forked from OSchip/llvm-project
6296 lines
246 KiB
C++
6296 lines
246 KiB
C++
//===- InstCombineCompares.cpp --------------------------------------------===//
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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 visitICmp and visitFCmp functions.
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//
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//===----------------------------------------------------------------------===//
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#include "InstCombineInternal.h"
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#include "llvm/ADT/APSInt.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/TargetLibraryInfo.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/KnownBits.h"
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#include "llvm/Transforms/InstCombine/InstCombiner.h"
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using namespace llvm;
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using namespace PatternMatch;
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#define DEBUG_TYPE "instcombine"
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// How many times is a select replaced by one of its operands?
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STATISTIC(NumSel, "Number of select opts");
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/// Compute Result = In1+In2, returning true if the result overflowed for this
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/// type.
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static bool addWithOverflow(APInt &Result, const APInt &In1,
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const APInt &In2, bool IsSigned = false) {
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bool Overflow;
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if (IsSigned)
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Result = In1.sadd_ov(In2, Overflow);
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else
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Result = In1.uadd_ov(In2, Overflow);
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return Overflow;
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}
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/// Compute Result = In1-In2, returning true if the result overflowed for this
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/// type.
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static bool subWithOverflow(APInt &Result, const APInt &In1,
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const APInt &In2, bool IsSigned = false) {
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bool Overflow;
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if (IsSigned)
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Result = In1.ssub_ov(In2, Overflow);
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else
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Result = In1.usub_ov(In2, Overflow);
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return Overflow;
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}
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/// Given an icmp instruction, return true if any use of this comparison is a
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/// branch on sign bit comparison.
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static bool hasBranchUse(ICmpInst &I) {
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for (auto *U : I.users())
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if (isa<BranchInst>(U))
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return true;
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return false;
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}
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/// Returns true if the exploded icmp can be expressed as a signed comparison
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/// to zero and updates the predicate accordingly.
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/// The signedness of the comparison is preserved.
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/// TODO: Refactor with decomposeBitTestICmp()?
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static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
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if (!ICmpInst::isSigned(Pred))
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return false;
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if (C.isNullValue())
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return ICmpInst::isRelational(Pred);
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if (C.isOneValue()) {
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if (Pred == ICmpInst::ICMP_SLT) {
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Pred = ICmpInst::ICMP_SLE;
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return true;
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}
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} else if (C.isAllOnesValue()) {
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if (Pred == ICmpInst::ICMP_SGT) {
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Pred = ICmpInst::ICMP_SGE;
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return true;
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}
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}
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return false;
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}
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/// This is called when we see this pattern:
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/// cmp pred (load (gep GV, ...)), cmpcst
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/// where GV is a global variable with a constant initializer. Try to simplify
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/// this into some simple computation that does not need the load. For example
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/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
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///
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/// If AndCst is non-null, then the loaded value is masked with that constant
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/// before doing the comparison. This handles cases like "A[i]&4 == 0".
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Instruction *
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InstCombinerImpl::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
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GlobalVariable *GV, CmpInst &ICI,
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ConstantInt *AndCst) {
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Constant *Init = GV->getInitializer();
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if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
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return nullptr;
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uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
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// Don't blow up on huge arrays.
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if (ArrayElementCount > MaxArraySizeForCombine)
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return nullptr;
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// There are many forms of this optimization we can handle, for now, just do
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// the simple index into a single-dimensional array.
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//
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// Require: GEP GV, 0, i {{, constant indices}}
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if (GEP->getNumOperands() < 3 ||
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!isa<ConstantInt>(GEP->getOperand(1)) ||
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!cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
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isa<Constant>(GEP->getOperand(2)))
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return nullptr;
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// Check that indices after the variable are constants and in-range for the
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// type they index. Collect the indices. This is typically for arrays of
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// structs.
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SmallVector<unsigned, 4> LaterIndices;
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Type *EltTy = Init->getType()->getArrayElementType();
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for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
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ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
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if (!Idx) return nullptr; // Variable index.
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uint64_t IdxVal = Idx->getZExtValue();
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if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
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if (StructType *STy = dyn_cast<StructType>(EltTy))
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EltTy = STy->getElementType(IdxVal);
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else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
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if (IdxVal >= ATy->getNumElements()) return nullptr;
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EltTy = ATy->getElementType();
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} else {
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return nullptr; // Unknown type.
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}
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LaterIndices.push_back(IdxVal);
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}
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enum { Overdefined = -3, Undefined = -2 };
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// Variables for our state machines.
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// FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
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// "i == 47 | i == 87", where 47 is the first index the condition is true for,
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// and 87 is the second (and last) index. FirstTrueElement is -2 when
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// undefined, otherwise set to the first true element. SecondTrueElement is
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// -2 when undefined, -3 when overdefined and >= 0 when that index is true.
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int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
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// FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
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// form "i != 47 & i != 87". Same state transitions as for true elements.
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int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
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/// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
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/// define a state machine that triggers for ranges of values that the index
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/// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
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/// This is -2 when undefined, -3 when overdefined, and otherwise the last
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/// index in the range (inclusive). We use -2 for undefined here because we
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/// use relative comparisons and don't want 0-1 to match -1.
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int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
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// MagicBitvector - This is a magic bitvector where we set a bit if the
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// comparison is true for element 'i'. If there are 64 elements or less in
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// the array, this will fully represent all the comparison results.
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uint64_t MagicBitvector = 0;
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// Scan the array and see if one of our patterns matches.
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Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
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for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
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Constant *Elt = Init->getAggregateElement(i);
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if (!Elt) return nullptr;
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// If this is indexing an array of structures, get the structure element.
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if (!LaterIndices.empty())
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Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
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// If the element is masked, handle it.
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if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
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// Find out if the comparison would be true or false for the i'th element.
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Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt,
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CompareRHS, DL, &TLI);
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// If the result is undef for this element, ignore it.
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if (isa<UndefValue>(C)) {
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// Extend range state machines to cover this element in case there is an
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// undef in the middle of the range.
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if (TrueRangeEnd == (int)i-1)
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TrueRangeEnd = i;
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if (FalseRangeEnd == (int)i-1)
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FalseRangeEnd = i;
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continue;
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}
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// If we can't compute the result for any of the elements, we have to give
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// up evaluating the entire conditional.
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if (!isa<ConstantInt>(C)) return nullptr;
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// Otherwise, we know if the comparison is true or false for this element,
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// update our state machines.
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bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
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// State machine for single/double/range index comparison.
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if (IsTrueForElt) {
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// Update the TrueElement state machine.
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if (FirstTrueElement == Undefined)
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FirstTrueElement = TrueRangeEnd = i; // First true element.
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else {
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// Update double-compare state machine.
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if (SecondTrueElement == Undefined)
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SecondTrueElement = i;
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else
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SecondTrueElement = Overdefined;
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// Update range state machine.
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if (TrueRangeEnd == (int)i-1)
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TrueRangeEnd = i;
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else
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TrueRangeEnd = Overdefined;
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}
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} else {
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// Update the FalseElement state machine.
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if (FirstFalseElement == Undefined)
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FirstFalseElement = FalseRangeEnd = i; // First false element.
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else {
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// Update double-compare state machine.
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if (SecondFalseElement == Undefined)
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SecondFalseElement = i;
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else
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SecondFalseElement = Overdefined;
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// Update range state machine.
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if (FalseRangeEnd == (int)i-1)
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FalseRangeEnd = i;
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else
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FalseRangeEnd = Overdefined;
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}
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}
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// If this element is in range, update our magic bitvector.
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if (i < 64 && IsTrueForElt)
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MagicBitvector |= 1ULL << i;
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// If all of our states become overdefined, bail out early. Since the
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// predicate is expensive, only check it every 8 elements. This is only
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// really useful for really huge arrays.
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if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
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SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
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FalseRangeEnd == Overdefined)
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return nullptr;
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}
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// Now that we've scanned the entire array, emit our new comparison(s). We
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// order the state machines in complexity of the generated code.
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Value *Idx = GEP->getOperand(2);
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// If the index is larger than the pointer size of the target, truncate the
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// index down like the GEP would do implicitly. We don't have to do this for
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// an inbounds GEP because the index can't be out of range.
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if (!GEP->isInBounds()) {
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Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
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unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
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if (Idx->getType()->getPrimitiveSizeInBits().getFixedSize() > PtrSize)
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Idx = Builder.CreateTrunc(Idx, IntPtrTy);
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}
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// If the comparison is only true for one or two elements, emit direct
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// comparisons.
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if (SecondTrueElement != Overdefined) {
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// None true -> false.
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if (FirstTrueElement == Undefined)
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return replaceInstUsesWith(ICI, Builder.getFalse());
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Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
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// True for one element -> 'i == 47'.
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if (SecondTrueElement == Undefined)
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return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
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// True for two elements -> 'i == 47 | i == 72'.
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Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
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Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
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Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
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return BinaryOperator::CreateOr(C1, C2);
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}
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// If the comparison is only false for one or two elements, emit direct
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// comparisons.
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if (SecondFalseElement != Overdefined) {
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// None false -> true.
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if (FirstFalseElement == Undefined)
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return replaceInstUsesWith(ICI, Builder.getTrue());
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Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
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// False for one element -> 'i != 47'.
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if (SecondFalseElement == Undefined)
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return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
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// False for two elements -> 'i != 47 & i != 72'.
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Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
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Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
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Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
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return BinaryOperator::CreateAnd(C1, C2);
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}
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// If the comparison can be replaced with a range comparison for the elements
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// where it is true, emit the range check.
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if (TrueRangeEnd != Overdefined) {
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assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
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// Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
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if (FirstTrueElement) {
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Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
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Idx = Builder.CreateAdd(Idx, Offs);
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}
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Value *End = ConstantInt::get(Idx->getType(),
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TrueRangeEnd-FirstTrueElement+1);
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return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
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}
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// False range check.
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if (FalseRangeEnd != Overdefined) {
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assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
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// Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
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if (FirstFalseElement) {
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Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
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Idx = Builder.CreateAdd(Idx, Offs);
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}
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Value *End = ConstantInt::get(Idx->getType(),
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FalseRangeEnd-FirstFalseElement);
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return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
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}
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// If a magic bitvector captures the entire comparison state
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// of this load, replace it with computation that does:
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// ((magic_cst >> i) & 1) != 0
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{
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Type *Ty = nullptr;
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// Look for an appropriate type:
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// - The type of Idx if the magic fits
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// - The smallest fitting legal type
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if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
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Ty = Idx->getType();
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else
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Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
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if (Ty) {
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Value *V = Builder.CreateIntCast(Idx, Ty, false);
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V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
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V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
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return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
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}
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}
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return nullptr;
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}
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/// Return a value that can be used to compare the *offset* implied by a GEP to
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/// zero. For example, if we have &A[i], we want to return 'i' for
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/// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
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/// are involved. The above expression would also be legal to codegen as
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/// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
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/// This latter form is less amenable to optimization though, and we are allowed
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/// to generate the first by knowing that pointer arithmetic doesn't overflow.
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///
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/// If we can't emit an optimized form for this expression, this returns null.
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///
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static Value *evaluateGEPOffsetExpression(User *GEP, InstCombinerImpl &IC,
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const DataLayout &DL) {
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gep_type_iterator GTI = gep_type_begin(GEP);
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// Check to see if this gep only has a single variable index. If so, and if
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// any constant indices are a multiple of its scale, then we can compute this
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// in terms of the scale of the variable index. For example, if the GEP
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// implies an offset of "12 + i*4", then we can codegen this as "3 + i",
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// because the expression will cross zero at the same point.
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unsigned i, e = GEP->getNumOperands();
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int64_t Offset = 0;
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for (i = 1; i != e; ++i, ++GTI) {
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if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
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// Compute the aggregate offset of constant indices.
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if (CI->isZero()) continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = GTI.getStructTypeOrNull()) {
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Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
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} else {
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uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
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Offset += Size*CI->getSExtValue();
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}
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} else {
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// Found our variable index.
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break;
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}
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}
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// If there are no variable indices, we must have a constant offset, just
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// evaluate it the general way.
