forked from OSchip/llvm-project
941 lines
32 KiB
C++
941 lines
32 KiB
C++
//===- CorrelatedValuePropagation.cpp - Propagate CFG-derived info --------===//
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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 implements the Correlated Value Propagation pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/DomTreeUpdater.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/LazyValueInfo.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/CFG.h"
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#include "llvm/IR/CallSite.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/Function.h"
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#include "llvm/IR/IRBuilder.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/Operator.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/Type.h"
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#include "llvm/IR/Value.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.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/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <cassert>
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#include <utility>
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using namespace llvm;
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#define DEBUG_TYPE "correlated-value-propagation"
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STATISTIC(NumPhis, "Number of phis propagated");
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STATISTIC(NumPhiCommon, "Number of phis deleted via common incoming value");
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STATISTIC(NumSelects, "Number of selects propagated");
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STATISTIC(NumMemAccess, "Number of memory access targets propagated");
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STATISTIC(NumCmps, "Number of comparisons propagated");
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STATISTIC(NumReturns, "Number of return values propagated");
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STATISTIC(NumDeadCases, "Number of switch cases removed");
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STATISTIC(NumSDivs, "Number of sdiv converted to udiv");
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STATISTIC(NumUDivs, "Number of udivs whose width was decreased");
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STATISTIC(NumAShrs, "Number of ashr converted to lshr");
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STATISTIC(NumSRems, "Number of srem converted to urem");
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STATISTIC(NumSExt, "Number of sext converted to zext");
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STATISTIC(NumAnd, "Number of ands removed");
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STATISTIC(NumNW, "Number of no-wrap deductions");
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STATISTIC(NumNSW, "Number of no-signed-wrap deductions");
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STATISTIC(NumNUW, "Number of no-unsigned-wrap deductions");
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STATISTIC(NumAddNW, "Number of no-wrap deductions for add");
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STATISTIC(NumAddNSW, "Number of no-signed-wrap deductions for add");
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STATISTIC(NumAddNUW, "Number of no-unsigned-wrap deductions for add");
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STATISTIC(NumSubNW, "Number of no-wrap deductions for sub");
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STATISTIC(NumSubNSW, "Number of no-signed-wrap deductions for sub");
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STATISTIC(NumSubNUW, "Number of no-unsigned-wrap deductions for sub");
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STATISTIC(NumMulNW, "Number of no-wrap deductions for mul");
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STATISTIC(NumMulNSW, "Number of no-signed-wrap deductions for mul");
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STATISTIC(NumMulNUW, "Number of no-unsigned-wrap deductions for mul");
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STATISTIC(NumShlNW, "Number of no-wrap deductions for shl");
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STATISTIC(NumShlNSW, "Number of no-signed-wrap deductions for shl");
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STATISTIC(NumShlNUW, "Number of no-unsigned-wrap deductions for shl");
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STATISTIC(NumOverflows, "Number of overflow checks removed");
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STATISTIC(NumSaturating,
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"Number of saturating arithmetics converted to normal arithmetics");
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static cl::opt<bool> DontAddNoWrapFlags("cvp-dont-add-nowrap-flags", cl::init(false));
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namespace {
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class CorrelatedValuePropagation : public FunctionPass {
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public:
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static char ID;
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CorrelatedValuePropagation(): FunctionPass(ID) {
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initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addRequired<DominatorTreeWrapperPass>();
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AU.addRequired<LazyValueInfoWrapperPass>();
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AU.addPreserved<GlobalsAAWrapperPass>();
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AU.addPreserved<DominatorTreeWrapperPass>();
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AU.addPreserved<LazyValueInfoWrapperPass>();
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}
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};
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} // end anonymous namespace
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char CorrelatedValuePropagation::ID = 0;
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INITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
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"Value Propagation", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
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INITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
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"Value Propagation", false, false)
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// Public interface to the Value Propagation pass
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Pass *llvm::createCorrelatedValuePropagationPass() {
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return new CorrelatedValuePropagation();
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}
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static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
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if (S->getType()->isVectorTy()) return false;
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if (isa<Constant>(S->getCondition())) return false;
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Constant *C = LVI->getConstant(S->getCondition(), S->getParent(), S);
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if (!C) return false;
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ConstantInt *CI = dyn_cast<ConstantInt>(C);
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if (!CI) return false;
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Value *ReplaceWith = CI->isOne() ? S->getTrueValue() : S->getFalseValue();
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S->replaceAllUsesWith(ReplaceWith);
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S->eraseFromParent();
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++NumSelects;
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return true;
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}
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/// Try to simplify a phi with constant incoming values that match the edge
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/// values of a non-constant value on all other edges:
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/// bb0:
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/// %isnull = icmp eq i8* %x, null
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/// br i1 %isnull, label %bb2, label %bb1
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/// bb1:
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/// br label %bb2
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/// bb2:
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/// %r = phi i8* [ %x, %bb1 ], [ null, %bb0 ]
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/// -->
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/// %r = %x
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static bool simplifyCommonValuePhi(PHINode *P, LazyValueInfo *LVI,
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DominatorTree *DT) {
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// Collect incoming constants and initialize possible common value.
