBitWidth;
|
|
// Note that we handle pointer operands here because of inttoptr/ptrtoint
|
|
// which fall through here.
|
|
Type *ScalarTy = SrcTy->getScalarType();
|
|
SrcBitWidth = ScalarTy->isPointerTy() ?
|
|
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
|
|
Q.DL.getTypeSizeInBits(ScalarTy);
|
|
|
|
assert(SrcBitWidth && "SrcBitWidth can't be zero");
|
|
Known = Known.anyextOrTrunc(SrcBitWidth);
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
Known = Known.zextOrTrunc(BitWidth);
|
|
break;
|
|
}
|
|
case Instruction::BitCast: {
|
|
Type *SrcTy = I->getOperand(0)->getType();
|
|
if (SrcTy->isIntOrPtrTy() &&
|
|
// TODO: For now, not handling conversions like:
|
|
// (bitcast i64 %x to <2 x i32>)
|
|
!I->getType()->isVectorTy()) {
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
break;
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::SExt: {
|
|
// Compute the bits in the result that are not present in the input.
|
|
unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
|
|
|
|
Known = Known.trunc(SrcBitWidth);
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
// If the sign bit of the input is known set or clear, then we know the
|
|
// top bits of the result.
|
|
Known = Known.sext(BitWidth);
|
|
break;
|
|
}
|
|
case Instruction::Shl: {
|
|
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
|
|
auto KF = [NSW](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
|
|
KnownBits Result = KnownBits::shl(KnownVal, KnownAmt);
|
|
// If this shift has "nsw" keyword, then the result is either a poison
|
|
// value or has the same sign bit as the first operand.
|
|
if (NSW) {
|
|
if (KnownVal.Zero.isSignBitSet())
|
|
Result.Zero.setSignBit();
|
|
if (KnownVal.One.isSignBitSet())
|
|
Result.One.setSignBit();
|
|
}
|
|
return Result;
|
|
};
|
|
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
|
|
KF);
|
|
// Trailing zeros of a right-shifted constant never decrease.
|
|
const APInt *C;
|
|
if (match(I->getOperand(0), m_APInt(C)))
|
|
Known.Zero.setLowBits(C->countTrailingZeros());
|
|
break;
|
|
}
|
|
case Instruction::LShr: {
|
|
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
|
|
return KnownBits::lshr(KnownVal, KnownAmt);
|
|
};
|
|
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
|
|
KF);
|
|
// Leading zeros of a left-shifted constant never decrease.
|
|
const APInt *C;
|
|
if (match(I->getOperand(0), m_APInt(C)))
|
|
Known.Zero.setHighBits(C->countLeadingZeros());
|
|
break;
|
|
}
|
|
case Instruction::AShr: {
|
|
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
|
|
return KnownBits::ashr(KnownVal, KnownAmt);
|
|
};
|
|
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
|
|
KF);
|
|
break;
|
|
}
|
|
case Instruction::Sub: {
|
|
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
|
|
computeKnownBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW,
|
|
DemandedElts, Known, Known2, Depth, Q);
|
|
break;
|
|
}
|
|
case Instruction::Add: {
|
|
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
|
|
computeKnownBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW,
|
|
DemandedElts, Known, Known2, Depth, Q);
|
|
break;
|
|
}
|
|
case Instruction::SRem:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::srem(Known, Known2);
|
|
break;
|
|
|
|
case Instruction::URem:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::urem(Known, Known2);
|
|
break;
|
|
case Instruction::Alloca:
|
|
Known.Zero.setLowBits(Log2(cast<AllocaInst>(I)->getAlign()));
|
|
break;
|
|
case Instruction::GetElementPtr: {
|
|
// Analyze all of the subscripts of this getelementptr instruction
|
|
// to determine if we can prove known low zero bits.
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
// Accumulate the constant indices in a separate variable
|
|
// to minimize the number of calls to computeForAddSub.
|
|
APInt AccConstIndices(BitWidth, 0, /*IsSigned*/ true);
|
|
|
|
gep_type_iterator GTI = gep_type_begin(I);
|
|
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
|
|
// TrailZ can only become smaller, short-circuit if we hit zero.
|
|
if (Known.isUnknown())
|
|
break;
|
|
|
|
Value *Index = I->getOperand(i);
|
|
|
|
// Handle case when index is zero.
|
|
Constant *CIndex = dyn_cast<Constant>(Index);
|
|
if (CIndex && CIndex->isZeroValue())
|
|
continue;
|
|
|
|
if (StructType *STy = GTI.getStructTypeOrNull()) {
|
|
// Handle struct member offset arithmetic.
|
|
|
|
assert(CIndex &&
|
|
"Access to structure field must be known at compile time");
|
|
|
|
if (CIndex->getType()->isVectorTy())
|
|
Index = CIndex->getSplatValue();
|
|
|
|
unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
|
|
const StructLayout *SL = Q.DL.getStructLayout(STy);
|
|
uint64_t Offset = SL->getElementOffset(Idx);
|
|
AccConstIndices += Offset;
|
|
continue;
|
|
}
|
|
|
|
// Handle array index arithmetic.
|
|
Type *IndexedTy = GTI.getIndexedType();
|
|
if (!IndexedTy->isSized()) {
|
|
Known.resetAll();
|
|
break;
|
|
}
|
|
|
|
unsigned IndexBitWidth = Index->getType()->getScalarSizeInBits();
|
|
KnownBits IndexBits(IndexBitWidth);
|
|
computeKnownBits(Index, IndexBits, Depth + 1, Q);
|
|
TypeSize IndexTypeSize = Q.DL.getTypeAllocSize(IndexedTy);
|
|
uint64_t TypeSizeInBytes = IndexTypeSize.getKnownMinSize();
|
|
KnownBits ScalingFactor(IndexBitWidth);
|
|
// Multiply by current sizeof type.
|
|
// &A[i] == A + i * sizeof(*A[i]).
|
|
if (IndexTypeSize.isScalable()) {
|
|
// For scalable types the only thing we know about sizeof is
|
|
// that this is a multiple of the minimum size.
|
|
ScalingFactor.Zero.setLowBits(countTrailingZeros(TypeSizeInBytes));
|
|
} else if (IndexBits.isConstant()) {
|
|
APInt IndexConst = IndexBits.getConstant();
|
|
APInt ScalingFactor(IndexBitWidth, TypeSizeInBytes);
|
|
IndexConst *= ScalingFactor;
|
|
AccConstIndices += IndexConst.sextOrTrunc(BitWidth);
|
|
continue;
|
|
} else {
|
|
ScalingFactor =
|
|
KnownBits::makeConstant(APInt(IndexBitWidth, TypeSizeInBytes));
|
|
}
|
|
IndexBits = KnownBits::mul(IndexBits, ScalingFactor);
|
|
|
|
// If the offsets have a different width from the pointer, according
|
|
// to the language reference we need to sign-extend or truncate them
|
|
// to the width of the pointer.
|
|
IndexBits = IndexBits.sextOrTrunc(BitWidth);
|
|
|
|
// Note that inbounds does *not* guarantee nsw for the addition, as only
|
|
// the offset is signed, while the base address is unsigned.
|
|
Known = KnownBits::computeForAddSub(
|
|
/*Add=*/true, /*NSW=*/false, Known, IndexBits);
|
|
}
|
|
if (!Known.isUnknown() && !AccConstIndices.isNullValue()) {
|
|
KnownBits Index = KnownBits::makeConstant(AccConstIndices);
|
|
Known = KnownBits::computeForAddSub(
|
|
/*Add=*/true, /*NSW=*/false, Known, Index);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::PHI: {
|
|
const PHINode *P = cast<PHINode>(I);
|
|
BinaryOperator *BO = nullptr;
|
|
Value *R = nullptr, *L = nullptr;
|
|
if (matchSimpleRecurrence(P, BO, R, L)) {
|
|
// Handle the case of a simple two-predecessor recurrence PHI.
|
|
// There's a lot more that could theoretically be done here, but
|
|
// this is sufficient to catch some interesting cases.
|
|
unsigned Opcode = BO->getOpcode();
|
|
|
|
// If this is a shift recurrence, we know the bits being shifted in.
|
|
// We can combine that with information about the start value of the
|
|
// recurrence to conclude facts about the result.
|
|
if ((Opcode == Instruction::LShr || Opcode == Instruction::AShr ||
|
|
Opcode == Instruction::Shl) &&
|
|
BO->getOperand(0) == I) {
|
|
|
|
// We have matched a recurrence of the form:
|
|
// %iv = [R, %entry], [%iv.next, %backedge]
|
|
// %iv.next = shift_op %iv, L
|
|
|
|
// Recurse with the phi context to avoid concern about whether facts
|
|
// inferred hold at original context instruction. TODO: It may be
|
|
// correct to use the original context. IF warranted, explore and
|
|
// add sufficient tests to cover.
|
|
Query RecQ = Q;
|
|
RecQ.CxtI = P;
|
|
computeKnownBits(R, DemandedElts, Known2, Depth + 1, RecQ);
|
|
switch (Opcode) {
|
|
case Instruction::Shl:
|
|
// A shl recurrence will only increase the tailing zeros
|
|
Known.Zero.setLowBits(Known2.countMinTrailingZeros());
|
|
break;
|
|
case Instruction::LShr:
|
|
// A lshr recurrence will preserve the leading zeros of the
|
|
// start value
|
|
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
|
|
break;
|
|
case Instruction::AShr:
|
|
// An ashr recurrence will extend the initial sign bit
|
|
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
|
|
Known.One.setHighBits(Known2.countMinLeadingOnes());
|
|
break;
|
|
};
|
|
}
|
|
|
|
// Check for operations that have the property that if
|
|
// both their operands have low zero bits, the result
|
|
// will have low zero bits.
|
|
if (Opcode == Instruction::Add ||
|
|
Opcode == Instruction::Sub ||
|
|
Opcode == Instruction::And ||
|
|
Opcode == Instruction::Or ||
|
|
Opcode == Instruction::Mul) {
|
|
// Change the context instruction to the "edge" that flows into the
|
|
// phi. This is important because that is where the value is actually
|
|
// "evaluated" even though it is used later somewhere else. (see also
|
|
// D69571).
|
|
Query RecQ = Q;
|
|
|
|
unsigned OpNum = P->getOperand(0) == R ? 0 : 1;
|
|
Instruction *RInst = P->getIncomingBlock(OpNum)->getTerminator();
|
|
Instruction *LInst = P->getIncomingBlock(1-OpNum)->getTerminator();
|
|
|
|
// Ok, we have a PHI of the form L op= R. Check for low
|
|
// zero bits.
|
|
RecQ.CxtI = RInst;
|
|
computeKnownBits(R, Known2, Depth + 1, RecQ);
|
|
|
|
// We need to take the minimum number of known bits
|
|
KnownBits Known3(BitWidth);
|
|
RecQ.CxtI = LInst;
|
|
computeKnownBits(L, Known3, Depth + 1, RecQ);
|
|
|
|
Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(),
|
|
Known3.countMinTrailingZeros()));
|
|
|
|
auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(BO);
|
|
if (OverflowOp && Q.IIQ.hasNoSignedWrap(OverflowOp)) {
|
|
// If initial value of recurrence is nonnegative, and we are adding
|
|
// a nonnegative number with nsw, the result can only be nonnegative
|
|
// or poison value regardless of the number of times we execute the
|
|
// add in phi recurrence. If initial value is negative and we are
|
|
// adding a negative number with nsw, the result can only be
|
|
// negative or poison value. Similar arguments apply to sub and mul.
|
|
//
|
|
// (add non-negative, non-negative) --> non-negative
|
|
// (add negative, negative) --> negative
|
|
if (Opcode == Instruction::Add) {
|
|
if (Known2.isNonNegative() && Known3.isNonNegative())
|
|
Known.makeNonNegative();
|
|
else if (Known2.isNegative() && Known3.isNegative())
|
|
Known.makeNegative();
|
|
}
|
|
|
|
// (sub nsw non-negative, negative) --> non-negative
|
|
// (sub nsw negative, non-negative) --> negative
|
|
else if (Opcode == Instruction::Sub && BO->getOperand(0) == I) {
|
|
if (Known2.isNonNegative() && Known3.isNegative())
|
|
Known.makeNonNegative();
|
|
else if (Known2.isNegative() && Known3.isNonNegative())
|
|
Known.makeNegative();
|
|
}
|
|
|
|
// (mul nsw non-negative, non-negative) --> non-negative
|
|
else if (Opcode == Instruction::Mul && Known2.isNonNegative() &&
|
|
Known3.isNonNegative())
|
|
Known.makeNonNegative();
|
|
}
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Unreachable blocks may have zero-operand PHI nodes.
|
|
if (P->getNumIncomingValues() == 0)
|
|
break;
|
|
|
|
// Otherwise take the unions of the known bit sets of the operands,
|
|
// taking conservative care to avoid excessive recursion.
|
|
if (Depth < MaxAnalysisRecursionDepth - 1 && !Known.Zero && !Known.One) {
|
|
// Skip if every incoming value references to ourself.
|
|
if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
|
|
break;
|
|
|
|
Known.Zero.setAllBits();
|
|
Known.One.setAllBits();
|
|
for (unsigned u = 0, e = P->getNumIncomingValues(); u < e; ++u) {
|
|
Value *IncValue = P->getIncomingValue(u);
|
|
// Skip direct self references.
|
|
if (IncValue == P) continue;
|
|
|
|
// Change the context instruction to the "edge" that flows into the
|
|
// phi. This is important because that is where the value is actually
|
|
// "evaluated" even though it is used later somewhere else. (see also
|
|
// D69571).
|
|
Query RecQ = Q;
|
|
RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
|
|
|
|
Known2 = KnownBits(BitWidth);
|
|
// Recurse, but cap the recursion to one level, because we don't
|
|
// want to waste time spinning around in loops.
|
|
computeKnownBits(IncValue, Known2, MaxAnalysisRecursionDepth - 1, RecQ);
|
|
Known = KnownBits::commonBits(Known, Known2);
|
|
// If all bits have been ruled out, there's no need to check
|
|
// more operands.
|
|
if (Known.isUnknown())
|
|
break;
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Call:
|
|
case Instruction::Invoke:
|
|
// If range metadata is attached to this call, set known bits from that,
|
|
// and then intersect with known bits based on other properties of the
|
|
// function.
|
|
if (MDNode *MD =
|
|
Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
|
|
computeKnownBitsFromRangeMetadata(*MD, Known);
|
|
if (const Value *RV = cast<CallBase>(I)->getReturnedArgOperand()) {
|
|
computeKnownBits(RV, Known2, Depth + 1, Q);
|
|
Known.Zero |= Known2.Zero;
|
|
Known.One |= Known2.One;
|
|
}
|
|
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::abs: {
|
|
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
|
|
bool IntMinIsPoison = match(II->getArgOperand(1), m_One());
|
|
Known = Known2.abs(IntMinIsPoison);
|
|
break;
|
|
}
|
|
case Intrinsic::bitreverse:
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
Known.Zero |= Known2.Zero.reverseBits();
|
|
Known.One |= Known2.One.reverseBits();
|
|
break;
|
|
case Intrinsic::bswap:
|
|
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
|
|
Known.Zero |= Known2.Zero.byteSwap();
|
|
Known.One |= Known2.One.byteSwap();
|
|
break;
|
|
case Intrinsic::ctlz: {
|
|
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
|
|
// If we have a known 1, its position is our upper bound.
|
|
unsigned PossibleLZ = Known2.countMaxLeadingZeros();
|
|
// If this call is undefined for 0, the result will be less than 2^n.
|
|
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
|
|
PossibleLZ = std::min(PossibleLZ, BitWidth - 1);
|
|
unsigned LowBits = Log2_32(PossibleLZ)+1;
|
|
Known.Zero.setBitsFrom(LowBits);
|
|
break;
|
|
}
|
|
case Intrinsic::cttz: {
|
|
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
|
|
// If we have a known 1, its position is our upper bound.
|
|
unsigned PossibleTZ = Known2.countMaxTrailingZeros();
|
|
// If this call is undefined for 0, the result will be less than 2^n.
|
|
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
|
|
PossibleTZ = std::min(PossibleTZ, BitWidth - 1);
|
|
unsigned LowBits = Log2_32(PossibleTZ)+1;
|
|
Known.Zero.setBitsFrom(LowBits);
|
|
break;
|
|
}
|
|
case Intrinsic::ctpop: {
|
|
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
|
|
// We can bound the space the count needs. Also, bits known to be zero
|
|
// can't contribute to the population.
|
|
unsigned BitsPossiblySet = Known2.countMaxPopulation();
|
|
unsigned LowBits = Log2_32(BitsPossiblySet)+1;
|
|
Known.Zero.setBitsFrom(LowBits);
|
|
// TODO: we could bound KnownOne using the lower bound on the number
|
|
// of bits which might be set provided by popcnt KnownOne2.
|
|
break;
|
|
}
|
|
case Intrinsic::fshr:
|
|
case Intrinsic::fshl: {
|
|
const APInt *SA;
|
|
if (!match(I->getOperand(2), m_APInt(SA)))
|
|
break;
|
|
|
|
// Normalize to funnel shift left.
|
|
uint64_t ShiftAmt = SA->urem(BitWidth);
|
|
if (II->getIntrinsicID() == Intrinsic::fshr)
|
|
ShiftAmt = BitWidth - ShiftAmt;
|
|
|
|
KnownBits Known3(BitWidth);
|
|
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known3, Depth + 1, Q);
|
|
|
|
Known.Zero =
|
|
Known2.Zero.shl(ShiftAmt) | Known3.Zero.lshr(BitWidth - ShiftAmt);
|
|
Known.One =
|
|
Known2.One.shl(ShiftAmt) | Known3.One.lshr(BitWidth - ShiftAmt);
|
|
break;
|
|
}
|
|
case Intrinsic::uadd_sat:
|
|
case Intrinsic::usub_sat: {
|
|
bool IsAdd = II->getIntrinsicID() == Intrinsic::uadd_sat;
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
|
|
// Add: Leading ones of either operand are preserved.
|
|
// Sub: Leading zeros of LHS and leading ones of RHS are preserved
|
|
// as leading zeros in the result.
|
|
unsigned LeadingKnown;
|
|
if (IsAdd)
|
|
LeadingKnown = std::max(Known.countMinLeadingOnes(),
|
|
Known2.countMinLeadingOnes());
|
|
else
|
|
LeadingKnown = std::max(Known.countMinLeadingZeros(),
|
|
Known2.countMinLeadingOnes());
|
|
|
|
Known = KnownBits::computeForAddSub(
|
|
IsAdd, /* NSW */ false, Known, Known2);
|
|
|
|
// We select between the operation result and all-ones/zero
|
|
// respectively, so we can preserve known ones/zeros.
|
|
if (IsAdd) {
|
|
Known.One.setHighBits(LeadingKnown);
|
|
Known.Zero.clearAllBits();
|
|
} else {
|
|
Known.Zero.setHighBits(LeadingKnown);
|
|
Known.One.clearAllBits();
|
|
}
|
|
break;
|
|
}
|
|
case Intrinsic::umin:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::umin(Known, Known2);
|
|
break;
|
|
case Intrinsic::umax:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::umax(Known, Known2);
|
|
break;
|
|
case Intrinsic::smin:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::smin(Known, Known2);
|
|
break;
|
|
case Intrinsic::smax:
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
|
|
Known = KnownBits::smax(Known, Known2);
|
|
break;
|
|
case Intrinsic::x86_sse42_crc32_64_64:
|
|
Known.Zero.setBitsFrom(32);
|
|
break;
|
|
case Intrinsic::riscv_vsetvli:
|
|
case Intrinsic::riscv_vsetvlimax:
|
|
// Assume that VL output is positive and would fit in an int32_t.
|
|
// TODO: VLEN might be capped at 16 bits in a future V spec update.
|
|
if (BitWidth >= 32)
|
|
Known.Zero.setBitsFrom(31);
|
|
break;
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::ShuffleVector: {
|
|
auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
|
|
// FIXME: Do we need to handle ConstantExpr involving shufflevectors?
|
|
if (!Shuf) {
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
// For undef elements, we don't know anything about the common state of
|
|
// the shuffle result.
|
|
APInt DemandedLHS, DemandedRHS;
|
|
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS)) {
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
Known.One.setAllBits();
|
|
Known.Zero.setAllBits();
|
|
if (!!DemandedLHS) {
|
|
const Value *LHS = Shuf->getOperand(0);
|
|
computeKnownBits(LHS, DemandedLHS, Known, Depth + 1, Q);
|
|
// If we don't know any bits, early out.
|
|
if (Known.isUnknown())
|
|
break;
|
|
}
|
|
if (!!DemandedRHS) {
|
|
const Value *RHS = Shuf->getOperand(1);
|
|
computeKnownBits(RHS, DemandedRHS, Known2, Depth + 1, Q);
|
|
Known = KnownBits::commonBits(Known, Known2);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::InsertElement: {
|
|
const Value *Vec = I->getOperand(0);
|
|
const Value *Elt = I->getOperand(1);
|
|
auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
|
|
// Early out if the index is non-constant or out-of-range.
|
|
unsigned NumElts = DemandedElts.getBitWidth();
|
|
if (!CIdx || CIdx->getValue().uge(NumElts)) {
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
Known.One.setAllBits();
|
|
Known.Zero.setAllBits();
|
|
unsigned EltIdx = CIdx->getZExtValue();
|
|
// Do we demand the inserted element?
|
|
if (DemandedElts[EltIdx]) {
|
|
computeKnownBits(Elt, Known, Depth + 1, Q);
|
|
// If we don't know any bits, early out.
|
|
if (Known.isUnknown())
|
|
break;
|
|
}
|
|
// We don't need the base vector element that has been inserted.
|
|
APInt DemandedVecElts = DemandedElts;
|
|
DemandedVecElts.clearBit(EltIdx);
|
|
if (!!DemandedVecElts) {
|
|
computeKnownBits(Vec, DemandedVecElts, Known2, Depth + 1, Q);
|
|
Known = KnownBits::commonBits(Known, Known2);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::ExtractElement: {
|
|
// Look through extract element. If the index is non-constant or
|
|
// out-of-range demand all elements, otherwise just the extracted element.
|
|
const Value *Vec = I->getOperand(0);
|
|
const Value *Idx = I->getOperand(1);
|
|
auto *CIdx = dyn_cast<ConstantInt>(Idx);
|
|
if (isa<ScalableVectorType>(Vec->getType())) {
|
|
// FIXME: there's probably *something* we can do with scalable vectors
|
|
Known.resetAll();
|
|
break;
|
|
}
|
|
unsigned NumElts = cast<FixedVectorType>(Vec->getType())->getNumElements();
|
|
APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
|
|
if (CIdx && CIdx->getValue().ult(NumElts))
|
|
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
|
|
computeKnownBits(Vec, DemandedVecElts, Known, Depth + 1, Q);
|
|
break;
|
|
}
|
|
case Instruction::ExtractValue:
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
|
|
const ExtractValueInst *EVI = cast<ExtractValueInst>(I);
|
|
if (EVI->getNumIndices() != 1) break;
|
|
if (EVI->getIndices()[0] == 0) {
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::uadd_with_overflow:
|
|
case Intrinsic::sadd_with_overflow:
|
|
computeKnownBitsAddSub(true, II->getArgOperand(0),
|
|
II->getArgOperand(1), false, DemandedElts,
|
|
Known, Known2, Depth, Q);
|
|
break;
|
|
case Intrinsic::usub_with_overflow:
|
|
case Intrinsic::ssub_with_overflow:
|
|
computeKnownBitsAddSub(false, II->getArgOperand(0),
|
|
II->getArgOperand(1), false, DemandedElts,
|
|
Known, Known2, Depth, Q);
|
|
break;
|
|
case Intrinsic::umul_with_overflow:
|
|
case Intrinsic::smul_with_overflow:
|
|
computeKnownBitsMul(II->getArgOperand(0), II->getArgOperand(1), false,
|
|
DemandedElts, Known, Known2, Depth, Q);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::Freeze:
|
|
if (isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
|
|
Depth + 1))
|
|
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/// Determine which bits of V are known to be either zero or one and return
|
|
/// them.
|
|
KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
|
|
unsigned Depth, const Query &Q) {
|
|
KnownBits Known(getBitWidth(V->getType(), Q.DL));
|
|
computeKnownBits(V, DemandedElts, Known, Depth, Q);
|
|
return Known;
|
|
}
|
|
|
|
/// Determine which bits of V are known to be either zero or one and return
|
|
/// them.
|
|
KnownBits computeKnownBits(const Value *V, unsigned Depth, const Query &Q) {
|
|
KnownBits Known(getBitWidth(V->getType(), Q.DL));
|
|
computeKnownBits(V, Known, Depth, Q);
|
|
return Known;
|
|
}
|
|
|
|
/// Determine which bits of V are known to be either zero or one and return
|
|
/// them in the Known bit set.
|
|
///
|
|
/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
|
|
/// we cannot optimize based on the assumption that it is zero without changing
|
|
/// it to be an explicit zero. If we don't change it to zero, other code could
|
|
/// optimized based on the contradictory assumption that it is non-zero.
|
|
/// Because instcombine aggressively folds operations with undef args anyway,
|
|
/// this won't lose us code quality.
|
|
///
|
|
/// This function is defined on values with integer type, values with pointer
|
|
/// type, and vectors of integers. In the case
|
|
/// where V is a vector, known zero, and known one values are the
|
|
/// same width as the vector element, and the bit is set only if it is true
|
|
/// for all of the demanded elements in the vector specified by DemandedElts.
|
|
void computeKnownBits(const Value *V, const APInt &DemandedElts,
|
|
KnownBits &Known, unsigned Depth, const Query &Q) {
|
|
if (!DemandedElts || isa<ScalableVectorType>(V->getType())) {
|
|
// No demanded elts or V is a scalable vector, better to assume we don't
|
|
// know anything.
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
|
|
assert(V && "No Value?");
|
|
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
|
|
|
|
#ifndef NDEBUG
|
|
Type *Ty = V->getType();
|
|
unsigned BitWidth = Known.getBitWidth();
|
|
|
|
assert((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) &&
|
|
"Not integer or pointer type!");
|
|
|
|
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
|
|
assert(
|
|
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
|
|
"DemandedElt width should equal the fixed vector number of elements");
|
|
} else {
|
|
assert(DemandedElts == APInt(1, 1) &&
|
|
"DemandedElt width should be 1 for scalars");
|
|
}
|
|
|
|
Type *ScalarTy = Ty->getScalarType();
|
|
if (ScalarTy->isPointerTy()) {
|
|
assert(BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&
|
|
"V and Known should have same BitWidth");
|
|
} else {
|
|
assert(BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) &&
|
|
"V and Known should have same BitWidth");
|
|
}
|
|
#endif
|
|
|
|
const APInt *C;
|
|
if (match(V, m_APInt(C))) {
|
|
// We know all of the bits for a scalar constant or a splat vector constant!
|
|
Known = KnownBits::makeConstant(*C);
|
|
return;
|
|
}
|
|
// Null and aggregate-zero are all-zeros.
|
|
if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) {
|
|
Known.setAllZero();
|
|
return;
|
|
}
|
|
// Handle a constant vector by taking the intersection of the known bits of
|
|
// each element.
|
|
if (const ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(V)) {
|
|
// We know that CDV must be a vector of integers. Take the intersection of
|
|
// each element.
|
|
Known.Zero.setAllBits(); Known.One.setAllBits();
|
|
for (unsigned i = 0, e = CDV->getNumElements(); i != e; ++i) {
|
|
if (!DemandedElts[i])
|
|
continue;
|
|
APInt Elt = CDV->getElementAsAPInt(i);
|
|
Known.Zero &= ~Elt;
|
|
Known.One &= Elt;
|
|
}
|
|
return;
|
|
}
|
|
|
|
if (const auto *CV = dyn_cast<ConstantVector>(V)) {
|
|
// We know that CV must be a vector of integers. Take the intersection of
|
|
// each element.
|
|
Known.Zero.setAllBits(); Known.One.setAllBits();
|
|
for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
|
|
if (!DemandedElts[i])
|
|
continue;
|
|
Constant *Element = CV->getAggregateElement(i);
|
|
auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
|
|
if (!ElementCI) {
|
|
Known.resetAll();
|
|
return;
|
|
}
|
|
const APInt &Elt = ElementCI->getValue();
|
|
Known.Zero &= ~Elt;
|
|
Known.One &= Elt;
|
|
}
|
|
return;
|
|
}
|
|
|
|
// Start out not knowing anything.
|
|
Known.resetAll();
|
|
|
|
// We can't imply anything about undefs.
|
|
if (isa<UndefValue>(V))
|
|
return;
|
|
|
|
// There's no point in looking through other users of ConstantData for
|
|
// assumptions. Confirm that we've handled them all.
|
|
assert(!isa<ConstantData>(V) && "Unhandled constant data!");
|
|
|
|
// All recursive calls that increase depth must come after this.