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if (i == e) return nullptr;
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Value *VariableIdx = GEP->getOperand(i);
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// Determine the scale factor of the variable element. For example, this is
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// 4 if the variable index is into an array of i32.
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uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
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// Verify that there are no other variable indices. If so, emit the hard way.
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for (++i, ++GTI; i != e; ++i, ++GTI) {
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ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
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if (!CI) return nullptr;
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// Compute the aggregate offset of constant indices.
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if (CI->isZero()) continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = GTI.getStructTypeOrNull()) {
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Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
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} else {
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uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
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Offset += Size*CI->getSExtValue();
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}
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}
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// Okay, we know we have a single variable index, which must be a
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// pointer/array/vector index. If there is no offset, life is simple, return
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// the index.
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Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
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unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
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if (Offset == 0) {
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// Cast to intptrty in case a truncation occurs. If an extension is needed,
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// we don't need to bother extending: the extension won't affect where the
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// computation crosses zero.
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if (VariableIdx->getType()->getPrimitiveSizeInBits().getFixedSize() >
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IntPtrWidth) {
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VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
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}
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return VariableIdx;
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}
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// Otherwise, there is an index. The computation we will do will be modulo
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// the pointer size.
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Offset = SignExtend64(Offset, IntPtrWidth);
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VariableScale = SignExtend64(VariableScale, IntPtrWidth);
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// To do this transformation, any constant index must be a multiple of the
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// variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
|
|
// but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
|
|
// multiple of the variable scale.
|
|
int64_t NewOffs = Offset / (int64_t)VariableScale;
|
|
if (Offset != NewOffs*(int64_t)VariableScale)
|
|
return nullptr;
|
|
|
|
// Okay, we can do this evaluation. Start by converting the index to intptr.
|
|
if (VariableIdx->getType() != IntPtrTy)
|
|
VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
|
|
true /*Signed*/);
|
|
Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
|
|
return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
|
|
}
|
|
|
|
/// Returns true if we can rewrite Start as a GEP with pointer Base
|
|
/// and some integer offset. The nodes that need to be re-written
|
|
/// for this transformation will be added to Explored.
|
|
static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
|
|
const DataLayout &DL,
|
|
SetVector<Value *> &Explored) {
|
|
SmallVector<Value *, 16> WorkList(1, Start);
|
|
Explored.insert(Base);
|
|
|
|
// The following traversal gives us an order which can be used
|
|
// when doing the final transformation. Since in the final
|
|
// transformation we create the PHI replacement instructions first,
|
|
// we don't have to get them in any particular order.
|
|
//
|
|
// However, for other instructions we will have to traverse the
|
|
// operands of an instruction first, which means that we have to
|
|
// do a post-order traversal.
|
|
while (!WorkList.empty()) {
|
|
SetVector<PHINode *> PHIs;
|
|
|
|
while (!WorkList.empty()) {
|
|
if (Explored.size() >= 100)
|
|
return false;
|
|
|
|
Value *V = WorkList.back();
|
|
|
|
if (Explored.contains(V)) {
|
|
WorkList.pop_back();
|
|
continue;
|
|
}
|
|
|
|
if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
|
|
!isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
|
|
// We've found some value that we can't explore which is different from
|
|
// the base. Therefore we can't do this transformation.
|
|
return false;
|
|
|
|
if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
|
|
auto *CI = cast<CastInst>(V);
|
|
if (!CI->isNoopCast(DL))
|
|
return false;
|
|
|
|
if (Explored.count(CI->getOperand(0)) == 0)
|
|
WorkList.push_back(CI->getOperand(0));
|
|
}
|
|
|
|
if (auto *GEP = dyn_cast<GEPOperator>(V)) {
|
|
// We're limiting the GEP to having one index. This will preserve
|
|
// the original pointer type. We could handle more cases in the
|
|
// future.
|
|
if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
|
|
GEP->getType() != Start->getType())
|
|
return false;
|
|
|
|
if (Explored.count(GEP->getOperand(0)) == 0)
|
|
WorkList.push_back(GEP->getOperand(0));
|
|
}
|
|
|
|
if (WorkList.back() == V) {
|
|
WorkList.pop_back();
|
|
// We've finished visiting this node, mark it as such.
|
|
Explored.insert(V);
|
|
}
|
|
|
|
if (auto *PN = dyn_cast<PHINode>(V)) {
|
|
// We cannot transform PHIs on unsplittable basic blocks.
|
|
if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
|
|
return false;
|
|
Explored.insert(PN);
|
|
PHIs.insert(PN);
|
|
}
|
|
}
|
|
|
|
// Explore the PHI nodes further.
|
|
for (auto *PN : PHIs)
|
|
for (Value *Op : PN->incoming_values())
|
|
if (Explored.count(Op) == 0)
|
|
WorkList.push_back(Op);
|
|
}
|
|
|
|
// Make sure that we can do this. Since we can't insert GEPs in a basic
|
|
// block before a PHI node, we can't easily do this transformation if
|
|
// we have PHI node users of transformed instructions.
|
|
for (Value *Val : Explored) {
|
|
for (Value *Use : Val->uses()) {
|
|
|
|
auto *PHI = dyn_cast<PHINode>(Use);
|
|
auto *Inst = dyn_cast<Instruction>(Val);
|
|
|
|
if (Inst == Base || Inst == PHI || !Inst || !PHI ||
|
|
Explored.count(PHI) == 0)
|
|
continue;
|
|
|
|
if (PHI->getParent() == Inst->getParent())
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// Sets the appropriate insert point on Builder where we can add
|
|
// a replacement Instruction for V (if that is possible).
|
|
static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
|
|
bool Before = true) {
|
|
if (auto *PHI = dyn_cast<PHINode>(V)) {
|
|
Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
|
|
return;
|
|
}
|
|
if (auto *I = dyn_cast<Instruction>(V)) {
|
|
if (!Before)
|
|
I = &*std::next(I->getIterator());
|
|
Builder.SetInsertPoint(I);
|
|
return;
|
|
}
|
|
if (auto *A = dyn_cast<Argument>(V)) {
|
|
// Set the insertion point in the entry block.
|
|
BasicBlock &Entry = A->getParent()->getEntryBlock();
|
|
Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
|
|
return;
|
|
}
|
|
// Otherwise, this is a constant and we don't need to set a new
|
|
// insertion point.
|
|
assert(isa<Constant>(V) && "Setting insertion point for unknown value!");
|
|
}
|
|
|
|
/// Returns a re-written value of Start as an indexed GEP using Base as a
|
|
/// pointer.
|
|
static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
|
|
const DataLayout &DL,
|
|
SetVector<Value *> &Explored) {
|
|
// Perform all the substitutions. This is a bit tricky because we can
|
|
// have cycles in our use-def chains.
|
|
// 1. Create the PHI nodes without any incoming values.
|
|
// 2. Create all the other values.
|
|
// 3. Add the edges for the PHI nodes.
|
|
// 4. Emit GEPs to get the original pointers.
|
|
// 5. Remove the original instructions.
|
|
Type *IndexType = IntegerType::get(
|
|
Base->getContext(), DL.getIndexTypeSizeInBits(Start->getType()));
|
|
|
|
DenseMap<Value *, Value *> NewInsts;
|
|
NewInsts[Base] = ConstantInt::getNullValue(IndexType);
|
|
|
|
// Create the new PHI nodes, without adding any incoming values.
|
|
for (Value *Val : Explored) {
|
|
if (Val == Base)
|
|
continue;
|
|
// Create empty phi nodes. This avoids cyclic dependencies when creating
|
|
// the remaining instructions.
|
|
if (auto *PHI = dyn_cast<PHINode>(Val))
|
|
NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
|
|
PHI->getName() + ".idx", PHI);
|
|
}
|
|
IRBuilder<> Builder(Base->getContext());
|
|
|
|
// Create all the other instructions.
|
|
for (Value *Val : Explored) {
|
|
|
|
if (NewInsts.find(Val) != NewInsts.end())
|
|
continue;
|
|
|
|
if (auto *CI = dyn_cast<CastInst>(Val)) {
|
|
// Don't get rid of the intermediate variable here; the store can grow
|
|
// the map which will invalidate the reference to the input value.
|
|
Value *V = NewInsts[CI->getOperand(0)];
|
|
NewInsts[CI] = V;
|
|
continue;
|
|
}
|
|
if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
|
|
Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
|
|
: GEP->getOperand(1);
|
|
setInsertionPoint(Builder, GEP);
|
|
// Indices might need to be sign extended. GEPs will magically do
|
|
// this, but we need to do it ourselves here.
|
|
if (Index->getType()->getScalarSizeInBits() !=
|
|
NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
|
|
Index = Builder.CreateSExtOrTrunc(
|
|
Index, NewInsts[GEP->getOperand(0)]->getType(),
|
|
GEP->getOperand(0)->getName() + ".sext");
|
|
}
|
|
|
|
auto *Op = NewInsts[GEP->getOperand(0)];
|
|
if (isa<ConstantInt>(Op) && cast<ConstantInt>(Op)->isZero())
|
|
NewInsts[GEP] = Index;
|
|
else
|
|
NewInsts[GEP] = Builder.CreateNSWAdd(
|
|
Op, Index, GEP->getOperand(0)->getName() + ".add");
|
|
continue;
|
|
}
|
|
if (isa<PHINode>(Val))
|
|
continue;
|
|
|
|
llvm_unreachable("Unexpected instruction type");
|
|
}
|
|
|
|
// Add the incoming values to the PHI nodes.
|
|
for (Value *Val : Explored) {
|
|
if (Val == Base)
|
|
continue;
|
|
// All the instructions have been created, we can now add edges to the
|
|
// phi nodes.
|
|
if (auto *PHI = dyn_cast<PHINode>(Val)) {
|
|
PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
|
|
for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
|
|
Value *NewIncoming = PHI->getIncomingValue(I);
|
|
|
|
if (NewInsts.find(NewIncoming) != NewInsts.end())
|
|
NewIncoming = NewInsts[NewIncoming];
|
|
|
|
NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
|
|
}
|
|
}
|
|
}
|
|
|
|
for (Value *Val : Explored) {
|
|
if (Val == Base)
|
|
continue;
|
|
|
|
// Depending on the type, for external users we have to emit
|
|
// a GEP or a GEP + ptrtoint.
|
|
setInsertionPoint(Builder, Val, false);
|
|
|
|
// If required, create an inttoptr instruction for Base.
|
|
Value *NewBase = Base;
|
|
if (!Base->getType()->isPointerTy())
|
|
NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
|
|
Start->getName() + "to.ptr");
|
|
|
|
Value *GEP = Builder.CreateInBoundsGEP(
|
|
Start->getType()->getPointerElementType(), NewBase,
|
|
makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
|
|
|
|
if (!Val->getType()->isPointerTy()) {
|
|
Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
|
|
Val->getName() + ".conv");
|
|
GEP = Cast;
|
|
}
|
|
Val->replaceAllUsesWith(GEP);
|
|
}
|
|
|
|
return NewInsts[Start];
|
|
}
|
|
|
|
/// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
|
|
/// the input Value as a constant indexed GEP. Returns a pair containing
|
|
/// the GEPs Pointer and Index.
|
|
static std::pair<Value *, Value *>
|
|
getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
|
|
Type *IndexType = IntegerType::get(V->getContext(),
|
|
DL.getIndexTypeSizeInBits(V->getType()));
|
|
|
|
Constant *Index = ConstantInt::getNullValue(IndexType);
|
|
while (true) {
|
|
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
|
|
// We accept only inbouds GEPs here to exclude the possibility of
|
|
// overflow.
|
|
if (!GEP->isInBounds())
|
|
break;
|
|
if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
|
|
GEP->getType() == V->getType()) {
|
|
V = GEP->getOperand(0);
|
|
Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
|
|
Index = ConstantExpr::getAdd(
|
|
Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
|
|
if (!CI->isNoopCast(DL))
|
|
break;
|
|
V = CI->getOperand(0);
|
|
continue;
|
|
}
|
|
if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
|
|
if (!CI->isNoopCast(DL))
|
|
break;
|
|
V = CI->getOperand(0);
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
return {V, Index};
|
|
}
|
|
|
|
/// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
|
|
/// We can look through PHIs, GEPs and casts in order to determine a common base
|
|
/// between GEPLHS and RHS.