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SmallVector<std::pair<Constant *, unsigned>, 4> IncomingConstants;
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Value *CommonValue = nullptr;
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for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
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Value *Incoming = P->getIncomingValue(i);
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if (auto *IncomingConstant = dyn_cast<Constant>(Incoming)) {
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IncomingConstants.push_back(std::make_pair(IncomingConstant, i));
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} else if (!CommonValue) {
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// The potential common value is initialized to the first non-constant.
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CommonValue = Incoming;
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} else if (Incoming != CommonValue) {
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// There can be only one non-constant common value.
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return false;
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}
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}
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if (!CommonValue || IncomingConstants.empty())
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return false;
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// The common value must be valid in all incoming blocks.
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BasicBlock *ToBB = P->getParent();
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if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
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if (!DT->dominates(CommonInst, ToBB))
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return false;
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// We have a phi with exactly 1 variable incoming value and 1 or more constant
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// incoming values. See if all constant incoming values can be mapped back to
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// the same incoming variable value.
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for (auto &IncomingConstant : IncomingConstants) {
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Constant *C = IncomingConstant.first;
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BasicBlock *IncomingBB = P->getIncomingBlock(IncomingConstant.second);
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if (C != LVI->getConstantOnEdge(CommonValue, IncomingBB, ToBB, P))
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return false;
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}
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// All constant incoming values map to the same variable along the incoming
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// edges of the phi. The phi is unnecessary. However, we must drop all
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// poison-generating flags to ensure that no poison is propagated to the phi
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// location by performing this substitution.
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// Warning: If the underlying analysis changes, this may not be enough to
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// guarantee that poison is not propagated.
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// TODO: We may be able to re-infer flags by re-analyzing the instruction.
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if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
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CommonInst->dropPoisonGeneratingFlags();
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P->replaceAllUsesWith(CommonValue);
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P->eraseFromParent();
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++NumPhiCommon;
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return true;
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}
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static bool processPHI(PHINode *P, LazyValueInfo *LVI, DominatorTree *DT,
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const SimplifyQuery &SQ) {
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bool Changed = false;
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BasicBlock *BB = P->getParent();
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for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
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Value *Incoming = P->getIncomingValue(i);
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if (isa<Constant>(Incoming)) continue;
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Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB, P);
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// Look if the incoming value is a select with a scalar condition for which
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// LVI can tells us the value. In that case replace the incoming value with
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// the appropriate value of the select. This often allows us to remove the
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// select later.
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if (!V) {
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SelectInst *SI = dyn_cast<SelectInst>(Incoming);
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if (!SI) continue;
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Value *Condition = SI->getCondition();
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if (!Condition->getType()->isVectorTy()) {
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if (Constant *C = LVI->getConstantOnEdge(
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Condition, P->getIncomingBlock(i), BB, P)) {
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if (C->isOneValue()) {
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V = SI->getTrueValue();
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} else if (C->isZeroValue()) {
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V = SI->getFalseValue();
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}
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// Once LVI learns to handle vector types, we could also add support
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// for vector type constants that are not all zeroes or all ones.
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}
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}
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// Look if the select has a constant but LVI tells us that the incoming
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// value can never be that constant. In that case replace the incoming
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// value with the other value of the select. This often allows us to
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// remove the select later.