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return;
|
|
|
|
// A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
|
|
// the bits of its aliasee.
|
|
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
|
|
if (!GA->isInterposable())
|
|
computeKnownBits(GA->getAliasee(), Known, Depth + 1, Q);
|
|
return;
|
|
}
|
|
|
|
if (const Operator *I = dyn_cast<Operator>(V))
|
|
computeKnownBitsFromOperator(I, DemandedElts, Known, Depth, Q);
|
|
|
|
// Aligned pointers have trailing zeros - refine Known.Zero set
|
|
if (isa<PointerType>(V->getType())) {
|
|
Align Alignment = V->getPointerAlignment(Q.DL);
|
|
Known.Zero.setLowBits(Log2(Alignment));
|
|
}
|
|
|
|
// computeKnownBitsFromAssume strictly refines Known.
|
|
// Therefore, we run them after computeKnownBitsFromOperator.
|
|
|
|
// Check whether a nearby assume intrinsic can determine some known bits.
|
|
computeKnownBitsFromAssume(V, Known, Depth, Q);
|
|
|
|
assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
|
|
}
|
|
|
|
/// Return true if the given value is known to have exactly one
|
|
/// bit set when defined. For vectors return true if every element is known to
|
|
/// be a power of two when defined. Supports values with integer or pointer
|
|
/// types and vectors of integers.
|
|
bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
|
|
const Query &Q) {
|
|
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
|
|
|
|
// Attempt to match against constants.
|
|
if (OrZero && match(V, m_Power2OrZero()))
|
|
return true;
|
|
if (match(V, m_Power2()))
|
|
return true;
|
|
|
|
// 1 << X is clearly a power of two if the one is not shifted off the end. If
|
|
// it is shifted off the end then the result is undefined.
|
|
if (match(V, m_Shl(m_One(), m_Value())))
|
|
return true;
|
|
|
|
// (signmask) >>l X is clearly a power of two if the one is not shifted off
|
|
// the bottom. If it is shifted off the bottom then the result is undefined.
|
|
if (match(V, m_LShr(m_SignMask(), m_Value())))
|
|
return true;
|
|
|
|
// The remaining tests are all recursive, so bail out if we hit the limit.
|
|
if (Depth++ == MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
Value *X = nullptr, *Y = nullptr;
|
|
// A shift left or a logical shift right of a power of two is a power of two
|
|
// or zero.
|
|
if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
|
|
match(V, m_LShr(m_Value(X), m_Value()))))
|
|
return isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q);
|
|
|
|
if (const ZExtInst *ZI = dyn_cast<ZExtInst>(V))
|
|
return isKnownToBeAPowerOfTwo(ZI->getOperand(0), OrZero, Depth, Q);
|
|
|
|
if (const SelectInst *SI = dyn_cast<SelectInst>(V))
|
|
return isKnownToBeAPowerOfTwo(SI->getTrueValue(), OrZero, Depth, Q) &&
|
|
isKnownToBeAPowerOfTwo(SI->getFalseValue(), OrZero, Depth, Q);
|
|
|
|
// Peek through min/max.
|
|
if (match(V, m_MaxOrMin(m_Value(X), m_Value(Y)))) {
|
|
return isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q) &&
|
|
isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q);
|
|
}
|
|
|
|
if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
|
|
// A power of two and'd with anything is a power of two or zero.
|
|
if (isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q) ||
|
|
isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, Depth, Q))
|
|
return true;
|
|
// X & (-X) is always a power of two or zero.
|
|
if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
// Adding a power-of-two or zero to the same power-of-two or zero yields
|
|
// either the original power-of-two, a larger power-of-two or zero.
|
|
if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
|
|
const OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
|
|
if (OrZero || Q.IIQ.hasNoUnsignedWrap(VOBO) ||
|
|
Q.IIQ.hasNoSignedWrap(VOBO)) {
|
|
if (match(X, m_And(m_Specific(Y), m_Value())) ||
|
|
match(X, m_And(m_Value(), m_Specific(Y))))
|
|
if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q))
|
|
return true;
|
|
if (match(Y, m_And(m_Specific(X), m_Value())) ||
|
|
match(Y, m_And(m_Value(), m_Specific(X))))
|
|
if (isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q))
|
|
return true;
|
|
|
|
unsigned BitWidth = V->getType()->getScalarSizeInBits();
|
|
KnownBits LHSBits(BitWidth);
|
|
computeKnownBits(X, LHSBits, Depth, Q);
|
|
|
|
KnownBits RHSBits(BitWidth);
|
|
computeKnownBits(Y, RHSBits, Depth, Q);
|
|
// If i8 V is a power of two or zero:
|
|
// ZeroBits: 1 1 1 0 1 1 1 1
|
|
// ~ZeroBits: 0 0 0 1 0 0 0 0
|
|
if ((~(LHSBits.Zero & RHSBits.Zero)).isPowerOf2())
|
|
// If OrZero isn't set, we cannot give back a zero result.
|
|
// Make sure either the LHS or RHS has a bit set.
|
|
if (OrZero || RHSBits.One.getBoolValue() || LHSBits.One.getBoolValue())
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// An exact divide or right shift can only shift off zero bits, so the result
|
|
// is a power of two only if the first operand is a power of two and not
|
|
// copying a sign bit (sdiv int_min, 2).
|
|
if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) ||
|
|
match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) {
|
|
return isKnownToBeAPowerOfTwo(cast<Operator>(V)->getOperand(0), OrZero,
|
|
Depth, Q);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// Test whether a GEP's result is known to be non-null.
|
|
///
|
|
/// Uses properties inherent in a GEP to try to determine whether it is known
|
|
/// to be non-null.
|
|
///
|
|
/// Currently this routine does not support vector GEPs.
|
|
static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
|
|
const Query &Q) {
|
|
const Function *F = nullptr;
|
|
if (const Instruction *I = dyn_cast<Instruction>(GEP))
|
|
F = I->getFunction();
|
|
|
|
if (!GEP->isInBounds() ||
|
|
NullPointerIsDefined(F, GEP->getPointerAddressSpace()))
|
|
return false;
|
|
|
|
// FIXME: Support vector-GEPs.
|
|
assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP");
|
|
|
|
// If the base pointer is non-null, we cannot walk to a null address with an
|
|
// inbounds GEP in address space zero.
|
|
if (isKnownNonZero(GEP->getPointerOperand(), Depth, Q))
|
|
return true;
|
|
|
|
// Walk the GEP operands and see if any operand introduces a non-zero offset.
|
|
// If so, then the GEP cannot produce a null pointer, as doing so would
|
|
// inherently violate the inbounds contract within address space zero.
|
|
for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
|
|
GTI != GTE; ++GTI) {
|
|
// Struct types are easy -- they must always be indexed by a constant.
|
|
if (StructType *STy = GTI.getStructTypeOrNull()) {
|
|
ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
|
|
unsigned ElementIdx = OpC->getZExtValue();
|
|
const StructLayout *SL = Q.DL.getStructLayout(STy);
|
|
uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
|
|
if (ElementOffset > 0)
|
|
return true;
|
|
continue;
|
|
}
|
|
|
|
// If we have a zero-sized type, the index doesn't matter. Keep looping.
|
|
if (Q.DL.getTypeAllocSize(GTI.getIndexedType()).getKnownMinSize() == 0)
|
|
continue;
|
|
|
|
// Fast path the constant operand case both for efficiency and so we don't
|
|
// increment Depth when just zipping down an all-constant GEP.
|
|
if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
|
|
if (!OpC->isZero())
|
|
return true;
|
|
continue;
|
|
}
|
|
|
|
// We post-increment Depth here because while isKnownNonZero increments it
|
|
// as well, when we pop back up that increment won't persist. We don't want
|
|
// to recurse 10k times just because we have 10k GEP operands. We don't
|
|
// bail completely out because we want to handle constant GEPs regardless
|
|
// of depth.
|
|
if (Depth++ >= MaxAnalysisRecursionDepth)
|
|
continue;
|
|
|
|
if (isKnownNonZero(GTI.getOperand(), Depth, Q))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool isKnownNonNullFromDominatingCondition(const Value *V,
|
|
const Instruction *CtxI,
|
|
const DominatorTree *DT) {
|
|
if (isa<Constant>(V))
|
|
return false;
|
|
|
|
if (!CtxI || !DT)
|
|
return false;
|
|
|
|
unsigned NumUsesExplored = 0;
|
|
for (auto *U : V->users()) {
|
|
// Avoid massive lists
|
|
if (NumUsesExplored >= DomConditionsMaxUses)
|
|
break;
|
|
NumUsesExplored++;
|
|
|
|
// If the value is used as an argument to a call or invoke, then argument
|
|
// attributes may provide an answer about null-ness.
|
|
if (const auto *CB = dyn_cast<CallBase>(U))
|
|
if (auto *CalledFunc = CB->getCalledFunction())
|
|
for (const Argument &Arg : CalledFunc->args())
|
|
if (CB->getArgOperand(Arg.getArgNo()) == V &&
|
|
Arg.hasNonNullAttr(/* AllowUndefOrPoison */ false) &&
|
|
DT->dominates(CB, CtxI))
|
|
return true;
|
|
|
|
// If the value is used as a load/store, then the pointer must be non null.
|
|
if (V == getLoadStorePointerOperand(U)) {
|
|
const Instruction *I = cast<Instruction>(U);
|
|
if (!NullPointerIsDefined(I->getFunction(),
|
|
V->getType()->getPointerAddressSpace()) &&
|
|
DT->dominates(I, CtxI))
|
|
return true;
|
|
}
|
|
|
|
// Consider only compare instructions uniquely controlling a branch
|
|
Value *RHS;
|
|
CmpInst::Predicate Pred;
|
|
if (!match(U, m_c_ICmp(Pred, m_Specific(V), m_Value(RHS))))
|
|
continue;
|
|
|
|
bool NonNullIfTrue;
|
|
if (cmpExcludesZero(Pred, RHS))
|
|
NonNullIfTrue = true;
|
|
else if (cmpExcludesZero(CmpInst::getInversePredicate(Pred), RHS))
|
|
NonNullIfTrue = false;
|
|
else
|
|
continue;
|
|
|
|
SmallVector<const User *, 4> WorkList;
|
|
SmallPtrSet<const User *, 4> Visited;
|
|
for (auto *CmpU : U->users()) {
|
|
assert(WorkList.empty() && "Should be!");
|
|
if (Visited.insert(CmpU).second)
|
|
WorkList.push_back(CmpU);
|
|
|
|
while (!WorkList.empty()) {
|
|
auto *Curr = WorkList.pop_back_val();
|
|
|
|
// If a user is an AND, add all its users to the work list. We only
|
|
// propagate "pred != null" condition through AND because it is only
|
|
// correct to assume that all conditions of AND are met in true branch.
|
|
// TODO: Support similar logic of OR and EQ predicate?
|
|
if (NonNullIfTrue)
|
|
if (match(Curr, m_LogicalAnd(m_Value(), m_Value()))) {
|
|
for (auto *CurrU : Curr->users())
|
|
if (Visited.insert(CurrU).second)
|
|
WorkList.push_back(CurrU);
|
|
continue;
|
|
}
|
|
|
|
if (const BranchInst *BI = dyn_cast<BranchInst>(Curr)) {
|
|
assert(BI->isConditional() && "uses a comparison!");
|
|
|
|
BasicBlock *NonNullSuccessor =
|
|
BI->getSuccessor(NonNullIfTrue ? 0 : 1);
|
|
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
|
|
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
|
|
return true;
|
|
} else if (NonNullIfTrue && isGuard(Curr) &&
|
|
DT->dominates(cast<Instruction>(Curr), CtxI)) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// Does the 'Range' metadata (which must be a valid MD_range operand list)
|
|
/// ensure that the value it's attached to is never Value? 'RangeType' is
|
|
/// is the type of the value described by the range.
|
|
static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value) {
|
|
const unsigned NumRanges = Ranges->getNumOperands() / 2;
|
|
assert(NumRanges >= 1);
|
|
for (unsigned i = 0; i < NumRanges; ++i) {
|
|
ConstantInt *Lower =
|
|
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 0));
|
|
ConstantInt *Upper =
|
|
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 1));
|
|
ConstantRange Range(Lower->getValue(), Upper->getValue());
|
|
if (Range.contains(Value))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Try to detect a recurrence that monotonically increases/decreases from a
|
|
/// non-zero starting value. These are common as induction variables.
|
|
static bool isNonZeroRecurrence(const PHINode *PN) {
|
|
BinaryOperator *BO = nullptr;
|
|
Value *Start = nullptr, *Step = nullptr;
|
|
const APInt *StartC, *StepC;
|
|
if (!matchSimpleRecurrence(PN, BO, Start, Step) ||
|
|
!match(Start, m_APInt(StartC)) || StartC->isNullValue())
|
|
return false;
|
|
|
|
switch (BO->getOpcode()) {
|
|
case Instruction::Add:
|
|
// Starting from non-zero and stepping away from zero can never wrap back
|
|
// to zero.
|
|
return BO->hasNoUnsignedWrap() ||
|
|
(BO->hasNoSignedWrap() && match(Step, m_APInt(StepC)) &&
|
|
StartC->isNegative() == StepC->isNegative());
|
|
case Instruction::Mul:
|
|
return (BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap()) &&
|
|
match(Step, m_APInt(StepC)) && !StepC->isNullValue();
|
|
case Instruction::Shl:
|
|
return BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap();
|
|
case Instruction::AShr:
|
|
case Instruction::LShr:
|
|
return BO->isExact();
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/// Return true if the given value is known to be non-zero when defined. For
|
|
/// vectors, return true if every demanded element is known to be non-zero when
|
|
/// defined. For pointers, if the context instruction and dominator tree are
|
|
/// specified, perform context-sensitive analysis and return true if the
|
|
/// pointer couldn't possibly be null at the specified instruction.
|
|
/// Supports values with integer or pointer type and vectors of integers.
|
|
bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
|
|
const Query &Q) {
|
|
// FIXME: We currently have no way to represent the DemandedElts of a scalable
|
|
// vector
|
|
if (isa<ScalableVectorType>(V->getType()))
|
|
return false;
|
|
|
|
if (auto *C = dyn_cast<Constant>(V)) {
|
|
if (C->isNullValue())
|
|
return false;
|
|
if (isa<ConstantInt>(C))
|
|
// Must be non-zero due to null test above.
|
|
return true;
|
|
|
|
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
|
|
// See the comment for IntToPtr/PtrToInt instructions below.
|
|
if (CE->getOpcode() == Instruction::IntToPtr ||
|
|
CE->getOpcode() == Instruction::PtrToInt)
|
|
if (Q.DL.getTypeSizeInBits(CE->getOperand(0)->getType())
|
|
.getFixedSize() <=
|
|
Q.DL.getTypeSizeInBits(CE->getType()).getFixedSize())
|
|
return isKnownNonZero(CE->getOperand(0), Depth, Q);
|
|
}
|
|
|
|
// For constant vectors, check that all elements are undefined or known
|
|
// non-zero to determine that the whole vector is known non-zero.
|
|
if (auto *VecTy = dyn_cast<FixedVectorType>(C->getType())) {
|
|
for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
|
|
if (!DemandedElts[i])
|
|
continue;
|
|
Constant *Elt = C->getAggregateElement(i);
|
|
if (!Elt || Elt->isNullValue())
|
|
return false;
|
|
if (!isa<UndefValue>(Elt) && !isa<ConstantInt>(Elt))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// A global variable in address space 0 is non null unless extern weak
|
|
// or an absolute symbol reference. Other address spaces may have null as a
|
|
// valid address for a global, so we can't assume anything.
|
|
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
|
|
if (!GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
|
|
GV->getType()->getAddressSpace() == 0)
|
|
return true;
|
|
} else
|
|
return false;
|
|
}
|
|
|
|
if (auto *I = dyn_cast<Instruction>(V)) {
|
|
if (MDNode *Ranges = Q.IIQ.getMetadata(I, LLVMContext::MD_range)) {
|
|
// If the possible ranges don't contain zero, then the value is
|
|
// definitely non-zero.
|
|
if (auto *Ty = dyn_cast<IntegerType>(V->getType())) {
|
|
const APInt ZeroValue(Ty->getBitWidth(), 0);
|
|
if (rangeMetadataExcludesValue(Ranges, ZeroValue))
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (isKnownNonZeroFromAssume(V, Q))
|
|
return true;
|
|
|
|
// Some of the tests below are recursive, so bail out if we hit the limit.
|
|
if (Depth++ >= MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
// Check for pointer simplifications.
|
|
|
|
if (PointerType *PtrTy = dyn_cast<PointerType>(V->getType())) {
|
|
// Alloca never returns null, malloc might.
|
|
if (isa<AllocaInst>(V) && Q.DL.getAllocaAddrSpace() == 0)
|
|
return true;
|
|
|
|
// A byval, inalloca may not be null in a non-default addres space. A
|
|
// nonnull argument is assumed never 0.
|
|
if (const Argument *A = dyn_cast<Argument>(V)) {
|
|
if (((A->hasPassPointeeByValueCopyAttr() &&
|
|
!NullPointerIsDefined(A->getParent(), PtrTy->getAddressSpace())) ||
|
|
A->hasNonNullAttr()))
|
|
return true;
|
|
}
|
|
|
|
// A Load tagged with nonnull metadata is never null.
|
|
if (const LoadInst *LI = dyn_cast<LoadInst>(V))
|
|
if (Q.IIQ.getMetadata(LI, LLVMContext::MD_nonnull))
|
|
return true;
|
|
|
|
if (const auto *Call = dyn_cast<CallBase>(V)) {
|
|
if (Call->isReturnNonNull())
|
|
return true;
|
|
if (const auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
|
|
return isKnownNonZero(RP, Depth, Q);
|
|
}
|
|
}
|
|
|
|
if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
|
|
return true;
|
|
|
|
// Check for recursive pointer simplifications.
|
|
if (V->getType()->isPointerTy()) {
|
|
// Look through bitcast operations, GEPs, and int2ptr instructions as they
|
|
// do not alter the value, or at least not the nullness property of the
|
|
// value, e.g., int2ptr is allowed to zero/sign extend the value.
|
|
//
|
|
// Note that we have to take special care to avoid looking through
|
|
// truncating casts, e.g., int2ptr/ptr2int with appropriate sizes, as well
|
|
// as casts that can alter the value, e.g., AddrSpaceCasts.
|
|
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V))
|
|
return isGEPKnownNonNull(GEP, Depth, Q);
|
|
|
|
if (auto *BCO = dyn_cast<BitCastOperator>(V))
|
|
return isKnownNonZero(BCO->getOperand(0), Depth, Q);
|
|
|
|
if (auto *I2P = dyn_cast<IntToPtrInst>(V))
|
|
if (Q.DL.getTypeSizeInBits(I2P->getSrcTy()).getFixedSize() <=
|
|
Q.DL.getTypeSizeInBits(I2P->getDestTy()).getFixedSize())
|
|
return isKnownNonZero(I2P->getOperand(0), Depth, Q);
|
|
}
|
|
|
|
// Similar to int2ptr above, we can look through ptr2int here if the cast
|
|
// is a no-op or an extend and not a truncate.
|
|
if (auto *P2I = dyn_cast<PtrToIntInst>(V))
|
|
if (Q.DL.getTypeSizeInBits(P2I->getSrcTy()).getFixedSize() <=
|
|
Q.DL.getTypeSizeInBits(P2I->getDestTy()).getFixedSize())
|
|
return isKnownNonZero(P2I->getOperand(0), Depth, Q);
|
|
|
|
unsigned BitWidth = getBitWidth(V->getType()->getScalarType(), Q.DL);
|
|
|
|
// X | Y != 0 if X != 0 or Y != 0.
|
|
Value *X = nullptr, *Y = nullptr;
|
|
if (match(V, m_Or(m_Value(X), m_Value(Y))))
|
|
return isKnownNonZero(X, DemandedElts, Depth, Q) ||
|
|
isKnownNonZero(Y, DemandedElts, Depth, Q);
|
|
|
|
// ext X != 0 if X != 0.
|
|
if (isa<SExtInst>(V) || isa<ZExtInst>(V))
|
|
return isKnownNonZero(cast<Instruction>(V)->getOperand(0), Depth, Q);
|
|
|
|
// shl X, Y != 0 if X is odd. Note that the value of the shift is undefined
|
|
// if the lowest bit is shifted off the end.
|
|
if (match(V, m_Shl(m_Value(X), m_Value(Y)))) {
|
|
// shl nuw can't remove any non-zero bits.
|
|
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
|
|
if (Q.IIQ.hasNoUnsignedWrap(BO))
|
|
return isKnownNonZero(X, Depth, Q);
|
|
|
|
KnownBits Known(BitWidth);
|
|
computeKnownBits(X, DemandedElts, Known, Depth, Q);
|
|
if (Known.One[0])
|
|
return true;
|
|
}
|
|
// shr X, Y != 0 if X is negative. Note that the value of the shift is not
|
|
// defined if the sign bit is shifted off the end.
|
|
else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
|
|
// shr exact can only shift out zero bits.
|
|
const PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
|
|
if (BO->isExact())
|
|
return isKnownNonZero(X, Depth, Q);
|
|
|
|
KnownBits Known = computeKnownBits(X, DemandedElts, Depth, Q);
|
|
if (Known.isNegative())
|
|
return true;
|
|
|
|
// If the shifter operand is a constant, and all of the bits shifted
|
|
// out are known to be zero, and X is known non-zero then at least one
|
|
// non-zero bit must remain.
|
|
if (ConstantInt *Shift = dyn_cast<ConstantInt>(Y)) {
|
|
auto ShiftVal = Shift->getLimitedValue(BitWidth - 1);
|
|
// Is there a known one in the portion not shifted out?
|
|
if (Known.countMaxLeadingZeros() < BitWidth - ShiftVal)
|
|
return true;
|
|
// Are all the bits to be shifted out known zero?
|
|
if (Known.countMinTrailingZeros() >= ShiftVal)
|
|
return isKnownNonZero(X, DemandedElts, Depth, Q);
|
|
}
|
|
}
|
|
// div exact can only produce a zero if the dividend is zero.
|
|
else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) {
|
|
return isKnownNonZero(X, DemandedElts, Depth, Q);
|
|
}
|
|
// X + Y.
|
|
else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
|
|
KnownBits XKnown = computeKnownBits(X, DemandedElts, Depth, Q);
|
|
KnownBits YKnown = computeKnownBits(Y, DemandedElts, Depth, Q);
|
|
|
|
// If X and Y are both non-negative (as signed values) then their sum is not
|
|
// zero unless both X and Y are zero.
|
|
if (XKnown.isNonNegative() && YKnown.isNonNegative())
|
|
if (isKnownNonZero(X, DemandedElts, Depth, Q) ||
|
|
isKnownNonZero(Y, DemandedElts, Depth, Q))
|
|
return true;
|
|
|
|
// If X and Y are both negative (as signed values) then their sum is not
|
|
// zero unless both X and Y equal INT_MIN.
|
|
if (XKnown.isNegative() && YKnown.isNegative()) {
|
|
APInt Mask = APInt::getSignedMaxValue(BitWidth);
|
|
// The sign bit of X is set. If some other bit is set then X is not equal
|
|
// to INT_MIN.
|
|
if (XKnown.One.intersects(Mask))
|
|
return true;
|
|
// The sign bit of Y is set. If some other bit is set then Y is not equal
|
|
// to INT_MIN.
|
|
if (YKnown.One.intersects(Mask))
|
|
return true;
|
|
}
|
|
|
|
// The sum of a non-negative number and a power of two is not zero.
|
|
if (XKnown.isNonNegative() &&
|
|
isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
|
|
return true;
|
|
if (YKnown.isNonNegative() &&
|
|
isKnownToBeAPowerOfTwo(X, /*OrZero*/ false, Depth, Q))
|
|
return true;
|
|
}
|
|
// X * Y.
|
|
else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
|
|
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
|
|
// If X and Y are non-zero then so is X * Y as long as the multiplication
|
|
// does not overflow.
|
|
if ((Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO)) &&
|
|
isKnownNonZero(X, DemandedElts, Depth, Q) &&
|
|
isKnownNonZero(Y, DemandedElts, Depth, Q))
|
|
return true;
|
|
}
|
|
// (C ? X : Y) != 0 if X != 0 and Y != 0.
|
|
else if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
|
|
if (isKnownNonZero(SI->getTrueValue(), DemandedElts, Depth, Q) &&
|
|
isKnownNonZero(SI->getFalseValue(), DemandedElts, Depth, Q))
|
|
return true;
|
|
}
|
|
// PHI
|
|
else if (const PHINode *PN = dyn_cast<PHINode>(V)) {
|
|
if (Q.IIQ.UseInstrInfo && isNonZeroRecurrence(PN))
|
|
return true;
|
|
|
|
// Check if all incoming values are non-zero using recursion.
|
|
Query RecQ = Q;
|
|
unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
|
|
return llvm::all_of(PN->operands(), [&](const Use &U) {
|
|
if (U.get() == PN)
|
|
return true;
|
|
RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
|
|
return isKnownNonZero(U.get(), DemandedElts, NewDepth, RecQ);
|
|
});
|
|
}
|
|
// ExtractElement
|
|
else if (const auto *EEI = dyn_cast<ExtractElementInst>(V)) {
|
|
const Value *Vec = EEI->getVectorOperand();
|
|
const Value *Idx = EEI->getIndexOperand();
|
|
auto *CIdx = dyn_cast<ConstantInt>(Idx);
|
|
if (auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType())) {
|
|
unsigned NumElts = VecTy->getNumElements();
|
|
APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
|
|
if (CIdx && CIdx->getValue().ult(NumElts))
|
|
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
|
|
return isKnownNonZero(Vec, DemandedVecElts, Depth, Q);
|
|
}
|
|
}
|
|
// Freeze
|
|
else if (const FreezeInst *FI = dyn_cast<FreezeInst>(V)) {
|
|
auto *Op = FI->getOperand(0);
|
|
if (isKnownNonZero(Op, Depth, Q) &&
|
|
isGuaranteedNotToBePoison(Op, Q.AC, Q.CxtI, Q.DT, Depth))
|
|
return true;
|
|
}
|
|
|
|
KnownBits Known(BitWidth);
|
|
computeKnownBits(V, DemandedElts, Known, Depth, Q);
|
|
return Known.One != 0;
|
|
}
|
|
|
|
bool isKnownNonZero(const Value* V, unsigned Depth, const Query& Q) {
|
|
// FIXME: We currently have no way to represent the DemandedElts of a scalable
|
|
// vector
|
|
if (isa<ScalableVectorType>(V->getType()))
|
|
return false;
|
|
|
|
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
|
|
APInt DemandedElts =
|
|
FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
|
|
return isKnownNonZero(V, DemandedElts, Depth, Q);
|
|
}
|
|
|
|
/// If the pair of operators are the same invertible function, return the
|
|
/// the operands of the function corresponding to each input. Otherwise,
|
|
/// return None. An invertible function is one that is 1-to-1 and maps
|
|
/// every input value to exactly one output value. This is equivalent to
|
|
/// saying that Op1 and Op2 are equal exactly when the specified pair of
|
|
/// operands are equal, (except that Op1 and Op2 may be poison more often.)
|
|
static Optional<std::pair<Value*, Value*>>
|
|
getInvertibleOperands(const Operator *Op1,
|
|
const Operator *Op2) {
|
|
if (Op1->getOpcode() != Op2->getOpcode())
|
|
return None;
|
|
|
|
auto getOperands = [&](unsigned OpNum) -> auto {
|
|
return std::make_pair(Op1->getOperand(OpNum), Op2->getOperand(OpNum));
|
|
};
|
|
|
|
switch (Op1->getOpcode()) {
|
|
default:
|
|
break;
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
if (Op1->getOperand(0) == Op2->getOperand(0))
|
|
return getOperands(1);
|
|
if (Op1->getOperand(1) == Op2->getOperand(1))
|
|
return getOperands(0);
|
|
break;
|
|
case Instruction::Mul: {
|
|
// invertible if A * B == (A * B) mod 2^N where A, and B are integers
|
|
// and N is the bitwdith. The nsw case is non-obvious, but proven by
|
|
// alive2: https://alive2.llvm.org/ce/z/Z6D5qK
|
|
auto *OBO1 = cast<OverflowingBinaryOperator>(Op1);
|
|
auto *OBO2 = cast<OverflowingBinaryOperator>(Op2);
|
|
if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
|
|
(!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
|
|
break;
|
|
|
|
// Assume operand order has been canonicalized
|
|
if (Op1->getOperand(1) == Op2->getOperand(1) &&
|
|
isa<ConstantInt>(Op1->getOperand(1)) &&
|
|
!cast<ConstantInt>(Op1->getOperand(1))->isZero())
|
|
return getOperands(0);
|
|
break;
|
|
}
|
|
case Instruction::Shl: {
|
|
// Same as multiplies, with the difference that we don't need to check
|
|
// for a non-zero multiply. Shifts always multiply by non-zero.
|
|
auto *OBO1 = cast<OverflowingBinaryOperator>(Op1);
|
|
auto *OBO2 = cast<OverflowingBinaryOperator>(Op2);
|
|
if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
|
|
(!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
|
|
break;
|
|
|
|
if (Op1->getOperand(1) == Op2->getOperand(1))
|
|
return getOperands(0);
|
|
break;
|
|
}
|
|
case Instruction::AShr:
|
|
case Instruction::LShr: {
|
|
auto *PEO1 = cast<PossiblyExactOperator>(Op1);
|
|
auto *PEO2 = cast<PossiblyExactOperator>(Op2);
|
|
if (!PEO1->isExact() || !PEO2->isExact())
|
|
break;
|
|
|
|
if (Op1->getOperand(1) == Op2->getOperand(1))
|
|
return getOperands(0);
|
|
break;
|
|
}
|
|
case Instruction::SExt:
|
|
case Instruction::ZExt:
|
|
if (Op1->getOperand(0)->getType() == Op2->getOperand(0)->getType())
|
|
return getOperands(0);
|
|
break;
|
|
case Instruction::PHI: {
|
|
const PHINode *PN1 = cast<PHINode>(Op1);
|
|
const PHINode *PN2 = cast<PHINode>(Op2);
|
|
|
|
// If PN1 and PN2 are both recurrences, can we prove the entire recurrences
|
|
// are a single invertible function of the start values? Note that repeated
|
|
// application of an invertible function is also invertible
|
|
BinaryOperator *BO1 = nullptr;
|
|
Value *Start1 = nullptr, *Step1 = nullptr;
|
|
BinaryOperator *BO2 = nullptr;
|
|
Value *Start2 = nullptr, *Step2 = nullptr;
|
|
if (PN1->getParent() != PN2->getParent() ||
|
|
!matchSimpleRecurrence(PN1, BO1, Start1, Step1) ||
|
|
!matchSimpleRecurrence(PN2, BO2, Start2, Step2))
|
|
break;
|
|
|
|
auto Values = getInvertibleOperands(cast<Operator>(BO1),
|
|
cast<Operator>(BO2));
|
|
if (!Values)
|
|
break;
|
|
|
|
// We have to be careful of mutually defined recurrences here. Ex:
|
|
// * X_i = X_(i-1) OP Y_(i-1), and Y_i = X_(i-1) OP V
|
|
// * X_i = Y_i = X_(i-1) OP Y_(i-1)
|
|
// The invertibility of these is complicated, and not worth reasoning
|
|
// about (yet?).