|
|
static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
|
|
ICmpInst::Predicate Cond,
|
|
const DataLayout &DL) {
|
|
// FIXME: Support vector of pointers.
|
|
if (GEPLHS->getType()->isVectorTy())
|
|
return nullptr;
|
|
|
|
if (!GEPLHS->hasAllConstantIndices())
|
|
return nullptr;
|
|
|
|
// Make sure the pointers have the same type.
|
|
if (GEPLHS->getType() != RHS->getType())
|
|
return nullptr;
|
|
|
|
Value *PtrBase, *Index;
|
|
std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
|
|
|
|
// The set of nodes that will take part in this transformation.
|
|
SetVector<Value *> Nodes;
|
|
|
|
if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
|
|
return nullptr;
|
|
|
|
// We know we can re-write this as
|
|
// ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
|
|
// Since we've only looked through inbouds GEPs we know that we
|
|
// can't have overflow on either side. We can therefore re-write
|
|
// this as:
|
|
// OFFSET1 cmp OFFSET2
|
|
Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
|
|
|
|
// RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
|
|
// GEP having PtrBase as the pointer base, and has returned in NewRHS the
|
|
// offset. Since Index is the offset of LHS to the base pointer, we will now
|
|
// compare the offsets instead of comparing the pointers.
|
|
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
|
|
}
|
|
|
|
/// Fold comparisons between a GEP instruction and something else. At this point
|
|
/// we know that the GEP is on the LHS of the comparison.
|
|
Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
|
|
ICmpInst::Predicate Cond,
|
|
Instruction &I) {
|
|
// Don't transform signed compares of GEPs into index compares. Even if the
|
|
// GEP is inbounds, the final add of the base pointer can have signed overflow
|
|
// and would change the result of the icmp.
|
|
// e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
|
|
// the maximum signed value for the pointer type.
|
|
if (ICmpInst::isSigned(Cond))
|
|
return nullptr;
|
|
|
|
// Look through bitcasts and addrspacecasts. We do not however want to remove
|
|
// 0 GEPs.
|
|
if (!isa<GetElementPtrInst>(RHS))
|
|
RHS = RHS->stripPointerCasts();
|
|
|
|
Value *PtrBase = GEPLHS->getOperand(0);
|
|
// FIXME: Support vector pointer GEPs.
|
|
if (PtrBase == RHS && GEPLHS->isInBounds() &&
|
|
!GEPLHS->getType()->isVectorTy()) {
|
|
// ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
|
|
// This transformation (ignoring the base and scales) is valid because we
|
|
// know pointers can't overflow since the gep is inbounds. See if we can
|
|
// output an optimized form.
|
|
Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
|
|
|
|
// If not, synthesize the offset the hard way.
|
|
if (!Offset)
|
|
Offset = EmitGEPOffset(GEPLHS);
|
|
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
|
|
Constant::getNullValue(Offset->getType()));
|
|
}
|
|
|
|
if (GEPLHS->isInBounds() && ICmpInst::isEquality(Cond) &&
|
|
isa<Constant>(RHS) && cast<Constant>(RHS)->isNullValue() &&
|
|
!NullPointerIsDefined(I.getFunction(),
|
|
RHS->getType()->getPointerAddressSpace())) {
|
|
// For most address spaces, an allocation can't be placed at null, but null
|
|
// itself is treated as a 0 size allocation in the in bounds rules. Thus,
|
|
// the only valid inbounds address derived from null, is null itself.
|
|
// Thus, we have four cases to consider:
|
|
// 1) Base == nullptr, Offset == 0 -> inbounds, null
|
|
// 2) Base == nullptr, Offset != 0 -> poison as the result is out of bounds
|
|
// 3) Base != nullptr, Offset == (-base) -> poison (crossing allocations)
|
|
// 4) Base != nullptr, Offset != (-base) -> nonnull (and possibly poison)
|
|
//
|
|
// (Note if we're indexing a type of size 0, that simply collapses into one
|
|
// of the buckets above.)
|
|
//
|
|
// In general, we're allowed to make values less poison (i.e. remove
|
|
// sources of full UB), so in this case, we just select between the two
|
|
// non-poison cases (1 and 4 above).
|
|
//
|
|
// For vectors, we apply the same reasoning on a per-lane basis.
|
|
auto *Base = GEPLHS->getPointerOperand();
|
|
if (GEPLHS->getType()->isVectorTy() && Base->getType()->isPointerTy()) {
|
|
auto EC = cast<VectorType>(GEPLHS->getType())->getElementCount();
|
|
Base = Builder.CreateVectorSplat(EC, Base);
|
|
}
|
|
return new ICmpInst(Cond, Base,
|
|
ConstantExpr::getPointerBitCastOrAddrSpaceCast(
|
|
cast<Constant>(RHS), Base->getType()));
|
|
} else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
|
|
// If the base pointers are different, but the indices are the same, just
|
|
// compare the base pointer.
|
|
if (PtrBase != GEPRHS->getOperand(0)) {
|
|
bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
|
|
IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
|
|
GEPRHS->getOperand(0)->getType();
|
|
if (IndicesTheSame)
|
|
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
|
|
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
|
|
IndicesTheSame = false;
|
|
break;
|
|
}
|
|
|
|
// If all indices are the same, just compare the base pointers.
|
|
Type *BaseType = GEPLHS->getOperand(0)->getType();
|
|
if (IndicesTheSame && CmpInst::makeCmpResultType(BaseType) == I.getType())
|
|
return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
|
|
|
|
// If we're comparing GEPs with two base pointers that only differ in type
|
|
// and both GEPs have only constant indices or just one use, then fold
|
|
// the compare with the adjusted indices.
|
|
// FIXME: Support vector of pointers.
|
|
if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
|
|
(GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
|
|
(GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
|
|
PtrBase->stripPointerCasts() ==
|
|
GEPRHS->getOperand(0)->stripPointerCasts() &&
|
|
!GEPLHS->getType()->isVectorTy()) {
|
|
Value *LOffset = EmitGEPOffset(GEPLHS);
|
|
Value *ROffset = EmitGEPOffset(GEPRHS);
|
|
|
|
// If we looked through an addrspacecast between different sized address
|
|
// spaces, the LHS and RHS pointers are different sized
|
|
// integers. Truncate to the smaller one.
|
|
Type *LHSIndexTy = LOffset->getType();
|
|
Type *RHSIndexTy = ROffset->getType();
|
|
if (LHSIndexTy != RHSIndexTy) {
|
|
if (LHSIndexTy->getPrimitiveSizeInBits().getFixedSize() <
|
|
RHSIndexTy->getPrimitiveSizeInBits().getFixedSize()) {
|
|
ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
|
|
} else
|
|
LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
|
|
}
|
|
|
|
Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
|
|
LOffset, ROffset);
|
|
return replaceInstUsesWith(I, Cmp);
|
|
}
|
|
|
|
// Otherwise, the base pointers are different and the indices are
|
|
// different. Try convert this to an indexed compare by looking through
|
|
// PHIs/casts.
|
|
return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
|
|
}
|
|
|
|
// If one of the GEPs has all zero indices, recurse.
|
|
// FIXME: Handle vector of pointers.
|
|
if (!GEPLHS->getType()->isVectorTy() && GEPLHS->hasAllZeroIndices())
|
|
return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
|
|
ICmpInst::getSwappedPredicate(Cond), I);
|
|
|
|
// If the other GEP has all zero indices, recurse.
|
|
// FIXME: Handle vector of pointers.
|
|
if (!GEPRHS->getType()->isVectorTy() && GEPRHS->hasAllZeroIndices())
|
|
return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
|
|
|
|
bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
|
|
if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
|
|
// If the GEPs only differ by one index, compare it.
|
|
unsigned NumDifferences = 0; // Keep track of # differences.
|
|
unsigned DiffOperand = 0; // The operand that differs.
|
|
for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
|
|
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
|
|
Type *LHSType = GEPLHS->getOperand(i)->getType();
|
|
Type *RHSType = GEPRHS->getOperand(i)->getType();
|
|
// FIXME: Better support for vector of pointers.
|
|
if (LHSType->getPrimitiveSizeInBits() !=
|
|
RHSType->getPrimitiveSizeInBits() ||
|
|
(GEPLHS->getType()->isVectorTy() &&
|
|
(!LHSType->isVectorTy() || !RHSType->isVectorTy()))) {
|
|
// Irreconcilable differences.
|
|
NumDifferences = 2;
|
|
break;
|
|
}
|
|
|
|
if (NumDifferences++) break;
|
|
DiffOperand = i;
|
|
}
|
|
|
|
if (NumDifferences == 0) // SAME GEP?
|
|
return replaceInstUsesWith(I, // No comparison is needed here.
|
|
ConstantInt::get(I.getType(), ICmpInst::isTrueWhenEqual(Cond)));
|
|
|
|
else if (NumDifferences == 1 && GEPsInBounds) {
|
|
Value *LHSV = GEPLHS->getOperand(DiffOperand);
|
|
Value *RHSV = GEPRHS->getOperand(DiffOperand);
|
|
// Make sure we do a signed comparison here.
|
|
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
|
|
}
|
|
}
|
|
|
|
// Only lower this if the icmp is the only user of the GEP or if we expect
|
|
// the result to fold to a constant!
|
|
if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
|
|
(isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
|
|
// ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
|
|
Value *L = EmitGEPOffset(GEPLHS);
|
|
Value *R = EmitGEPOffset(GEPRHS);
|
|
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
|
|
}
|
|
}
|
|
|
|
// Try convert this to an indexed compare by looking through PHIs/casts as a
|
|
// last resort.
|
|
return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::foldAllocaCmp(ICmpInst &ICI,
|
|
const AllocaInst *Alloca,
|
|
const Value *Other) {
|
|
assert(ICI.isEquality() && "Cannot fold non-equality comparison.");
|
|
|
|
// It would be tempting to fold away comparisons between allocas and any
|
|
// pointer not based on that alloca (e.g. an argument). However, even
|
|
// though such pointers cannot alias, they can still compare equal.
|
|
//
|
|
// But LLVM doesn't specify where allocas get their memory, so if the alloca
|
|
// doesn't escape we can argue that it's impossible to guess its value, and we
|
|
// can therefore act as if any such guesses are wrong.
|
|
//
|
|
// The code below checks that the alloca doesn't escape, and that it's only
|
|
// used in a comparison once (the current instruction). The
|
|
// single-comparison-use condition ensures that we're trivially folding all
|
|
// comparisons against the alloca consistently, and avoids the risk of
|
|
// erroneously folding a comparison of the pointer with itself.
|
|
|
|
unsigned MaxIter = 32; // Break cycles and bound to constant-time.
|
|
|
|
SmallVector<const Use *, 32> Worklist;
|
|
for (const Use &U : Alloca->uses()) {
|
|
if (Worklist.size() >= MaxIter)
|
|
return nullptr;
|
|
Worklist.push_back(&U);
|
|
}
|
|
|
|
unsigned NumCmps = 0;
|
|
while (!Worklist.empty()) {
|
|
assert(Worklist.size() <= MaxIter);
|
|
const Use *U = Worklist.pop_back_val();
|
|
const Value *V = U->getUser();
|
|
--MaxIter;
|
|
|
|
if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
|
|
isa<SelectInst>(V)) {
|
|
// Track the uses.
|
|
} else if (isa<LoadInst>(V)) {
|
|
// Loading from the pointer doesn't escape it.
|
|
continue;
|
|
} else if (const auto *SI = dyn_cast<StoreInst>(V)) {
|
|
// Storing *to* the pointer is fine, but storing the pointer escapes it.