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if (!V) {
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Constant *C = dyn_cast<Constant>(SI->getFalseValue());
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if (!C) continue;
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if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
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P->getIncomingBlock(i), BB, P) !=
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LazyValueInfo::False)
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continue;
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V = SI->getTrueValue();
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}
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LLVM_DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
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}
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P->setIncomingValue(i, V);
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Changed = true;
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}
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if (Value *V = SimplifyInstruction(P, SQ)) {
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P->replaceAllUsesWith(V);
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P->eraseFromParent();
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Changed = true;
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}
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if (!Changed)
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Changed = simplifyCommonValuePhi(P, LVI, DT);
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if (Changed)
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++NumPhis;
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return Changed;
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}
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static bool processMemAccess(Instruction *I, LazyValueInfo *LVI) {
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Value *Pointer = nullptr;
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if (LoadInst *L = dyn_cast<LoadInst>(I))
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Pointer = L->getPointerOperand();
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else
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Pointer = cast<StoreInst>(I)->getPointerOperand();
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if (isa<Constant>(Pointer)) return false;
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Constant *C = LVI->getConstant(Pointer, I->getParent(), I);
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if (!C) return false;
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++NumMemAccess;
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I->replaceUsesOfWith(Pointer, C);
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return true;
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}
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/// See if LazyValueInfo's ability to exploit edge conditions or range
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/// information is sufficient to prove this comparison. Even for local
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/// conditions, this can sometimes prove conditions instcombine can't by
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/// exploiting range information.
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static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
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Value *Op0 = Cmp->getOperand(0);
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auto *C = dyn_cast<Constant>(Cmp->getOperand(1));
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if (!C)
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return false;
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// As a policy choice, we choose not to waste compile time on anything where
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// the comparison is testing local values. While LVI can sometimes reason
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// about such cases, it's not its primary purpose. We do make sure to do
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// the block local query for uses from terminator instructions, but that's
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// handled in the code for each terminator. As an exception, we allow phi
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// nodes, for which LVI can thread the condition into predecessors.
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auto *I = dyn_cast<Instruction>(Op0);
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if (I && I->getParent() == Cmp->getParent() && !isa<PHINode>(I))
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return false;
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LazyValueInfo::Tristate Result =
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LVI->getPredicateAt(Cmp->getPredicate(), Op0, C, Cmp);
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if (Result == LazyValueInfo::Unknown)
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return false;
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++NumCmps;
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Constant *TorF = ConstantInt::get(Type::getInt1Ty(Cmp->getContext()), Result);
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Cmp->replaceAllUsesWith(TorF);
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Cmp->eraseFromParent();
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return true;
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}
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/// Simplify a switch instruction by removing cases which can never fire. If the
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/// uselessness of a case could be determined locally then constant propagation
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/// would already have figured it out. Instead, walk the predecessors and
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/// statically evaluate cases based on information available on that edge. Cases
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/// that cannot fire no matter what the incoming edge can safely be removed. If
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/// a case fires on every incoming edge then the entire switch can be removed
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/// and replaced with a branch to the case destination.
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static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
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DominatorTree *DT) {
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DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Lazy);
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Value *Cond = I->getCondition();
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BasicBlock *BB = I->getParent();
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// If the condition was defined in same block as the switch then LazyValueInfo
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// currently won't say anything useful about it, though in theory it could.
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if (isa<Instruction>(Cond) && cast<Instruction>(Cond)->getParent() == BB)
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return false;
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// If the switch is unreachable then trying to improve it is a waste of time.
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pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
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if (PB == PE) return false;
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// Analyse each switch case in turn.
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bool Changed = false;
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DenseMap<BasicBlock*, int> SuccessorsCount;
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for (auto *Succ : successors(BB))
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SuccessorsCount[Succ]++;
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{ // Scope for SwitchInstProfUpdateWrapper. It must not live during
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// ConstantFoldTerminator() as the underlying SwitchInst can be changed.
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SwitchInstProfUpdateWrapper SI(*I);
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for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
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ConstantInt *Case = CI->getCaseValue();
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// Check to see if the switch condition is equal to/not equal to the case
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// value on every incoming edge, equal/not equal being the same each time.
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LazyValueInfo::Tristate State = LazyValueInfo::Unknown;
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for (pred_iterator PI = PB; PI != PE; ++PI) {
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// Is the switch condition equal to the case value?
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LazyValueInfo::Tristate Value = LVI->getPredicateOnEdge(CmpInst::ICMP_EQ,
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Cond, Case, *PI,
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BB, SI);
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// Give up on this case if nothing is known.
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if (Value == LazyValueInfo::Unknown) {
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State = LazyValueInfo::Unknown;
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break;
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}
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// If this was the first edge to be visited, record that all other edges
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// need to give the same result.
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if (PI == PB) {
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State = Value;
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continue;
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}
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// If this case is known to fire for some edges and known not to fire for
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// others then there is nothing we can do - give up.