|
|
if (Values->first != PN1 || Values->second != PN2)
|
|
break;
|
|
|
|
return std::make_pair(Start1, Start2);
|
|
}
|
|
}
|
|
return None;
|
|
}
|
|
|
|
/// Return true if V2 == V1 + X, where X is known non-zero.
|
|
static bool isAddOfNonZero(const Value *V1, const Value *V2, unsigned Depth,
|
|
const Query &Q) {
|
|
const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
|
|
if (!BO || BO->getOpcode() != Instruction::Add)
|
|
return false;
|
|
Value *Op = nullptr;
|
|
if (V2 == BO->getOperand(0))
|
|
Op = BO->getOperand(1);
|
|
else if (V2 == BO->getOperand(1))
|
|
Op = BO->getOperand(0);
|
|
else
|
|
return false;
|
|
return isKnownNonZero(Op, Depth + 1, Q);
|
|
}
|
|
|
|
/// Return true if V2 == V1 * C, where V1 is known non-zero, C is not 0/1 and
|
|
/// the multiplication is nuw or nsw.
|
|
static bool isNonEqualMul(const Value *V1, const Value *V2, unsigned Depth,
|
|
const Query &Q) {
|
|
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
|
|
const APInt *C;
|
|
return match(OBO, m_Mul(m_Specific(V1), m_APInt(C))) &&
|
|
(OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
|
|
!C->isNullValue() && !C->isOneValue() &&
|
|
isKnownNonZero(V1, Depth + 1, Q);
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Return true if V2 == V1 << C, where V1 is known non-zero, C is not 0 and
|
|
/// the shift is nuw or nsw.
|
|
static bool isNonEqualShl(const Value *V1, const Value *V2, unsigned Depth,
|
|
const Query &Q) {
|
|
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
|
|
const APInt *C;
|
|
return match(OBO, m_Shl(m_Specific(V1), m_APInt(C))) &&
|
|
(OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
|
|
!C->isNullValue() && isKnownNonZero(V1, Depth + 1, Q);
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
|
|
unsigned Depth, const Query &Q) {
|
|
// Check two PHIs are in same block.
|
|
if (PN1->getParent() != PN2->getParent())
|
|
return false;
|
|
|
|
SmallPtrSet<const BasicBlock *, 8> VisitedBBs;
|
|
bool UsedFullRecursion = false;
|
|
for (const BasicBlock *IncomBB : PN1->blocks()) {
|
|
if (!VisitedBBs.insert(IncomBB).second)
|
|
continue; // Don't reprocess blocks that we have dealt with already.
|
|
const Value *IV1 = PN1->getIncomingValueForBlock(IncomBB);
|
|
const Value *IV2 = PN2->getIncomingValueForBlock(IncomBB);
|
|
const APInt *C1, *C2;
|
|
if (match(IV1, m_APInt(C1)) && match(IV2, m_APInt(C2)) && *C1 != *C2)
|
|
continue;
|
|
|
|
// Only one pair of phi operands is allowed for full recursion.
|
|
if (UsedFullRecursion)
|
|
return false;
|
|
|
|
Query RecQ = Q;
|
|
RecQ.CxtI = IncomBB->getTerminator();
|
|
if (!isKnownNonEqual(IV1, IV2, Depth + 1, RecQ))
|
|
return false;
|
|
UsedFullRecursion = true;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Return true if it is known that V1 != V2.
|
|
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
|
|
const Query &Q) {
|
|
if (V1 == V2)
|
|
return false;
|
|
if (V1->getType() != V2->getType())
|
|
// We can't look through casts yet.
|
|
return false;
|
|
|
|
if (Depth >= MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
// See if we can recurse through (exactly one of) our operands. This
|
|
// requires our operation be 1-to-1 and map every input value to exactly
|
|
// one output value. Such an operation is invertible.
|
|
auto *O1 = dyn_cast<Operator>(V1);
|
|
auto *O2 = dyn_cast<Operator>(V2);
|
|
if (O1 && O2 && O1->getOpcode() == O2->getOpcode()) {
|
|
if (auto Values = getInvertibleOperands(O1, O2))
|
|
return isKnownNonEqual(Values->first, Values->second, Depth + 1, Q);
|
|
|
|
if (const PHINode *PN1 = dyn_cast<PHINode>(V1)) {
|
|
const PHINode *PN2 = cast<PHINode>(V2);
|
|
// FIXME: This is missing a generalization to handle the case where one is
|
|
// a PHI and another one isn't.
|
|
if (isNonEqualPHIs(PN1, PN2, Depth, Q))
|
|
return true;
|
|
};
|
|
}
|
|
|
|
if (isAddOfNonZero(V1, V2, Depth, Q) || isAddOfNonZero(V2, V1, Depth, Q))
|
|
return true;
|
|
|
|
if (isNonEqualMul(V1, V2, Depth, Q) || isNonEqualMul(V2, V1, Depth, Q))
|
|
return true;
|
|
|
|
if (isNonEqualShl(V1, V2, Depth, Q) || isNonEqualShl(V2, V1, Depth, Q))
|
|
return true;
|
|
|
|
if (V1->getType()->isIntOrIntVectorTy()) {
|
|
// Are any known bits in V1 contradictory to known bits in V2? If V1
|
|
// has a known zero where V2 has a known one, they must not be equal.
|
|
KnownBits Known1 = computeKnownBits(V1, Depth, Q);
|
|
KnownBits Known2 = computeKnownBits(V2, Depth, Q);
|
|
|
|
if (Known1.Zero.intersects(Known2.One) ||
|
|
Known2.Zero.intersects(Known1.One))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Return true if 'V & Mask' is known to be zero. We use this predicate to
|
|
/// simplify operations downstream. Mask is known to be zero for bits that V
|
|
/// cannot have.
|
|
///
|
|
/// This function is defined on values with integer type, values with pointer
|
|
/// type, and vectors of integers. In the case
|
|
/// where V is a vector, the mask, known zero, and known one values are the
|
|
/// same width as the vector element, and the bit is set only if it is true
|
|
/// for all of the elements in the vector.
|
|
bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
|
|
const Query &Q) {
|
|
KnownBits Known(Mask.getBitWidth());
|
|
computeKnownBits(V, Known, Depth, Q);
|
|
return Mask.isSubsetOf(Known.Zero);
|
|
}
|
|
|
|
// Match a signed min+max clamp pattern like smax(smin(In, CHigh), CLow).
|
|
// Returns the input and lower/upper bounds.
|
|
static bool isSignedMinMaxClamp(const Value *Select, const Value *&In,
|
|
const APInt *&CLow, const APInt *&CHigh) {
|
|
assert(isa<Operator>(Select) &&
|
|
cast<Operator>(Select)->getOpcode() == Instruction::Select &&
|
|
"Input should be a Select!");
|
|
|
|
const Value *LHS = nullptr, *RHS = nullptr;
|
|
SelectPatternFlavor SPF = matchSelectPattern(Select, LHS, RHS).Flavor;
|
|
if (SPF != SPF_SMAX && SPF != SPF_SMIN)
|
|
return false;
|
|
|
|
if (!match(RHS, m_APInt(CLow)))
|
|
return false;
|
|
|
|
const Value *LHS2 = nullptr, *RHS2 = nullptr;
|
|
SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor;
|
|
if (getInverseMinMaxFlavor(SPF) != SPF2)
|
|
return false;
|
|
|
|
if (!match(RHS2, m_APInt(CHigh)))
|
|
return false;
|
|
|
|
if (SPF == SPF_SMIN)
|
|
std::swap(CLow, CHigh);
|
|
|
|
In = LHS2;
|
|
return CLow->sle(*CHigh);
|
|
}
|
|
|
|
/// For vector constants, loop over the elements and find the constant with the
|
|
/// minimum number of sign bits. Return 0 if the value is not a vector constant
|
|
/// or if any element was not analyzed; otherwise, return the count for the
|
|
/// element with the minimum number of sign bits.
|
|
static unsigned computeNumSignBitsVectorConstant(const Value *V,
|
|
const APInt &DemandedElts,
|
|
unsigned TyBits) {
|
|
const auto *CV = dyn_cast<Constant>(V);
|
|
if (!CV || !isa<FixedVectorType>(CV->getType()))
|
|
return 0;
|
|
|
|
unsigned MinSignBits = TyBits;
|
|
unsigned NumElts = cast<FixedVectorType>(CV->getType())->getNumElements();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
if (!DemandedElts[i])
|
|
continue;
|
|
// If we find a non-ConstantInt, bail out.
|
|
auto *Elt = dyn_cast_or_null<ConstantInt>(CV->getAggregateElement(i));
|
|
if (!Elt)
|
|
return 0;
|
|
|
|
MinSignBits = std::min(MinSignBits, Elt->getValue().getNumSignBits());
|
|
}
|
|
|
|
return MinSignBits;
|
|
}
|
|
|
|
static unsigned ComputeNumSignBitsImpl(const Value *V,
|
|
const APInt &DemandedElts,
|
|
unsigned Depth, const Query &Q);
|
|
|
|
static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
|
|
unsigned Depth, const Query &Q) {
|
|
unsigned Result = ComputeNumSignBitsImpl(V, DemandedElts, Depth, Q);
|
|
assert(Result > 0 && "At least one sign bit needs to be present!");
|
|
return Result;
|
|
}
|
|
|
|
/// Return the number of times the sign bit of the register is replicated into
|
|
/// the other bits. We know that at least 1 bit is always equal to the sign bit
|
|
/// (itself), but other cases can give us information. For example, immediately
|
|
/// after an "ashr X, 2", we know that the top 3 bits are all equal to each
|
|
/// other, so we return 3. For vectors, return the number of sign bits for the
|
|
/// vector element with the minimum number of known sign bits of the demanded
|
|
/// elements in the vector specified by DemandedElts.
|
|
static unsigned ComputeNumSignBitsImpl(const Value *V,
|
|
const APInt &DemandedElts,
|
|
unsigned Depth, const Query &Q) {
|
|
Type *Ty = V->getType();
|
|
|
|
// FIXME: We currently have no way to represent the DemandedElts of a scalable
|
|
// vector
|
|
if (isa<ScalableVectorType>(Ty))
|
|
return 1;
|
|
|
|
#ifndef NDEBUG
|
|
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
|
|
|
|
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
|
|
assert(
|
|
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
|
|
"DemandedElt width should equal the fixed vector number of elements");
|
|
} else {
|
|
assert(DemandedElts == APInt(1, 1) &&
|
|
"DemandedElt width should be 1 for scalars");
|
|
}
|
|
#endif
|
|
|
|
// We return the minimum number of sign bits that are guaranteed to be present
|
|
// in V, so for undef we have to conservatively return 1. We don't have the
|
|
// same behavior for poison though -- that's a FIXME today.
|
|
|
|
Type *ScalarTy = Ty->getScalarType();
|
|
unsigned TyBits = ScalarTy->isPointerTy() ?
|
|
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
|
|
Q.DL.getTypeSizeInBits(ScalarTy);
|
|
|
|
unsigned Tmp, Tmp2;
|
|
unsigned FirstAnswer = 1;
|
|
|
|
// Note that ConstantInt is handled by the general computeKnownBits case
|
|
// below.
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return 1;
|
|
|
|
if (auto *U = dyn_cast<Operator>(V)) {
|
|
switch (Operator::getOpcode(V)) {
|
|
default: break;
|
|
case Instruction::SExt:
|
|
Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
|
|
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q) + Tmp;
|
|
|
|
case Instruction::SDiv: {
|
|
const APInt *Denominator;
|
|
// sdiv X, C -> adds log(C) sign bits.
|
|
if (match(U->getOperand(1), m_APInt(Denominator))) {
|
|
|
|
// Ignore non-positive denominator.
|
|
if (!Denominator->isStrictlyPositive())
|
|
break;
|
|
|
|
// Calculate the incoming numerator bits.
|
|
unsigned NumBits = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
|
|
// Add floor(log(C)) bits to the numerator bits.
|
|
return std::min(TyBits, NumBits + Denominator->logBase2());
|
|
}
|
|
break;
|
|
}
|
|
|
|
case Instruction::SRem: {
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
|
|
const APInt *Denominator;
|
|
// srem X, C -> we know that the result is within [-C+1,C) when C is a
|
|
// positive constant. This let us put a lower bound on the number of sign
|
|
// bits.
|
|
if (match(U->getOperand(1), m_APInt(Denominator))) {
|
|
|
|
// Ignore non-positive denominator.
|
|
if (Denominator->isStrictlyPositive()) {
|
|
// Calculate the leading sign bit constraints by examining the
|
|
// denominator. Given that the denominator is positive, there are two
|
|
// cases:
|
|
//
|
|
// 1. The numerator is positive. The result range is [0,C) and
|
|
// [0,C) u< (1 << ceilLogBase2(C)).
|
|
//
|
|
// 2. The numerator is negative. Then the result range is (-C,0] and
|
|
// integers in (-C,0] are either 0 or >u (-1 << ceilLogBase2(C)).
|
|
//
|
|
// Thus a lower bound on the number of sign bits is `TyBits -
|
|
// ceilLogBase2(C)`.
|
|
|
|
unsigned ResBits = TyBits - Denominator->ceilLogBase2();
|
|
Tmp = std::max(Tmp, ResBits);
|
|
}
|
|
}
|
|
return Tmp;
|
|
}
|
|
|
|
case Instruction::AShr: {
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
// ashr X, C -> adds C sign bits. Vectors too.
|
|
const APInt *ShAmt;
|
|
if (match(U->getOperand(1), m_APInt(ShAmt))) {
|
|
if (ShAmt->uge(TyBits))
|
|
break; // Bad shift.
|
|
unsigned ShAmtLimited = ShAmt->getZExtValue();
|
|
Tmp += ShAmtLimited;
|
|
if (Tmp > TyBits) Tmp = TyBits;
|
|
}
|
|
return Tmp;
|
|
}
|
|
case Instruction::Shl: {
|
|
const APInt *ShAmt;
|
|
if (match(U->getOperand(1), m_APInt(ShAmt))) {
|
|
// shl destroys sign bits.
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (ShAmt->uge(TyBits) || // Bad shift.
|
|
ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
|
|
Tmp2 = ShAmt->getZExtValue();
|
|
return Tmp - Tmp2;
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
case Instruction::Xor: // NOT is handled here.
|
|
// Logical binary ops preserve the number of sign bits at the worst.
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (Tmp != 1) {
|
|
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
|
|
FirstAnswer = std::min(Tmp, Tmp2);
|
|
// We computed what we know about the sign bits as our first
|
|
// answer. Now proceed to the generic code that uses
|
|
// computeKnownBits, and pick whichever answer is better.
|
|
}
|
|
break;
|
|
|
|
case Instruction::Select: {
|
|
// If we have a clamp pattern, we know that the number of sign bits will
|
|
// be the minimum of the clamp min/max range.
|
|
const Value *X;
|
|
const APInt *CLow, *CHigh;
|
|
if (isSignedMinMaxClamp(U, X, CLow, CHigh))
|
|
return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
|
|
|
|
Tmp = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
|
|
if (Tmp == 1) break;
|
|
Tmp2 = ComputeNumSignBits(U->getOperand(2), Depth + 1, Q);
|
|
return std::min(Tmp, Tmp2);
|
|
}
|
|
|
|
case Instruction::Add:
|
|
// Add can have at most one carry bit. Thus we know that the output
|
|
// is, at worst, one more bit than the inputs.
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (Tmp == 1) break;
|
|
|
|
// Special case decrementing a value (ADD X, -1):
|
|
if (const auto *CRHS = dyn_cast<Constant>(U->getOperand(1)))
|
|
if (CRHS->isAllOnesValue()) {
|
|
KnownBits Known(TyBits);
|
|
computeKnownBits(U->getOperand(0), Known, Depth + 1, Q);
|
|
|
|
// If the input is known to be 0 or 1, the output is 0/-1, which is
|
|
// all sign bits set.
|
|
if ((Known.Zero | 1).isAllOnesValue())
|
|
return TyBits;
|
|
|
|
// If we are subtracting one from a positive number, there is no carry
|
|
// out of the result.
|
|
if (Known.isNonNegative())
|
|
return Tmp;
|
|
}
|
|
|
|
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
|
|
if (Tmp2 == 1) break;
|
|
return std::min(Tmp, Tmp2) - 1;
|
|
|
|
case Instruction::Sub:
|
|
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
|
|
if (Tmp2 == 1) break;
|
|
|
|
// Handle NEG.
|
|
if (const auto *CLHS = dyn_cast<Constant>(U->getOperand(0)))
|
|
if (CLHS->isNullValue()) {
|
|
KnownBits Known(TyBits);
|
|
computeKnownBits(U->getOperand(1), Known, Depth + 1, Q);
|
|
// If the input is known to be 0 or 1, the output is 0/-1, which is
|
|
// all sign bits set.
|
|
if ((Known.Zero | 1).isAllOnesValue())
|
|
return TyBits;
|
|
|
|
// If the input is known to be positive (the sign bit is known clear),
|
|
// the output of the NEG has the same number of sign bits as the
|
|
// input.
|
|
if (Known.isNonNegative())
|
|
return Tmp2;
|
|
|
|
// Otherwise, we treat this like a SUB.
|
|
}
|
|
|
|
// Sub can have at most one carry bit. Thus we know that the output
|
|
// is, at worst, one more bit than the inputs.
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (Tmp == 1) break;
|
|
return std::min(Tmp, Tmp2) - 1;
|
|
|
|
case Instruction::Mul: {
|
|
// The output of the Mul can be at most twice the valid bits in the
|
|
// inputs.
|
|
unsigned SignBitsOp0 = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (SignBitsOp0 == 1) break;
|
|
unsigned SignBitsOp1 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
|
|
if (SignBitsOp1 == 1) break;
|
|
unsigned OutValidBits =
|
|
(TyBits - SignBitsOp0 + 1) + (TyBits - SignBitsOp1 + 1);
|
|
return OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
|
|
}
|
|
|
|
case Instruction::PHI: {
|
|
const PHINode *PN = cast<PHINode>(U);
|
|
unsigned NumIncomingValues = PN->getNumIncomingValues();
|
|
// Don't analyze large in-degree PHIs.
|
|
if (NumIncomingValues > 4) break;
|
|
// Unreachable blocks may have zero-operand PHI nodes.
|
|
if (NumIncomingValues == 0) break;
|
|
|
|
// Take the minimum of all incoming values. This can't infinitely loop
|
|
// because of our depth threshold.
|
|
Query RecQ = Q;
|
|
Tmp = TyBits;
|
|
for (unsigned i = 0, e = NumIncomingValues; i != e; ++i) {
|
|
if (Tmp == 1) return Tmp;
|
|
RecQ.CxtI = PN->getIncomingBlock(i)->getTerminator();
|
|
Tmp = std::min(
|
|
Tmp, ComputeNumSignBits(PN->getIncomingValue(i), Depth + 1, RecQ));
|
|
}
|
|
return Tmp;
|
|
}
|
|
|
|
case Instruction::Trunc:
|
|
// FIXME: it's tricky to do anything useful for this, but it is an
|
|
// important case for targets like X86.
|
|
break;
|
|
|
|
case Instruction::ExtractElement:
|
|
// Look through extract element. At the moment we keep this simple and
|
|
// skip tracking the specific element. But at least we might find
|
|
// information valid for all elements of the vector (for example if vector
|
|
// is sign extended, shifted, etc).
|
|
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
|
|
case Instruction::ShuffleVector: {
|
|
// Collect the minimum number of sign bits that are shared by every vector
|
|
// element referenced by the shuffle.
|
|
auto *Shuf = dyn_cast<ShuffleVectorInst>(U);
|
|
if (!Shuf) {
|
|
// FIXME: Add support for shufflevector constant expressions.
|
|
return 1;
|
|
}
|
|
APInt DemandedLHS, DemandedRHS;
|
|
// For undef elements, we don't know anything about the common state of
|
|
// the shuffle result.
|
|
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
|
|
return 1;
|
|
Tmp = std::numeric_limits<unsigned>::max();
|
|
if (!!DemandedLHS) {
|
|
const Value *LHS = Shuf->getOperand(0);
|
|
Tmp = ComputeNumSignBits(LHS, DemandedLHS, Depth + 1, Q);
|
|
}
|
|
// If we don't know anything, early out and try computeKnownBits
|
|
// fall-back.
|
|
if (Tmp == 1)
|
|
break;
|
|
if (!!DemandedRHS) {
|
|
const Value *RHS = Shuf->getOperand(1);
|
|
Tmp2 = ComputeNumSignBits(RHS, DemandedRHS, Depth + 1, Q);
|
|
Tmp = std::min(Tmp, Tmp2);
|
|
}
|
|
// If we don't know anything, early out and try computeKnownBits
|
|
// fall-back.
|
|
if (Tmp == 1)
|
|
break;
|
|
assert(Tmp <= TyBits && "Failed to determine minimum sign bits");
|
|
return Tmp;
|
|
}
|
|
case Instruction::Call: {
|
|
if (const auto *II = dyn_cast<IntrinsicInst>(U)) {
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::abs:
|
|
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
|
|
if (Tmp == 1) break;
|
|
|
|
// Absolute value reduces number of sign bits by at most 1.
|
|
return Tmp - 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Finally, if we can prove that the top bits of the result are 0's or 1's,
|
|
// use this information.
|
|
|
|
// If we can examine all elements of a vector constant successfully, we're
|
|
// done (we can't do any better than that). If not, keep trying.
|
|
if (unsigned VecSignBits =
|
|
computeNumSignBitsVectorConstant(V, DemandedElts, TyBits))
|
|
return VecSignBits;
|
|
|
|
KnownBits Known(TyBits);
|
|
computeKnownBits(V, DemandedElts, Known, Depth, Q);
|
|
|
|
// If we know that the sign bit is either zero or one, determine the number of
|
|
// identical bits in the top of the input value.
|
|
return std::max(FirstAnswer, Known.countMinSignBits());
|
|
}
|
|
|
|
/// This function computes the integer multiple of Base that equals V.
|
|
/// If successful, it returns true and returns the multiple in
|
|
/// Multiple. If unsuccessful, it returns false. It looks
|
|
/// through SExt instructions only if LookThroughSExt is true.
|
|
bool llvm::ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
|
|
bool LookThroughSExt, unsigned Depth) {
|
|
assert(V && "No Value?");
|
|
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
|
|
assert(V->getType()->isIntegerTy() && "Not integer or pointer type!");
|
|
|
|
Type *T = V->getType();
|
|
|
|
ConstantInt *CI = dyn_cast<ConstantInt>(V);
|
|
|
|
if (Base == 0)
|
|
return false;
|
|
|
|
if (Base == 1) {
|
|
Multiple = V;
|
|
return true;
|
|
}
|
|
|
|
ConstantExpr *CO = dyn_cast<ConstantExpr>(V);
|
|
Constant *BaseVal = ConstantInt::get(T, Base);
|
|
if (CO && CO == BaseVal) {
|
|
// Multiple is 1.
|
|
Multiple = ConstantInt::get(T, 1);
|
|
return true;
|
|
}
|
|
|
|
if (CI && CI->getZExtValue() % Base == 0) {
|
|
Multiple = ConstantInt::get(T, CI->getZExtValue() / Base);
|
|
return true;
|
|
}
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth) return false;
|
|
|
|
Operator *I = dyn_cast<Operator>(V);
|
|
if (!I) return false;
|
|
|
|
switch (I->getOpcode()) {
|
|
default: break;
|
|
case Instruction::SExt:
|
|
if (!LookThroughSExt) return false;
|
|
// otherwise fall through to ZExt
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::ZExt:
|
|
return ComputeMultiple(I->getOperand(0), Base, Multiple,
|
|
LookThroughSExt, Depth+1);
|
|
case Instruction::Shl:
|
|
case Instruction::Mul: {
|
|
Value *Op0 = I->getOperand(0);
|
|
Value *Op1 = I->getOperand(1);
|
|
|
|
if (I->getOpcode() == Instruction::Shl) {
|
|
ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1);
|
|
if (!Op1CI) return false;
|
|
// Turn Op0 << Op1 into Op0 * 2^Op1
|
|
APInt Op1Int = Op1CI->getValue();
|
|
uint64_t BitToSet = Op1Int.getLimitedValue(Op1Int.getBitWidth() - 1);
|
|
APInt API(Op1Int.getBitWidth(), 0);
|
|
API.setBit(BitToSet);
|
|
Op1 = ConstantInt::get(V->getContext(), API);
|
|
}
|
|
|
|
Value *Mul0 = nullptr;
|
|
if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) {
|
|
if (Constant *Op1C = dyn_cast<Constant>(Op1))
|
|
if (Constant *MulC = dyn_cast<Constant>(Mul0)) {
|
|
if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() <
|
|
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
|
|
Op1C = ConstantExpr::getZExt(Op1C, MulC->getType());
|
|
if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() >
|
|
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
|
|
MulC = ConstantExpr::getZExt(MulC, Op1C->getType());
|
|
|
|
// V == Base * (Mul0 * Op1), so return (Mul0 * Op1)
|
|
Multiple = ConstantExpr::getMul(MulC, Op1C);
|
|
return true;
|
|
}
|
|
|
|
if (ConstantInt *Mul0CI = dyn_cast<ConstantInt>(Mul0))
|
|
if (Mul0CI->getValue() == 1) {
|
|
// V == Base * Op1, so return Op1
|
|
Multiple = Op1;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
Value *Mul1 = nullptr;
|
|
if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) {
|
|
if (Constant *Op0C = dyn_cast<Constant>(Op0))
|
|
if (Constant *MulC = dyn_cast<Constant>(Mul1)) {
|
|
if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() <
|
|
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
|
|
Op0C = ConstantExpr::getZExt(Op0C, MulC->getType());
|
|
if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() >
|
|
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
|
|
MulC = ConstantExpr::getZExt(MulC, Op0C->getType());
|
|
|
|
// V == Base * (Mul1 * Op0), so return (Mul1 * Op0)
|
|
Multiple = ConstantExpr::getMul(MulC, Op0C);
|
|
return true;
|
|
}
|
|
|
|
if (ConstantInt *Mul1CI = dyn_cast<ConstantInt>(Mul1))
|
|
if (Mul1CI->getValue() == 1) {
|
|
// V == Base * Op0, so return Op0
|
|
Multiple = Op0;
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// We could not determine if V is a multiple of Base.
|
|
return false;
|
|
}
|
|
|
|
Intrinsic::ID llvm::getIntrinsicForCallSite(const CallBase &CB,
|
|
const TargetLibraryInfo *TLI) {
|
|
const Function *F = CB.getCalledFunction();
|
|
if (!F)
|
|
return Intrinsic::not_intrinsic;
|
|
|
|
if (F->isIntrinsic())
|
|
return F->getIntrinsicID();
|
|
|
|
// We are going to infer semantics of a library function based on mapping it
|
|
// to an LLVM intrinsic. Check that the library function is available from
|
|
// this callbase and in this environment.
|
|
LibFunc Func;
|
|
if (F->hasLocalLinkage() || !TLI || !TLI->getLibFunc(CB, Func) ||
|
|
!CB.onlyReadsMemory())
|
|
return Intrinsic::not_intrinsic;
|
|
|
|
switch (Func) {
|
|
default:
|
|
break;
|
|
case LibFunc_sin:
|
|
case LibFunc_sinf:
|
|
case LibFunc_sinl:
|
|
return Intrinsic::sin;
|
|
case LibFunc_cos:
|
|
case LibFunc_cosf:
|
|
case LibFunc_cosl:
|
|
return Intrinsic::cos;
|
|
case LibFunc_exp:
|
|
case LibFunc_expf:
|
|
case LibFunc_expl:
|
|
return Intrinsic::exp;
|
|
case LibFunc_exp2:
|
|
case LibFunc_exp2f:
|
|
case LibFunc_exp2l:
|
|
return Intrinsic::exp2;
|
|
case LibFunc_log:
|
|
case LibFunc_logf:
|
|
case LibFunc_logl:
|
|
return Intrinsic::log;
|
|
case LibFunc_log10:
|
|
case LibFunc_log10f:
|
|
case LibFunc_log10l:
|
|
return Intrinsic::log10;
|
|
case LibFunc_log2:
|
|
case LibFunc_log2f:
|
|
case LibFunc_log2l:
|
|
return Intrinsic::log2;
|
|
case LibFunc_fabs:
|
|
case LibFunc_fabsf:
|
|
case LibFunc_fabsl:
|
|
return Intrinsic::fabs;
|
|
case LibFunc_fmin:
|
|
case LibFunc_fminf:
|
|
case LibFunc_fminl:
|
|
return Intrinsic::minnum;
|
|
case LibFunc_fmax:
|
|
case LibFunc_fmaxf:
|
|
case LibFunc_fmaxl:
|
|
return Intrinsic::maxnum;
|
|
case LibFunc_copysign:
|
|
case LibFunc_copysignf:
|
|
case LibFunc_copysignl:
|
|
return Intrinsic::copysign;
|
|
case LibFunc_floor:
|
|
case LibFunc_floorf:
|
|
case LibFunc_floorl:
|
|
return Intrinsic::floor;
|
|
case LibFunc_ceil:
|
|
case LibFunc_ceilf:
|
|
case LibFunc_ceill:
|
|
return Intrinsic::ceil;
|
|
case LibFunc_trunc:
|
|
case LibFunc_truncf:
|
|
case LibFunc_truncl:
|
|
return Intrinsic::trunc;
|
|
case LibFunc_rint:
|
|
case LibFunc_rintf:
|
|
case LibFunc_rintl:
|
|
return Intrinsic::rint;
|
|
case LibFunc_nearbyint:
|
|
case LibFunc_nearbyintf:
|
|
case LibFunc_nearbyintl:
|
|
return Intrinsic::nearbyint;
|
|
case LibFunc_round:
|
|
case LibFunc_roundf:
|
|
case LibFunc_roundl:
|
|
return Intrinsic::round;
|
|
case LibFunc_roundeven:
|
|
case LibFunc_roundevenf:
|
|
case LibFunc_roundevenl:
|
|
return Intrinsic::roundeven;
|
|
case LibFunc_pow:
|
|
case LibFunc_powf:
|
|
case LibFunc_powl:
|
|
return Intrinsic::pow;
|
|
case LibFunc_sqrt:
|
|
case LibFunc_sqrtf:
|
|
case LibFunc_sqrtl:
|
|
return Intrinsic::sqrt;
|
|
}
|
|
|
|
return Intrinsic::not_intrinsic;
|
|
}
|
|
|
|
/// Return true if we can prove that the specified FP value is never equal to
|
|
/// -0.0.
|
|
/// NOTE: Do not check 'nsz' here because that fast-math-flag does not guarantee
|
|
/// that a value is not -0.0. It only guarantees that -0.0 may be treated
|
|
/// the same as +0.0 in floating-point ops.
|
|
///
|
|
/// NOTE: this function will need to be revisited when we support non-default
|
|
/// rounding modes!
|
|
bool llvm::CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
|
|
unsigned Depth) {
|
|
if (auto *CFP = dyn_cast<ConstantFP>(V))
|
|
return !CFP->getValueAPF().isNegZero();
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
auto *Op = dyn_cast<Operator>(V);
|
|
if (!Op)
|
|
return false;
|
|
|
|
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
|
|
if (match(Op, m_FAdd(m_Value(), m_PosZeroFP())))
|
|
return true;
|
|
|
|
// sitofp and uitofp turn into +0.0 for zero.
|
|
if (isa<SIToFPInst>(Op) || isa<UIToFPInst>(Op))
|
|
return true;
|
|
|
|
if (auto *Call = dyn_cast<CallInst>(Op)) {
|
|
Intrinsic::ID IID = getIntrinsicForCallSite(*Call, TLI);
|
|
switch (IID) {
|
|
default:
|
|
break;
|
|
// sqrt(-0.0) = -0.0, no other negative results are possible.
|
|
case Intrinsic::sqrt:
|
|
case Intrinsic::canonicalize:
|
|
return CannotBeNegativeZero(Call->getArgOperand(0), TLI, Depth + 1);
|
|
// fabs(x) != -0.0
|
|
case Intrinsic::fabs:
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// If \p SignBitOnly is true, test for a known 0 sign bit rather than a
|
|
/// standard ordered compare. e.g. make -0.0 olt 0.0 be true because of the sign
|
|
/// bit despite comparing equal.
|
|
static bool cannotBeOrderedLessThanZeroImpl(const Value *V,
|
|
const TargetLibraryInfo *TLI,
|
|
bool SignBitOnly,
|
|
unsigned Depth) {
|
|
// TODO: This function does not do the right thing when SignBitOnly is true
|
|
// and we're lowering to a hypothetical IEEE 754-compliant-but-evil platform
|
|
// which flips the sign bits of NaNs. See
|
|
// https://llvm.org/bugs/show_bug.cgi?id=31702.
|
|
|
|
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
|
|
return !CFP->getValueAPF().isNegative() ||
|
|
(!SignBitOnly && CFP->getValueAPF().isZero());
|
|
}
|
|
|
|
// Handle vector of constants.
|
|
if (auto *CV = dyn_cast<Constant>(V)) {
|
|
if (auto *CVFVTy = dyn_cast<FixedVectorType>(CV->getType())) {
|
|
unsigned NumElts = CVFVTy->getNumElements();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i));
|
|
if (!CFP)
|
|
return false;
|
|
if (CFP->getValueAPF().isNegative() &&
|
|
(SignBitOnly || !CFP->getValueAPF().isZero()))
|
|
return false;
|
|
}
|
|
|
|
// All non-negative ConstantFPs.