|
|
if (SI->getValueOperand() == U->get())
|
|
return nullptr;
|
|
continue;
|
|
} else if (isa<ICmpInst>(V)) {
|
|
if (NumCmps++)
|
|
return nullptr; // Found more than one cmp.
|
|
continue;
|
|
} else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
|
|
switch (Intrin->getIntrinsicID()) {
|
|
// These intrinsics don't escape or compare the pointer. Memset is safe
|
|
// because we don't allow ptrtoint. Memcpy and memmove are safe because
|
|
// we don't allow stores, so src cannot point to V.
|
|
case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
|
|
case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
|
|
continue;
|
|
default:
|
|
return nullptr;
|
|
}
|
|
} else {
|
|
return nullptr;
|
|
}
|
|
for (const Use &U : V->uses()) {
|
|
if (Worklist.size() >= MaxIter)
|
|
return nullptr;
|
|
Worklist.push_back(&U);
|
|
}
|
|
}
|
|
|
|
Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
|
|
return replaceInstUsesWith(
|
|
ICI,
|
|
ConstantInt::get(CmpTy, !CmpInst::isTrueWhenEqual(ICI.getPredicate())));
|
|
}
|
|
|
|
/// Fold "icmp pred (X+C), X".
|
|
Instruction *InstCombinerImpl::foldICmpAddOpConst(Value *X, const APInt &C,
|
|
ICmpInst::Predicate Pred) {
|
|
// From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
|
|
// so the values can never be equal. Similarly for all other "or equals"
|
|
// operators.
|
|
assert(!!C && "C should not be zero!");
|
|
|
|
// (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
|
|
// (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
|
|
// (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
|
|
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
|
|
Constant *R = ConstantInt::get(X->getType(),
|
|
APInt::getMaxValue(C.getBitWidth()) - C);
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
|
|
}
|
|
|
|
// (X+1) >u X --> X <u (0-1) --> X != 255
|
|
// (X+2) >u X --> X <u (0-2) --> X <u 254
|
|
// (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
|
|
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
|
|
return new ICmpInst(ICmpInst::ICMP_ULT, X,
|
|
ConstantInt::get(X->getType(), -C));
|
|
|
|
APInt SMax = APInt::getSignedMaxValue(C.getBitWidth());
|
|
|
|
// (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
|
|
// (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
|
|
// (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
|
|
// (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
|
|
// (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
|
|
// (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
|
|
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, X,
|
|
ConstantInt::get(X->getType(), SMax - C));
|
|
|
|
// (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
|
|
// (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
|
|
// (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
|
|
// (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
|
|
// (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
|
|
// (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
|
|
|
|
assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, X,
|
|
ConstantInt::get(X->getType(), SMax - (C - 1)));
|
|
}
|
|
|
|
/// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
|
|
/// (icmp eq/ne A, Log2(AP2/AP1)) ->
|
|
/// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
|
|
Instruction *InstCombinerImpl::foldICmpShrConstConst(ICmpInst &I, Value *A,
|
|
const APInt &AP1,
|
|
const APInt &AP2) {
|
|
assert(I.isEquality() && "Cannot fold icmp gt/lt");
|
|
|
|
auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
|
|
if (I.getPredicate() == I.ICMP_NE)
|
|
Pred = CmpInst::getInversePredicate(Pred);
|
|
return new ICmpInst(Pred, LHS, RHS);
|
|
};
|
|
|
|
// Don't bother doing any work for cases which InstSimplify handles.
|
|
if (AP2.isNullValue())
|
|
return nullptr;
|
|
|
|
bool IsAShr = isa<AShrOperator>(I.getOperand(0));
|
|
if (IsAShr) {
|
|
if (AP2.isAllOnesValue())
|
|
return nullptr;
|
|
if (AP2.isNegative() != AP1.isNegative())
|
|
return nullptr;
|
|
if (AP2.sgt(AP1))
|
|
return nullptr;
|
|
}
|
|
|
|
if (!AP1)
|
|
// 'A' must be large enough to shift out the highest set bit.
|
|
return getICmp(I.ICMP_UGT, A,
|
|
ConstantInt::get(A->getType(), AP2.logBase2()));
|
|
|
|
if (AP1 == AP2)
|
|
return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
|
|
|
|
int Shift;
|
|
if (IsAShr && AP1.isNegative())
|
|
Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
|
|
else
|
|
Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
|
|
|
|
if (Shift > 0) {
|
|
if (IsAShr && AP1 == AP2.ashr(Shift)) {
|
|
// There are multiple solutions if we are comparing against -1 and the LHS
|
|
// of the ashr is not a power of two.
|
|
if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
|
|
return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
|
|
return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
|
|
} else if (AP1 == AP2.lshr(Shift)) {
|
|
return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
|
|
}
|
|
}
|
|
|
|
// Shifting const2 will never be equal to const1.
|
|
// FIXME: This should always be handled by InstSimplify?
|
|
auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
|
|
return replaceInstUsesWith(I, TorF);
|
|
}
|
|
|
|
/// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
|
|
/// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
|
|
Instruction *InstCombinerImpl::foldICmpShlConstConst(ICmpInst &I, Value *A,
|
|
const APInt &AP1,
|
|
const APInt &AP2) {
|
|
assert(I.isEquality() && "Cannot fold icmp gt/lt");
|
|
|
|
auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
|
|
if (I.getPredicate() == I.ICMP_NE)
|
|
Pred = CmpInst::getInversePredicate(Pred);
|
|
return new ICmpInst(Pred, LHS, RHS);
|
|
};
|
|
|
|
// Don't bother doing any work for cases which InstSimplify handles.
|
|
if (AP2.isNullValue())
|
|
return nullptr;
|
|
|
|
unsigned AP2TrailingZeros = AP2.countTrailingZeros();
|
|
|
|
if (!AP1 && AP2TrailingZeros != 0)
|
|
return getICmp(
|
|
I.ICMP_UGE, A,
|
|
ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
|
|
|
|
if (AP1 == AP2)
|
|
return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
|
|
|
|
// Get the distance between the lowest bits that are set.
|
|
int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
|
|
|
|
if (Shift > 0 && AP2.shl(Shift) == AP1)
|
|
return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
|
|
|
|
// Shifting const2 will never be equal to const1.
|
|
// FIXME: This should always be handled by InstSimplify?
|
|
auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
|
|
return replaceInstUsesWith(I, TorF);
|
|
}
|
|
|
|
/// The caller has matched a pattern of the form:
|
|
/// I = icmp ugt (add (add A, B), CI2), CI1
|
|
/// If this is of the form:
|
|
/// sum = a + b
|
|
/// if (sum+128 >u 255)
|
|
/// Then replace it with llvm.sadd.with.overflow.i8.
|
|
///
|
|
static Instruction *processUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
|
|
ConstantInt *CI2, ConstantInt *CI1,
|
|
InstCombinerImpl &IC) {
|
|
// The transformation we're trying to do here is to transform this into an
|
|
// llvm.sadd.with.overflow. To do this, we have to replace the original add
|
|
// with a narrower add, and discard the add-with-constant that is part of the
|
|
// range check (if we can't eliminate it, this isn't profitable).
|
|
|
|
// In order to eliminate the add-with-constant, the compare can be its only
|
|
// use.
|
|
Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
|
|
if (!AddWithCst->hasOneUse())
|
|
return nullptr;
|
|
|
|
// If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
|
|
if (!CI2->getValue().isPowerOf2())
|
|
return nullptr;
|
|
unsigned NewWidth = CI2->getValue().countTrailingZeros();
|
|
if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
|
|
return nullptr;
|
|
|
|
// The width of the new add formed is 1 more than the bias.
|
|
++NewWidth;
|
|
|
|
// Check to see that CI1 is an all-ones value with NewWidth bits.
|
|
if (CI1->getBitWidth() == NewWidth ||
|
|
CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
|
|
return nullptr;
|
|
|
|
// This is only really a signed overflow check if the inputs have been
|
|
// sign-extended; check for that condition. For example, if CI2 is 2^31 and
|
|
// the operands of the add are 64 bits wide, we need at least 33 sign bits.
|
|
unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
|
|
if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
|
|
IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
|
|
return nullptr;
|
|
|
|
// In order to replace the original add with a narrower
|
|
// llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
|
|
// and truncates that discard the high bits of the add. Verify that this is
|
|
// the case.
|
|
Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
|
|
for (User *U : OrigAdd->users()) {
|
|
if (U == AddWithCst)
|
|
continue;
|
|
|
|
// Only accept truncates for now. We would really like a nice recursive
|
|
// predicate like SimplifyDemandedBits, but which goes downwards the use-def
|
|
// chain to see which bits of a value are actually demanded. If the
|
|
// original add had another add which was then immediately truncated, we
|
|
// could still do the transformation.
|
|
TruncInst *TI = dyn_cast<TruncInst>(U);
|
|
if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
|
|
return nullptr;
|
|
}
|
|
|
|
// If the pattern matches, truncate the inputs to the narrower type and
|
|
// use the sadd_with_overflow intrinsic to efficiently compute both the
|
|
// result and the overflow bit.
|
|
Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
|
|
Function *F = Intrinsic::getDeclaration(
|
|
I.getModule(), Intrinsic::sadd_with_overflow, NewType);
|
|
|
|
InstCombiner::BuilderTy &Builder = IC.Builder;
|
|
|
|
// Put the new code above the original add, in case there are any uses of the
|
|
// add between the add and the compare.
|
|
Builder.SetInsertPoint(OrigAdd);
|
|
|
|
Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
|
|
Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
|
|
CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
|
|
Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
|
|
Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
|
|
|
|
// The inner add was the result of the narrow add, zero extended to the
|
|
// wider type. Replace it with the result computed by the intrinsic.
|
|
IC.replaceInstUsesWith(*OrigAdd, ZExt);
|
|
IC.eraseInstFromFunction(*OrigAdd);
|
|
|
|
// The original icmp gets replaced with the overflow value.
|
|
return ExtractValueInst::Create(Call, 1, "sadd.overflow");
|
|
}
|
|
|
|
/// If we have:
|
|
/// icmp eq/ne (urem/srem %x, %y), 0
|
|
/// iff %y is a power-of-two, we can replace this with a bit test:
|
|
/// icmp eq/ne (and %x, (add %y, -1)), 0
|
|
Instruction *InstCombinerImpl::foldIRemByPowerOfTwoToBitTest(ICmpInst &I) {
|
|
// This fold is only valid for equality predicates.
|
|
if (!I.isEquality())
|
|
return nullptr;
|
|
ICmpInst::Predicate Pred;
|
|
Value *X, *Y, *Zero;
|
|
if (!match(&I, m_ICmp(Pred, m_OneUse(m_IRem(m_Value(X), m_Value(Y))),
|
|
m_CombineAnd(m_Zero(), m_Value(Zero)))))
|
|
return nullptr;
|
|
if (!isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, 0, &I))
|
|
return nullptr;
|
|
// This may increase instruction count, we don't enforce that Y is a constant.
|
|
Value *Mask = Builder.CreateAdd(Y, Constant::getAllOnesValue(Y->getType()));
|
|
Value *Masked = Builder.CreateAnd(X, Mask);
|
|
return ICmpInst::Create(Instruction::ICmp, Pred, Masked, Zero);
|
|
}
|
|
|
|
/// Fold equality-comparison between zero and any (maybe truncated) right-shift
|
|
/// by one-less-than-bitwidth into a sign test on the original value.