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if (Value != State) {
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State = LazyValueInfo::Unknown;
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break;
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}
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}
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if (State == LazyValueInfo::False) {
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// This case never fires - remove it.
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BasicBlock *Succ = CI->getCaseSuccessor();
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Succ->removePredecessor(BB);
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CI = SI.removeCase(CI);
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CE = SI->case_end();
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// The condition can be modified by removePredecessor's PHI simplification
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// logic.
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Cond = SI->getCondition();
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++NumDeadCases;
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Changed = true;
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if (--SuccessorsCount[Succ] == 0)
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DTU.applyUpdatesPermissive({{DominatorTree::Delete, BB, Succ}});
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continue;
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}
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if (State == LazyValueInfo::True) {
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// This case always fires. Arrange for the switch to be turned into an
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// unconditional branch by replacing the switch condition with the case
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// value.
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SI->setCondition(Case);
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NumDeadCases += SI->getNumCases();
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Changed = true;
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break;
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}
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// Increment the case iterator since we didn't delete it.
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++CI;
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}
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}
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if (Changed)
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// If the switch has been simplified to the point where it can be replaced
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// by a branch then do so now.
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ConstantFoldTerminator(BB, /*DeleteDeadConditions = */ false,
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/*TLI = */ nullptr, &DTU);
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return Changed;
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}
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// See if we can prove that the given binary op intrinsic will not overflow.
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static bool willNotOverflow(BinaryOpIntrinsic *BO, LazyValueInfo *LVI) {
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ConstantRange LRange = LVI->getConstantRange(
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BO->getLHS(), BO->getParent(), BO);
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ConstantRange RRange = LVI->getConstantRange(
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BO->getRHS(), BO->getParent(), BO);
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ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
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BO->getBinaryOp(), RRange, BO->getNoWrapKind());
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return NWRegion.contains(LRange);
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}
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static void setDeducedOverflowingFlags(Value *V, Instruction::BinaryOps Opcode,
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bool NewNSW, bool NewNUW) {
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Statistic *OpcNW, *OpcNSW, *OpcNUW;
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switch (Opcode) {
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case Instruction::Add:
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OpcNW = &NumAddNW;
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OpcNSW = &NumAddNSW;
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OpcNUW = &NumAddNUW;
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break;
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case Instruction::Sub:
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OpcNW = &NumSubNW;
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OpcNSW = &NumSubNSW;
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OpcNUW = &NumSubNUW;
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break;
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case Instruction::Mul:
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OpcNW = &NumMulNW;
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OpcNSW = &NumMulNSW;
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OpcNUW = &NumMulNUW;
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break;
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case Instruction::Shl:
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OpcNW = &NumShlNW;
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OpcNSW = &NumShlNSW;
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OpcNUW = &NumShlNUW;
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break;
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default:
|
|
llvm_unreachable("Will not be called with other binops");
|
|
}
|
|
|
|
auto *Inst = dyn_cast<Instruction>(V);
|
|
if (NewNSW) {
|
|
++NumNW;
|
|
++*OpcNW;
|
|
++NumNSW;
|
|
++*OpcNSW;
|
|
if (Inst)
|
|
Inst->setHasNoSignedWrap();
|
|
}
|
|
if (NewNUW) {
|
|
++NumNW;
|
|
++*OpcNW;
|
|
++NumNUW;
|
|
++*OpcNUW;
|
|
if (Inst)
|
|
Inst->setHasNoUnsignedWrap();
|
|
}
|
|
}
|
|
|
|
static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI);
|
|
|
|
// Rewrite this with.overflow intrinsic as non-overflowing.
|
|
static void processOverflowIntrinsic(WithOverflowInst *WO, LazyValueInfo *LVI) {
|
|
IRBuilder<> B(WO);
|
|
Instruction::BinaryOps Opcode = WO->getBinaryOp();
|
|
bool NSW = WO->isSigned();
|
|
bool NUW = !WO->isSigned();
|
|
|
|
Value *NewOp =
|
|
B.CreateBinOp(Opcode, WO->getLHS(), WO->getRHS(), WO->getName());
|
|
setDeducedOverflowingFlags(NewOp, Opcode, NSW, NUW);
|
|
|
|
StructType *ST = cast<StructType>(WO->getType());
|
|
Constant *Struct = ConstantStruct::get(ST,
|
|
{ UndefValue::get(ST->getElementType(0)),
|
|
ConstantInt::getFalse(ST->getElementType(1)) });
|
|
Value *NewI = B.CreateInsertValue(Struct, NewOp, 0);
|
|
WO->replaceAllUsesWith(NewI);
|
|
WO->eraseFromParent();
|
|
++NumOverflows;
|
|
|
|
// See if we can infer the other no-wrap too.