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
const Operator *I = dyn_cast<Operator>(V);
|
|
if (!I)
|
|
return false;
|
|
|
|
switch (I->getOpcode()) {
|
|
default:
|
|
break;
|
|
// Unsigned integers are always nonnegative.
|
|
case Instruction::UIToFP:
|
|
return true;
|
|
case Instruction::FMul:
|
|
case Instruction::FDiv:
|
|
// X * X is always non-negative or a NaN.
|
|
// X / X is always exactly 1.0 or a NaN.
|
|
if (I->getOperand(0) == I->getOperand(1) &&
|
|
(!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()))
|
|
return true;
|
|
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::FAdd:
|
|
case Instruction::FRem:
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1) &&
|
|
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Instruction::Select:
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
|
|
Depth + 1) &&
|
|
cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Instruction::FPExt:
|
|
case Instruction::FPTrunc:
|
|
// Widening/narrowing never change sign.
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Instruction::ExtractElement:
|
|
// Look through extract element. At the moment we keep this simple and skip
|
|
// tracking the specific element. But at least we might find information
|
|
// valid for all elements of the vector.
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Instruction::Call:
|
|
const auto *CI = cast<CallInst>(I);
|
|
Intrinsic::ID IID = getIntrinsicForCallSite(*CI, TLI);
|
|
switch (IID) {
|
|
default:
|
|
break;
|
|
case Intrinsic::maxnum: {
|
|
Value *V0 = I->getOperand(0), *V1 = I->getOperand(1);
|
|
auto isPositiveNum = [&](Value *V) {
|
|
if (SignBitOnly) {
|
|
// With SignBitOnly, this is tricky because the result of
|
|
// maxnum(+0.0, -0.0) is unspecified. Just check if the operand is
|
|
// a constant strictly greater than 0.0.
|
|
const APFloat *C;
|
|
return match(V, m_APFloat(C)) &&
|
|
*C > APFloat::getZero(C->getSemantics());
|
|
}
|
|
|
|
// -0.0 compares equal to 0.0, so if this operand is at least -0.0,
|
|
// maxnum can't be ordered-less-than-zero.
|
|
return isKnownNeverNaN(V, TLI) &&
|
|
cannotBeOrderedLessThanZeroImpl(V, TLI, false, Depth + 1);
|
|
};
|
|
|
|
// TODO: This could be improved. We could also check that neither operand
|
|
// has its sign bit set (and at least 1 is not-NAN?).
|
|
return isPositiveNum(V0) || isPositiveNum(V1);
|
|
}
|
|
|
|
case Intrinsic::maximum:
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1) ||
|
|
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Intrinsic::minnum:
|
|
case Intrinsic::minimum:
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1) &&
|
|
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
case Intrinsic::exp:
|
|
case Intrinsic::exp2:
|
|
case Intrinsic::fabs:
|
|
return true;
|
|
|
|
case Intrinsic::sqrt:
|
|
// sqrt(x) is always >= -0 or NaN. Moreover, sqrt(x) == -0 iff x == -0.
|
|
if (!SignBitOnly)
|
|
return true;
|
|
return CI->hasNoNaNs() && (CI->hasNoSignedZeros() ||
|
|
CannotBeNegativeZero(CI->getOperand(0), TLI));
|
|
|
|
case Intrinsic::powi:
|
|
if (ConstantInt *Exponent = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
// powi(x,n) is non-negative if n is even.
|
|
if (Exponent->getBitWidth() <= 64 && Exponent->getSExtValue() % 2u == 0)
|
|
return true;
|
|
}
|
|
// TODO: This is not correct. Given that exp is an integer, here are the
|
|
// ways that pow can return a negative value:
|
|
//
|
|
// pow(x, exp) --> negative if exp is odd and x is negative.
|
|
// pow(-0, exp) --> -inf if exp is negative odd.
|
|
// pow(-0, exp) --> -0 if exp is positive odd.
|
|
// pow(-inf, exp) --> -0 if exp is negative odd.
|
|
// pow(-inf, exp) --> -inf if exp is positive odd.
|
|
//
|
|
// Therefore, if !SignBitOnly, we can return true if x >= +0 or x is NaN,
|
|
// but we must return false if x == -0. Unfortunately we do not currently
|
|
// have a way of expressing this constraint. See details in
|
|
// https://llvm.org/bugs/show_bug.cgi?id=31702.
|
|
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
|
|
case Intrinsic::fma:
|
|
case Intrinsic::fmuladd:
|
|
// x*x+y is non-negative if y is non-negative.
|
|
return I->getOperand(0) == I->getOperand(1) &&
|
|
(!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()) &&
|
|
cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
|
|
Depth + 1);
|
|
}
|
|
break;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool llvm::CannotBeOrderedLessThanZero(const Value *V,
|
|
const TargetLibraryInfo *TLI) {
|
|
return cannotBeOrderedLessThanZeroImpl(V, TLI, false, 0);
|
|
}
|
|
|
|
bool llvm::SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI) {
|
|
return cannotBeOrderedLessThanZeroImpl(V, TLI, true, 0);
|
|
}
|
|
|
|
bool llvm::isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
|
|
unsigned Depth) {
|
|
assert(V->getType()->isFPOrFPVectorTy() && "Querying for Inf on non-FP type");
|
|
|
|
// If we're told that infinities won't happen, assume they won't.
|
|
if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
|
|
if (FPMathOp->hasNoInfs())
|
|
return true;
|
|
|
|
// Handle scalar constants.
|
|
if (auto *CFP = dyn_cast<ConstantFP>(V))
|
|
return !CFP->isInfinity();
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
if (auto *Inst = dyn_cast<Instruction>(V)) {
|
|
switch (Inst->getOpcode()) {
|
|
case Instruction::Select: {
|
|
return isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1) &&
|
|
isKnownNeverInfinity(Inst->getOperand(2), TLI, Depth + 1);
|
|
}
|
|
case Instruction::SIToFP:
|
|
case Instruction::UIToFP: {
|
|
// Get width of largest magnitude integer (remove a bit if signed).
|
|
// This still works for a signed minimum value because the largest FP
|
|
// value is scaled by some fraction close to 2.0 (1.0 + 0.xxxx).
|
|
int IntSize = Inst->getOperand(0)->getType()->getScalarSizeInBits();
|
|
if (Inst->getOpcode() == Instruction::SIToFP)
|
|
--IntSize;
|
|
|
|
// If the exponent of the largest finite FP value can hold the largest
|
|
// integer, the result of the cast must be finite.
|
|
Type *FPTy = Inst->getType()->getScalarType();
|
|
return ilogb(APFloat::getLargest(FPTy->getFltSemantics())) >= IntSize;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
// try to handle fixed width vector constants
|
|
auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
|
|
if (VFVTy && isa<Constant>(V)) {
|
|
// For vectors, verify that each element is not infinity.
|
|
unsigned NumElts = VFVTy->getNumElements();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
|
|
if (!Elt)
|
|
return false;
|
|
if (isa<UndefValue>(Elt))
|
|
continue;
|
|
auto *CElt = dyn_cast<ConstantFP>(Elt);
|
|
if (!CElt || CElt->isInfinity())
|
|
return false;
|
|
}
|
|
// All elements were confirmed non-infinity or undefined.
|
|
return true;
|
|
}
|
|
|
|
// was not able to prove that V never contains infinity
|
|
return false;
|
|
}
|
|
|
|
bool llvm::isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
|
|
unsigned Depth) {
|
|
assert(V->getType()->isFPOrFPVectorTy() && "Querying for NaN on non-FP type");
|
|
|
|
// If we're told that NaNs won't happen, assume they won't.
|
|
if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
|
|
if (FPMathOp->hasNoNaNs())
|
|
return true;
|
|
|
|
// Handle scalar constants.
|
|
if (auto *CFP = dyn_cast<ConstantFP>(V))
|
|
return !CFP->isNaN();
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
if (auto *Inst = dyn_cast<Instruction>(V)) {
|
|
switch (Inst->getOpcode()) {
|
|
case Instruction::FAdd:
|
|
case Instruction::FSub:
|
|
// Adding positive and negative infinity produces NaN.
|
|
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
|
|
isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
|
|
(isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) ||
|
|
isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1));
|
|
|
|
case Instruction::FMul:
|
|
// Zero multiplied with infinity produces NaN.
|
|
// FIXME: If neither side can be zero fmul never produces NaN.
|
|
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
|
|
isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) &&
|
|
isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
|
|
isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1);
|
|
|
|
case Instruction::FDiv:
|
|
case Instruction::FRem:
|
|
// FIXME: Only 0/0, Inf/Inf, Inf REM x and x REM 0 produce NaN.
|
|
return false;
|
|
|
|
case Instruction::Select: {
|
|
return isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
|
|
isKnownNeverNaN(Inst->getOperand(2), TLI, Depth + 1);
|
|
}
|
|
case Instruction::SIToFP:
|
|
case Instruction::UIToFP:
|
|
return true;
|
|
case Instruction::FPTrunc:
|
|
case Instruction::FPExt:
|
|
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1);
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
|
|
switch (II->getIntrinsicID()) {
|
|
case Intrinsic::canonicalize:
|
|
case Intrinsic::fabs:
|
|
case Intrinsic::copysign:
|
|
case Intrinsic::exp:
|
|
case Intrinsic::exp2:
|
|
case Intrinsic::floor:
|
|
case Intrinsic::ceil:
|
|
case Intrinsic::trunc:
|
|
case Intrinsic::rint:
|
|
case Intrinsic::nearbyint:
|
|
case Intrinsic::round:
|
|
case Intrinsic::roundeven:
|
|
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1);
|
|
case Intrinsic::sqrt:
|
|
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) &&
|
|
CannotBeOrderedLessThanZero(II->getArgOperand(0), TLI);
|
|
case Intrinsic::minnum:
|
|
case Intrinsic::maxnum:
|
|
// If either operand is not NaN, the result is not NaN.
|
|
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) ||
|
|
isKnownNeverNaN(II->getArgOperand(1), TLI, Depth + 1);
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Try to handle fixed width vector constants
|
|
auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
|
|
if (VFVTy && isa<Constant>(V)) {
|
|
// For vectors, verify that each element is not NaN.
|
|
unsigned NumElts = VFVTy->getNumElements();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
|
|
if (!Elt)
|
|
return false;
|
|
if (isa<UndefValue>(Elt))
|
|
continue;
|
|
auto *CElt = dyn_cast<ConstantFP>(Elt);
|
|
if (!CElt || CElt->isNaN())
|
|
return false;
|
|
}
|
|
// All elements were confirmed not-NaN or undefined.
|
|
return true;
|
|
}
|
|
|
|
// Was not able to prove that V never contains NaN
|
|
return false;
|
|
}
|
|
|
|
Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
|
|
|
|
// All byte-wide stores are splatable, even of arbitrary variables.
|
|
if (V->getType()->isIntegerTy(8))
|
|
return V;
|
|
|
|
LLVMContext &Ctx = V->getContext();
|
|
|
|
// Undef don't care.
|
|
auto *UndefInt8 = UndefValue::get(Type::getInt8Ty(Ctx));
|
|
if (isa<UndefValue>(V))
|
|
return UndefInt8;
|
|
|
|
// Return Undef for zero-sized type.
|
|
if (!DL.getTypeStoreSize(V->getType()).isNonZero())
|
|
return UndefInt8;
|
|
|
|
Constant *C = dyn_cast<Constant>(V);
|
|
if (!C) {
|
|
// Conceptually, we could handle things like:
|
|
// %a = zext i8 %X to i16
|
|
// %b = shl i16 %a, 8
|
|
// %c = or i16 %a, %b
|
|
// but until there is an example that actually needs this, it doesn't seem
|
|
// worth worrying about.
|
|
return nullptr;
|
|
}
|
|
|
|
// Handle 'null' ConstantArrayZero etc.
|
|
if (C->isNullValue())
|
|
return Constant::getNullValue(Type::getInt8Ty(Ctx));
|
|
|
|
// Constant floating-point values can be handled as integer values if the
|
|
// corresponding integer value is "byteable". An important case is 0.0.
|
|
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
|
|
Type *Ty = nullptr;
|
|
if (CFP->getType()->isHalfTy())
|
|
Ty = Type::getInt16Ty(Ctx);
|
|
else if (CFP->getType()->isFloatTy())
|
|
Ty = Type::getInt32Ty(Ctx);
|
|
else if (CFP->getType()->isDoubleTy())
|
|
Ty = Type::getInt64Ty(Ctx);
|
|
// Don't handle long double formats, which have strange constraints.
|
|
return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
|
|
: nullptr;
|
|
}
|
|
|
|
// We can handle constant integers that are multiple of 8 bits.
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
|
|
if (CI->getBitWidth() % 8 == 0) {
|
|
assert(CI->getBitWidth() > 8 && "8 bits should be handled above!");
|
|
if (!CI->getValue().isSplat(8))
|
|
return nullptr;
|
|
return ConstantInt::get(Ctx, CI->getValue().trunc(8));
|
|
}
|
|
}
|
|
|
|
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
|
|
if (CE->getOpcode() == Instruction::IntToPtr) {
|
|
if (auto *PtrTy = dyn_cast<PointerType>(CE->getType())) {
|
|
unsigned BitWidth = DL.getPointerSizeInBits(PtrTy->getAddressSpace());
|
|
return isBytewiseValue(
|
|
ConstantExpr::getIntegerCast(CE->getOperand(0),
|
|
Type::getIntNTy(Ctx, BitWidth), false),
|
|
DL);
|
|
}
|
|
}
|
|
}
|
|
|
|
auto Merge = [&](Value *LHS, Value *RHS) -> Value * {
|
|
if (LHS == RHS)
|
|
return LHS;
|
|
if (!LHS || !RHS)
|
|
return nullptr;
|
|
if (LHS == UndefInt8)
|
|
return RHS;
|
|
if (RHS == UndefInt8)
|
|
return LHS;
|
|
return nullptr;
|
|
};
|
|
|
|
if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
|
|
Value *Val = UndefInt8;
|
|
for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
|
|
if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I), DL))))
|
|
return nullptr;
|
|
return Val;
|
|
}
|
|
|
|
if (isa<ConstantAggregate>(C)) {
|
|
Value *Val = UndefInt8;
|
|
for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
|
|
if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I), DL))))
|
|
return nullptr;
|
|
return Val;
|
|
}
|
|
|
|
// Don't try to handle the handful of other constants.
|
|
return nullptr;
|
|
}
|
|
|
|
// This is the recursive version of BuildSubAggregate. It takes a few different
|
|
// arguments. Idxs is the index within the nested struct From that we are
|
|
// looking at now (which is of type IndexedType). IdxSkip is the number of
|
|
// indices from Idxs that should be left out when inserting into the resulting
|
|
// struct. To is the result struct built so far, new insertvalue instructions
|
|
// build on that.
|
|
static Value *BuildSubAggregate(Value *From, Value* To, Type *IndexedType,
|
|
SmallVectorImpl<unsigned> &Idxs,
|
|
unsigned IdxSkip,
|
|
Instruction *InsertBefore) {
|
|
StructType *STy = dyn_cast<StructType>(IndexedType);
|
|
if (STy) {
|
|
// Save the original To argument so we can modify it
|
|
Value *OrigTo = To;
|
|
// General case, the type indexed by Idxs is a struct
|
|
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
|
|
// Process each struct element recursively
|
|
Idxs.push_back(i);
|
|
Value *PrevTo = To;
|
|
To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
|
|
InsertBefore);
|
|
Idxs.pop_back();
|
|
if (!To) {
|
|
// Couldn't find any inserted value for this index? Cleanup
|
|
while (PrevTo != OrigTo) {
|
|
InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
|
|
PrevTo = Del->getAggregateOperand();
|
|
Del->eraseFromParent();
|
|
}
|
|
// Stop processing elements
|
|
break;
|
|
}
|
|
}
|
|
// If we successfully found a value for each of our subaggregates
|
|
if (To)
|
|
return To;
|
|
}
|
|
// Base case, the type indexed by SourceIdxs is not a struct, or not all of
|
|
// the struct's elements had a value that was inserted directly. In the latter
|
|
// case, perhaps we can't determine each of the subelements individually, but
|
|
// we might be able to find the complete struct somewhere.
|
|
|
|
// Find the value that is at that particular spot
|
|
Value *V = FindInsertedValue(From, Idxs);
|
|
|
|
if (!V)
|
|
return nullptr;
|
|
|
|
// Insert the value in the new (sub) aggregate
|
|
return InsertValueInst::Create(To, V, makeArrayRef(Idxs).slice(IdxSkip),
|
|
"tmp", InsertBefore);
|
|
}
|
|
|
|
// This helper takes a nested struct and extracts a part of it (which is again a
|
|
// struct) into a new value. For example, given the struct:
|
|
// { a, { b, { c, d }, e } }
|
|
// and the indices "1, 1" this returns
|
|
// { c, d }.
|
|
//
|
|
// It does this by inserting an insertvalue for each element in the resulting
|
|
// struct, as opposed to just inserting a single struct. This will only work if
|
|
// each of the elements of the substruct are known (ie, inserted into From by an
|
|
// insertvalue instruction somewhere).
|
|
//
|
|
// All inserted insertvalue instructions are inserted before InsertBefore
|
|
static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range,
|
|
Instruction *InsertBefore) {
|
|
assert(InsertBefore && "Must have someplace to insert!");
|
|
Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
|
|
idx_range);
|
|
Value *To = UndefValue::get(IndexedType);
|
|
SmallVector<unsigned, 10> Idxs(idx_range.begin(), idx_range.end());
|
|
unsigned IdxSkip = Idxs.size();
|
|
|
|
return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
|
|
}
|
|
|
|
/// Given an aggregate and a sequence of indices, see if the scalar value
|
|
/// indexed is already around as a register, for example if it was inserted
|
|
/// directly into the aggregate.
|
|
///
|
|
/// If InsertBefore is not null, this function will duplicate (modified)
|
|
/// insertvalues when a part of a nested struct is extracted.
|
|
Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
|
|
Instruction *InsertBefore) {
|
|
// Nothing to index? Just return V then (this is useful at the end of our
|
|
// recursion).
|
|
if (idx_range.empty())
|
|
return V;
|
|
// We have indices, so V should have an indexable type.
|
|
assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&
|
|
"Not looking at a struct or array?");
|
|
assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&
|
|
"Invalid indices for type?");
|
|
|
|
if (Constant *C = dyn_cast<Constant>(V)) {
|
|
C = C->getAggregateElement(idx_range[0]);
|
|
if (!C) return nullptr;
|
|
return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
|
|
}
|
|
|
|
if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
|
|
// Loop the indices for the insertvalue instruction in parallel with the
|
|
// requested indices
|
|
const unsigned *req_idx = idx_range.begin();
|
|
for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
|
|
i != e; ++i, ++req_idx) {
|
|
if (req_idx == idx_range.end()) {
|
|
// We can't handle this without inserting insertvalues
|
|
if (!InsertBefore)
|
|
return nullptr;
|
|
|
|
// The requested index identifies a part of a nested aggregate. Handle
|
|
// this specially. For example,
|
|
// %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
|
|
// %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
|
|
// %C = extractvalue {i32, { i32, i32 } } %B, 1
|
|
// This can be changed into
|
|
// %A = insertvalue {i32, i32 } undef, i32 10, 0
|
|
// %C = insertvalue {i32, i32 } %A, i32 11, 1
|
|
// which allows the unused 0,0 element from the nested struct to be
|
|
// removed.
|
|
return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx),
|
|
InsertBefore);
|
|
}
|
|
|
|
// This insert value inserts something else than what we are looking for.
|
|
// See if the (aggregate) value inserted into has the value we are
|
|
// looking for, then.
|
|
if (*req_idx != *i)
|
|
return FindInsertedValue(I->getAggregateOperand(), idx_range,
|
|
InsertBefore);
|
|
}
|
|
// If we end up here, the indices of the insertvalue match with those
|
|
// requested (though possibly only partially). Now we recursively look at
|
|
// the inserted value, passing any remaining indices.
|
|
return FindInsertedValue(I->getInsertedValueOperand(),
|
|
makeArrayRef(req_idx, idx_range.end()),
|
|
InsertBefore);
|
|
}
|
|
|
|
if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
|
|
// If we're extracting a value from an aggregate that was extracted from
|
|
// something else, we can extract from that something else directly instead.
|
|
// However, we will need to chain I's indices with the requested indices.
|
|
|
|
// Calculate the number of indices required
|
|
unsigned size = I->getNumIndices() + idx_range.size();
|
|
// Allocate some space to put the new indices in
|
|
SmallVector<unsigned, 5> Idxs;
|
|
Idxs.reserve(size);
|
|
// Add indices from the extract value instruction
|
|
Idxs.append(I->idx_begin(), I->idx_end());
|
|
|
|
// Add requested indices
|
|
Idxs.append(idx_range.begin(), idx_range.end());
|
|
|
|
assert(Idxs.size() == size
|
|
&& "Number of indices added not correct?");
|
|
|
|
return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
|
|
}
|
|
// Otherwise, we don't know (such as, extracting from a function return value
|
|
// or load instruction)
|
|
return nullptr;
|
|
}
|
|
|
|
bool llvm::isGEPBasedOnPointerToString(const GEPOperator *GEP,
|
|
unsigned CharSize) {
|
|
// Make sure the GEP has exactly three arguments.
|
|
if (GEP->getNumOperands() != 3)
|
|
return false;
|
|
|
|
// Make sure the index-ee is a pointer to array of \p CharSize integers.
|
|
// CharSize.
|
|
ArrayType *AT = dyn_cast<ArrayType>(GEP->getSourceElementType());
|
|
if (!AT || !AT->getElementType()->isIntegerTy(CharSize))
|
|
return false;
|
|
|
|
// Check to make sure that the first operand of the GEP is an integer and
|
|
// has value 0 so that we are sure we're indexing into the initializer.
|
|
const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
|
|
if (!FirstIdx || !FirstIdx->isZero())
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
bool llvm::getConstantDataArrayInfo(const Value *V,
|
|
ConstantDataArraySlice &Slice,
|
|
unsigned ElementSize, uint64_t Offset) {
|
|
assert(V);
|
|
|
|
// Look through bitcast instructions and geps.
|
|
V = V->stripPointerCasts();
|
|
|
|
// If the value is a GEP instruction or constant expression, treat it as an
|
|
// offset.
|
|
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
|
|
// The GEP operator should be based on a pointer to string constant, and is
|
|
// indexing into the string constant.
|
|
if (!isGEPBasedOnPointerToString(GEP, ElementSize))
|
|
return false;
|
|
|
|
// If the second index isn't a ConstantInt, then this is a variable index
|
|
// into the array. If this occurs, we can't say anything meaningful about
|
|
// the string.
|
|
uint64_t StartIdx = 0;
|
|
if (const ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
|
|
StartIdx = CI->getZExtValue();
|
|
else
|
|
return false;
|
|
return getConstantDataArrayInfo(GEP->getOperand(0), Slice, ElementSize,
|
|
StartIdx + Offset);
|
|
}
|
|
|
|
// The GEP instruction, constant or instruction, must reference a global
|
|
// variable that is a constant and is initialized. The referenced constant
|
|
// initializer is the array that we'll use for optimization.
|
|
const GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
|
|
if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
|
|
return false;
|
|
|
|
const ConstantDataArray *Array;
|
|
ArrayType *ArrayTy;
|
|
if (GV->getInitializer()->isNullValue()) {
|
|
Type *GVTy = GV->getValueType();
|
|
if ( (ArrayTy = dyn_cast<ArrayType>(GVTy)) ) {
|
|
// A zeroinitializer for the array; there is no ConstantDataArray.
|
|
Array = nullptr;
|
|
} else {
|
|
const DataLayout &DL = GV->getParent()->getDataLayout();
|
|
uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy).getFixedSize();
|
|
uint64_t Length = SizeInBytes / (ElementSize / 8);
|
|
if (Length <= Offset)
|
|
return false;
|
|
|
|
Slice.Array = nullptr;
|
|
Slice.Offset = 0;
|
|
Slice.Length = Length - Offset;
|
|
return true;
|
|
}
|
|
} else {
|
|
// This must be a ConstantDataArray.
|
|
Array = dyn_cast<ConstantDataArray>(GV->getInitializer());
|
|
if (!Array)
|
|
return false;
|
|
ArrayTy = Array->getType();
|
|
}
|
|
if (!ArrayTy->getElementType()->isIntegerTy(ElementSize))
|
|
return false;
|
|
|
|
uint64_t NumElts = ArrayTy->getArrayNumElements();
|
|
if (Offset > NumElts)
|
|
return false;
|
|
|
|
Slice.Array = Array;
|
|
Slice.Offset = Offset;
|
|
Slice.Length = NumElts - Offset;
|
|
return true;
|
|
}
|
|
|
|
/// This function computes the length of a null-terminated C string pointed to
|
|
/// by V. If successful, it returns true and returns the string in Str.
|
|
/// If unsuccessful, it returns false.
|
|
bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
|
|
uint64_t Offset, bool TrimAtNul) {
|
|
ConstantDataArraySlice Slice;
|
|
if (!getConstantDataArrayInfo(V, Slice, 8, Offset))
|
|
return false;
|
|
|
|
if (Slice.Array == nullptr) {
|
|
if (TrimAtNul) {
|
|
Str = StringRef();
|
|
return true;
|
|
}
|
|
if (Slice.Length == 1) {
|
|
Str = StringRef("", 1);
|
|
return true;
|
|
}
|
|
// We cannot instantiate a StringRef as we do not have an appropriate string
|
|
// of 0s at hand.
|
|
return false;
|
|
}
|
|
|
|
// Start out with the entire array in the StringRef.
|
|
Str = Slice.Array->getAsString();
|
|
// Skip over 'offset' bytes.
|
|
Str = Str.substr(Slice.Offset);
|
|
|
|
if (TrimAtNul) {
|
|
// Trim off the \0 and anything after it. If the array is not nul
|
|
// terminated, we just return the whole end of string. The client may know
|
|
// some other way that the string is length-bound.
|
|
Str = Str.substr(0, Str.find('\0'));
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// These next two are very similar to the above, but also look through PHI
|
|
// nodes.