|
|
Instruction *InstCombinerImpl::foldSignBitTest(ICmpInst &I) {
|
|
Instruction *Val;
|
|
ICmpInst::Predicate Pred;
|
|
if (!I.isEquality() || !match(&I, m_ICmp(Pred, m_Instruction(Val), m_Zero())))
|
|
return nullptr;
|
|
|
|
Value *X;
|
|
Type *XTy;
|
|
|
|
Constant *C;
|
|
if (match(Val, m_TruncOrSelf(m_Shr(m_Value(X), m_Constant(C))))) {
|
|
XTy = X->getType();
|
|
unsigned XBitWidth = XTy->getScalarSizeInBits();
|
|
if (!match(C, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_EQ,
|
|
APInt(XBitWidth, XBitWidth - 1))))
|
|
return nullptr;
|
|
} else if (isa<BinaryOperator>(Val) &&
|
|
(X = reassociateShiftAmtsOfTwoSameDirectionShifts(
|
|
cast<BinaryOperator>(Val), SQ.getWithInstruction(Val),
|
|
/*AnalyzeForSignBitExtraction=*/true))) {
|
|
XTy = X->getType();
|
|
} else
|
|
return nullptr;
|
|
|
|
return ICmpInst::Create(Instruction::ICmp,
|
|
Pred == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_SGE
|
|
: ICmpInst::ICMP_SLT,
|
|
X, ConstantInt::getNullValue(XTy));
|
|
}
|
|
|
|
// Handle icmp pred X, 0
|
|
Instruction *InstCombinerImpl::foldICmpWithZero(ICmpInst &Cmp) {
|
|
CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (!match(Cmp.getOperand(1), m_Zero()))
|
|
return nullptr;
|
|
|
|
// (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
|
|
if (Pred == ICmpInst::ICMP_SGT) {
|
|
Value *A, *B;
|
|
SelectPatternResult SPR = matchSelectPattern(Cmp.getOperand(0), A, B);
|
|
if (SPR.Flavor == SPF_SMIN) {
|
|
if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
|
|
return new ICmpInst(Pred, B, Cmp.getOperand(1));
|
|
if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
|
|
return new ICmpInst(Pred, A, Cmp.getOperand(1));
|
|
}
|
|
}
|
|
|
|
if (Instruction *New = foldIRemByPowerOfTwoToBitTest(Cmp))
|
|
return New;
|
|
|
|
// Given:
|
|
// icmp eq/ne (urem %x, %y), 0
|
|
// Iff %x has 0 or 1 bits set, and %y has at least 2 bits set, omit 'urem':
|
|
// icmp eq/ne %x, 0
|
|
Value *X, *Y;
|
|
if (match(Cmp.getOperand(0), m_URem(m_Value(X), m_Value(Y))) &&
|
|
ICmpInst::isEquality(Pred)) {
|
|
KnownBits XKnown = computeKnownBits(X, 0, &Cmp);
|
|
KnownBits YKnown = computeKnownBits(Y, 0, &Cmp);
|
|
if (XKnown.countMaxPopulation() == 1 && YKnown.countMinPopulation() >= 2)
|
|
return new ICmpInst(Pred, X, Cmp.getOperand(1));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp Pred X, C.
|
|
/// TODO: This code structure does not make sense. The saturating add fold
|
|
/// should be moved to some other helper and extended as noted below (it is also
|
|
/// possible that code has been made unnecessary - do we canonicalize IR to
|
|
/// overflow/saturating intrinsics or not?).
|
|
Instruction *InstCombinerImpl::foldICmpWithConstant(ICmpInst &Cmp) {
|
|
// Match the following pattern, which is a common idiom when writing
|
|
// overflow-safe integer arithmetic functions. The source performs an addition
|
|
// in wider type and explicitly checks for overflow using comparisons against
|
|
// INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
|
|
//
|
|
// TODO: This could probably be generalized to handle other overflow-safe
|
|
// operations if we worked out the formulas to compute the appropriate magic
|
|
// constants.
|
|
//
|
|
// sum = a + b
|
|
// if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
|
|
CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *Op0 = Cmp.getOperand(0), *Op1 = Cmp.getOperand(1);
|
|
Value *A, *B;
|
|
ConstantInt *CI, *CI2; // I = icmp ugt (add (add A, B), CI2), CI
|
|
if (Pred == ICmpInst::ICMP_UGT && match(Op1, m_ConstantInt(CI)) &&
|
|
match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
|
|
if (Instruction *Res = processUGT_ADDCST_ADD(Cmp, A, B, CI2, CI, *this))
|
|
return Res;
|
|
|
|
// icmp(phi(C1, C2, ...), C) -> phi(icmp(C1, C), icmp(C2, C), ...).
|
|
Constant *C = dyn_cast<Constant>(Op1);
|
|
if (!C)
|
|
return nullptr;
|
|
|
|
if (auto *Phi = dyn_cast<PHINode>(Op0))
|
|
if (all_of(Phi->operands(), [](Value *V) { return isa<Constant>(V); })) {
|
|
Type *Ty = Cmp.getType();
|
|
Builder.SetInsertPoint(Phi);
|
|
PHINode *NewPhi =
|
|
Builder.CreatePHI(Ty, Phi->getNumOperands());
|
|
for (BasicBlock *Predecessor : predecessors(Phi->getParent())) {
|
|
auto *Input =
|
|
cast<Constant>(Phi->getIncomingValueForBlock(Predecessor));
|
|
auto *BoolInput = ConstantExpr::getCompare(Pred, Input, C);
|
|
NewPhi->addIncoming(BoolInput, Predecessor);
|
|
}
|
|
NewPhi->takeName(&Cmp);
|
|
return replaceInstUsesWith(Cmp, NewPhi);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Canonicalize icmp instructions based on dominating conditions.
|
|
Instruction *InstCombinerImpl::foldICmpWithDominatingICmp(ICmpInst &Cmp) {
|
|
// This is a cheap/incomplete check for dominance - just match a single
|
|
// predecessor with a conditional branch.
|
|
BasicBlock *CmpBB = Cmp.getParent();
|
|
BasicBlock *DomBB = CmpBB->getSinglePredecessor();
|
|
if (!DomBB)
|
|
return nullptr;
|
|
|
|
Value *DomCond;
|
|
BasicBlock *TrueBB, *FalseBB;
|
|
if (!match(DomBB->getTerminator(), m_Br(m_Value(DomCond), TrueBB, FalseBB)))
|
|
return nullptr;
|
|
|
|
assert((TrueBB == CmpBB || FalseBB == CmpBB) &&
|
|
"Predecessor block does not point to successor?");
|
|
|
|
// The branch should get simplified. Don't bother simplifying this condition.
|
|
if (TrueBB == FalseBB)
|
|
return nullptr;
|
|
|
|
// Try to simplify this compare to T/F based on the dominating condition.
|
|
Optional<bool> Imp = isImpliedCondition(DomCond, &Cmp, DL, TrueBB == CmpBB);
|
|
if (Imp)
|
|
return replaceInstUsesWith(Cmp, ConstantInt::get(Cmp.getType(), *Imp));
|
|
|
|
CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *X = Cmp.getOperand(0), *Y = Cmp.getOperand(1);
|
|
ICmpInst::Predicate DomPred;
|
|
const APInt *C, *DomC;
|
|
if (match(DomCond, m_ICmp(DomPred, m_Specific(X), m_APInt(DomC))) &&
|
|
match(Y, m_APInt(C))) {
|
|
// We have 2 compares of a variable with constants. Calculate the constant
|
|
// ranges of those compares to see if we can transform the 2nd compare:
|
|
// DomBB:
|
|
// DomCond = icmp DomPred X, DomC
|
|
// br DomCond, CmpBB, FalseBB
|
|
// CmpBB:
|
|
// Cmp = icmp Pred X, C
|
|
ConstantRange CR = ConstantRange::makeAllowedICmpRegion(Pred, *C);
|
|
ConstantRange DominatingCR =
|
|
(CmpBB == TrueBB) ? ConstantRange::makeExactICmpRegion(DomPred, *DomC)
|
|
: ConstantRange::makeExactICmpRegion(
|
|
CmpInst::getInversePredicate(DomPred), *DomC);
|
|
ConstantRange Intersection = DominatingCR.intersectWith(CR);
|
|
ConstantRange Difference = DominatingCR.difference(CR);
|
|
if (Intersection.isEmptySet())
|
|
return replaceInstUsesWith(Cmp, Builder.getFalse());
|
|
if (Difference.isEmptySet())
|
|
return replaceInstUsesWith(Cmp, Builder.getTrue());
|
|
|
|
// Canonicalizing a sign bit comparison that gets used in a branch,
|
|
// pessimizes codegen by generating branch on zero instruction instead
|
|
// of a test and branch. So we avoid canonicalizing in such situations
|
|
// because test and branch instruction has better branch displacement
|
|
// than compare and branch instruction.
|
|
bool UnusedBit;
|
|
bool IsSignBit = isSignBitCheck(Pred, *C, UnusedBit);
|
|
if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
|
|
return nullptr;
|
|
|
|
if (const APInt *EqC = Intersection.getSingleElement())
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*EqC));
|
|
if (const APInt *NeC = Difference.getSingleElement())
|
|
return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*NeC));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (trunc X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpTruncConstant(ICmpInst &Cmp,
|
|
TruncInst *Trunc,
|
|
const APInt &C) {
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *X = Trunc->getOperand(0);
|
|
if (C.isOneValue() && C.getBitWidth() > 1) {
|
|
// icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
|
|
Value *V = nullptr;
|
|
if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, V,
|
|
ConstantInt::get(V->getType(), 1));
|
|
}
|
|
|
|
if (Cmp.isEquality() && Trunc->hasOneUse()) {
|
|
// Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
|
|
// of the high bits truncated out of x are known.
|
|
unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
|
|
SrcBits = X->getType()->getScalarSizeInBits();
|
|
KnownBits Known = computeKnownBits(X, 0, &Cmp);
|
|
|
|
// If all the high bits are known, we can do this xform.
|
|
if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
|
|
// Pull in the high bits from known-ones set.
|
|
APInt NewRHS = C.zext(SrcBits);
|
|
NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (xor X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpXorConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Xor,
|
|
const APInt &C) {
|
|
Value *X = Xor->getOperand(0);
|
|
Value *Y = Xor->getOperand(1);
|
|
const APInt *XorC;
|
|
if (!match(Y, m_APInt(XorC)))
|
|
return nullptr;
|
|
|
|
// If this is a comparison that tests the signbit (X < 0) or (x > -1),
|
|
// fold the xor.
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
bool TrueIfSigned = false;
|
|
if (isSignBitCheck(Cmp.getPredicate(), C, TrueIfSigned)) {
|
|
|
|
// If the sign bit of the XorCst is not set, there is no change to
|
|
// the operation, just stop using the Xor.
|
|
if (!XorC->isNegative())
|
|
return replaceOperand(Cmp, 0, X);
|
|
|
|
// Emit the opposite comparison.
|
|
if (TrueIfSigned)
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, X,
|
|
ConstantInt::getAllOnesValue(X->getType()));
|
|
else
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, X,
|
|
ConstantInt::getNullValue(X->getType()));
|
|
}
|
|
|
|
if (Xor->hasOneUse()) {
|
|
// (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
|
|
if (!Cmp.isEquality() && XorC->isSignMask()) {
|
|
Pred = Cmp.getFlippedSignednessPredicate();
|
|
return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
|
|
}
|
|
|
|
// (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
|
|
if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
|
|
Pred = Cmp.getFlippedSignednessPredicate();
|
|
Pred = Cmp.getSwappedPredicate(Pred);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
|
|
}
|
|
}
|
|
|
|
// Mask constant magic can eliminate an 'xor' with unsigned compares.
|
|
if (Pred == ICmpInst::ICMP_UGT) {
|
|
// (xor X, ~C) >u C --> X <u ~C (when C+1 is a power of 2)
|
|
if (*XorC == ~C && (C + 1).isPowerOf2())
|
|
return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
|
|
// (xor X, C) >u C --> X >u C (when C+1 is a power of 2)
|
|
if (*XorC == C && (C + 1).isPowerOf2())
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
|
|
}
|
|
if (Pred == ICmpInst::ICMP_ULT) {
|
|
// (xor X, -C) <u C --> X >u ~C (when C is a power of 2)
|
|
if (*XorC == -C && C.isPowerOf2())
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, X,
|
|
ConstantInt::get(X->getType(), ~C));
|
|
// (xor X, C) <u C --> X >u ~C (when -C is a power of 2)
|
|
if (*XorC == C && (-C).isPowerOf2())
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, X,
|
|
ConstantInt::get(X->getType(), ~C));
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (and (sh X, Y), C2), C1.