|
|
if (auto *BO = dyn_cast<BinaryOperator>(NewOp))
|
|
processBinOp(BO, LVI);
|
|
}
|
|
|
|
static void processSaturatingInst(SaturatingInst *SI, LazyValueInfo *LVI) {
|
|
Instruction::BinaryOps Opcode = SI->getBinaryOp();
|
|
bool NSW = SI->isSigned();
|
|
bool NUW = !SI->isSigned();
|
|
BinaryOperator *BinOp = BinaryOperator::Create(
|
|
Opcode, SI->getLHS(), SI->getRHS(), SI->getName(), SI);
|
|
BinOp->setDebugLoc(SI->getDebugLoc());
|
|
setDeducedOverflowingFlags(BinOp, Opcode, NSW, NUW);
|
|
|
|
SI->replaceAllUsesWith(BinOp);
|
|
SI->eraseFromParent();
|
|
++NumSaturating;
|
|
|
|
// See if we can infer the other no-wrap too.
|
|
if (auto *BO = dyn_cast<BinaryOperator>(BinOp))
|
|
processBinOp(BO, LVI);
|
|
}
|
|
|
|
/// Infer nonnull attributes for the arguments at the specified callsite.
|
|
static bool processCallSite(CallSite CS, LazyValueInfo *LVI) {
|
|
SmallVector<unsigned, 4> ArgNos;
|
|
unsigned ArgNo = 0;
|
|
|
|
if (auto *WO = dyn_cast<WithOverflowInst>(CS.getInstruction())) {
|
|
if (WO->getLHS()->getType()->isIntegerTy() && willNotOverflow(WO, LVI)) {
|
|
processOverflowIntrinsic(WO, LVI);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (auto *SI = dyn_cast<SaturatingInst>(CS.getInstruction())) {
|
|
if (SI->getType()->isIntegerTy() && willNotOverflow(SI, LVI)) {
|
|
processSaturatingInst(SI, LVI);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Deopt bundle operands are intended to capture state with minimal
|
|
// perturbance of the code otherwise. If we can find a constant value for
|
|
// any such operand and remove a use of the original value, that's
|
|
// desireable since it may allow further optimization of that value (e.g. via
|
|
// single use rules in instcombine). Since deopt uses tend to,
|
|
// idiomatically, appear along rare conditional paths, it's reasonable likely
|
|
// we may have a conditional fact with which LVI can fold.
|
|
if (auto DeoptBundle = CS.getOperandBundle(LLVMContext::OB_deopt)) {
|
|
bool Progress = false;
|
|
for (const Use &ConstU : DeoptBundle->Inputs) {
|
|
Use &U = const_cast<Use&>(ConstU);
|
|
Value *V = U.get();
|
|
if (V->getType()->isVectorTy()) continue;
|
|
if (isa<Constant>(V)) continue;
|
|
|
|
Constant *C = LVI->getConstant(V, CS.getParent(), CS.getInstruction());
|
|
if (!C) continue;
|
|
U.set(C);
|
|
Progress = true;
|
|
}
|
|
if (Progress)
|
|
return true;
|
|
}
|
|
|
|
for (Value *V : CS.args()) {
|
|
PointerType *Type = dyn_cast<PointerType>(V->getType());
|
|
// Try to mark pointer typed parameters as non-null. We skip the
|
|
// relatively expensive analysis for constants which are obviously either
|
|
// null or non-null to start with.
|
|
if (Type && !CS.paramHasAttr(ArgNo, Attribute::NonNull) &&
|
|
!isa<Constant>(V) &&
|
|
LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
|
|
ConstantPointerNull::get(Type),
|
|
CS.getInstruction()) == LazyValueInfo::False)
|
|
ArgNos.push_back(ArgNo);
|
|
ArgNo++;
|
|
}
|
|
|
|
assert(ArgNo == CS.arg_size() && "sanity check");
|
|
|
|
if (ArgNos.empty())
|
|
return false;
|
|
|
|
AttributeList AS = CS.getAttributes();
|
|
LLVMContext &Ctx = CS.getInstruction()->getContext();
|
|
AS = AS.addParamAttribute(Ctx, ArgNos,
|
|
Attribute::get(Ctx, Attribute::NonNull));
|
|
CS.setAttributes(AS);
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool hasPositiveOperands(BinaryOperator *SDI, LazyValueInfo *LVI) {
|
|
Constant *Zero = ConstantInt::get(SDI->getType(), 0);
|
|
for (Value *O : SDI->operands()) {
|
|
auto Result = LVI->getPredicateAt(ICmpInst::ICMP_SGE, O, Zero, SDI);
|
|
if (Result != LazyValueInfo::True)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Try to shrink a udiv/urem's width down to the smallest power of two that's
|
|
/// sufficient to contain its operands.