|
|
// TODO: See if we can integrate these two together.
|
|
|
|
/// If we can compute the length of the string pointed to by
|
|
/// the specified pointer, return 'len+1'. If we can't, return 0.
|
|
static uint64_t GetStringLengthH(const Value *V,
|
|
SmallPtrSetImpl<const PHINode*> &PHIs,
|
|
unsigned CharSize) {
|
|
// Look through noop bitcast instructions.
|
|
V = V->stripPointerCasts();
|
|
|
|
// If this is a PHI node, there are two cases: either we have already seen it
|
|
// or we haven't.
|
|
if (const PHINode *PN = dyn_cast<PHINode>(V)) {
|
|
if (!PHIs.insert(PN).second)
|
|
return ~0ULL; // already in the set.
|
|
|
|
// If it was new, see if all the input strings are the same length.
|
|
uint64_t LenSoFar = ~0ULL;
|
|
for (Value *IncValue : PN->incoming_values()) {
|
|
uint64_t Len = GetStringLengthH(IncValue, PHIs, CharSize);
|
|
if (Len == 0) return 0; // Unknown length -> unknown.
|
|
|
|
if (Len == ~0ULL) continue;
|
|
|
|
if (Len != LenSoFar && LenSoFar != ~0ULL)
|
|
return 0; // Disagree -> unknown.
|
|
LenSoFar = Len;
|
|
}
|
|
|
|
// Success, all agree.
|
|
return LenSoFar;
|
|
}
|
|
|
|
// strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
|
|
if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
|
|
uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs, CharSize);
|
|
if (Len1 == 0) return 0;
|
|
uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs, CharSize);
|
|
if (Len2 == 0) return 0;
|
|
if (Len1 == ~0ULL) return Len2;
|
|
if (Len2 == ~0ULL) return Len1;
|
|
if (Len1 != Len2) return 0;
|
|
return Len1;
|
|
}
|
|
|
|
// Otherwise, see if we can read the string.
|
|
ConstantDataArraySlice Slice;
|
|
if (!getConstantDataArrayInfo(V, Slice, CharSize))
|
|
return 0;
|
|
|
|
if (Slice.Array == nullptr)
|
|
return 1;
|
|
|
|
// Search for nul characters
|
|
unsigned NullIndex = 0;
|
|
for (unsigned E = Slice.Length; NullIndex < E; ++NullIndex) {
|
|
if (Slice.Array->getElementAsInteger(Slice.Offset + NullIndex) == 0)
|
|
break;
|
|
}
|
|
|
|
return NullIndex + 1;
|
|
}
|
|
|
|
/// If we can compute the length of the string pointed to by
|
|
/// the specified pointer, return 'len+1'. If we can't, return 0.
|
|
uint64_t llvm::GetStringLength(const Value *V, unsigned CharSize) {
|
|
if (!V->getType()->isPointerTy())
|
|
return 0;
|
|
|
|
SmallPtrSet<const PHINode*, 32> PHIs;
|
|
uint64_t Len = GetStringLengthH(V, PHIs, CharSize);
|
|
// If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
|
|
// an empty string as a length.
|
|
return Len == ~0ULL ? 1 : Len;
|
|
}
|
|
|
|
const Value *
|
|
llvm::getArgumentAliasingToReturnedPointer(const CallBase *Call,
|
|
bool MustPreserveNullness) {
|
|
assert(Call &&
|
|
"getArgumentAliasingToReturnedPointer only works on nonnull calls");
|
|
if (const Value *RV = Call->getReturnedArgOperand())
|
|
return RV;
|
|
// This can be used only as a aliasing property.
|
|
if (isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
|
|
Call, MustPreserveNullness))
|
|
return Call->getArgOperand(0);
|
|
return nullptr;
|
|
}
|
|
|
|
bool llvm::isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
|
|
const CallBase *Call, bool MustPreserveNullness) {
|
|
switch (Call->getIntrinsicID()) {
|
|
case Intrinsic::launder_invariant_group:
|
|
case Intrinsic::strip_invariant_group:
|
|
case Intrinsic::aarch64_irg:
|
|
case Intrinsic::aarch64_tagp:
|
|
return true;
|
|
case Intrinsic::ptrmask:
|
|
return !MustPreserveNullness;
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/// \p PN defines a loop-variant pointer to an object. Check if the
|
|
/// previous iteration of the loop was referring to the same object as \p PN.
|
|
static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
|
|
const LoopInfo *LI) {
|
|
// Find the loop-defined value.
|
|
Loop *L = LI->getLoopFor(PN->getParent());
|
|
if (PN->getNumIncomingValues() != 2)
|
|
return true;
|
|
|
|
// Find the value from previous iteration.
|
|
auto *PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(0));
|
|
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
|
|
PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(1));
|
|
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
|
|
return true;
|
|
|
|
// If a new pointer is loaded in the loop, the pointer references a different
|
|
// object in every iteration. E.g.:
|
|
// for (i)
|
|
// int *p = a[i];
|
|
// ...
|
|
if (auto *Load = dyn_cast<LoadInst>(PrevValue))
|
|
if (!L->isLoopInvariant(Load->getPointerOperand()))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
const Value *llvm::getUnderlyingObject(const Value *V, unsigned MaxLookup) {
|
|
if (!V->getType()->isPointerTy())
|
|
return V;
|
|
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
|
|
if (auto *GEP = dyn_cast<GEPOperator>(V)) {
|
|
V = GEP->getPointerOperand();
|
|
} else if (Operator::getOpcode(V) == Instruction::BitCast ||
|
|
Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
|
|
V = cast<Operator>(V)->getOperand(0);
|
|
if (!V->getType()->isPointerTy())
|
|
return V;
|
|
} else if (auto *GA = dyn_cast<GlobalAlias>(V)) {
|
|
if (GA->isInterposable())
|
|
return V;
|
|
V = GA->getAliasee();
|
|
} else {
|
|
if (auto *PHI = dyn_cast<PHINode>(V)) {
|
|
// Look through single-arg phi nodes created by LCSSA.
|
|
if (PHI->getNumIncomingValues() == 1) {
|
|
V = PHI->getIncomingValue(0);
|
|
continue;
|
|
}
|
|
} else if (auto *Call = dyn_cast<CallBase>(V)) {
|
|
// CaptureTracking can know about special capturing properties of some
|
|
// intrinsics like launder.invariant.group, that can't be expressed with
|
|
// the attributes, but have properties like returning aliasing pointer.
|
|
// Because some analysis may assume that nocaptured pointer is not
|
|
// returned from some special intrinsic (because function would have to
|
|
// be marked with returns attribute), it is crucial to use this function
|
|
// because it should be in sync with CaptureTracking. Not using it may
|
|
// cause weird miscompilations where 2 aliasing pointers are assumed to
|
|
// noalias.
|
|
if (auto *RP = getArgumentAliasingToReturnedPointer(Call, false)) {
|
|
V = RP;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
return V;
|
|
}
|
|
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
|
|
}
|
|
return V;
|
|
}
|
|
|
|
void llvm::getUnderlyingObjects(const Value *V,
|
|
SmallVectorImpl<const Value *> &Objects,
|
|
LoopInfo *LI, unsigned MaxLookup) {
|
|
SmallPtrSet<const Value *, 4> Visited;
|
|
SmallVector<const Value *, 4> Worklist;
|
|
Worklist.push_back(V);
|
|
do {
|
|
const Value *P = Worklist.pop_back_val();
|
|
P = getUnderlyingObject(P, MaxLookup);
|
|
|
|
if (!Visited.insert(P).second)
|
|
continue;
|
|
|
|
if (auto *SI = dyn_cast<SelectInst>(P)) {
|
|
Worklist.push_back(SI->getTrueValue());
|
|
Worklist.push_back(SI->getFalseValue());
|
|
continue;
|
|
}
|
|
|
|
if (auto *PN = dyn_cast<PHINode>(P)) {
|
|
// If this PHI changes the underlying object in every iteration of the
|
|
// loop, don't look through it. Consider:
|
|
// int **A;
|
|
// for (i) {
|
|
// Prev = Curr; // Prev = PHI (Prev_0, Curr)
|
|
// Curr = A[i];
|
|
// *Prev, *Curr;
|
|
//
|
|
// Prev is tracking Curr one iteration behind so they refer to different
|
|
// underlying objects.
|
|
if (!LI || !LI->isLoopHeader(PN->getParent()) ||
|
|
isSameUnderlyingObjectInLoop(PN, LI))
|
|
append_range(Worklist, PN->incoming_values());
|
|
continue;
|
|
}
|
|
|
|
Objects.push_back(P);
|
|
} while (!Worklist.empty());
|
|
}
|
|
|
|
/// This is the function that does the work of looking through basic
|
|
/// ptrtoint+arithmetic+inttoptr sequences.
|
|
static const Value *getUnderlyingObjectFromInt(const Value *V) {
|
|
do {
|
|
if (const Operator *U = dyn_cast<Operator>(V)) {
|
|
// If we find a ptrtoint, we can transfer control back to the
|
|
// regular getUnderlyingObjectFromInt.
|
|
if (U->getOpcode() == Instruction::PtrToInt)
|
|
return U->getOperand(0);
|
|
// If we find an add of a constant, a multiplied value, or a phi, it's
|
|
// likely that the other operand will lead us to the base
|
|
// object. We don't have to worry about the case where the
|
|
// object address is somehow being computed by the multiply,
|
|
// because our callers only care when the result is an
|
|
// identifiable object.
|
|
if (U->getOpcode() != Instruction::Add ||
|
|
(!isa<ConstantInt>(U->getOperand(1)) &&
|
|
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
|
|
!isa<PHINode>(U->getOperand(1))))
|
|
return V;
|
|
V = U->getOperand(0);
|
|
} else {
|
|
return V;
|
|
}
|
|
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
|
|
} while (true);
|
|
}
|
|
|
|
/// This is a wrapper around getUnderlyingObjects and adds support for basic
|
|
/// ptrtoint+arithmetic+inttoptr sequences.
|
|
/// It returns false if unidentified object is found in getUnderlyingObjects.
|
|
bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
|
|
SmallVectorImpl<Value *> &Objects) {
|
|
SmallPtrSet<const Value *, 16> Visited;
|
|
SmallVector<const Value *, 4> Working(1, V);
|
|
do {
|
|
V = Working.pop_back_val();
|
|
|
|
SmallVector<const Value *, 4> Objs;
|
|
getUnderlyingObjects(V, Objs);
|
|
|
|
for (const Value *V : Objs) {
|
|
if (!Visited.insert(V).second)
|
|
continue;
|
|
if (Operator::getOpcode(V) == Instruction::IntToPtr) {
|
|
const Value *O =
|
|
getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
|
|
if (O->getType()->isPointerTy()) {
|
|
Working.push_back(O);
|
|
continue;
|
|
}
|
|
}
|
|
// If getUnderlyingObjects fails to find an identifiable object,
|
|
// getUnderlyingObjectsForCodeGen also fails for safety.
|
|
if (!isIdentifiedObject(V)) {
|
|
Objects.clear();
|
|
return false;
|
|
}
|
|
Objects.push_back(const_cast<Value *>(V));
|
|
}
|
|
} while (!Working.empty());
|
|
return true;
|
|
}
|
|
|
|
AllocaInst *llvm::findAllocaForValue(Value *V, bool OffsetZero) {
|
|
AllocaInst *Result = nullptr;
|
|
SmallPtrSet<Value *, 4> Visited;
|
|
SmallVector<Value *, 4> Worklist;
|
|
|
|
auto AddWork = [&](Value *V) {
|
|
if (Visited.insert(V).second)
|
|
Worklist.push_back(V);
|
|
};
|
|
|
|
AddWork(V);
|
|
do {
|
|
V = Worklist.pop_back_val();
|
|
assert(Visited.count(V));
|
|
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
|
|
if (Result && Result != AI)
|
|
return nullptr;
|
|
Result = AI;
|
|
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
|
|
AddWork(CI->getOperand(0));
|
|
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
|
|
for (Value *IncValue : PN->incoming_values())
|
|
AddWork(IncValue);
|
|
} else if (auto *SI = dyn_cast<SelectInst>(V)) {
|
|
AddWork(SI->getTrueValue());
|
|
AddWork(SI->getFalseValue());
|
|
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
|
|
if (OffsetZero && !GEP->hasAllZeroIndices())
|
|
return nullptr;
|
|
AddWork(GEP->getPointerOperand());
|
|
} else {
|
|
return nullptr;
|
|
}
|
|
} while (!Worklist.empty());
|
|
|
|
return Result;
|
|
}
|
|
|
|
static bool onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
|
|
const Value *V, bool AllowLifetime, bool AllowDroppable) {
|
|
for (const User *U : V->users()) {
|
|
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
|
|
if (!II)
|
|
return false;
|
|
|
|
if (AllowLifetime && II->isLifetimeStartOrEnd())
|
|
continue;
|
|
|
|
if (AllowDroppable && II->isDroppable())
|
|
continue;
|
|
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
|
|
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
|
|
V, /* AllowLifetime */ true, /* AllowDroppable */ false);
|
|
}
|
|
bool llvm::onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V) {
|
|
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
|
|
V, /* AllowLifetime */ true, /* AllowDroppable */ true);
|
|
}
|
|
|
|
bool llvm::mustSuppressSpeculation(const LoadInst &LI) {
|
|
if (!LI.isUnordered())
|
|
return true;
|
|
const Function &F = *LI.getFunction();
|
|
// Speculative load may create a race that did not exist in the source.
|
|
return F.hasFnAttribute(Attribute::SanitizeThread) ||
|
|
// Speculative load may load data from dirty regions.
|
|
F.hasFnAttribute(Attribute::SanitizeAddress) ||
|
|
F.hasFnAttribute(Attribute::SanitizeHWAddress);
|
|
}
|
|
|
|
|
|
bool llvm::isSafeToSpeculativelyExecute(const Value *V,
|
|
const Instruction *CtxI,
|
|
const DominatorTree *DT,
|
|
const TargetLibraryInfo *TLI) {
|
|
const Operator *Inst = dyn_cast<Operator>(V);
|
|
if (!Inst)
|
|
return false;
|
|
|
|
for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
|
|
if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
|
|
if (C->canTrap())
|
|
return false;
|
|
|
|
switch (Inst->getOpcode()) {
|
|
default:
|
|
return true;
|
|
case Instruction::UDiv:
|
|
case Instruction::URem: {
|
|
// x / y is undefined if y == 0.
|
|
const APInt *V;
|
|
if (match(Inst->getOperand(1), m_APInt(V)))
|
|
return *V != 0;
|
|
return false;
|
|
}
|
|
case Instruction::SDiv:
|
|
case Instruction::SRem: {
|
|
// x / y is undefined if y == 0 or x == INT_MIN and y == -1
|
|
const APInt *Numerator, *Denominator;
|
|
if (!match(Inst->getOperand(1), m_APInt(Denominator)))
|
|
return false;
|
|
// We cannot hoist this division if the denominator is 0.
|
|
if (*Denominator == 0)
|
|
return false;
|
|
// It's safe to hoist if the denominator is not 0 or -1.
|
|
if (!Denominator->isAllOnesValue())
|
|
return true;
|
|
// At this point we know that the denominator is -1. It is safe to hoist as
|
|
// long we know that the numerator is not INT_MIN.
|
|
if (match(Inst->getOperand(0), m_APInt(Numerator)))
|
|
return !Numerator->isMinSignedValue();
|
|
// The numerator *might* be MinSignedValue.
|
|
return false;
|
|
}
|
|
case Instruction::Load: {
|
|
const LoadInst *LI = cast<LoadInst>(Inst);
|
|
if (mustSuppressSpeculation(*LI))
|
|
return false;
|
|
const DataLayout &DL = LI->getModule()->getDataLayout();
|
|
return isDereferenceableAndAlignedPointer(
|
|
LI->getPointerOperand(), LI->getType(), MaybeAlign(LI->getAlignment()),
|
|
DL, CtxI, DT, TLI);
|
|
}
|
|
case Instruction::Call: {
|
|
auto *CI = cast<const CallInst>(Inst);
|
|
const Function *Callee = CI->getCalledFunction();
|
|
|
|
// The called function could have undefined behavior or side-effects, even
|
|
// if marked readnone nounwind.
|
|
return Callee && Callee->isSpeculatable();
|
|
}
|
|
case Instruction::VAArg:
|
|
case Instruction::Alloca:
|
|
case Instruction::Invoke:
|
|
case Instruction::CallBr:
|
|
case Instruction::PHI:
|
|
case Instruction::Store:
|
|
case Instruction::Ret:
|
|
case Instruction::Br:
|
|
case Instruction::IndirectBr:
|
|
case Instruction::Switch:
|
|
case Instruction::Unreachable:
|
|
case Instruction::Fence:
|
|
case Instruction::AtomicRMW:
|
|
case Instruction::AtomicCmpXchg:
|
|
case Instruction::LandingPad:
|
|
case Instruction::Resume:
|
|
case Instruction::CatchSwitch:
|
|
case Instruction::CatchPad:
|
|
case Instruction::CatchRet:
|
|
case Instruction::CleanupPad:
|
|
case Instruction::CleanupRet:
|
|
return false; // Misc instructions which have effects
|
|
}
|
|
}
|
|
|
|
bool llvm::mayBeMemoryDependent(const Instruction &I) {
|
|
return I.mayReadOrWriteMemory() || !isSafeToSpeculativelyExecute(&I);
|
|
}
|
|
|
|
/// Convert ConstantRange OverflowResult into ValueTracking OverflowResult.
|
|
static OverflowResult mapOverflowResult(ConstantRange::OverflowResult OR) {
|
|
switch (OR) {
|
|
case ConstantRange::OverflowResult::MayOverflow:
|
|
return OverflowResult::MayOverflow;
|
|
case ConstantRange::OverflowResult::AlwaysOverflowsLow:
|
|
return OverflowResult::AlwaysOverflowsLow;
|
|
case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
|
|
return OverflowResult::AlwaysOverflowsHigh;
|
|
case ConstantRange::OverflowResult::NeverOverflows:
|
|
return OverflowResult::NeverOverflows;
|
|
}
|
|
llvm_unreachable("Unknown OverflowResult");
|
|
}
|
|
|
|
/// Combine constant ranges from computeConstantRange() and computeKnownBits().
|
|
static ConstantRange computeConstantRangeIncludingKnownBits(
|
|
const Value *V, bool ForSigned, const DataLayout &DL, unsigned Depth,
|
|
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
|
|
OptimizationRemarkEmitter *ORE = nullptr, bool UseInstrInfo = true) {
|
|
KnownBits Known = computeKnownBits(
|
|
V, DL, Depth, AC, CxtI, DT, ORE, UseInstrInfo);
|
|
ConstantRange CR1 = ConstantRange::fromKnownBits(Known, ForSigned);
|
|
ConstantRange CR2 = computeConstantRange(V, UseInstrInfo);
|
|
ConstantRange::PreferredRangeType RangeType =
|
|
ForSigned ? ConstantRange::Signed : ConstantRange::Unsigned;
|
|
return CR1.intersectWith(CR2, RangeType);
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForUnsignedMul(
|
|
const Value *LHS, const Value *RHS, const DataLayout &DL,
|
|
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
|
|
bool UseInstrInfo) {
|
|
KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
ConstantRange LHSRange = ConstantRange::fromKnownBits(LHSKnown, false);
|
|
ConstantRange RHSRange = ConstantRange::fromKnownBits(RHSKnown, false);
|
|
return mapOverflowResult(LHSRange.unsignedMulMayOverflow(RHSRange));
|
|
}
|
|
|
|
OverflowResult
|
|
llvm::computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL, AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT, bool UseInstrInfo) {
|
|
// Multiplying n * m significant bits yields a result of n + m significant
|
|
// bits. If the total number of significant bits does not exceed the
|
|
// result bit width (minus 1), there is no overflow.
|
|
// This means if we have enough leading sign bits in the operands
|
|
// we can guarantee that the result does not overflow.
|
|
// Ref: "Hacker's Delight" by Henry Warren
|
|
unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
|
|
|
|
// Note that underestimating the number of sign bits gives a more
|
|
// conservative answer.
|
|
unsigned SignBits = ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) +
|
|
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT);
|
|
|
|
// First handle the easy case: if we have enough sign bits there's
|
|
// definitely no overflow.
|
|
if (SignBits > BitWidth + 1)
|
|
return OverflowResult::NeverOverflows;
|
|
|
|
// There are two ambiguous cases where there can be no overflow:
|
|
// SignBits == BitWidth + 1 and
|
|
// SignBits == BitWidth
|
|
// The second case is difficult to check, therefore we only handle the
|
|
// first case.
|
|
if (SignBits == BitWidth + 1) {
|
|
// It overflows only when both arguments are negative and the true
|
|
// product is exactly the minimum negative number.
|
|
// E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
|
|
// For simplicity we just check if at least one side is not negative.
|
|
KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
|
|
return OverflowResult::NeverOverflows;
|
|
}
|
|
return OverflowResult::MayOverflow;
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForUnsignedAdd(
|
|
const Value *LHS, const Value *RHS, const DataLayout &DL,
|
|
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
|
|
bool UseInstrInfo) {
|
|
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
|
|
LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
|
|
RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
|
|
nullptr, UseInstrInfo);
|
|
return mapOverflowResult(LHSRange.unsignedAddMayOverflow(RHSRange));
|
|
}
|
|
|
|
static OverflowResult computeOverflowForSignedAdd(const Value *LHS,
|
|
const Value *RHS,
|
|
const AddOperator *Add,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
if (Add && Add->hasNoSignedWrap()) {
|
|
return OverflowResult::NeverOverflows;
|
|
}
|
|
|
|
// If LHS and RHS each have at least two sign bits, the addition will look
|
|
// like
|
|
//
|
|
// XX..... +
|
|
// YY.....
|
|
//
|
|
// If the carry into the most significant position is 0, X and Y can't both
|
|
// be 1 and therefore the carry out of the addition is also 0.
|
|
//
|
|
// If the carry into the most significant position is 1, X and Y can't both
|
|
// be 0 and therefore the carry out of the addition is also 1.
|
|
//
|
|
// Since the carry into the most significant position is always equal to
|
|
// the carry out of the addition, there is no signed overflow.
|
|
if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
|
|
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
|
|
return OverflowResult::NeverOverflows;
|
|
|
|
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
|
|
LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
|
|
RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
OverflowResult OR =
|
|
mapOverflowResult(LHSRange.signedAddMayOverflow(RHSRange));
|
|
if (OR != OverflowResult::MayOverflow)
|
|
return OR;
|
|
|
|
// The remaining code needs Add to be available. Early returns if not so.
|
|
if (!Add)
|
|
return OverflowResult::MayOverflow;
|
|
|
|
// If the sign of Add is the same as at least one of the operands, this add
|
|
// CANNOT overflow. If this can be determined from the known bits of the
|
|
// operands the above signedAddMayOverflow() check will have already done so.
|
|
// The only other way to improve on the known bits is from an assumption, so
|
|
// call computeKnownBitsFromAssume() directly.
|
|
bool LHSOrRHSKnownNonNegative =
|
|
(LHSRange.isAllNonNegative() || RHSRange.isAllNonNegative());
|
|
bool LHSOrRHSKnownNegative =
|
|
(LHSRange.isAllNegative() || RHSRange.isAllNegative());
|
|
if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) {
|
|
KnownBits AddKnown(LHSRange.getBitWidth());
|
|
computeKnownBitsFromAssume(
|
|
Add, AddKnown, /*Depth=*/0, Query(DL, AC, CxtI, DT, true));
|
|
if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) ||
|
|
(AddKnown.isNegative() && LHSOrRHSKnownNegative))
|
|
return OverflowResult::NeverOverflows;
|
|
}
|
|
|
|
return OverflowResult::MayOverflow;
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForUnsignedSub(const Value *LHS,
|
|
const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
// Checking for conditions implied by dominating conditions may be expensive.
|
|
// Limit it to usub_with_overflow calls for now.
|
|
if (match(CxtI,
|
|
m_Intrinsic<Intrinsic::usub_with_overflow>(m_Value(), m_Value())))
|
|
if (auto C =
|
|
isImpliedByDomCondition(CmpInst::ICMP_UGE, LHS, RHS, CxtI, DL)) {
|
|
if (*C)
|
|
return OverflowResult::NeverOverflows;
|
|
return OverflowResult::AlwaysOverflowsLow;
|
|
}
|
|
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
|
|
LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
|
|
RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
return mapOverflowResult(LHSRange.unsignedSubMayOverflow(RHSRange));
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForSignedSub(const Value *LHS,
|
|
const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
// If LHS and RHS each have at least two sign bits, the subtraction
|
|
// cannot overflow.
|
|
if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
|
|
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
|
|
return OverflowResult::NeverOverflows;
|
|
|
|
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
|
|
LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
|
|
RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
|
|
return mapOverflowResult(LHSRange.signedSubMayOverflow(RHSRange));
|
|
}
|
|
|
|
bool llvm::isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
|
|
const DominatorTree &DT) {
|
|
SmallVector<const BranchInst *, 2> GuardingBranches;
|
|
SmallVector<const ExtractValueInst *, 2> Results;
|
|
|
|
for (const User *U : WO->users()) {
|
|
if (const auto *EVI = dyn_cast<ExtractValueInst>(U)) {
|
|
assert(EVI->getNumIndices() == 1 && "Obvious from CI's type");
|
|
|
|
if (EVI->getIndices()[0] == 0)
|
|
Results.push_back(EVI);
|
|
else {
|
|
assert(EVI->getIndices()[0] == 1 && "Obvious from CI's type");
|
|
|
|
for (const auto *U : EVI->users())
|
|
if (const auto *B = dyn_cast<BranchInst>(U)) {
|
|
assert(B->isConditional() && "How else is it using an i1?");
|
|
GuardingBranches.push_back(B);
|
|
}
|
|
}
|
|
} else {
|
|
// We are using the aggregate directly in a way we don't want to analyze
|
|
// here (storing it to a global, say).
|
|
return false;
|
|
}
|
|
}
|
|
|
|
auto AllUsesGuardedByBranch = [&](const BranchInst *BI) {
|
|
BasicBlockEdge NoWrapEdge(BI->getParent(), BI->getSuccessor(1));
|
|
if (!NoWrapEdge.isSingleEdge())
|
|
return false;
|
|
|
|
// Check if all users of the add are provably no-wrap.
|
|
for (const auto *Result : Results) {
|
|
// If the extractvalue itself is not executed on overflow, the we don't
|
|
// need to check each use separately, since domination is transitive.
|
|
if (DT.dominates(NoWrapEdge, Result->getParent()))
|
|
continue;
|
|
|
|
for (auto &RU : Result->uses())
|
|
if (!DT.dominates(NoWrapEdge, RU))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
};
|
|
|
|
return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
|
|
}
|
|
|
|
static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly) {
|
|
// See whether I has flags that may create poison
|
|
if (const auto *OvOp = dyn_cast<OverflowingBinaryOperator>(Op)) {
|
|
if (OvOp->hasNoSignedWrap() || OvOp->hasNoUnsignedWrap())
|
|
return true;
|
|
}
|
|
if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(Op))
|
|
if (ExactOp->isExact())
|
|
return true;
|
|
if (const auto *FP = dyn_cast<FPMathOperator>(Op)) {
|
|
auto FMF = FP->getFastMathFlags();
|
|
if (FMF.noNaNs() || FMF.noInfs())
|
|
return true;
|
|
}
|
|
|
|
unsigned Opcode = Op->getOpcode();
|
|
|
|
// Check whether opcode is a poison/undef-generating operation
|
|
switch (Opcode) {
|
|
case Instruction::Shl:
|
|
case Instruction::AShr:
|
|
case Instruction::LShr: {
|
|
// Shifts return poison if shiftwidth is larger than the bitwidth.
|
|
if (auto *C = dyn_cast<Constant>(Op->getOperand(1))) {
|
|
SmallVector<Constant *, 4> ShiftAmounts;
|
|
if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
|
|
unsigned NumElts = FVTy->getNumElements();
|
|
for (unsigned i = 0; i < NumElts; ++i)
|
|
ShiftAmounts.push_back(C->getAggregateElement(i));
|
|
} else if (isa<ScalableVectorType>(C->getType()))
|
|
return true; // Can't tell, just return true to be safe
|
|
else
|
|
ShiftAmounts.push_back(C);
|
|
|
|
bool Safe = llvm::all_of(ShiftAmounts, [](Constant *C) {
|
|
auto *CI = dyn_cast_or_null<ConstantInt>(C);
|
|
return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
|
|
});
|
|
return !Safe;
|
|
}
|
|
return true;
|
|
}
|
|
case Instruction::FPToSI:
|
|
case Instruction::FPToUI:
|
|
// fptosi/ui yields poison if the resulting value does not fit in the
|
|
// destination type.
|
|
return true;
|
|
case Instruction::Call:
|
|
if (auto *II = dyn_cast<IntrinsicInst>(Op)) {
|
|
switch (II->getIntrinsicID()) {
|
|
// TODO: Add more intrinsics.
|
|
case Intrinsic::ctpop:
|
|
case Intrinsic::sadd_with_overflow:
|
|
case Intrinsic::ssub_with_overflow:
|
|
case Intrinsic::smul_with_overflow:
|
|
case Intrinsic::uadd_with_overflow:
|
|
case Intrinsic::usub_with_overflow:
|
|
case Intrinsic::umul_with_overflow:
|
|
return false;
|
|
}
|
|
}
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::CallBr:
|
|
case Instruction::Invoke: {
|
|
const auto *CB = cast<CallBase>(Op);
|
|
return !CB->hasRetAttr(Attribute::NoUndef);
|
|
}
|
|
case Instruction::InsertElement:
|
|
case Instruction::ExtractElement: {
|
|
// If index exceeds the length of the vector, it returns poison
|
|
auto *VTy = cast<VectorType>(Op->getOperand(0)->getType());
|
|
unsigned IdxOp = Op->getOpcode() == Instruction::InsertElement ? 2 : 1;
|
|
auto *Idx = dyn_cast<ConstantInt>(Op->getOperand(IdxOp));
|
|
if (!Idx || Idx->getValue().uge(VTy->getElementCount().getKnownMinValue()))
|
|
return true;
|
|
return false;
|
|
}
|
|
case Instruction::ShuffleVector: {
|
|
// shufflevector may return undef.
|
|
if (PoisonOnly)
|
|
return false;
|
|
ArrayRef<int> Mask = isa<ConstantExpr>(Op)
|
|
? cast<ConstantExpr>(Op)->getShuffleMask()
|
|
: cast<ShuffleVectorInst>(Op)->getShuffleMask();
|
|
return is_contained(Mask, UndefMaskElem);
|
|
}
|
|
case Instruction::FNeg:
|
|
case Instruction::PHI:
|
|
case Instruction::Select:
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
case Instruction::ExtractValue:
|
|
case Instruction::InsertValue:
|
|
case Instruction::Freeze:
|
|
case Instruction::ICmp:
|
|
case Instruction::FCmp:
|
|
return false;
|
|
case Instruction::GetElementPtr: {
|
|
const auto *GEP = cast<GEPOperator>(Op);
|
|
return GEP->isInBounds();
|
|
}
|
|
default: {
|
|
const auto *CE = dyn_cast<ConstantExpr>(Op);
|
|
if (isa<CastInst>(Op) || (CE && CE->isCast()))
|
|
return false;
|
|
else if (Instruction::isBinaryOp(Opcode))
|
|
return false;
|
|
// Be conservative and return true.