|
|
Instruction *InstCombinerImpl::foldICmpAndShift(ICmpInst &Cmp,
|
|
BinaryOperator *And,
|
|
const APInt &C1,
|
|
const APInt &C2) {
|
|
BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
|
|
if (!Shift || !Shift->isShift())
|
|
return nullptr;
|
|
|
|
// If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
|
|
// exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
|
|
// code produced by the clang front-end, for bitfield access.
|
|
// This seemingly simple opportunity to fold away a shift turns out to be
|
|
// rather complicated. See PR17827 for details.
|
|
unsigned ShiftOpcode = Shift->getOpcode();
|
|
bool IsShl = ShiftOpcode == Instruction::Shl;
|
|
const APInt *C3;
|
|
if (match(Shift->getOperand(1), m_APInt(C3))) {
|
|
APInt NewAndCst, NewCmpCst;
|
|
bool AnyCmpCstBitsShiftedOut;
|
|
if (ShiftOpcode == Instruction::Shl) {
|
|
// For a left shift, we can fold if the comparison is not signed. We can
|
|
// also fold a signed comparison if the mask value and comparison value
|
|
// are not negative. These constraints may not be obvious, but we can
|
|
// prove that they are correct using an SMT solver.
|
|
if (Cmp.isSigned() && (C2.isNegative() || C1.isNegative()))
|
|
return nullptr;
|
|
|
|
NewCmpCst = C1.lshr(*C3);
|
|
NewAndCst = C2.lshr(*C3);
|
|
AnyCmpCstBitsShiftedOut = NewCmpCst.shl(*C3) != C1;
|
|
} else if (ShiftOpcode == Instruction::LShr) {
|
|
// For a logical right shift, we can fold if the comparison is not signed.
|
|
// We can also fold a signed comparison if the shifted mask value and the
|
|
// shifted comparison value are not negative. These constraints may not be
|
|
// obvious, but we can prove that they are correct using an SMT solver.
|
|
NewCmpCst = C1.shl(*C3);
|
|
NewAndCst = C2.shl(*C3);
|
|
AnyCmpCstBitsShiftedOut = NewCmpCst.lshr(*C3) != C1;
|
|
if (Cmp.isSigned() && (NewAndCst.isNegative() || NewCmpCst.isNegative()))
|
|
return nullptr;
|
|
} else {
|
|
// For an arithmetic shift, check that both constants don't use (in a
|
|
// signed sense) the top bits being shifted out.
|
|
assert(ShiftOpcode == Instruction::AShr && "Unknown shift opcode");
|
|
NewCmpCst = C1.shl(*C3);
|
|
NewAndCst = C2.shl(*C3);
|
|
AnyCmpCstBitsShiftedOut = NewCmpCst.ashr(*C3) != C1;
|
|
if (NewAndCst.ashr(*C3) != C2)
|
|
return nullptr;
|
|
}
|
|
|
|
if (AnyCmpCstBitsShiftedOut) {
|
|
// If we shifted bits out, the fold is not going to work out. As a
|
|
// special case, check to see if this means that the result is always
|
|
// true or false now.
|
|
if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
|
|
return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
|
|
if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
|
|
return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
|
|
} else {
|
|
Value *NewAnd = Builder.CreateAnd(
|
|
Shift->getOperand(0), ConstantInt::get(And->getType(), NewAndCst));
|
|
return new ICmpInst(Cmp.getPredicate(),
|
|
NewAnd, ConstantInt::get(And->getType(), NewCmpCst));
|
|
}
|
|
}
|
|
|
|
// Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
|
|
// preferable because it allows the C2 << Y expression to be hoisted out of a
|
|
// loop if Y is invariant and X is not.
|
|
if (Shift->hasOneUse() && C1.isNullValue() && Cmp.isEquality() &&
|
|
!Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
|
|
// Compute C2 << Y.
|
|
Value *NewShift =
|
|
IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
|
|
: Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
|
|
|
|
// Compute X & (C2 << Y).
|
|
Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
|
|
return replaceOperand(Cmp, 0, NewAnd);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (and X, C2), C1.
|
|
Instruction *InstCombinerImpl::foldICmpAndConstConst(ICmpInst &Cmp,
|
|
BinaryOperator *And,
|
|
const APInt &C1) {
|
|
bool isICMP_NE = Cmp.getPredicate() == ICmpInst::ICMP_NE;
|
|
|
|
// For vectors: icmp ne (and X, 1), 0 --> trunc X to N x i1
|
|
// TODO: We canonicalize to the longer form for scalars because we have
|
|
// better analysis/folds for icmp, and codegen may be better with icmp.
|
|
if (isICMP_NE && Cmp.getType()->isVectorTy() && C1.isNullValue() &&
|
|
match(And->getOperand(1), m_One()))
|
|
return new TruncInst(And->getOperand(0), Cmp.getType());
|
|
|
|
const APInt *C2;
|
|
Value *X;
|
|
if (!match(And, m_And(m_Value(X), m_APInt(C2))))
|
|
return nullptr;
|
|
|
|
// Don't perform the following transforms if the AND has multiple uses
|
|
if (!And->hasOneUse())
|
|
return nullptr;
|
|
|
|
if (Cmp.isEquality() && C1.isNullValue()) {
|
|
// Restrict this fold to single-use 'and' (PR10267).
|
|
// Replace (and X, (1 << size(X)-1) != 0) with X s< 0
|
|
if (C2->isSignMask()) {
|
|
Constant *Zero = Constant::getNullValue(X->getType());
|
|
auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
|
|
return new ICmpInst(NewPred, X, Zero);
|
|
}
|
|
|
|
// Restrict this fold only for single-use 'and' (PR10267).
|
|
// ((%x & C) == 0) --> %x u< (-C) iff (-C) is power of two.
|
|
if ((~(*C2) + 1).isPowerOf2()) {
|
|
Constant *NegBOC =
|
|
ConstantExpr::getNeg(cast<Constant>(And->getOperand(1)));
|
|
auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
|
|
return new ICmpInst(NewPred, X, NegBOC);
|
|
}
|
|
}
|
|
|
|
// If the LHS is an 'and' of a truncate and we can widen the and/compare to
|
|
// the input width without changing the value produced, eliminate the cast:
|
|
//
|
|
// icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
|
|
//
|
|
// We can do this transformation if the constants do not have their sign bits
|
|
// set or if it is an equality comparison. Extending a relational comparison
|
|
// when we're checking the sign bit would not work.
|
|
Value *W;
|
|
if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
|
|
(Cmp.isEquality() || (!C1.isNegative() && !C2->isNegative()))) {
|
|
// TODO: Is this a good transform for vectors? Wider types may reduce
|
|
// throughput. Should this transform be limited (even for scalars) by using
|
|
// shouldChangeType()?
|
|
if (!Cmp.getType()->isVectorTy()) {
|
|
Type *WideType = W->getType();
|
|
unsigned WideScalarBits = WideType->getScalarSizeInBits();
|
|
Constant *ZextC1 = ConstantInt::get(WideType, C1.zext(WideScalarBits));
|
|
Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
|
|
Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
|
|
return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
|
|
}
|
|
}
|
|
|
|
if (Instruction *I = foldICmpAndShift(Cmp, And, C1, *C2))
|
|
return I;
|
|
|
|
// (icmp pred (and (or (lshr A, B), A), 1), 0) -->
|
|
// (icmp pred (and A, (or (shl 1, B), 1), 0))
|
|
//
|
|
// iff pred isn't signed
|
|
if (!Cmp.isSigned() && C1.isNullValue() && And->getOperand(0)->hasOneUse() &&
|
|
match(And->getOperand(1), m_One())) {
|
|
Constant *One = cast<Constant>(And->getOperand(1));
|
|
Value *Or = And->getOperand(0);
|
|
Value *A, *B, *LShr;
|
|
if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
|
|
match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
|
|
unsigned UsesRemoved = 0;
|
|
if (And->hasOneUse())
|
|
++UsesRemoved;
|
|
if (Or->hasOneUse())
|
|
++UsesRemoved;
|
|
if (LShr->hasOneUse())
|
|
++UsesRemoved;
|
|
|
|
// Compute A & ((1 << B) | 1)
|
|
Value *NewOr = nullptr;
|
|
if (auto *C = dyn_cast<Constant>(B)) {
|
|
if (UsesRemoved >= 1)
|
|
NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
|
|
} else {
|
|
if (UsesRemoved >= 3)
|
|
NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
|
|
/*HasNUW=*/true),
|
|
One, Or->getName());
|
|
}
|
|
if (NewOr) {
|
|
Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
|
|
return replaceOperand(Cmp, 0, NewAnd);
|
|
}
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (and X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpAndConstant(ICmpInst &Cmp,
|
|
BinaryOperator *And,
|
|
const APInt &C) {
|
|
if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
|
|
return I;
|
|
|
|
// TODO: These all require that Y is constant too, so refactor with the above.
|
|
|
|
// Try to optimize things like "A[i] & 42 == 0" to index computations.
|
|
Value *X = And->getOperand(0);
|
|
Value *Y = And->getOperand(1);
|
|
if (auto *LI = dyn_cast<LoadInst>(X))
|
|
if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
|
|
if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
|
|
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
|
|
!LI->isVolatile() && isa<ConstantInt>(Y)) {
|
|
ConstantInt *C2 = cast<ConstantInt>(Y);
|
|
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
|
|
return Res;
|
|
}
|
|
|
|
if (!Cmp.isEquality())
|
|
return nullptr;
|
|
|
|
// X & -C == -C -> X > u ~C
|
|
// X & -C != -C -> X <= u ~C
|
|
// iff C is a power of 2
|
|
if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
|
|
auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
|
|
: CmpInst::ICMP_ULE;
|
|
return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
|
|
}
|
|
|
|
// (X & C2) == 0 -> (trunc X) >= 0
|
|
// (X & C2) != 0 -> (trunc X) < 0
|
|
// iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
|
|
const APInt *C2;
|
|
if (And->hasOneUse() && C.isNullValue() && match(Y, m_APInt(C2))) {
|
|
int32_t ExactLogBase2 = C2->exactLogBase2();
|
|
if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
|
|
Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
|
|
if (auto *AndVTy = dyn_cast<VectorType>(And->getType()))
|
|
NTy = VectorType::get(NTy, AndVTy->getElementCount());
|
|
Value *Trunc = Builder.CreateTrunc(X, NTy);
|
|
auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
|
|
: CmpInst::ICMP_SLT;
|
|
return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (or X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpOrConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Or,
|
|
const APInt &C) {
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (C.isOneValue()) {
|
|
// icmp slt signum(V) 1 --> icmp slt V, 1
|
|
Value *V = nullptr;
|
|
if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, V,
|
|
ConstantInt::get(V->getType(), 1));
|
|
}
|
|
|
|
Value *OrOp0 = Or->getOperand(0), *OrOp1 = Or->getOperand(1);
|
|
const APInt *MaskC;
|
|
if (match(OrOp1, m_APInt(MaskC)) && Cmp.isEquality()) {
|
|
if (*MaskC == C && (C + 1).isPowerOf2()) {
|
|
// X | C == C --> X <=u C
|
|
// X | C != C --> X >u C
|
|
// iff C+1 is a power of 2 (C is a bitmask of the low bits)
|
|
Pred = (Pred == CmpInst::ICMP_EQ) ? CmpInst::ICMP_ULE : CmpInst::ICMP_UGT;
|
|
return new ICmpInst(Pred, OrOp0, OrOp1);
|
|
}
|
|
|
|
// More general: canonicalize 'equality with set bits mask' to
|
|
// 'equality with clear bits mask'.
|
|
// (X | MaskC) == C --> (X & ~MaskC) == C ^ MaskC
|
|
// (X | MaskC) != C --> (X & ~MaskC) != C ^ MaskC
|
|
if (Or->hasOneUse()) {
|
|
Value *And = Builder.CreateAnd(OrOp0, ~(*MaskC));
|
|
Constant *NewC = ConstantInt::get(Or->getType(), C ^ (*MaskC));
|
|
return new ICmpInst(Pred, And, NewC);
|
|
}
|
|
}
|
|
|
|
if (!Cmp.isEquality() || !C.isNullValue() || !Or->hasOneUse())
|
|
return nullptr;
|
|
|
|
Value *P, *Q;
|
|
if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
|
|
// Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
|
|
// -> and (icmp eq P, null), (icmp eq Q, null).
|
|
Value *CmpP =
|
|
Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
|
|
Value *CmpQ =
|
|
Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
|
|
auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
|
|
return BinaryOperator::Create(BOpc, CmpP, CmpQ);
|
|
}
|
|
|
|
// Are we using xors to bitwise check for a pair of (in)equalities? Convert to
|
|
// a shorter form that has more potential to be folded even further.
|
|
Value *X1, *X2, *X3, *X4;
|
|
if (match(OrOp0, m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
|
|
match(OrOp1, m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
|
|
// ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
|
|
// ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
|
|
Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
|
|
Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
|
|
auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
|
|
return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (mul X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpMulConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Mul,
|
|
const APInt &C) {
|
|
const APInt *MulC;
|
|
if (!match(Mul->getOperand(1), m_APInt(MulC)))
|
|
return nullptr;
|
|
|
|
// If this is a test of the sign bit and the multiply is sign-preserving with
|
|
// a constant operand, use the multiply LHS operand instead.