|
|
static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
|
|
assert(Instr->getOpcode() == Instruction::UDiv ||
|
|
Instr->getOpcode() == Instruction::URem);
|
|
if (Instr->getType()->isVectorTy())
|
|
return false;
|
|
|
|
// Find the smallest power of two bitwidth that's sufficient to hold Instr's
|
|
// operands.
|
|
auto OrigWidth = Instr->getType()->getIntegerBitWidth();
|
|
ConstantRange OperandRange(OrigWidth, /*isFullSet=*/false);
|
|
for (Value *Operand : Instr->operands()) {
|
|
OperandRange = OperandRange.unionWith(
|
|
LVI->getConstantRange(Operand, Instr->getParent()));
|
|
}
|
|
// Don't shrink below 8 bits wide.
|
|
unsigned NewWidth = std::max<unsigned>(
|
|
PowerOf2Ceil(OperandRange.getUnsignedMax().getActiveBits()), 8);
|
|
// NewWidth might be greater than OrigWidth if OrigWidth is not a power of
|
|
// two.
|
|
if (NewWidth >= OrigWidth)
|
|
return false;
|
|
|
|
++NumUDivs;
|
|
IRBuilder<> B{Instr};
|
|
auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
|
|
auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
|
|
Instr->getName() + ".lhs.trunc");
|
|
auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
|
|
Instr->getName() + ".rhs.trunc");
|
|
auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
|
|
auto *Zext = B.CreateZExt(BO, Instr->getType(), Instr->getName() + ".zext");
|
|
if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
|
|
if (BinOp->getOpcode() == Instruction::UDiv)
|
|
BinOp->setIsExact(Instr->isExact());
|
|
|
|
Instr->replaceAllUsesWith(Zext);
|
|
Instr->eraseFromParent();
|
|
return true;
|
|
}
|
|
|
|
static bool processSRem(BinaryOperator *SDI, LazyValueInfo *LVI) {
|
|
if (SDI->getType()->isVectorTy() || !hasPositiveOperands(SDI, LVI))
|
|
return false;
|
|
|
|
++NumSRems;
|
|
auto *BO = BinaryOperator::CreateURem(SDI->getOperand(0), SDI->getOperand(1),
|
|
SDI->getName(), SDI);
|
|
BO->setDebugLoc(SDI->getDebugLoc());
|
|
SDI->replaceAllUsesWith(BO);
|
|
SDI->eraseFromParent();
|
|
|
|
// Try to process our new urem.
|
|
processUDivOrURem(BO, LVI);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// See if LazyValueInfo's ability to exploit edge conditions or range
|
|
/// information is sufficient to prove the both operands of this SDiv are
|
|
/// positive. If this is the case, replace the SDiv with a UDiv. Even for local
|
|
/// conditions, this can sometimes prove conditions instcombine can't by
|
|
/// exploiting range information.
|
|
static bool processSDiv(BinaryOperator *SDI, LazyValueInfo *LVI) {
|
|
if (SDI->getType()->isVectorTy() || !hasPositiveOperands(SDI, LVI))
|
|
return false;
|
|
|
|
++NumSDivs;
|
|
auto *BO = BinaryOperator::CreateUDiv(SDI->getOperand(0), SDI->getOperand(1),
|
|
SDI->getName(), SDI);
|
|
BO->setDebugLoc(SDI->getDebugLoc());
|
|
BO->setIsExact(SDI->isExact());
|
|
SDI->replaceAllUsesWith(BO);
|
|
SDI->eraseFromParent();
|
|
|
|
// Try to simplify our new udiv.