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
bool llvm::canCreateUndefOrPoison(const Operator *Op) {
|
|
return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/false);
|
|
}
|
|
|
|
bool llvm::canCreatePoison(const Operator *Op) {
|
|
return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/true);
|
|
}
|
|
|
|
static bool directlyImpliesPoison(const Value *ValAssumedPoison,
|
|
const Value *V, unsigned Depth) {
|
|
if (ValAssumedPoison == V)
|
|
return true;
|
|
|
|
const unsigned MaxDepth = 2;
|
|
if (Depth >= MaxDepth)
|
|
return false;
|
|
|
|
if (const auto *I = dyn_cast<Instruction>(V)) {
|
|
if (propagatesPoison(cast<Operator>(I)))
|
|
return any_of(I->operands(), [=](const Value *Op) {
|
|
return directlyImpliesPoison(ValAssumedPoison, Op, Depth + 1);
|
|
});
|
|
|
|
// 'select ValAssumedPoison, _, _' is poison.
|
|
if (const auto *SI = dyn_cast<SelectInst>(I))
|
|
return directlyImpliesPoison(ValAssumedPoison, SI->getCondition(),
|
|
Depth + 1);
|
|
// V = extractvalue V0, idx
|
|
// V2 = extractvalue V0, idx2
|
|
// V0's elements are all poison or not. (e.g., add_with_overflow)
|
|
const WithOverflowInst *II;
|
|
if (match(I, m_ExtractValue(m_WithOverflowInst(II))) &&
|
|
(match(ValAssumedPoison, m_ExtractValue(m_Specific(II))) ||
|
|
llvm::is_contained(II->arg_operands(), ValAssumedPoison)))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static bool impliesPoison(const Value *ValAssumedPoison, const Value *V,
|
|
unsigned Depth) {
|
|
if (isGuaranteedNotToBeUndefOrPoison(ValAssumedPoison))
|
|
return true;
|
|
|
|
if (directlyImpliesPoison(ValAssumedPoison, V, /* Depth */ 0))
|
|
return true;
|
|
|
|
const unsigned MaxDepth = 2;
|
|
if (Depth >= MaxDepth)
|
|
return false;
|
|
|
|
const auto *I = dyn_cast<Instruction>(ValAssumedPoison);
|
|
if (I && !canCreatePoison(cast<Operator>(I))) {
|
|
return all_of(I->operands(), [=](const Value *Op) {
|
|
return impliesPoison(Op, V, Depth + 1);
|
|
});
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool llvm::impliesPoison(const Value *ValAssumedPoison, const Value *V) {
|
|
return ::impliesPoison(ValAssumedPoison, V, /* Depth */ 0);
|
|
}
|
|
|
|
static bool programUndefinedIfUndefOrPoison(const Value *V,
|
|
bool PoisonOnly);
|
|
|
|
static bool isGuaranteedNotToBeUndefOrPoison(const Value *V,
|
|
AssumptionCache *AC,
|
|
const Instruction *CtxI,
|
|
const DominatorTree *DT,
|
|
unsigned Depth, bool PoisonOnly) {
|
|
if (Depth >= MaxAnalysisRecursionDepth)
|
|
return false;
|
|
|
|
if (isa<MetadataAsValue>(V))
|
|
return false;
|
|
|
|
if (const auto *A = dyn_cast<Argument>(V)) {
|
|
if (A->hasAttribute(Attribute::NoUndef))
|
|
return true;
|
|
}
|
|
|
|
if (auto *C = dyn_cast<Constant>(V)) {
|
|
if (isa<UndefValue>(C))
|
|
return PoisonOnly && !isa<PoisonValue>(C);
|
|
|
|
if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
|
|
isa<ConstantPointerNull>(C) || isa<Function>(C))
|
|
return true;
|
|
|
|
if (C->getType()->isVectorTy() && !isa<ConstantExpr>(C))
|
|
return (PoisonOnly ? !C->containsPoisonElement()
|
|
: !C->containsUndefOrPoisonElement()) &&
|
|
!C->containsConstantExpression();
|
|
}
|
|
|
|
// Strip cast operations from a pointer value.
|
|
// Note that stripPointerCastsSameRepresentation can strip off getelementptr
|
|
// inbounds with zero offset. To guarantee that the result isn't poison, the
|
|
// stripped pointer is checked as it has to be pointing into an allocated
|
|
// object or be null `null` to ensure `inbounds` getelement pointers with a
|
|
// zero offset could not produce poison.
|
|
// It can strip off addrspacecast that do not change bit representation as
|
|
// well. We believe that such addrspacecast is equivalent to no-op.
|
|
auto *StrippedV = V->stripPointerCastsSameRepresentation();
|
|
if (isa<AllocaInst>(StrippedV) || isa<GlobalVariable>(StrippedV) ||
|
|
isa<Function>(StrippedV) || isa<ConstantPointerNull>(StrippedV))
|
|
return true;
|
|
|
|
auto OpCheck = [&](const Value *V) {
|
|
return isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth + 1,
|
|
PoisonOnly);
|
|
};
|
|
|
|
if (auto *Opr = dyn_cast<Operator>(V)) {
|
|
// If the value is a freeze instruction, then it can never
|
|
// be undef or poison.
|
|
if (isa<FreezeInst>(V))
|
|
return true;
|
|
|
|
if (const auto *CB = dyn_cast<CallBase>(V)) {
|
|
if (CB->hasRetAttr(Attribute::NoUndef))
|
|
return true;
|
|
}
|
|
|
|
if (const auto *PN = dyn_cast<PHINode>(V)) {
|
|
unsigned Num = PN->getNumIncomingValues();
|
|
bool IsWellDefined = true;
|
|
for (unsigned i = 0; i < Num; ++i) {
|
|
auto *TI = PN->getIncomingBlock(i)->getTerminator();
|
|
if (!isGuaranteedNotToBeUndefOrPoison(PN->getIncomingValue(i), AC, TI,
|
|
DT, Depth + 1, PoisonOnly)) {
|
|
IsWellDefined = false;
|
|
break;
|
|
}
|
|
}
|
|
if (IsWellDefined)
|
|
return true;
|
|
} else if (!canCreateUndefOrPoison(Opr) && all_of(Opr->operands(), OpCheck))
|
|
return true;
|
|
}
|
|
|
|
if (auto *I = dyn_cast<LoadInst>(V))
|
|
if (I->getMetadata(LLVMContext::MD_noundef))
|
|
return true;
|
|
|
|
if (programUndefinedIfUndefOrPoison(V, PoisonOnly))
|
|
return true;
|
|
|
|
// CxtI may be null or a cloned instruction.
|
|
if (!CtxI || !CtxI->getParent() || !DT)
|
|
return false;
|
|
|
|
auto *DNode = DT->getNode(CtxI->getParent());
|
|
if (!DNode)
|
|
// Unreachable block
|
|
return false;
|
|
|
|
// If V is used as a branch condition before reaching CtxI, V cannot be
|
|
// undef or poison.
|
|
// br V, BB1, BB2
|
|
// BB1:
|
|
// CtxI ; V cannot be undef or poison here
|
|
auto *Dominator = DNode->getIDom();
|
|
while (Dominator) {
|
|
auto *TI = Dominator->getBlock()->getTerminator();
|
|
|
|
Value *Cond = nullptr;
|
|
if (auto BI = dyn_cast<BranchInst>(TI)) {
|
|
if (BI->isConditional())
|
|
Cond = BI->getCondition();
|
|
} else if (auto SI = dyn_cast<SwitchInst>(TI)) {
|
|
Cond = SI->getCondition();
|
|
}
|
|
|
|
if (Cond) {
|
|
if (Cond == V)
|
|
return true;
|
|
else if (PoisonOnly && isa<Operator>(Cond)) {
|
|
// For poison, we can analyze further
|
|
auto *Opr = cast<Operator>(Cond);
|
|
if (propagatesPoison(Opr) && is_contained(Opr->operand_values(), V))
|
|
return true;
|
|
}
|
|
}
|
|
|
|
Dominator = Dominator->getIDom();
|
|
}
|
|
|
|
SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NoUndef};
|
|
if (getKnowledgeValidInContext(V, AttrKinds, CtxI, DT, AC))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V, AssumptionCache *AC,
|
|
const Instruction *CtxI,
|
|
const DominatorTree *DT,
|
|
unsigned Depth) {
|
|
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, false);
|
|
}
|
|
|
|
bool llvm::isGuaranteedNotToBePoison(const Value *V, AssumptionCache *AC,
|
|
const Instruction *CtxI,
|
|
const DominatorTree *DT, unsigned Depth) {
|
|
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, true);
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForSignedAdd(const AddOperator *Add,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
return ::computeOverflowForSignedAdd(Add->getOperand(0), Add->getOperand(1),
|
|
Add, DL, AC, CxtI, DT);
|
|
}
|
|
|
|
OverflowResult llvm::computeOverflowForSignedAdd(const Value *LHS,
|
|
const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
return ::computeOverflowForSignedAdd(LHS, RHS, nullptr, DL, AC, CxtI, DT);
|
|
}
|
|
|
|
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
|
|
// Note: An atomic operation isn't guaranteed to return in a reasonable amount
|
|
// of time because it's possible for another thread to interfere with it for an
|
|
// arbitrary length of time, but programs aren't allowed to rely on that.
|
|
|
|
// If there is no successor, then execution can't transfer to it.
|
|
if (isa<ReturnInst>(I))
|
|
return false;
|
|
if (isa<UnreachableInst>(I))
|
|
return false;
|
|
|
|
// An instruction that returns without throwing must transfer control flow
|
|
// to a successor.
|
|
return !I->mayThrow() && I->willReturn();
|
|
}
|
|
|
|
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
|
|
// TODO: This is slightly conservative for invoke instruction since exiting
|
|
// via an exception *is* normal control for them.
|
|
for (const Instruction &I : *BB)
|
|
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
|
|
const Loop *L) {
|
|
// The loop header is guaranteed to be executed for every iteration.
|
|
//
|
|
// FIXME: Relax this constraint to cover all basic blocks that are
|
|
// guaranteed to be executed at every iteration.
|
|
if (I->getParent() != L->getHeader()) return false;
|
|
|
|
for (const Instruction &LI : *L->getHeader()) {
|
|
if (&LI == I) return true;
|
|
if (!isGuaranteedToTransferExecutionToSuccessor(&LI)) return false;
|
|
}
|
|
llvm_unreachable("Instruction not contained in its own parent basic block.");
|
|
}
|
|
|
|
bool llvm::propagatesPoison(const Operator *I) {
|
|
switch (I->getOpcode()) {
|
|
case Instruction::Freeze:
|
|
case Instruction::Select:
|
|
case Instruction::PHI:
|
|
case Instruction::Invoke:
|
|
return false;
|
|
case Instruction::Call:
|
|
if (auto *II = dyn_cast<IntrinsicInst>(I)) {
|
|
switch (II->getIntrinsicID()) {
|
|
// TODO: Add more intrinsics.
|
|
case Intrinsic::sadd_with_overflow:
|
|
case Intrinsic::ssub_with_overflow:
|
|
case Intrinsic::smul_with_overflow:
|
|
case Intrinsic::uadd_with_overflow:
|
|
case Intrinsic::usub_with_overflow:
|
|
case Intrinsic::umul_with_overflow:
|
|
// If an input is a vector containing a poison element, the
|
|
// two output vectors (calculated results, overflow bits)'
|
|
// corresponding lanes are poison.
|
|
return true;
|
|
case Intrinsic::ctpop:
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
case Instruction::ICmp:
|
|
case Instruction::FCmp:
|
|
case Instruction::GetElementPtr:
|
|
return true;
|
|
default:
|
|
if (isa<BinaryOperator>(I) || isa<UnaryOperator>(I) || isa<CastInst>(I))
|
|
return true;
|
|
|
|
// Be conservative and return false.
|
|
return false;
|
|
}
|
|
}
|
|
|
|
void llvm::getGuaranteedWellDefinedOps(
|
|
const Instruction *I, SmallPtrSetImpl<const Value *> &Operands) {
|
|
switch (I->getOpcode()) {
|
|
case Instruction::Store:
|
|
Operands.insert(cast<StoreInst>(I)->getPointerOperand());
|
|
break;
|
|
|
|
case Instruction::Load:
|
|
Operands.insert(cast<LoadInst>(I)->getPointerOperand());
|
|
break;
|
|
|
|
// Since dereferenceable attribute imply noundef, atomic operations
|
|
// also implicitly have noundef pointers too
|
|
case Instruction::AtomicCmpXchg:
|
|
Operands.insert(cast<AtomicCmpXchgInst>(I)->getPointerOperand());
|
|
break;
|
|
|
|
case Instruction::AtomicRMW:
|
|
Operands.insert(cast<AtomicRMWInst>(I)->getPointerOperand());
|
|
break;
|
|
|
|
case Instruction::Call:
|
|
case Instruction::Invoke: {
|
|
const CallBase *CB = cast<CallBase>(I);
|
|
if (CB->isIndirectCall())
|
|
Operands.insert(CB->getCalledOperand());
|
|
for (unsigned i = 0; i < CB->arg_size(); ++i) {
|
|
if (CB->paramHasAttr(i, Attribute::NoUndef) ||
|
|
CB->paramHasAttr(i, Attribute::Dereferenceable))
|
|
Operands.insert(CB->getArgOperand(i));
|
|
}
|
|
break;
|
|
}
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
void llvm::getGuaranteedNonPoisonOps(const Instruction *I,
|
|
SmallPtrSetImpl<const Value *> &Operands) {
|
|
getGuaranteedWellDefinedOps(I, Operands);
|
|
switch (I->getOpcode()) {
|
|
// Divisors of these operations are allowed to be partially undef.
|
|
case Instruction::UDiv:
|
|
case Instruction::SDiv:
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
Operands.insert(I->getOperand(1));
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
bool llvm::mustTriggerUB(const Instruction *I,
|
|
const SmallSet<const Value *, 16>& KnownPoison) {
|
|
SmallPtrSet<const Value *, 4> NonPoisonOps;
|
|
getGuaranteedNonPoisonOps(I, NonPoisonOps);
|
|
|
|
for (const auto *V : NonPoisonOps)
|
|
if (KnownPoison.count(V))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool programUndefinedIfUndefOrPoison(const Value *V,
|
|
bool PoisonOnly) {
|
|
// We currently only look for uses of values within the same basic
|
|
// block, as that makes it easier to guarantee that the uses will be
|
|
// executed given that Inst is executed.
|
|
//
|
|
// FIXME: Expand this to consider uses beyond the same basic block. To do
|
|
// this, look out for the distinction between post-dominance and strong
|
|
// post-dominance.
|
|
const BasicBlock *BB = nullptr;
|
|
BasicBlock::const_iterator Begin;
|
|
if (const auto *Inst = dyn_cast<Instruction>(V)) {
|
|
BB = Inst->getParent();
|
|
Begin = Inst->getIterator();
|
|
Begin++;
|
|
} else if (const auto *Arg = dyn_cast<Argument>(V)) {
|
|
BB = &Arg->getParent()->getEntryBlock();
|
|
Begin = BB->begin();
|
|
} else {
|
|
return false;
|
|
}
|
|
|
|
// Limit number of instructions we look at, to avoid scanning through large
|
|
// blocks. The current limit is chosen arbitrarily.
|
|
unsigned ScanLimit = 32;
|
|
BasicBlock::const_iterator End = BB->end();
|
|
|
|
if (!PoisonOnly) {
|
|
// Since undef does not propagate eagerly, be conservative & just check
|
|
// whether a value is directly passed to an instruction that must take
|
|
// well-defined operands.
|
|
|
|
for (auto &I : make_range(Begin, End)) {
|
|
if (isa<DbgInfoIntrinsic>(I))
|
|
continue;
|
|
if (--ScanLimit == 0)
|
|
break;
|
|
|
|
SmallPtrSet<const Value *, 4> WellDefinedOps;
|
|
getGuaranteedWellDefinedOps(&I, WellDefinedOps);
|
|
if (WellDefinedOps.contains(V))
|
|
return true;
|
|
|
|
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
|
|
break;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Set of instructions that we have proved will yield poison if Inst
|
|
// does.
|
|
SmallSet<const Value *, 16> YieldsPoison;
|
|
SmallSet<const BasicBlock *, 4> Visited;
|
|
|
|
YieldsPoison.insert(V);
|
|
auto Propagate = [&](const User *User) {
|
|
if (propagatesPoison(cast<Operator>(User)))
|
|
YieldsPoison.insert(User);
|
|
};
|
|
for_each(V->users(), Propagate);
|
|
Visited.insert(BB);
|
|
|
|
while (true) {
|
|
for (auto &I : make_range(Begin, End)) {
|
|
if (isa<DbgInfoIntrinsic>(I))
|
|
continue;
|
|
if (--ScanLimit == 0)
|
|
return false;
|
|
if (mustTriggerUB(&I, YieldsPoison))
|
|
return true;
|
|
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
|
|
return false;
|
|
|
|
// Mark poison that propagates from I through uses of I.
|
|
if (YieldsPoison.count(&I))
|
|
for_each(I.users(), Propagate);
|
|
}
|
|
|
|
BB = BB->getSingleSuccessor();
|
|
if (!BB || !Visited.insert(BB).second)
|
|
break;
|
|
|
|
Begin = BB->getFirstNonPHI()->getIterator();
|
|
End = BB->end();
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool llvm::programUndefinedIfUndefOrPoison(const Instruction *Inst) {
|
|
return ::programUndefinedIfUndefOrPoison(Inst, false);
|
|
}
|
|
|
|
bool llvm::programUndefinedIfPoison(const Instruction *Inst) {
|
|
return ::programUndefinedIfUndefOrPoison(Inst, true);
|
|
}
|
|
|
|
static bool isKnownNonNaN(const Value *V, FastMathFlags FMF) {
|
|
if (FMF.noNaNs())
|
|
return true;
|
|
|
|
if (auto *C = dyn_cast<ConstantFP>(V))
|
|
return !C->isNaN();
|
|
|
|
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
|
|
if (!C->getElementType()->isFloatingPointTy())
|
|
return false;
|
|
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
|
|
if (C->getElementAsAPFloat(I).isNaN())
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
if (isa<ConstantAggregateZero>(V))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool isKnownNonZero(const Value *V) {
|
|
if (auto *C = dyn_cast<ConstantFP>(V))
|
|
return !C->isZero();
|
|
|
|
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
|
|
if (!C->getElementType()->isFloatingPointTy())
|
|
return false;
|
|
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
|
|
if (C->getElementAsAPFloat(I).isZero())
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// Match clamp pattern for float types without care about NaNs or signed zeros.
|
|
/// Given non-min/max outer cmp/select from the clamp pattern this
|
|
/// function recognizes if it can be substitued by a "canonical" min/max
|
|
/// pattern.
|
|
static SelectPatternResult matchFastFloatClamp(CmpInst::Predicate Pred,
|
|
Value *CmpLHS, Value *CmpRHS,
|
|
Value *TrueVal, Value *FalseVal,
|
|
Value *&LHS, Value *&RHS) {
|
|
// Try to match
|
|
// X < C1 ? C1 : Min(X, C2) --> Max(C1, Min(X, C2))
|
|
// X > C1 ? C1 : Max(X, C2) --> Min(C1, Max(X, C2))
|
|
// and return description of the outer Max/Min.
|
|
|
|
// First, check if select has inverse order:
|
|
if (CmpRHS == FalseVal) {
|
|
std::swap(TrueVal, FalseVal);
|
|
Pred = CmpInst::getInversePredicate(Pred);
|
|
}
|
|
|
|
// Assume success now. If there's no match, callers should not use these anyway.
|
|
LHS = TrueVal;
|
|
RHS = FalseVal;
|
|
|
|
const APFloat *FC1;
|
|
if (CmpRHS != TrueVal || !match(CmpRHS, m_APFloat(FC1)) || !FC1->isFinite())
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
const APFloat *FC2;
|
|
switch (Pred) {
|
|
case CmpInst::FCMP_OLT:
|
|
case CmpInst::FCMP_OLE:
|
|
case CmpInst::FCMP_ULT:
|
|
case CmpInst::FCMP_ULE:
|
|
if (match(FalseVal,
|
|
m_CombineOr(m_OrdFMin(m_Specific(CmpLHS), m_APFloat(FC2)),
|
|
m_UnordFMin(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
|
|
*FC1 < *FC2)
|
|
return {SPF_FMAXNUM, SPNB_RETURNS_ANY, false};
|
|
break;
|
|
case CmpInst::FCMP_OGT:
|
|
case CmpInst::FCMP_OGE:
|
|
case CmpInst::FCMP_UGT:
|
|
case CmpInst::FCMP_UGE:
|
|
if (match(FalseVal,
|
|
m_CombineOr(m_OrdFMax(m_Specific(CmpLHS), m_APFloat(FC2)),
|
|
m_UnordFMax(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
|
|
*FC1 > *FC2)
|
|
return {SPF_FMINNUM, SPNB_RETURNS_ANY, false};
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
/// Recognize variations of:
|
|
/// CLAMP(v,l,h) ==> ((v) < (l) ? (l) : ((v) > (h) ? (h) : (v)))
|
|
static SelectPatternResult matchClamp(CmpInst::Predicate Pred,
|
|
Value *CmpLHS, Value *CmpRHS,
|
|
Value *TrueVal, Value *FalseVal) {
|
|
// Swap the select operands and predicate to match the patterns below.
|
|
if (CmpRHS != TrueVal) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
std::swap(TrueVal, FalseVal);
|
|
}
|
|
const APInt *C1;
|
|
if (CmpRHS == TrueVal && match(CmpRHS, m_APInt(C1))) {
|
|
const APInt *C2;
|
|
// (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
|
|
if (match(FalseVal, m_SMin(m_Specific(CmpLHS), m_APInt(C2))) &&
|
|
C1->slt(*C2) && Pred == CmpInst::ICMP_SLT)
|
|
return {SPF_SMAX, SPNB_NA, false};
|
|
|
|
// (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
|
|
if (match(FalseVal, m_SMax(m_Specific(CmpLHS), m_APInt(C2))) &&
|
|
C1->sgt(*C2) && Pred == CmpInst::ICMP_SGT)
|
|
return {SPF_SMIN, SPNB_NA, false};
|
|
|
|
// (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
|
|
if (match(FalseVal, m_UMin(m_Specific(CmpLHS), m_APInt(C2))) &&
|
|
C1->ult(*C2) && Pred == CmpInst::ICMP_ULT)
|
|
return {SPF_UMAX, SPNB_NA, false};
|
|
|
|
// (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
|
|
if (match(FalseVal, m_UMax(m_Specific(CmpLHS), m_APInt(C2))) &&
|
|
C1->ugt(*C2) && Pred == CmpInst::ICMP_UGT)
|
|
return {SPF_UMIN, SPNB_NA, false};
|
|
}
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
/// Recognize variations of:
|
|
/// a < c ? min(a,b) : min(b,c) ==> min(min(a,b),min(b,c))
|
|
static SelectPatternResult matchMinMaxOfMinMax(CmpInst::Predicate Pred,
|
|
Value *CmpLHS, Value *CmpRHS,
|
|
Value *TVal, Value *FVal,
|
|
unsigned Depth) {
|
|
// TODO: Allow FP min/max with nnan/nsz.
|
|
assert(CmpInst::isIntPredicate(Pred) && "Expected integer comparison");
|
|
|
|
Value *A = nullptr, *B = nullptr;
|
|
SelectPatternResult L = matchSelectPattern(TVal, A, B, nullptr, Depth + 1);
|
|
if (!SelectPatternResult::isMinOrMax(L.Flavor))
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
Value *C = nullptr, *D = nullptr;
|
|
SelectPatternResult R = matchSelectPattern(FVal, C, D, nullptr, Depth + 1);
|
|
if (L.Flavor != R.Flavor)
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
// We have something like: x Pred y ? min(a, b) : min(c, d).
|
|
// Try to match the compare to the min/max operations of the select operands.
|
|
// First, make sure we have the right compare predicate.
|
|
switch (L.Flavor) {
|
|
case SPF_SMIN:
|
|
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
std::swap(CmpLHS, CmpRHS);
|
|
}
|
|
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
|
|
break;
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
case SPF_SMAX:
|
|
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
std::swap(CmpLHS, CmpRHS);
|
|
}
|
|
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
|
|
break;
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
case SPF_UMIN:
|
|
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
std::swap(CmpLHS, CmpRHS);
|
|
}
|
|
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE)
|
|
break;
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
case SPF_UMAX:
|
|
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
std::swap(CmpLHS, CmpRHS);
|
|
}
|
|
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
|
|
break;
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
default:
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
// If there is a common operand in the already matched min/max and the other
|
|
// min/max operands match the compare operands (either directly or inverted),
|
|
// then this is min/max of the same flavor.
|
|
|
|
// a pred c ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
|
|
// ~c pred ~a ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
|
|
if (D == B) {
|
|
if ((CmpLHS == A && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
|
|
match(A, m_Not(m_Specific(CmpRHS)))))
|
|
return {L.Flavor, SPNB_NA, false};
|
|
}
|
|
// a pred d ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
|
|
// ~d pred ~a ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
|
|
if (C == B) {
|
|
if ((CmpLHS == A && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
|
|
match(A, m_Not(m_Specific(CmpRHS)))))
|
|
return {L.Flavor, SPNB_NA, false};
|
|
}
|
|
// b pred c ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
|
|
// ~c pred ~b ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
|
|
if (D == A) {
|
|
if ((CmpLHS == B && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
|
|
match(B, m_Not(m_Specific(CmpRHS)))))
|
|
return {L.Flavor, SPNB_NA, false};
|
|
}
|
|
// b pred d ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
|
|
// ~d pred ~b ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
|
|
if (C == A) {
|
|
if ((CmpLHS == B && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
|
|
match(B, m_Not(m_Specific(CmpRHS)))))
|
|
return {L.Flavor, SPNB_NA, false};
|
|
}
|
|
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
/// If the input value is the result of a 'not' op, constant integer, or vector
|
|
/// splat of a constant integer, return the bitwise-not source value.
|
|
/// TODO: This could be extended to handle non-splat vector integer constants.
|
|
static Value *getNotValue(Value *V) {
|
|
Value *NotV;
|
|
if (match(V, m_Not(m_Value(NotV))))
|
|
return NotV;
|
|
|
|
const APInt *C;
|
|
if (match(V, m_APInt(C)))
|
|
return ConstantInt::get(V->getType(), ~(*C));
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Match non-obvious integer minimum and maximum sequences.
|
|
static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
|
|
Value *CmpLHS, Value *CmpRHS,
|
|
Value *TrueVal, Value *FalseVal,
|
|
Value *&LHS, Value *&RHS,
|
|
unsigned Depth) {
|
|
// Assume success. If there's no match, callers should not use these anyway.
|
|
LHS = TrueVal;
|
|
RHS = FalseVal;
|
|
|
|
SelectPatternResult SPR = matchClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal);
|
|
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
|
|
return SPR;
|
|
|
|
SPR = matchMinMaxOfMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, Depth);
|
|
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
|
|
return SPR;
|
|
|
|
// Look through 'not' ops to find disguised min/max.