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (isSignTest(Pred, C) && Mul->hasNoSignedWrap()) {
|
|
if (MulC->isNegative())
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
return new ICmpInst(Pred, Mul->getOperand(0),
|
|
Constant::getNullValue(Mul->getType()));
|
|
}
|
|
|
|
// If the multiply does not wrap, try to divide the compare constant by the
|
|
// multiplication factor.
|
|
if (Cmp.isEquality() && !MulC->isNullValue()) {
|
|
// (mul nsw X, MulC) == C --> X == C /s MulC
|
|
if (Mul->hasNoSignedWrap() && C.srem(*MulC).isNullValue()) {
|
|
Constant *NewC = ConstantInt::get(Mul->getType(), C.sdiv(*MulC));
|
|
return new ICmpInst(Pred, Mul->getOperand(0), NewC);
|
|
}
|
|
// (mul nuw X, MulC) == C --> X == C /u MulC
|
|
if (Mul->hasNoUnsignedWrap() && C.urem(*MulC).isNullValue()) {
|
|
Constant *NewC = ConstantInt::get(Mul->getType(), C.udiv(*MulC));
|
|
return new ICmpInst(Pred, Mul->getOperand(0), NewC);
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (shl 1, Y), C.
|
|
static Instruction *foldICmpShlOne(ICmpInst &Cmp, Instruction *Shl,
|
|
const APInt &C) {
|
|
Value *Y;
|
|
if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
|
|
return nullptr;
|
|
|
|
Type *ShiftType = Shl->getType();
|
|
unsigned TypeBits = C.getBitWidth();
|
|
bool CIsPowerOf2 = C.isPowerOf2();
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (Cmp.isUnsigned()) {
|
|
// (1 << Y) pred C -> Y pred Log2(C)
|
|
if (!CIsPowerOf2) {
|
|
// (1 << Y) < 30 -> Y <= 4
|
|
// (1 << Y) <= 30 -> Y <= 4
|
|
// (1 << Y) >= 30 -> Y > 4
|
|
// (1 << Y) > 30 -> Y > 4
|
|
if (Pred == ICmpInst::ICMP_ULT)
|
|
Pred = ICmpInst::ICMP_ULE;
|
|
else if (Pred == ICmpInst::ICMP_UGE)
|
|
Pred = ICmpInst::ICMP_UGT;
|
|
}
|
|
|
|
// (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
|
|
// (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
|
|
unsigned CLog2 = C.logBase2();
|
|
if (CLog2 == TypeBits - 1) {
|
|
if (Pred == ICmpInst::ICMP_UGE)
|
|
Pred = ICmpInst::ICMP_EQ;
|
|
else if (Pred == ICmpInst::ICMP_ULT)
|
|
Pred = ICmpInst::ICMP_NE;
|
|
}
|
|
return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
|
|
} else if (Cmp.isSigned()) {
|
|
Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
|
|
if (C.isAllOnesValue()) {
|
|
// (1 << Y) <= -1 -> Y == 31
|
|
if (Pred == ICmpInst::ICMP_SLE)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
|
|
|
|
// (1 << Y) > -1 -> Y != 31
|
|
if (Pred == ICmpInst::ICMP_SGT)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
|
|
} else if (!C) {
|
|
// (1 << Y) < 0 -> Y == 31
|
|
// (1 << Y) <= 0 -> Y == 31
|
|
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
|
|
|
|
// (1 << Y) >= 0 -> Y != 31
|
|
// (1 << Y) > 0 -> Y != 31
|
|
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
|
|
}
|
|
} else if (Cmp.isEquality() && CIsPowerOf2) {
|
|
return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C.logBase2()));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (shl X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpShlConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Shl,
|
|
const APInt &C) {
|
|
const APInt *ShiftVal;
|
|
if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
|
|
return foldICmpShlConstConst(Cmp, Shl->getOperand(1), C, *ShiftVal);
|
|
|
|
const APInt *ShiftAmt;
|
|
if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
|
|
return foldICmpShlOne(Cmp, Shl, C);
|
|
|
|
// Check that the shift amount is in range. If not, don't perform undefined
|
|
// shifts. When the shift is visited, it will be simplified.
|
|
unsigned TypeBits = C.getBitWidth();
|
|
if (ShiftAmt->uge(TypeBits))
|
|
return nullptr;
|
|
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *X = Shl->getOperand(0);
|
|
Type *ShType = Shl->getType();
|
|
|
|
// NSW guarantees that we are only shifting out sign bits from the high bits,
|
|
// so we can ASHR the compare constant without needing a mask and eliminate
|
|
// the shift.
|
|
if (Shl->hasNoSignedWrap()) {
|
|
if (Pred == ICmpInst::ICMP_SGT) {
|
|
// icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
|
|
APInt ShiftedC = C.ashr(*ShiftAmt);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
|
|
C.ashr(*ShiftAmt).shl(*ShiftAmt) == C) {
|
|
APInt ShiftedC = C.ashr(*ShiftAmt);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
if (Pred == ICmpInst::ICMP_SLT) {
|
|
// SLE is the same as above, but SLE is canonicalized to SLT, so convert:
|
|
// (X << S) <=s C is equiv to X <=s (C >> S) for all C
|
|
// (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
|
|
// (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
|
|
assert(!C.isMinSignedValue() && "Unexpected icmp slt");
|
|
APInt ShiftedC = (C - 1).ashr(*ShiftAmt) + 1;
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
// If this is a signed comparison to 0 and the shift is sign preserving,
|
|
// use the shift LHS operand instead; isSignTest may change 'Pred', so only
|
|
// do that if we're sure to not continue on in this function.
|
|
if (isSignTest(Pred, C))
|
|
return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
|
|
}
|
|
|
|
// NUW guarantees that we are only shifting out zero bits from the high bits,
|
|
// so we can LSHR the compare constant without needing a mask and eliminate
|
|
// the shift.
|
|
if (Shl->hasNoUnsignedWrap()) {
|
|
if (Pred == ICmpInst::ICMP_UGT) {
|
|
// icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
|
|
APInt ShiftedC = C.lshr(*ShiftAmt);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
|
|
C.lshr(*ShiftAmt).shl(*ShiftAmt) == C) {
|
|
APInt ShiftedC = C.lshr(*ShiftAmt);
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
if (Pred == ICmpInst::ICMP_ULT) {
|
|
// ULE is the same as above, but ULE is canonicalized to ULT, so convert:
|
|
// (X << S) <=u C is equiv to X <=u (C >> S) for all C
|
|
// (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
|
|
// (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
|
|
assert(C.ugt(0) && "ult 0 should have been eliminated");
|
|
APInt ShiftedC = (C - 1).lshr(*ShiftAmt) + 1;
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
|
|
}
|
|
}
|
|
|
|
if (Cmp.isEquality() && Shl->hasOneUse()) {
|
|
// Strength-reduce the shift into an 'and'.
|
|
Constant *Mask = ConstantInt::get(
|
|
ShType,
|
|
APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
|
|
Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
|
|
Constant *LShrC = ConstantInt::get(ShType, C.lshr(*ShiftAmt));
|
|
return new ICmpInst(Pred, And, LShrC);
|
|
}
|
|
|
|
// Otherwise, if this is a comparison of the sign bit, simplify to and/test.
|
|
bool TrueIfSigned = false;
|
|
if (Shl->hasOneUse() && isSignBitCheck(Pred, C, TrueIfSigned)) {
|
|
// (X << 31) <s 0 --> (X & 1) != 0
|
|
Constant *Mask = ConstantInt::get(
|
|
ShType,
|
|
APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
|
|
Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
|
|
return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
|
|
And, Constant::getNullValue(ShType));
|
|
}
|
|
|
|
// Simplify 'shl' inequality test into 'and' equality test.
|
|
if (Cmp.isUnsigned() && Shl->hasOneUse()) {
|
|
// (X l<< C2) u<=/u> C1 iff C1+1 is power of two -> X & (~C1 l>> C2) ==/!= 0
|
|
if ((C + 1).isPowerOf2() &&
|
|
(Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_UGT)) {
|
|
Value *And = Builder.CreateAnd(X, (~C).lshr(ShiftAmt->getZExtValue()));
|
|
return new ICmpInst(Pred == ICmpInst::ICMP_ULE ? ICmpInst::ICMP_EQ
|
|
: ICmpInst::ICMP_NE,
|
|
And, Constant::getNullValue(ShType));
|
|
}
|
|
// (X l<< C2) u</u>= C1 iff C1 is power of two -> X & (-C1 l>> C2) ==/!= 0
|
|
if (C.isPowerOf2() &&
|
|
(Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE)) {
|
|
Value *And =
|
|
Builder.CreateAnd(X, (~(C - 1)).lshr(ShiftAmt->getZExtValue()));
|
|
return new ICmpInst(Pred == ICmpInst::ICMP_ULT ? ICmpInst::ICMP_EQ
|
|
: ICmpInst::ICMP_NE,
|
|
And, Constant::getNullValue(ShType));
|
|
}
|
|
}
|
|
|
|
// Transform (icmp pred iM (shl iM %v, N), C)
|
|
// -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
|
|
// Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
|
|
// This enables us to get rid of the shift in favor of a trunc that may be
|
|
// free on the target. It has the additional benefit of comparing to a
|
|
// smaller constant that may be more target-friendly.
|
|
unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
|
|
if (Shl->hasOneUse() && Amt != 0 && C.countTrailingZeros() >= Amt &&
|
|
DL.isLegalInteger(TypeBits - Amt)) {
|
|
Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
|
|
if (auto *ShVTy = dyn_cast<VectorType>(ShType))
|
|
TruncTy = VectorType::get(TruncTy, ShVTy->getElementCount());
|
|
Constant *NewC =
|
|
ConstantInt::get(TruncTy, C.ashr(*ShiftAmt).trunc(TypeBits - Amt));
|
|
return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp ({al}shr X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpShrConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Shr,
|
|
const APInt &C) {
|
|
// An exact shr only shifts out zero bits, so:
|
|
// icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
|
|
Value *X = Shr->getOperand(0);
|
|
CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
|
|
C.isNullValue())
|
|
return new ICmpInst(Pred, X, Cmp.getOperand(1));
|
|
|
|
const APInt *ShiftVal;
|
|
if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
|
|
return foldICmpShrConstConst(Cmp, Shr->getOperand(1), C, *ShiftVal);
|
|
|
|
const APInt *ShiftAmt;
|
|
if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
|
|
return nullptr;
|
|
|
|
// Check that the shift amount is in range. If not, don't perform undefined
|
|
// shifts. When the shift is visited it will be simplified.