|
|
processUDivOrURem(BO, LVI);
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
|
|
if (SDI->getType()->isVectorTy())
|
|
return false;
|
|
|
|
Constant *Zero = ConstantInt::get(SDI->getType(), 0);
|
|
if (LVI->getPredicateAt(ICmpInst::ICMP_SGE, SDI->getOperand(0), Zero, SDI) !=
|
|
LazyValueInfo::True)
|
|
return false;
|
|
|
|
++NumAShrs;
|
|
auto *BO = BinaryOperator::CreateLShr(SDI->getOperand(0), SDI->getOperand(1),
|
|
SDI->getName(), SDI);
|
|
BO->setDebugLoc(SDI->getDebugLoc());
|
|
BO->setIsExact(SDI->isExact());
|
|
SDI->replaceAllUsesWith(BO);
|
|
SDI->eraseFromParent();
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
|
|
if (SDI->getType()->isVectorTy())
|
|
return false;
|
|
|
|
Value *Base = SDI->getOperand(0);
|
|
|
|
Constant *Zero = ConstantInt::get(Base->getType(), 0);
|
|
if (LVI->getPredicateAt(ICmpInst::ICMP_SGE, Base, Zero, SDI) !=
|
|
LazyValueInfo::True)
|
|
return false;
|
|
|
|
++NumSExt;
|
|
auto *ZExt =
|
|
CastInst::CreateZExtOrBitCast(Base, SDI->getType(), SDI->getName(), SDI);
|
|
ZExt->setDebugLoc(SDI->getDebugLoc());
|
|
SDI->replaceAllUsesWith(ZExt);
|
|
SDI->eraseFromParent();
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
|
|
using OBO = OverflowingBinaryOperator;
|
|
|
|
if (DontAddNoWrapFlags)
|
|
return false;
|
|
|
|
if (BinOp->getType()->isVectorTy())
|
|
return false;
|
|
|
|
bool NSW = BinOp->hasNoSignedWrap();
|
|
bool NUW = BinOp->hasNoUnsignedWrap();
|
|
if (NSW && NUW)
|
|
return false;
|
|
|
|
BasicBlock *BB = BinOp->getParent();
|
|
|
|
Instruction::BinaryOps Opcode = BinOp->getOpcode();
|
|
Value *LHS = BinOp->getOperand(0);
|
|
Value *RHS = BinOp->getOperand(1);
|
|
|
|
ConstantRange LRange = LVI->getConstantRange(LHS, BB, BinOp);
|
|
ConstantRange RRange = LVI->getConstantRange(RHS, BB, BinOp);
|
|
|
|
bool Changed = false;
|
|
bool NewNUW = false, NewNSW = false;
|
|
if (!NUW) {
|
|
ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
|
|
Opcode, RRange, OBO::NoUnsignedWrap);
|
|
NewNUW = NUWRange.contains(LRange);
|
|
Changed |= NewNUW;
|
|
}
|
|
if (!NSW) {
|
|
ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
|
|
Opcode, RRange, OBO::NoSignedWrap);
|
|
NewNSW = NSWRange.contains(LRange);
|
|
Changed |= NewNSW;
|
|
}
|
|
|
|
setDeducedOverflowingFlags(BinOp, Opcode, NewNSW, NewNUW);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
|
|
if (BinOp->getType()->isVectorTy())
|
|
return false;
|
|
|
|
// Pattern match (and lhs, C) where C includes a superset of bits which might
|
|
// be set in lhs. This is a common truncation idiom created by instcombine.
|
|
BasicBlock *BB = BinOp->getParent();
|
|
Value *LHS = BinOp->getOperand(0);
|
|
ConstantInt *RHS = dyn_cast<ConstantInt>(BinOp->getOperand(1));
|
|
if (!RHS || !RHS->getValue().isMask())
|
|
return false;
|
|
|
|
// We can only replace the AND with LHS based on range info if the range does
|
|
// not include undef.
|
|
ConstantRange LRange =
|
|
LVI->getConstantRange(LHS, BB, BinOp, /*UndefAllowed=*/false);
|
|
if (!LRange.getUnsignedMax().ule(RHS->getValue()))
|
|
return false;
|
|
|
|
BinOp->replaceAllUsesWith(LHS);
|
|
BinOp->eraseFromParent();
|
|
NumAnd++;
|
|
return true;
|
|
}
|
|
|
|
|
|
static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
|
|
if (Constant *C = LVI->getConstant(V, At->getParent(), At))
|
|
return C;
|
|
|
|
// TODO: The following really should be sunk inside LVI's core algorithm, or
|
|
// at least the outer shims around such.
|
|
auto *C = dyn_cast<CmpInst>(V);
|
|
if (!C) return nullptr;
|
|
|
|
Value *Op0 = C->getOperand(0);
|
|
Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
|
|
if (!Op1) return nullptr;
|
|
|
|
LazyValueInfo::Tristate Result =
|
|
LVI->getPredicateAt(C->getPredicate(), Op0, Op1, At);
|
|
if (Result == LazyValueInfo::Unknown)
|
|
return nullptr;
|
|
|
|
return (Result == LazyValueInfo::True) ?