|
|
// (X > Y) ? ~X : ~Y ==> (~X < ~Y) ? ~X : ~Y ==> MIN(~X, ~Y)
|
|
// (X < Y) ? ~X : ~Y ==> (~X > ~Y) ? ~X : ~Y ==> MAX(~X, ~Y)
|
|
if (CmpLHS == getNotValue(TrueVal) && CmpRHS == getNotValue(FalseVal)) {
|
|
switch (Pred) {
|
|
case CmpInst::ICMP_SGT: return {SPF_SMIN, SPNB_NA, false};
|
|
case CmpInst::ICMP_SLT: return {SPF_SMAX, SPNB_NA, false};
|
|
case CmpInst::ICMP_UGT: return {SPF_UMIN, SPNB_NA, false};
|
|
case CmpInst::ICMP_ULT: return {SPF_UMAX, SPNB_NA, false};
|
|
default: break;
|
|
}
|
|
}
|
|
|
|
// (X > Y) ? ~Y : ~X ==> (~X < ~Y) ? ~Y : ~X ==> MAX(~Y, ~X)
|
|
// (X < Y) ? ~Y : ~X ==> (~X > ~Y) ? ~Y : ~X ==> MIN(~Y, ~X)
|
|
if (CmpLHS == getNotValue(FalseVal) && CmpRHS == getNotValue(TrueVal)) {
|
|
switch (Pred) {
|
|
case CmpInst::ICMP_SGT: return {SPF_SMAX, SPNB_NA, false};
|
|
case CmpInst::ICMP_SLT: return {SPF_SMIN, SPNB_NA, false};
|
|
case CmpInst::ICMP_UGT: return {SPF_UMAX, SPNB_NA, false};
|
|
case CmpInst::ICMP_ULT: return {SPF_UMIN, SPNB_NA, false};
|
|
default: break;
|
|
}
|
|
}
|
|
|
|
if (Pred != CmpInst::ICMP_SGT && Pred != CmpInst::ICMP_SLT)
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
// Z = X -nsw Y
|
|
// (X >s Y) ? 0 : Z ==> (Z >s 0) ? 0 : Z ==> SMIN(Z, 0)
|
|
// (X <s Y) ? 0 : Z ==> (Z <s 0) ? 0 : Z ==> SMAX(Z, 0)
|
|
if (match(TrueVal, m_Zero()) &&
|
|
match(FalseVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
|
|
return {Pred == CmpInst::ICMP_SGT ? SPF_SMIN : SPF_SMAX, SPNB_NA, false};
|
|
|
|
// Z = X -nsw Y
|
|
// (X >s Y) ? Z : 0 ==> (Z >s 0) ? Z : 0 ==> SMAX(Z, 0)
|
|
// (X <s Y) ? Z : 0 ==> (Z <s 0) ? Z : 0 ==> SMIN(Z, 0)
|
|
if (match(FalseVal, m_Zero()) &&
|
|
match(TrueVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
|
|
return {Pred == CmpInst::ICMP_SGT ? SPF_SMAX : SPF_SMIN, SPNB_NA, false};
|
|
|
|
const APInt *C1;
|
|
if (!match(CmpRHS, m_APInt(C1)))
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
// An unsigned min/max can be written with a signed compare.
|
|
const APInt *C2;
|
|
if ((CmpLHS == TrueVal && match(FalseVal, m_APInt(C2))) ||
|
|
(CmpLHS == FalseVal && match(TrueVal, m_APInt(C2)))) {
|
|
// Is the sign bit set?
|
|
// (X <s 0) ? X : MAXVAL ==> (X >u MAXVAL) ? X : MAXVAL ==> UMAX
|
|
// (X <s 0) ? MAXVAL : X ==> (X >u MAXVAL) ? MAXVAL : X ==> UMIN
|
|
if (Pred == CmpInst::ICMP_SLT && C1->isNullValue() &&
|
|
C2->isMaxSignedValue())
|
|
return {CmpLHS == TrueVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
|
|
|
|
// Is the sign bit clear?
|
|
// (X >s -1) ? MINVAL : X ==> (X <u MINVAL) ? MINVAL : X ==> UMAX
|
|
// (X >s -1) ? X : MINVAL ==> (X <u MINVAL) ? X : MINVAL ==> UMIN
|
|
if (Pred == CmpInst::ICMP_SGT && C1->isAllOnesValue() &&
|
|
C2->isMinSignedValue())
|
|
return {CmpLHS == FalseVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
|
|
}
|
|
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
|
|
assert(X && Y && "Invalid operand");
|
|
|
|
// X = sub (0, Y) || X = sub nsw (0, Y)
|
|
if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
|
|
(NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
|
|
return true;
|
|
|
|
// Y = sub (0, X) || Y = sub nsw (0, X)
|
|
if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
|
|
(NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
|
|
return true;
|
|
|
|
// X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
|
|
Value *A, *B;
|
|
return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
|
|
match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
|
|
(NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
|
|
match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
|
|
}
|
|
|
|
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
|
|
FastMathFlags FMF,
|
|
Value *CmpLHS, Value *CmpRHS,
|
|
Value *TrueVal, Value *FalseVal,
|
|
Value *&LHS, Value *&RHS,
|
|
unsigned Depth) {
|
|
if (CmpInst::isFPPredicate(Pred)) {
|
|
// IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one
|
|
// 0.0 operand, set the compare's 0.0 operands to that same value for the
|
|
// purpose of identifying min/max. Disregard vector constants with undefined
|
|
// elements because those can not be back-propagated for analysis.
|
|
Value *OutputZeroVal = nullptr;
|
|
if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) &&
|
|
!cast<Constant>(TrueVal)->containsUndefOrPoisonElement())
|
|
OutputZeroVal = TrueVal;
|
|
else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) &&
|
|
!cast<Constant>(FalseVal)->containsUndefOrPoisonElement())
|
|
OutputZeroVal = FalseVal;
|
|
|
|
if (OutputZeroVal) {
|
|
if (match(CmpLHS, m_AnyZeroFP()))
|
|
CmpLHS = OutputZeroVal;
|
|
if (match(CmpRHS, m_AnyZeroFP()))
|
|
CmpRHS = OutputZeroVal;
|
|
}
|
|
}
|
|
|
|
LHS = CmpLHS;
|
|
RHS = CmpRHS;
|
|
|
|
// Signed zero may return inconsistent results between implementations.
|
|
// (0.0 <= -0.0) ? 0.0 : -0.0 // Returns 0.0
|
|
// minNum(0.0, -0.0) // May return -0.0 or 0.0 (IEEE 754-2008 5.3.1)
|
|
// Therefore, we behave conservatively and only proceed if at least one of the
|
|
// operands is known to not be zero or if we don't care about signed zero.
|
|
switch (Pred) {
|
|
default: break;
|
|
// FIXME: Include OGT/OLT/UGT/ULT.
|
|
case CmpInst::FCMP_OGE: case CmpInst::FCMP_OLE:
|
|
case CmpInst::FCMP_UGE: case CmpInst::FCMP_ULE:
|
|
if (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
|
|
!isKnownNonZero(CmpRHS))
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
|
|
SelectPatternNaNBehavior NaNBehavior = SPNB_NA;
|
|
bool Ordered = false;
|
|
|
|
// When given one NaN and one non-NaN input:
|
|
// - maxnum/minnum (C99 fmaxf()/fminf()) return the non-NaN input.
|
|
// - A simple C99 (a < b ? a : b) construction will return 'b' (as the
|
|
// ordered comparison fails), which could be NaN or non-NaN.
|
|
// so here we discover exactly what NaN behavior is required/accepted.
|
|
if (CmpInst::isFPPredicate(Pred)) {
|
|
bool LHSSafe = isKnownNonNaN(CmpLHS, FMF);
|
|
bool RHSSafe = isKnownNonNaN(CmpRHS, FMF);
|
|
|
|
if (LHSSafe && RHSSafe) {
|
|
// Both operands are known non-NaN.
|
|
NaNBehavior = SPNB_RETURNS_ANY;
|
|
} else if (CmpInst::isOrdered(Pred)) {
|
|
// An ordered comparison will return false when given a NaN, so it
|
|
// returns the RHS.
|
|
Ordered = true;
|
|
if (LHSSafe)
|
|
// LHS is non-NaN, so if RHS is NaN then NaN will be returned.
|
|
NaNBehavior = SPNB_RETURNS_NAN;
|
|
else if (RHSSafe)
|
|
NaNBehavior = SPNB_RETURNS_OTHER;
|
|
else
|
|
// Completely unsafe.
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
} else {
|
|
Ordered = false;
|
|
// An unordered comparison will return true when given a NaN, so it
|
|
// returns the LHS.
|
|
if (LHSSafe)
|
|
// LHS is non-NaN, so if RHS is NaN then non-NaN will be returned.
|
|
NaNBehavior = SPNB_RETURNS_OTHER;
|
|
else if (RHSSafe)
|
|
NaNBehavior = SPNB_RETURNS_NAN;
|
|
else
|
|
// Completely unsafe.
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
}
|
|
}
|
|
|
|
if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
|
|
std::swap(CmpLHS, CmpRHS);
|
|
Pred = CmpInst::getSwappedPredicate(Pred);
|
|
if (NaNBehavior == SPNB_RETURNS_NAN)
|
|
NaNBehavior = SPNB_RETURNS_OTHER;
|
|
else if (NaNBehavior == SPNB_RETURNS_OTHER)
|
|
NaNBehavior = SPNB_RETURNS_NAN;
|
|
Ordered = !Ordered;
|
|
}
|
|
|
|
// ([if]cmp X, Y) ? X : Y
|
|
if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
|
|
switch (Pred) {
|
|
default: return {SPF_UNKNOWN, SPNB_NA, false}; // Equality.
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_UGE: return {SPF_UMAX, SPNB_NA, false};
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_SGE: return {SPF_SMAX, SPNB_NA, false};
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_ULE: return {SPF_UMIN, SPNB_NA, false};
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_SLE: return {SPF_SMIN, SPNB_NA, false};
|
|
case FCmpInst::FCMP_UGT:
|
|
case FCmpInst::FCMP_UGE:
|
|
case FCmpInst::FCMP_OGT:
|
|
case FCmpInst::FCMP_OGE: return {SPF_FMAXNUM, NaNBehavior, Ordered};
|
|
case FCmpInst::FCMP_ULT:
|
|
case FCmpInst::FCMP_ULE:
|
|
case FCmpInst::FCMP_OLT:
|
|
case FCmpInst::FCMP_OLE: return {SPF_FMINNUM, NaNBehavior, Ordered};
|
|
}
|
|
}
|
|
|
|
if (isKnownNegation(TrueVal, FalseVal)) {
|
|
// Sign-extending LHS does not change its sign, so TrueVal/FalseVal can
|
|
// match against either LHS or sext(LHS).
|
|
auto MaybeSExtCmpLHS =
|
|
m_CombineOr(m_Specific(CmpLHS), m_SExt(m_Specific(CmpLHS)));
|
|
auto ZeroOrAllOnes = m_CombineOr(m_ZeroInt(), m_AllOnes());
|
|
auto ZeroOrOne = m_CombineOr(m_ZeroInt(), m_One());
|
|
if (match(TrueVal, MaybeSExtCmpLHS)) {
|
|
// Set the return values. If the compare uses the negated value (-X >s 0),
|
|
// swap the return values because the negated value is always 'RHS'.
|
|
LHS = TrueVal;
|
|
RHS = FalseVal;
|
|
if (match(CmpLHS, m_Neg(m_Specific(FalseVal))))
|
|
std::swap(LHS, RHS);
|
|
|
|
// (X >s 0) ? X : -X or (X >s -1) ? X : -X --> ABS(X)
|
|
// (-X >s 0) ? -X : X or (-X >s -1) ? -X : X --> ABS(X)
|
|
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
|
|
return {SPF_ABS, SPNB_NA, false};
|
|
|
|
// (X >=s 0) ? X : -X or (X >=s 1) ? X : -X --> ABS(X)
|
|
if (Pred == ICmpInst::ICMP_SGE && match(CmpRHS, ZeroOrOne))
|
|
return {SPF_ABS, SPNB_NA, false};
|
|
|
|
// (X <s 0) ? X : -X or (X <s 1) ? X : -X --> NABS(X)
|
|
// (-X <s 0) ? -X : X or (-X <s 1) ? -X : X --> NABS(X)
|
|
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
|
|
return {SPF_NABS, SPNB_NA, false};
|
|
}
|
|
else if (match(FalseVal, MaybeSExtCmpLHS)) {
|
|
// Set the return values. If the compare uses the negated value (-X >s 0),
|
|
// swap the return values because the negated value is always 'RHS'.
|
|
LHS = FalseVal;
|
|
RHS = TrueVal;
|
|
if (match(CmpLHS, m_Neg(m_Specific(TrueVal))))
|
|
std::swap(LHS, RHS);
|
|
|
|
// (X >s 0) ? -X : X or (X >s -1) ? -X : X --> NABS(X)
|
|
// (-X >s 0) ? X : -X or (-X >s -1) ? X : -X --> NABS(X)
|
|
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
|
|
return {SPF_NABS, SPNB_NA, false};
|
|
|
|
// (X <s 0) ? -X : X or (X <s 1) ? -X : X --> ABS(X)
|
|
// (-X <s 0) ? X : -X or (-X <s 1) ? X : -X --> ABS(X)
|
|
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
|
|
return {SPF_ABS, SPNB_NA, false};
|
|
}
|
|
}
|
|
|
|
if (CmpInst::isIntPredicate(Pred))
|
|
return matchMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS, Depth);
|
|
|
|
// According to (IEEE 754-2008 5.3.1), minNum(0.0, -0.0) and similar
|
|
// may return either -0.0 or 0.0, so fcmp/select pair has stricter
|
|
// semantics than minNum. Be conservative in such case.
|
|
if (NaNBehavior != SPNB_RETURNS_ANY ||
|
|
(!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
|
|
!isKnownNonZero(CmpRHS)))
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
|
|
}
|
|
|
|
/// Helps to match a select pattern in case of a type mismatch.
|
|
///
|
|
/// The function processes the case when type of true and false values of a
|
|
/// select instruction differs from type of the cmp instruction operands because
|
|
/// of a cast instruction. The function checks if it is legal to move the cast
|
|
/// operation after "select". If yes, it returns the new second value of
|
|
/// "select" (with the assumption that cast is moved):
|
|
/// 1. As operand of cast instruction when both values of "select" are same cast
|
|
/// instructions.
|
|
/// 2. As restored constant (by applying reverse cast operation) when the first
|
|
/// value of the "select" is a cast operation and the second value is a
|
|
/// constant.
|
|
/// NOTE: We return only the new second value because the first value could be
|
|
/// accessed as operand of cast instruction.
|
|
static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
|
|
Instruction::CastOps *CastOp) {
|
|
auto *Cast1 = dyn_cast<CastInst>(V1);
|
|
if (!Cast1)
|
|
return nullptr;
|
|
|
|
*CastOp = Cast1->getOpcode();
|
|
Type *SrcTy = Cast1->getSrcTy();
|
|
if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
|
|
// If V1 and V2 are both the same cast from the same type, look through V1.
|
|
if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
|
|
return Cast2->getOperand(0);
|
|
return nullptr;
|
|
}
|
|
|
|
auto *C = dyn_cast<Constant>(V2);
|
|
if (!C)
|
|
return nullptr;
|
|
|
|
Constant *CastedTo = nullptr;
|
|
switch (*CastOp) {
|
|
case Instruction::ZExt:
|
|
if (CmpI->isUnsigned())
|
|
CastedTo = ConstantExpr::getTrunc(C, SrcTy);
|
|
break;
|
|
case Instruction::SExt:
|
|
if (CmpI->isSigned())
|
|
CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
|
|
break;
|
|
case Instruction::Trunc:
|
|
Constant *CmpConst;
|
|
if (match(CmpI->getOperand(1), m_Constant(CmpConst)) &&
|
|
CmpConst->getType() == SrcTy) {
|
|
// Here we have the following case:
|
|
//
|
|
// %cond = cmp iN %x, CmpConst
|
|
// %tr = trunc iN %x to iK
|
|
// %narrowsel = select i1 %cond, iK %t, iK C
|
|
//
|
|
// We can always move trunc after select operation:
|
|
//
|
|
// %cond = cmp iN %x, CmpConst
|
|
// %widesel = select i1 %cond, iN %x, iN CmpConst
|
|
// %tr = trunc iN %widesel to iK
|
|
//
|
|
// Note that C could be extended in any way because we don't care about
|
|
// upper bits after truncation. It can't be abs pattern, because it would
|
|
// look like:
|
|
//
|
|
// select i1 %cond, x, -x.
|
|
//
|
|
// So only min/max pattern could be matched. Such match requires widened C
|
|
// == CmpConst. That is why set widened C = CmpConst, condition trunc
|
|
// CmpConst == C is checked below.
|
|
CastedTo = CmpConst;
|
|
} else {
|
|
CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
|
|
}
|
|
break;
|
|
case Instruction::FPTrunc:
|
|
CastedTo = ConstantExpr::getFPExtend(C, SrcTy, true);
|
|
break;
|
|
case Instruction::FPExt:
|
|
CastedTo = ConstantExpr::getFPTrunc(C, SrcTy, true);
|
|
break;
|
|
case Instruction::FPToUI:
|
|
CastedTo = ConstantExpr::getUIToFP(C, SrcTy, true);
|
|
break;
|
|
case Instruction::FPToSI:
|
|
CastedTo = ConstantExpr::getSIToFP(C, SrcTy, true);
|
|
break;
|
|
case Instruction::UIToFP:
|
|
CastedTo = ConstantExpr::getFPToUI(C, SrcTy, true);
|
|
break;
|
|
case Instruction::SIToFP:
|
|
CastedTo = ConstantExpr::getFPToSI(C, SrcTy, true);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
if (!CastedTo)
|
|
return nullptr;
|
|
|
|
// Make sure the cast doesn't lose any information.
|
|
Constant *CastedBack =
|
|
ConstantExpr::getCast(*CastOp, CastedTo, C->getType(), true);
|
|
if (CastedBack != C)
|
|
return nullptr;
|
|
|
|
return CastedTo;
|
|
}
|
|
|
|
SelectPatternResult llvm::matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
|
|
Instruction::CastOps *CastOp,
|
|
unsigned Depth) {
|
|
if (Depth >= MaxAnalysisRecursionDepth)
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
SelectInst *SI = dyn_cast<SelectInst>(V);
|
|
if (!SI) return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
CmpInst *CmpI = dyn_cast<CmpInst>(SI->getCondition());
|
|
if (!CmpI) return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
Value *TrueVal = SI->getTrueValue();
|
|
Value *FalseVal = SI->getFalseValue();
|
|
|
|
return llvm::matchDecomposedSelectPattern(CmpI, TrueVal, FalseVal, LHS, RHS,
|
|
CastOp, Depth);
|
|
}
|
|
|
|
SelectPatternResult llvm::matchDecomposedSelectPattern(
|
|
CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS,
|
|
Instruction::CastOps *CastOp, unsigned Depth) {
|
|
CmpInst::Predicate Pred = CmpI->getPredicate();
|
|
Value *CmpLHS = CmpI->getOperand(0);
|
|
Value *CmpRHS = CmpI->getOperand(1);
|
|
FastMathFlags FMF;
|
|
if (isa<FPMathOperator>(CmpI))
|
|
FMF = CmpI->getFastMathFlags();
|
|
|
|
// Bail out early.
|
|
if (CmpI->isEquality())
|
|
return {SPF_UNKNOWN, SPNB_NA, false};
|
|
|
|
// Deal with type mismatches.
|
|
if (CastOp && CmpLHS->getType() != TrueVal->getType()) {
|
|
if (Value *C = lookThroughCast(CmpI, TrueVal, FalseVal, CastOp)) {
|
|
// If this is a potential fmin/fmax with a cast to integer, then ignore
|
|
// -0.0 because there is no corresponding integer value.
|
|
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
|
|
FMF.setNoSignedZeros();
|
|
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
|
|
cast<CastInst>(TrueVal)->getOperand(0), C,
|
|
LHS, RHS, Depth);
|
|
}
|
|
if (Value *C = lookThroughCast(CmpI, FalseVal, TrueVal, CastOp)) {
|
|
// If this is a potential fmin/fmax with a cast to integer, then ignore
|
|
// -0.0 because there is no corresponding integer value.
|
|
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
|
|
FMF.setNoSignedZeros();
|
|
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
|
|
C, cast<CastInst>(FalseVal)->getOperand(0),
|
|
LHS, RHS, Depth);
|
|
}
|
|
}
|
|
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS, TrueVal, FalseVal,
|
|
LHS, RHS, Depth);
|
|
}
|
|
|
|
CmpInst::Predicate llvm::getMinMaxPred(SelectPatternFlavor SPF, bool Ordered) {
|
|
if (SPF == SPF_SMIN) return ICmpInst::ICMP_SLT;
|
|
if (SPF == SPF_UMIN) return ICmpInst::ICMP_ULT;
|
|
if (SPF == SPF_SMAX) return ICmpInst::ICMP_SGT;
|
|
if (SPF == SPF_UMAX) return ICmpInst::ICMP_UGT;
|
|
if (SPF == SPF_FMINNUM)
|
|
return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT;
|
|
if (SPF == SPF_FMAXNUM)
|
|
return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT;
|
|
llvm_unreachable("unhandled!");
|
|
}
|
|
|
|
SelectPatternFlavor llvm::getInverseMinMaxFlavor(SelectPatternFlavor SPF) {
|
|
if (SPF == SPF_SMIN) return SPF_SMAX;
|
|
if (SPF == SPF_UMIN) return SPF_UMAX;
|
|
if (SPF == SPF_SMAX) return SPF_SMIN;
|
|
if (SPF == SPF_UMAX) return SPF_UMIN;
|
|
llvm_unreachable("unhandled!");
|
|
}
|
|
|
|
Intrinsic::ID llvm::getInverseMinMaxIntrinsic(Intrinsic::ID MinMaxID) {
|
|
switch (MinMaxID) {
|
|
case Intrinsic::smax: return Intrinsic::smin;
|
|
case Intrinsic::smin: return Intrinsic::smax;
|
|
case Intrinsic::umax: return Intrinsic::umin;
|
|
case Intrinsic::umin: return Intrinsic::umax;
|
|
default: llvm_unreachable("Unexpected intrinsic");
|
|
}
|
|
}
|
|
|
|
CmpInst::Predicate llvm::getInverseMinMaxPred(SelectPatternFlavor SPF) {
|
|
return getMinMaxPred(getInverseMinMaxFlavor(SPF));
|
|
}
|
|
|
|
std::pair<Intrinsic::ID, bool>
|
|
llvm::canConvertToMinOrMaxIntrinsic(ArrayRef<Value *> VL) {
|
|
// Check if VL contains select instructions that can be folded into a min/max
|
|
// vector intrinsic and return the intrinsic if it is possible.
|
|
// TODO: Support floating point min/max.
|
|
bool AllCmpSingleUse = true;
|
|
SelectPatternResult SelectPattern;
|
|
SelectPattern.Flavor = SPF_UNKNOWN;
|
|
if (all_of(VL, [&SelectPattern, &AllCmpSingleUse](Value *I) {
|
|
Value *LHS, *RHS;
|
|
auto CurrentPattern = matchSelectPattern(I, LHS, RHS);
|
|
if (!SelectPatternResult::isMinOrMax(CurrentPattern.Flavor) ||
|
|
CurrentPattern.Flavor == SPF_FMINNUM ||
|
|
CurrentPattern.Flavor == SPF_FMAXNUM ||
|
|
!I->getType()->isIntOrIntVectorTy())
|
|
return false;
|
|
if (SelectPattern.Flavor != SPF_UNKNOWN &&
|
|
SelectPattern.Flavor != CurrentPattern.Flavor)
|
|
return false;
|
|
SelectPattern = CurrentPattern;
|
|
AllCmpSingleUse &=
|
|
match(I, m_Select(m_OneUse(m_Value()), m_Value(), m_Value()));
|
|
return true;
|
|
})) {
|
|
switch (SelectPattern.Flavor) {
|
|
case SPF_SMIN:
|
|
return {Intrinsic::smin, AllCmpSingleUse};
|
|
case SPF_UMIN:
|
|
return {Intrinsic::umin, AllCmpSingleUse};
|
|
case SPF_SMAX:
|
|
return {Intrinsic::smax, AllCmpSingleUse};
|
|
case SPF_UMAX:
|
|
return {Intrinsic::umax, AllCmpSingleUse};
|
|
default:
|
|
llvm_unreachable("unexpected select pattern flavor");
|
|
}
|
|
}
|
|
return {Intrinsic::not_intrinsic, false};
|
|
}
|
|
|
|
bool llvm::matchSimpleRecurrence(const PHINode *P, BinaryOperator *&BO,
|
|
Value *&Start, Value *&Step) {
|
|
// Handle the case of a simple two-predecessor recurrence PHI.
|
|
// There's a lot more that could theoretically be done here, but
|
|
// this is sufficient to catch some interesting cases.
|
|
if (P->getNumIncomingValues() != 2)
|
|
return false;
|
|
|
|
for (unsigned i = 0; i != 2; ++i) {
|
|
Value *L = P->getIncomingValue(i);
|
|
Value *R = P->getIncomingValue(!i);
|
|
Operator *LU = dyn_cast<Operator>(L);
|
|
if (!LU)
|
|
continue;
|
|
unsigned Opcode = LU->getOpcode();
|
|
|
|
switch (Opcode) {
|
|
default:
|
|
continue;
|
|
// TODO: Expand list -- xor, div, gep, uaddo, etc..
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
case Instruction::Shl:
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
case Instruction::Mul: {
|
|
Value *LL = LU->getOperand(0);
|
|
Value *LR = LU->getOperand(1);
|
|
// Find a recurrence.
|
|
if (LL == P)
|
|
L = LR;
|
|
else if (LR == P)
|
|
L = LL;
|
|
else
|
|
continue; // Check for recurrence with L and R flipped.
|
|
|
|
break; // Match!
|
|
}
|
|
};
|
|
|
|
// We have matched a recurrence of the form:
|
|
// %iv = [R, %entry], [%iv.next, %backedge]
|
|
// %iv.next = binop %iv, L
|
|
// OR
|
|
// %iv = [R, %entry], [%iv.next, %backedge]
|
|
// %iv.next = binop L, %iv
|
|
BO = cast<BinaryOperator>(LU);
|
|
Start = R;
|
|
Step = L;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool llvm::matchSimpleRecurrence(const BinaryOperator *I, PHINode *&P,
|
|
Value *&Start, Value *&Step) {
|
|
BinaryOperator *BO = nullptr;
|
|
P = dyn_cast<PHINode>(I->getOperand(0));
|
|
if (!P)
|
|
P = dyn_cast<PHINode>(I->getOperand(1));
|
|
return P && matchSimpleRecurrence(P, BO, Start, Step) && BO == I;
|
|
}
|
|
|
|
/// Return true if "icmp Pred LHS RHS" is always true.
|
|
static bool isTruePredicate(CmpInst::Predicate Pred, const Value *LHS,
|
|
const Value *RHS, const DataLayout &DL,
|
|
unsigned Depth) {
|
|
assert(!LHS->getType()->isVectorTy() && "TODO: extend to handle vectors!");
|
|
if (ICmpInst::isTrueWhenEqual(Pred) && LHS == RHS)
|
|
return true;
|
|
|
|
switch (Pred) {
|
|
default:
|
|
return false;
|
|
|
|
case CmpInst::ICMP_SLE: {
|
|
const APInt *C;
|
|
|
|
// LHS s<= LHS +_{nsw} C if C >= 0
|
|
if (match(RHS, m_NSWAdd(m_Specific(LHS), m_APInt(C))))
|
|
return !C->isNegative();
|
|
return false;
|
|
}
|
|
|
|
case CmpInst::ICMP_ULE: {
|
|
const APInt *C;
|
|
|
|
// LHS u<= LHS +_{nuw} C for any C
|
|
if (match(RHS, m_NUWAdd(m_Specific(LHS), m_APInt(C))))
|
|
return true;
|
|
|
|
// Match A to (X +_{nuw} CA) and B to (X +_{nuw} CB)
|
|
auto MatchNUWAddsToSameValue = [&](const Value *A, const Value *B,
|
|
const Value *&X,
|
|
const APInt *&CA, const APInt *&CB) {
|
|
if (match(A, m_NUWAdd(m_Value(X), m_APInt(CA))) &&
|
|
match(B, m_NUWAdd(m_Specific(X), m_APInt(CB))))
|
|
return true;
|
|
|
|
// If X & C == 0 then (X | C) == X +_{nuw} C
|
|
if (match(A, m_Or(m_Value(X), m_APInt(CA))) &&
|
|
match(B, m_Or(m_Specific(X), m_APInt(CB)))) {
|
|
KnownBits Known(CA->getBitWidth());
|
|
computeKnownBits(X, Known, DL, Depth + 1, /*AC*/ nullptr,
|
|
/*CxtI*/ nullptr, /*DT*/ nullptr);
|
|
if (CA->isSubsetOf(Known.Zero) && CB->isSubsetOf(Known.Zero))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
};
|
|
|
|
const Value *X;
|
|
const APInt *CLHS, *CRHS;
|
|
if (MatchNUWAddsToSameValue(LHS, RHS, X, CLHS, CRHS))
|
|
return CLHS->ule(*CRHS);
|
|
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Return true if "icmp Pred BLHS BRHS" is true whenever "icmp Pred
|
|
/// ALHS ARHS" is true. Otherwise, return None.
|
|
static Optional<bool>
|
|
isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
|
|
const Value *ARHS, const Value *BLHS, const Value *BRHS,
|
|
const DataLayout &DL, unsigned Depth) {
|
|
switch (Pred) {
|
|
default:
|
|
return None;
|
|
|
|
case CmpInst::ICMP_SLT:
|
|
case CmpInst::ICMP_SLE:
|
|
if (isTruePredicate(CmpInst::ICMP_SLE, BLHS, ALHS, DL, Depth) &&
|
|
isTruePredicate(CmpInst::ICMP_SLE, ARHS, BRHS, DL, Depth))
|
|
return true;
|
|
return None;
|
|
|
|
case CmpInst::ICMP_ULT:
|
|
case CmpInst::ICMP_ULE:
|
|
if (isTruePredicate(CmpInst::ICMP_ULE, BLHS, ALHS, DL, Depth) &&
|
|
isTruePredicate(CmpInst::ICMP_ULE, ARHS, BRHS, DL, Depth))
|
|
return true;
|
|
return None;
|
|
}
|
|
}
|
|
|
|
/// Return true if the operands of the two compares match. IsSwappedOps is true
|
|
/// when the operands match, but are swapped.
|
|
static bool isMatchingOps(const Value *ALHS, const Value *ARHS,
|
|
const Value *BLHS, const Value *BRHS,
|
|
bool &IsSwappedOps) {
|
|
|
|
bool IsMatchingOps = (ALHS == BLHS && ARHS == BRHS);
|
|
IsSwappedOps = (ALHS == BRHS && ARHS == BLHS);
|
|
return IsMatchingOps || IsSwappedOps;
|
|
}
|
|
|
|
/// Return true if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is true.
|
|
/// Return false if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is false.
|
|
/// Otherwise, return None if we can't infer anything.