|
|
ConstantInt::getTrue(C->getContext()) :
|
|
ConstantInt::getFalse(C->getContext());
|
|
}
|
|
|
|
static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
|
|
const SimplifyQuery &SQ) {
|
|
bool FnChanged = false;
|
|
// Visiting in a pre-order depth-first traversal causes us to simplify early
|
|
// blocks before querying later blocks (which require us to analyze early
|
|
// blocks). Eagerly simplifying shallow blocks means there is strictly less
|
|
// work to do for deep blocks. This also means we don't visit unreachable
|
|
// blocks.
|
|
for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
|
|
bool BBChanged = false;
|
|
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
|
|
Instruction *II = &*BI++;
|
|
switch (II->getOpcode()) {
|
|
case Instruction::Select:
|
|
BBChanged |= processSelect(cast<SelectInst>(II), LVI);
|
|
break;
|
|
case Instruction::PHI:
|
|
BBChanged |= processPHI(cast<PHINode>(II), LVI, DT, SQ);
|
|
break;
|
|
case Instruction::ICmp:
|
|
case Instruction::FCmp:
|
|
BBChanged |= processCmp(cast<CmpInst>(II), LVI);
|
|
break;
|
|
case Instruction::Load:
|
|
case Instruction::Store:
|
|
BBChanged |= processMemAccess(II, LVI);
|
|
break;
|
|
case Instruction::Call:
|
|
case Instruction::Invoke:
|
|
BBChanged |= processCallSite(CallSite(II), LVI);
|
|
break;
|
|
case Instruction::SRem:
|
|
BBChanged |= processSRem(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
case Instruction::SDiv:
|
|
BBChanged |= processSDiv(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
case Instruction::UDiv:
|
|
case Instruction::URem:
|
|
BBChanged |= processUDivOrURem(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
case Instruction::AShr:
|
|
BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
case Instruction::SExt:
|
|
BBChanged |= processSExt(cast<SExtInst>(II), LVI);
|
|
break;
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::Mul:
|
|
case Instruction::Shl:
|
|
BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
case Instruction::And:
|
|
BBChanged |= processAnd(cast<BinaryOperator>(II), LVI);
|
|
break;
|
|
}
|
|
}
|
|
|
|
Instruction *Term = BB->getTerminator();
|
|
switch (Term->getOpcode()) {
|
|
case Instruction::Switch:
|
|
BBChanged |= processSwitch(cast<SwitchInst>(Term), LVI, DT);
|
|
break;
|
|
case Instruction::Ret: {
|
|
auto *RI = cast<ReturnInst>(Term);
|
|
// Try to determine the return value if we can. This is mainly here to
|
|
// simplify the writing of unit tests, but also helps to enable IPO by
|
|
// constant folding the return values of callees.
|
|
auto *RetVal = RI->getReturnValue();
|
|
if (!RetVal) break; // handle "ret void"
|
|
if (isa<Constant>(RetVal)) break; // nothing to do
|
|
if (auto *C = getConstantAt(RetVal, RI, LVI)) {
|
|
++NumReturns;
|
|
RI->replaceUsesOfWith(RetVal, C);
|
|
BBChanged = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
FnChanged |= BBChanged;
|
|
}
|
|
|
|
return FnChanged;
|
|
}
|
|
|
|
bool CorrelatedValuePropagation::runOnFunction(Function &F) {
|
|
if (skipFunction(F))
|
|
return false;
|
|
|
|
LazyValueInfo *LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
|
|
DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
|
|
return runImpl(F, LVI, DT, getBestSimplifyQuery(*this, F));
|
|
}
|
|
|
|
PreservedAnalyses
|
|
CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
|
|
LazyValueInfo *LVI = &AM.getResult<LazyValueAnalysis>(F);
|
|
DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
|
|
|
|
bool Changed = runImpl(F, LVI, DT, getBestSimplifyQuery(AM, F));
|
|
|
|
if (!Changed)
|
|
return PreservedAnalyses::all();
|
|
PreservedAnalyses PA;
|
|
PA.preserve<GlobalsAA>();
|
|
PA.preserve<DominatorTreeAnalysis>();
|
|
PA.preserve<LazyValueAnalysis>();
|
|
return PA;
|
|
}
|