|
|
static Optional<bool> isImpliedCondMatchingOperands(CmpInst::Predicate APred,
|
|
CmpInst::Predicate BPred,
|
|
bool AreSwappedOps) {
|
|
// Canonicalize the predicate as if the operands were not commuted.
|
|
if (AreSwappedOps)
|
|
BPred = ICmpInst::getSwappedPredicate(BPred);
|
|
|
|
if (CmpInst::isImpliedTrueByMatchingCmp(APred, BPred))
|
|
return true;
|
|
if (CmpInst::isImpliedFalseByMatchingCmp(APred, BPred))
|
|
return false;
|
|
|
|
return None;
|
|
}
|
|
|
|
/// Return true if "icmp APred X, C1" implies "icmp BPred X, C2" is true.
|
|
/// Return false if "icmp APred X, C1" implies "icmp BPred X, C2" is false.
|
|
/// Otherwise, return None if we can't infer anything.
|
|
static Optional<bool>
|
|
isImpliedCondMatchingImmOperands(CmpInst::Predicate APred,
|
|
const ConstantInt *C1,
|
|
CmpInst::Predicate BPred,
|
|
const ConstantInt *C2) {
|
|
ConstantRange DomCR =
|
|
ConstantRange::makeExactICmpRegion(APred, C1->getValue());
|
|
ConstantRange CR =
|
|
ConstantRange::makeAllowedICmpRegion(BPred, C2->getValue());
|
|
ConstantRange Intersection = DomCR.intersectWith(CR);
|
|
ConstantRange Difference = DomCR.difference(CR);
|
|
if (Intersection.isEmptySet())
|
|
return false;
|
|
if (Difference.isEmptySet())
|
|
return true;
|
|
return None;
|
|
}
|
|
|
|
/// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
|
|
/// false. Otherwise, return None if we can't infer anything.
|
|
static Optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
|
|
CmpInst::Predicate BPred,
|
|
const Value *BLHS, const Value *BRHS,
|
|
const DataLayout &DL, bool LHSIsTrue,
|
|
unsigned Depth) {
|
|
Value *ALHS = LHS->getOperand(0);
|
|
Value *ARHS = LHS->getOperand(1);
|
|
|
|
// The rest of the logic assumes the LHS condition is true. If that's not the
|
|
// case, invert the predicate to make it so.
|
|
CmpInst::Predicate APred =
|
|
LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
|
|
|
|
// Can we infer anything when the two compares have matching operands?
|
|
bool AreSwappedOps;
|
|
if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, AreSwappedOps)) {
|
|
if (Optional<bool> Implication = isImpliedCondMatchingOperands(
|
|
APred, BPred, AreSwappedOps))
|
|
return Implication;
|
|
// No amount of additional analysis will infer the second condition, so
|
|
// early exit.
|
|
return None;
|
|
}
|
|
|
|
// Can we infer anything when the LHS operands match and the RHS operands are
|
|
// constants (not necessarily matching)?
|
|
if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
|
|
if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
|
|
APred, cast<ConstantInt>(ARHS), BPred, cast<ConstantInt>(BRHS)))
|
|
return Implication;
|
|
// No amount of additional analysis will infer the second condition, so
|
|
// early exit.
|
|
return None;
|
|
}
|
|
|
|
if (APred == BPred)
|
|
return isImpliedCondOperands(APred, ALHS, ARHS, BLHS, BRHS, DL, Depth);
|
|
return None;
|
|
}
|
|
|
|
/// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
|
|
/// false. Otherwise, return None if we can't infer anything. We expect the
|
|
/// RHS to be an icmp and the LHS to be an 'and', 'or', or a 'select' instruction.
|
|
static Optional<bool>
|
|
isImpliedCondAndOr(const Instruction *LHS, CmpInst::Predicate RHSPred,
|
|
const Value *RHSOp0, const Value *RHSOp1,
|
|
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
|
|
// The LHS must be an 'or', 'and', or a 'select' instruction.
|
|
assert((LHS->getOpcode() == Instruction::And ||
|
|
LHS->getOpcode() == Instruction::Or ||
|
|
LHS->getOpcode() == Instruction::Select) &&
|
|
"Expected LHS to be 'and', 'or', or 'select'.");
|
|
|
|
assert(Depth <= MaxAnalysisRecursionDepth && "Hit recursion limit");
|
|
|
|
// If the result of an 'or' is false, then we know both legs of the 'or' are
|
|
// false. Similarly, if the result of an 'and' is true, then we know both
|
|
// legs of the 'and' are true.
|
|
const Value *ALHS, *ARHS;
|
|
if ((!LHSIsTrue && match(LHS, m_LogicalOr(m_Value(ALHS), m_Value(ARHS)))) ||
|
|
(LHSIsTrue && match(LHS, m_LogicalAnd(m_Value(ALHS), m_Value(ARHS))))) {
|
|
// FIXME: Make this non-recursion.
|
|
if (Optional<bool> Implication = isImpliedCondition(
|
|
ALHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
|
|
return Implication;
|
|
if (Optional<bool> Implication = isImpliedCondition(
|
|
ARHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
|
|
return Implication;
|
|
return None;
|
|
}
|
|
return None;
|
|
}
|
|
|
|
Optional<bool>
|
|
llvm::isImpliedCondition(const Value *LHS, CmpInst::Predicate RHSPred,
|
|
const Value *RHSOp0, const Value *RHSOp1,
|
|
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
|
|
// Bail out when we hit the limit.
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return None;
|
|
|
|
// A mismatch occurs when we compare a scalar cmp to a vector cmp, for
|
|
// example.
|
|
if (RHSOp0->getType()->isVectorTy() != LHS->getType()->isVectorTy())
|
|
return None;
|
|
|
|
Type *OpTy = LHS->getType();
|
|
assert(OpTy->isIntOrIntVectorTy(1) && "Expected integer type only!");
|
|
|
|
// FIXME: Extending the code below to handle vectors.
|
|
if (OpTy->isVectorTy())
|
|
return None;
|
|
|
|
assert(OpTy->isIntegerTy(1) && "implied by above");
|
|
|
|
// Both LHS and RHS are icmps.
|
|
const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
|
|
if (LHSCmp)
|
|
return isImpliedCondICmps(LHSCmp, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue,
|
|
Depth);
|
|
|
|
/// The LHS should be an 'or', 'and', or a 'select' instruction. We expect
|
|
/// the RHS to be an icmp.
|
|
/// FIXME: Add support for and/or/select on the RHS.
|
|
if (const Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
|
|
if ((LHSI->getOpcode() == Instruction::And ||
|
|
LHSI->getOpcode() == Instruction::Or ||
|
|
LHSI->getOpcode() == Instruction::Select))
|
|
return isImpliedCondAndOr(LHSI, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue,
|
|
Depth);
|
|
}
|
|
return None;
|
|
}
|
|
|
|
Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL, bool LHSIsTrue,
|
|
unsigned Depth) {
|
|
// LHS ==> RHS by definition
|
|
if (LHS == RHS)
|
|
return LHSIsTrue;
|
|
|
|
const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS);
|
|
if (RHSCmp)
|
|
return isImpliedCondition(LHS, RHSCmp->getPredicate(),
|
|
RHSCmp->getOperand(0), RHSCmp->getOperand(1), DL,
|
|
LHSIsTrue, Depth);
|
|
return None;
|
|
}
|
|
|
|
// Returns a pair (Condition, ConditionIsTrue), where Condition is a branch
|
|
// condition dominating ContextI or nullptr, if no condition is found.
|
|
static std::pair<Value *, bool>
|
|
getDomPredecessorCondition(const Instruction *ContextI) {
|
|
if (!ContextI || !ContextI->getParent())
|
|
return {nullptr, false};
|
|
|
|
// TODO: This is a poor/cheap way to determine dominance. Should we use a
|
|
// dominator tree (eg, from a SimplifyQuery) instead?
|
|
const BasicBlock *ContextBB = ContextI->getParent();
|
|
const BasicBlock *PredBB = ContextBB->getSinglePredecessor();
|
|
if (!PredBB)
|
|
return {nullptr, false};
|
|
|
|
// We need a conditional branch in the predecessor.
|
|
Value *PredCond;
|
|
BasicBlock *TrueBB, *FalseBB;
|
|
if (!match(PredBB->getTerminator(), m_Br(m_Value(PredCond), TrueBB, FalseBB)))
|
|
return {nullptr, false};
|
|
|
|
// The branch should get simplified. Don't bother simplifying this condition.
|
|
if (TrueBB == FalseBB)
|
|
return {nullptr, false};
|
|
|
|
assert((TrueBB == ContextBB || FalseBB == ContextBB) &&
|
|
"Predecessor block does not point to successor?");
|
|
|
|
// Is this condition implied by the predecessor condition?
|
|
return {PredCond, TrueBB == ContextBB};
|
|
}
|
|
|
|
Optional<bool> llvm::isImpliedByDomCondition(const Value *Cond,
|
|
const Instruction *ContextI,
|
|
const DataLayout &DL) {
|
|
assert(Cond->getType()->isIntOrIntVectorTy(1) && "Condition must be bool");
|
|
auto PredCond = getDomPredecessorCondition(ContextI);
|
|
if (PredCond.first)
|
|
return isImpliedCondition(PredCond.first, Cond, DL, PredCond.second);
|
|
return None;
|
|
}
|
|
|
|
Optional<bool> llvm::isImpliedByDomCondition(CmpInst::Predicate Pred,
|
|
const Value *LHS, const Value *RHS,
|
|
const Instruction *ContextI,
|
|
const DataLayout &DL) {
|
|
auto PredCond = getDomPredecessorCondition(ContextI);
|
|
if (PredCond.first)
|
|
return isImpliedCondition(PredCond.first, Pred, LHS, RHS, DL,
|
|
PredCond.second);
|
|
return None;
|
|
}
|
|
|
|
static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
|
|
APInt &Upper, const InstrInfoQuery &IIQ) {
|
|
unsigned Width = Lower.getBitWidth();
|
|
const APInt *C;
|
|
switch (BO.getOpcode()) {
|
|
case Instruction::Add:
|
|
if (match(BO.getOperand(1), m_APInt(C)) && !C->isNullValue()) {
|
|
// FIXME: If we have both nuw and nsw, we should reduce the range further.
|
|
if (IIQ.hasNoUnsignedWrap(cast<OverflowingBinaryOperator>(&BO))) {
|
|
// 'add nuw x, C' produces [C, UINT_MAX].
|
|
Lower = *C;
|
|
} else if (IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(&BO))) {
|
|
if (C->isNegative()) {
|
|
// 'add nsw x, -C' produces [SINT_MIN, SINT_MAX - C].
|
|
Lower = APInt::getSignedMinValue(Width);
|
|
Upper = APInt::getSignedMaxValue(Width) + *C + 1;
|
|
} else {
|
|
// 'add nsw x, +C' produces [SINT_MIN + C, SINT_MAX].
|
|
Lower = APInt::getSignedMinValue(Width) + *C;
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
|
|
case Instruction::And:
|
|
if (match(BO.getOperand(1), m_APInt(C)))
|
|
// 'and x, C' produces [0, C].
|
|
Upper = *C + 1;
|
|
break;
|
|
|
|
case Instruction::Or:
|
|
if (match(BO.getOperand(1), m_APInt(C)))
|
|
// 'or x, C' produces [C, UINT_MAX].
|
|
Lower = *C;
|
|
break;
|
|
|
|
case Instruction::AShr:
|
|
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
|
|
// 'ashr x, C' produces [INT_MIN >> C, INT_MAX >> C].
|
|
Lower = APInt::getSignedMinValue(Width).ashr(*C);
|
|
Upper = APInt::getSignedMaxValue(Width).ashr(*C) + 1;
|
|
} else if (match(BO.getOperand(0), m_APInt(C))) {
|
|
unsigned ShiftAmount = Width - 1;
|
|
if (!C->isNullValue() && IIQ.isExact(&BO))
|
|
ShiftAmount = C->countTrailingZeros();
|
|
if (C->isNegative()) {
|
|
// 'ashr C, x' produces [C, C >> (Width-1)]
|
|
Lower = *C;
|
|
Upper = C->ashr(ShiftAmount) + 1;
|
|
} else {
|
|
// 'ashr C, x' produces [C >> (Width-1), C]
|
|
Lower = C->ashr(ShiftAmount);
|
|
Upper = *C + 1;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case Instruction::LShr:
|
|
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
|
|
// 'lshr x, C' produces [0, UINT_MAX >> C].
|
|
Upper = APInt::getAllOnesValue(Width).lshr(*C) + 1;
|
|
} else if (match(BO.getOperand(0), m_APInt(C))) {
|
|
// 'lshr C, x' produces [C >> (Width-1), C].
|
|
unsigned ShiftAmount = Width - 1;
|
|
if (!C->isNullValue() && IIQ.isExact(&BO))
|
|
ShiftAmount = C->countTrailingZeros();
|
|
Lower = C->lshr(ShiftAmount);
|
|
Upper = *C + 1;
|
|
}
|
|
break;
|
|
|
|
case Instruction::Shl:
|
|
if (match(BO.getOperand(0), m_APInt(C))) {
|
|
if (IIQ.hasNoUnsignedWrap(&BO)) {
|
|
// 'shl nuw C, x' produces [C, C << CLZ(C)]
|
|
Lower = *C;
|
|
Upper = Lower.shl(Lower.countLeadingZeros()) + 1;
|
|
} else if (BO.hasNoSignedWrap()) { // TODO: What if both nuw+nsw?
|
|
if (C->isNegative()) {
|
|
// 'shl nsw C, x' produces [C << CLO(C)-1, C]
|
|
unsigned ShiftAmount = C->countLeadingOnes() - 1;
|
|
Lower = C->shl(ShiftAmount);
|
|
Upper = *C + 1;
|
|
} else {
|
|
// 'shl nsw C, x' produces [C, C << CLZ(C)-1]
|
|
unsigned ShiftAmount = C->countLeadingZeros() - 1;
|
|
Lower = *C;
|
|
Upper = C->shl(ShiftAmount) + 1;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
|
|
case Instruction::SDiv:
|
|
if (match(BO.getOperand(1), m_APInt(C))) {
|
|
APInt IntMin = APInt::getSignedMinValue(Width);
|
|
APInt IntMax = APInt::getSignedMaxValue(Width);
|
|
if (C->isAllOnesValue()) {
|
|
// 'sdiv x, -1' produces [INT_MIN + 1, INT_MAX]
|
|
// where C != -1 and C != 0 and C != 1
|
|
Lower = IntMin + 1;
|
|
Upper = IntMax + 1;
|
|
} else if (C->countLeadingZeros() < Width - 1) {
|
|
// 'sdiv x, C' produces [INT_MIN / C, INT_MAX / C]
|
|
// where C != -1 and C != 0 and C != 1
|
|
Lower = IntMin.sdiv(*C);
|
|
Upper = IntMax.sdiv(*C);
|
|
if (Lower.sgt(Upper))
|
|
std::swap(Lower, Upper);
|
|
Upper = Upper + 1;
|
|
assert(Upper != Lower && "Upper part of range has wrapped!");
|
|
}
|
|
} else if (match(BO.getOperand(0), m_APInt(C))) {
|
|
if (C->isMinSignedValue()) {
|
|
// 'sdiv INT_MIN, x' produces [INT_MIN, INT_MIN / -2].
|
|
Lower = *C;
|
|
Upper = Lower.lshr(1) + 1;
|
|
} else {
|
|
// 'sdiv C, x' produces [-|C|, |C|].
|
|
Upper = C->abs() + 1;
|
|
Lower = (-Upper) + 1;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case Instruction::UDiv:
|
|
if (match(BO.getOperand(1), m_APInt(C)) && !C->isNullValue()) {
|
|
// 'udiv x, C' produces [0, UINT_MAX / C].
|
|
Upper = APInt::getMaxValue(Width).udiv(*C) + 1;
|
|
} else if (match(BO.getOperand(0), m_APInt(C))) {
|
|
// 'udiv C, x' produces [0, C].
|
|
Upper = *C + 1;
|
|
}
|
|
break;
|
|
|
|
case Instruction::SRem:
|
|
if (match(BO.getOperand(1), m_APInt(C))) {
|
|
// 'srem x, C' produces (-|C|, |C|).
|
|
Upper = C->abs();
|
|
Lower = (-Upper) + 1;
|
|
}
|
|
break;
|
|
|
|
case Instruction::URem:
|
|
if (match(BO.getOperand(1), m_APInt(C)))
|
|
// 'urem x, C' produces [0, C).
|
|
Upper = *C;
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void setLimitsForIntrinsic(const IntrinsicInst &II, APInt &Lower,
|
|
APInt &Upper) {
|
|
unsigned Width = Lower.getBitWidth();
|
|
const APInt *C;
|
|
switch (II.getIntrinsicID()) {
|
|
case Intrinsic::ctpop:
|
|
case Intrinsic::ctlz:
|
|
case Intrinsic::cttz:
|
|
// Maximum of set/clear bits is the bit width.
|
|
assert(Lower == 0 && "Expected lower bound to be zero");
|
|
Upper = Width + 1;
|
|
break;
|
|
case Intrinsic::uadd_sat:
|
|
// uadd.sat(x, C) produces [C, UINT_MAX].
|
|
if (match(II.getOperand(0), m_APInt(C)) ||
|
|
match(II.getOperand(1), m_APInt(C)))
|
|
Lower = *C;
|
|
break;
|
|
case Intrinsic::sadd_sat:
|
|
if (match(II.getOperand(0), m_APInt(C)) ||
|
|
match(II.getOperand(1), m_APInt(C))) {
|
|
if (C->isNegative()) {
|
|
// sadd.sat(x, -C) produces [SINT_MIN, SINT_MAX + (-C)].
|
|
Lower = APInt::getSignedMinValue(Width);
|
|
Upper = APInt::getSignedMaxValue(Width) + *C + 1;
|
|
} else {
|
|
// sadd.sat(x, +C) produces [SINT_MIN + C, SINT_MAX].
|
|
Lower = APInt::getSignedMinValue(Width) + *C;
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
}
|
|
}
|
|
break;
|
|
case Intrinsic::usub_sat:
|
|
// usub.sat(C, x) produces [0, C].
|
|
if (match(II.getOperand(0), m_APInt(C)))
|
|
Upper = *C + 1;
|
|
// usub.sat(x, C) produces [0, UINT_MAX - C].
|
|
else if (match(II.getOperand(1), m_APInt(C)))
|
|
Upper = APInt::getMaxValue(Width) - *C + 1;
|
|
break;
|
|
case Intrinsic::ssub_sat:
|
|
if (match(II.getOperand(0), m_APInt(C))) {
|
|
if (C->isNegative()) {
|
|
// ssub.sat(-C, x) produces [SINT_MIN, -SINT_MIN + (-C)].
|
|
Lower = APInt::getSignedMinValue(Width);
|
|
Upper = *C - APInt::getSignedMinValue(Width) + 1;
|
|
} else {
|
|
// ssub.sat(+C, x) produces [-SINT_MAX + C, SINT_MAX].
|
|
Lower = *C - APInt::getSignedMaxValue(Width);
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
}
|
|
} else if (match(II.getOperand(1), m_APInt(C))) {
|
|
if (C->isNegative()) {
|
|
// ssub.sat(x, -C) produces [SINT_MIN - (-C), SINT_MAX]:
|
|
Lower = APInt::getSignedMinValue(Width) - *C;
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
} else {
|
|
// ssub.sat(x, +C) produces [SINT_MIN, SINT_MAX - C].
|
|
Lower = APInt::getSignedMinValue(Width);
|
|
Upper = APInt::getSignedMaxValue(Width) - *C + 1;
|
|
}
|
|
}
|
|
break;
|
|
case Intrinsic::umin:
|
|
case Intrinsic::umax:
|
|
case Intrinsic::smin:
|
|
case Intrinsic::smax:
|
|
if (!match(II.getOperand(0), m_APInt(C)) &&
|
|
!match(II.getOperand(1), m_APInt(C)))
|
|
break;
|
|
|
|
switch (II.getIntrinsicID()) {
|
|
case Intrinsic::umin:
|
|
Upper = *C + 1;
|
|
break;
|
|
case Intrinsic::umax:
|
|
Lower = *C;
|
|
break;
|
|
case Intrinsic::smin:
|
|
Lower = APInt::getSignedMinValue(Width);
|
|
Upper = *C + 1;
|
|
break;
|
|
case Intrinsic::smax:
|
|
Lower = *C;
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
break;
|
|
default:
|
|
llvm_unreachable("Must be min/max intrinsic");
|
|
}
|
|
break;
|
|
case Intrinsic::abs:
|
|
// If abs of SIGNED_MIN is poison, then the result is [0..SIGNED_MAX],
|
|
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
|
|
if (match(II.getOperand(1), m_One()))
|
|
Upper = APInt::getSignedMaxValue(Width) + 1;
|
|
else
|
|
Upper = APInt::getSignedMinValue(Width) + 1;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void setLimitsForSelectPattern(const SelectInst &SI, APInt &Lower,
|
|
APInt &Upper, const InstrInfoQuery &IIQ) {
|
|
const Value *LHS = nullptr, *RHS = nullptr;
|
|
SelectPatternResult R = matchSelectPattern(&SI, LHS, RHS);
|
|
if (R.Flavor == SPF_UNKNOWN)
|
|
return;
|
|
|
|
unsigned BitWidth = SI.getType()->getScalarSizeInBits();
|
|
|
|
if (R.Flavor == SelectPatternFlavor::SPF_ABS) {
|
|
// If the negation part of the abs (in RHS) has the NSW flag,
|
|
// then the result of abs(X) is [0..SIGNED_MAX],
|
|
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
|
|
Lower = APInt::getNullValue(BitWidth);
|
|
if (match(RHS, m_Neg(m_Specific(LHS))) &&
|
|
IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
|
|
Upper = APInt::getSignedMaxValue(BitWidth) + 1;
|
|
else
|
|
Upper = APInt::getSignedMinValue(BitWidth) + 1;
|
|
return;
|
|
}
|
|
|
|
if (R.Flavor == SelectPatternFlavor::SPF_NABS) {
|
|
// The result of -abs(X) is <= 0.
|
|
Lower = APInt::getSignedMinValue(BitWidth);
|
|
Upper = APInt(BitWidth, 1);
|
|
return;
|
|
}
|
|
|
|
const APInt *C;
|
|
if (!match(LHS, m_APInt(C)) && !match(RHS, m_APInt(C)))
|
|
return;
|
|
|
|
switch (R.Flavor) {
|
|
case SPF_UMIN:
|
|
Upper = *C + 1;
|
|
break;
|
|
case SPF_UMAX:
|
|
Lower = *C;
|
|
break;
|
|
case SPF_SMIN:
|
|
Lower = APInt::getSignedMinValue(BitWidth);
|
|
Upper = *C + 1;
|
|
break;
|
|
case SPF_SMAX:
|
|
Lower = *C;
|
|
Upper = APInt::getSignedMaxValue(BitWidth) + 1;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo,
|
|
AssumptionCache *AC,
|
|
const Instruction *CtxI,
|
|
unsigned Depth) {
|
|
assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction");
|
|
|
|
if (Depth == MaxAnalysisRecursionDepth)
|
|
return ConstantRange::getFull(V->getType()->getScalarSizeInBits());
|
|
|
|
const APInt *C;
|
|
if (match(V, m_APInt(C)))
|
|
return ConstantRange(*C);
|
|
|
|
InstrInfoQuery IIQ(UseInstrInfo);
|
|
unsigned BitWidth = V->getType()->getScalarSizeInBits();
|
|
APInt Lower = APInt(BitWidth, 0);
|
|
APInt Upper = APInt(BitWidth, 0);
|
|
if (auto *BO = dyn_cast<BinaryOperator>(V))
|
|
setLimitsForBinOp(*BO, Lower, Upper, IIQ);
|
|
else if (auto *II = dyn_cast<IntrinsicInst>(V))
|
|
setLimitsForIntrinsic(*II, Lower, Upper);
|
|
else if (auto *SI = dyn_cast<SelectInst>(V))
|
|
setLimitsForSelectPattern(*SI, Lower, Upper, IIQ);
|
|
|
|
ConstantRange CR = ConstantRange::getNonEmpty(Lower, Upper);
|
|
|
|
if (auto *I = dyn_cast<Instruction>(V))
|
|
if (auto *Range = IIQ.getMetadata(I, LLVMContext::MD_range))
|
|
CR = CR.intersectWith(getConstantRangeFromMetadata(*Range));
|
|
|
|
if (CtxI && AC) {
|
|
// Try to restrict the range based on information from assumptions.
|
|
for (auto &AssumeVH : AC->assumptionsFor(V)) {
|
|
if (!AssumeVH)
|
|
continue;
|
|
CallInst *I = cast<CallInst>(AssumeVH);
|
|
assert(I->getParent()->getParent() == CtxI->getParent()->getParent() &&
|
|
"Got assumption for the wrong function!");
|
|
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
|
|
"must be an assume intrinsic");
|
|
|
|
if (!isValidAssumeForContext(I, CtxI, nullptr))
|
|
continue;
|
|
Value *Arg = I->getArgOperand(0);
|
|
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
|
|
// Currently we just use information from comparisons.
|
|
if (!Cmp || Cmp->getOperand(0) != V)
|
|
continue;
|
|
ConstantRange RHS = computeConstantRange(Cmp->getOperand(1), UseInstrInfo,
|
|
AC, I, Depth + 1);
|
|
CR = CR.intersectWith(
|
|
ConstantRange::makeSatisfyingICmpRegion(Cmp->getPredicate(), RHS));
|
|
}
|
|
}
|
|
|
|
return CR;
|
|
}
|
|
|
|
static Optional<int64_t>
|
|
getOffsetFromIndex(const GEPOperator *GEP, unsigned Idx, const DataLayout &DL) {
|
|
// Skip over the first indices.
|
|
gep_type_iterator GTI = gep_type_begin(GEP);
|
|
for (unsigned i = 1; i != Idx; ++i, ++GTI)
|
|
/*skip along*/;
|
|
|
|
// Compute the offset implied by the rest of the indices.
|
|
int64_t Offset = 0;
|
|
for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
|
|
ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
|
|
if (!OpC)
|
|
return None;
|
|
if (OpC->isZero())
|
|
continue; // No offset.
|
|
|
|
// Handle struct indices, which add their field offset to the pointer.
|
|
if (StructType *STy = GTI.getStructTypeOrNull()) {
|
|
Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, we have a sequential type like an array or fixed-length
|
|
// vector. Multiply the index by the ElementSize.
|
|
TypeSize Size = DL.getTypeAllocSize(GTI.getIndexedType());
|
|
if (Size.isScalable())
|
|
return None;
|
|
Offset += Size.getFixedSize() * OpC->getSExtValue();
|
|
}
|
|
|
|
return Offset;
|
|
}
|
|
|
|
Optional<int64_t> llvm::isPointerOffset(const Value *Ptr1, const Value *Ptr2,
|
|
const DataLayout &DL) {
|
|
Ptr1 = Ptr1->stripPointerCasts();
|
|
Ptr2 = Ptr2->stripPointerCasts();
|
|
|
|
// Handle the trivial case first.
|
|
if (Ptr1 == Ptr2) {
|
|
return 0;
|
|
}
|
|
|
|
const GEPOperator *GEP1 = dyn_cast<GEPOperator>(Ptr1);
|
|
const GEPOperator *GEP2 = dyn_cast<GEPOperator>(Ptr2);
|
|
|
|
// If one pointer is a GEP see if the GEP is a constant offset from the base,
|
|
// as in "P" and "gep P, 1".
|
|
// Also do this iteratively to handle the the following case:
|
|
// Ptr_t1 = GEP Ptr1, c1
|
|
// Ptr_t2 = GEP Ptr_t1, c2
|
|
// Ptr2 = GEP Ptr_t2, c3
|
|
// where we will return c1+c2+c3.
|
|
// TODO: Handle the case when both Ptr1 and Ptr2 are GEPs of some common base
|
|
// -- replace getOffsetFromBase with getOffsetAndBase, check that the bases
|
|
// are the same, and return the difference between offsets.
|
|
auto getOffsetFromBase = [&DL](const GEPOperator *GEP,
|
|
const Value *Ptr) -> Optional<int64_t> {
|
|
const GEPOperator *GEP_T = GEP;
|
|
int64_t OffsetVal = 0;
|
|
bool HasSameBase = false;
|
|
while (GEP_T) {
|
|
auto Offset = getOffsetFromIndex(GEP_T, 1, DL);
|
|
if (!Offset)
|
|
return None;
|
|
OffsetVal += *Offset;
|
|
auto Op0 = GEP_T->getOperand(0)->stripPointerCasts();
|
|
if (Op0 == Ptr) {
|
|
HasSameBase = true;
|
|
break;
|
|
}
|
|
GEP_T = dyn_cast<GEPOperator>(Op0);
|
|
}
|
|
if (!HasSameBase)
|
|
return None;
|
|
return OffsetVal;
|
|
};
|
|
|
|
if (GEP1) {
|
|
auto Offset = getOffsetFromBase(GEP1, Ptr2);
|
|
if (Offset)
|
|
return -*Offset;
|
|
}
|
|
if (GEP2) {
|
|
auto Offset = getOffsetFromBase(GEP2, Ptr1);
|
|
if (Offset)
|
|
return Offset;
|
|
}
|
|
|
|
// Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
|
|
// base. After that base, they may have some number of common (and
|
|
// potentially variable) indices. After that they handle some constant
|
|
// offset, which determines their offset from each other. At this point, we
|
|
// handle no other case.
|
|
if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
|
|
return None;
|
|
|
|
// Skip any common indices and track the GEP types.
|
|
unsigned Idx = 1;
|
|
for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
|
|
if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx))
|
|
break;
|
|
|
|
auto Offset1 = getOffsetFromIndex(GEP1, Idx, DL);
|
|
auto Offset2 = getOffsetFromIndex(GEP2, Idx, DL);
|
|
if (!Offset1 || !Offset2)
|
|
return None;
|
|
return *Offset2 - *Offset1;
|
|
}
|