|
|
unsigned TypeBits = C.getBitWidth();
|
|
unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
|
|
if (ShAmtVal >= TypeBits || ShAmtVal == 0)
|
|
return nullptr;
|
|
|
|
bool IsAShr = Shr->getOpcode() == Instruction::AShr;
|
|
bool IsExact = Shr->isExact();
|
|
Type *ShrTy = Shr->getType();
|
|
// TODO: If we could guarantee that InstSimplify would handle all of the
|
|
// constant-value-based preconditions in the folds below, then we could assert
|
|
// those conditions rather than checking them. This is difficult because of
|
|
// undef/poison (PR34838).
|
|
if (IsAShr) {
|
|
if (Pred == CmpInst::ICMP_SLT || (Pred == CmpInst::ICMP_SGT && IsExact)) {
|
|
// icmp slt (ashr X, ShAmtC), C --> icmp slt X, (C << ShAmtC)
|
|
// icmp sgt (ashr exact X, ShAmtC), C --> icmp sgt X, (C << ShAmtC)
|
|
APInt ShiftedC = C.shl(ShAmtVal);
|
|
if (ShiftedC.ashr(ShAmtVal) == C)
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
|
|
}
|
|
if (Pred == CmpInst::ICMP_SGT) {
|
|
// icmp sgt (ashr X, ShAmtC), C --> icmp sgt X, ((C + 1) << ShAmtC) - 1
|
|
APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
|
|
if (!C.isMaxSignedValue() && !(C + 1).shl(ShAmtVal).isMinSignedValue() &&
|
|
(ShiftedC + 1).ashr(ShAmtVal) == (C + 1))
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
|
|
}
|
|
|
|
// If the compare constant has significant bits above the lowest sign-bit,
|
|
// then convert an unsigned cmp to a test of the sign-bit:
|
|
// (ashr X, ShiftC) u> C --> X s< 0
|
|
// (ashr X, ShiftC) u< C --> X s> -1
|
|
if (C.getBitWidth() > 2 && C.getNumSignBits() <= ShAmtVal) {
|
|
if (Pred == CmpInst::ICMP_UGT) {
|
|
return new ICmpInst(CmpInst::ICMP_SLT, X,
|
|
ConstantInt::getNullValue(ShrTy));
|
|
}
|
|
if (Pred == CmpInst::ICMP_ULT) {
|
|
return new ICmpInst(CmpInst::ICMP_SGT, X,
|
|
ConstantInt::getAllOnesValue(ShrTy));
|
|
}
|
|
}
|
|
} else {
|
|
if (Pred == CmpInst::ICMP_ULT || (Pred == CmpInst::ICMP_UGT && IsExact)) {
|
|
// icmp ult (lshr X, ShAmtC), C --> icmp ult X, (C << ShAmtC)
|
|
// icmp ugt (lshr exact X, ShAmtC), C --> icmp ugt X, (C << ShAmtC)
|
|
APInt ShiftedC = C.shl(ShAmtVal);
|
|
if (ShiftedC.lshr(ShAmtVal) == C)
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
|
|
}
|
|
if (Pred == CmpInst::ICMP_UGT) {
|
|
// icmp ugt (lshr X, ShAmtC), C --> icmp ugt X, ((C + 1) << ShAmtC) - 1
|
|
APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
|
|
if ((ShiftedC + 1).lshr(ShAmtVal) == (C + 1))
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
|
|
}
|
|
}
|
|
|
|
if (!Cmp.isEquality())
|
|
return nullptr;
|
|
|
|
// Handle equality comparisons of shift-by-constant.
|
|
|
|
// If the comparison constant changes with the shift, the comparison cannot
|
|
// succeed (bits of the comparison constant cannot match the shifted value).
|
|
// This should be known by InstSimplify and already be folded to true/false.
|
|
assert(((IsAShr && C.shl(ShAmtVal).ashr(ShAmtVal) == C) ||
|
|
(!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&
|
|
"Expected icmp+shr simplify did not occur.");
|
|
|
|
// If the bits shifted out are known zero, compare the unshifted value:
|
|
// (X & 4) >> 1 == 2 --> (X & 4) == 4.
|
|
if (Shr->isExact())
|
|
return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, C << ShAmtVal));
|
|
|
|
if (Shr->hasOneUse()) {
|
|
// Canonicalize the shift into an 'and':
|
|
// icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
|
|
APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
|
|
Constant *Mask = ConstantInt::get(ShrTy, Val);
|
|
Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
|
|
return new ICmpInst(Pred, And, ConstantInt::get(ShrTy, C << ShAmtVal));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::foldICmpSRemConstant(ICmpInst &Cmp,
|
|
BinaryOperator *SRem,
|
|
const APInt &C) {
|
|
// Match an 'is positive' or 'is negative' comparison of remainder by a
|
|
// constant power-of-2 value:
|
|
// (X % pow2C) sgt/slt 0
|
|
const ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
if (Pred != ICmpInst::ICMP_SGT && Pred != ICmpInst::ICMP_SLT)
|
|
return nullptr;
|
|
|
|
// TODO: The one-use check is standard because we do not typically want to
|
|
// create longer instruction sequences, but this might be a special-case
|
|
// because srem is not good for analysis or codegen.
|
|
if (!SRem->hasOneUse())
|
|
return nullptr;
|
|
|
|
const APInt *DivisorC;
|
|
if (!C.isNullValue() || !match(SRem->getOperand(1), m_Power2(DivisorC)))
|
|
return nullptr;
|
|
|
|
// Mask off the sign bit and the modulo bits (low-bits).
|
|
Type *Ty = SRem->getType();
|
|
APInt SignMask = APInt::getSignMask(Ty->getScalarSizeInBits());
|
|
Constant *MaskC = ConstantInt::get(Ty, SignMask | (*DivisorC - 1));
|
|
Value *And = Builder.CreateAnd(SRem->getOperand(0), MaskC);
|
|
|
|
// For 'is positive?' check that the sign-bit is clear and at least 1 masked
|
|
// bit is set. Example:
|
|
// (i8 X % 32) s> 0 --> (X & 159) s> 0
|
|
if (Pred == ICmpInst::ICMP_SGT)
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, And, ConstantInt::getNullValue(Ty));
|
|
|
|
// For 'is negative?' check that the sign-bit is set and at least 1 masked
|
|
// bit is set. Example:
|
|
// (i16 X % 4) s< 0 --> (X & 32771) u> 32768
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, And, ConstantInt::get(Ty, SignMask));
|
|
}
|
|
|
|
/// Fold icmp (udiv X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpUDivConstant(ICmpInst &Cmp,
|
|
BinaryOperator *UDiv,
|
|
const APInt &C) {
|
|
const APInt *C2;
|
|
if (!match(UDiv->getOperand(0), m_APInt(C2)))
|
|
return nullptr;
|
|
|
|
assert(*C2 != 0 && "udiv 0, X should have been simplified already.");
|
|
|
|
// (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
|
|
Value *Y = UDiv->getOperand(1);
|
|
if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
|
|
assert(!C.isMaxValue() &&
|
|
"icmp ugt X, UINT_MAX should have been simplified already.");
|
|
return new ICmpInst(ICmpInst::ICMP_ULE, Y,
|
|
ConstantInt::get(Y->getType(), C2->udiv(C + 1)));
|
|
}
|
|
|
|
// (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
|
|
if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
|
|
assert(C != 0 && "icmp ult X, 0 should have been simplified already.");
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, Y,
|
|
ConstantInt::get(Y->getType(), C2->udiv(C)));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp ({su}div X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpDivConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Div,
|
|
const APInt &C) {
|
|
// Fold: icmp pred ([us]div X, C2), C -> range test
|
|
// Fold this div into the comparison, producing a range check.
|
|
// Determine, based on the divide type, what the range is being
|
|
// checked. If there is an overflow on the low or high side, remember
|
|
// it, otherwise compute the range [low, hi) bounding the new value.
|
|
// See: InsertRangeTest above for the kinds of replacements possible.
|
|
const APInt *C2;
|
|
if (!match(Div->getOperand(1), m_APInt(C2)))
|
|
return nullptr;
|
|
|
|
// FIXME: If the operand types don't match the type of the divide
|
|
// then don't attempt this transform. The code below doesn't have the
|
|
// logic to deal with a signed divide and an unsigned compare (and
|
|
// vice versa). This is because (x /s C2) <s C produces different
|
|
// results than (x /s C2) <u C or (x /u C2) <s C or even
|
|
// (x /u C2) <u C. Simply casting the operands and result won't
|
|
// work. :( The if statement below tests that condition and bails
|
|
// if it finds it.
|
|
bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
|
|
if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
|
|
return nullptr;
|
|
|
|
// The ProdOV computation fails on divide by 0 and divide by -1. Cases with
|
|
// INT_MIN will also fail if the divisor is 1. Although folds of all these
|
|
// division-by-constant cases should be present, we can not assert that they
|
|
// have happened before we reach this icmp instruction.
|
|
if (C2->isNullValue() || C2->isOneValue() ||
|
|
(DivIsSigned && C2->isAllOnesValue()))
|
|
return nullptr;
|
|
|
|
// Compute Prod = C * C2. We are essentially solving an equation of
|
|
// form X / C2 = C. We solve for X by multiplying C2 and C.
|
|
// By solving for X, we can turn this into a range check instead of computing
|
|
// a divide.
|
|
APInt Prod = C * *C2;
|
|
|
|
// Determine if the product overflows by seeing if the product is not equal to
|
|
// the divide. Make sure we do the same kind of divide as in the LHS
|
|
// instruction that we're folding.
|
|
bool ProdOV = (DivIsSigned ? Prod.sdiv(*C2) : Prod.udiv(*C2)) != C;
|
|
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
|
|
// If the division is known to be exact, then there is no remainder from the
|
|
// divide, so the covered range size is unit, otherwise it is the divisor.
|
|
APInt RangeSize = Div->isExact() ? APInt(C2->getBitWidth(), 1) : *C2;
|
|
|
|
// Figure out the interval that is being checked. For example, a comparison
|
|
// like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
|
|
// Compute this interval based on the constants involved and the signedness of
|
|
// the compare/divide. This computes a half-open interval, keeping track of
|
|
// whether either value in the interval overflows. After analysis each
|
|
// overflow variable is set to 0 if it's corresponding bound variable is valid
|
|
// -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
|
|
int LoOverflow = 0, HiOverflow = 0;
|
|
APInt LoBound, HiBound;
|
|
|
|
if (!DivIsSigned) { // udiv
|
|
// e.g. X/5 op 3 --> [15, 20)
|
|
LoBound = Prod;
|
|
HiOverflow = LoOverflow = ProdOV;
|
|
if (!HiOverflow) {
|
|
// If this is not an exact divide, then many values in the range collapse
|
|
// to the same result value.
|
|
HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
|
|
}
|
|
} else if (C2->isStrictlyPositive()) { // Divisor is > 0.
|
|
if (C.isNullValue()) { // (X / pos) op 0
|
|
// Can't overflow. e.g. X/2 op 0 --> [-1, 2)
|
|
LoBound = -(RangeSize - 1);
|
|
HiBound = RangeSize;
|
|
} else if (C.isStrictlyPositive()) { // (X / pos) op pos
|
|
LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
|
|
HiOverflow = LoOverflow = ProdOV;
|
|
if (!HiOverflow)
|
|
HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
|
|
} else { // (X / pos) op neg
|
|
// e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
|
|
HiBound = Prod + 1;
|
|
LoOverflow = HiOverflow = ProdOV ? -1 : 0;
|
|
if (!LoOverflow) {
|
|
APInt DivNeg = -RangeSize;
|
|
LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
|
|
}
|
|
}
|
|
} else if (C2->isNegative()) { // Divisor is < 0.
|
|
if (Div->isExact())
|
|
RangeSize.negate();
|
|
if (C.isNullValue()) { // (X / neg) op 0
|
|
// e.g. X/-5 op 0 --> [-4, 5)
|
|
LoBound = RangeSize + 1;
|
|
HiBound = -RangeSize;
|
|
if (HiBound == *C2) { // -INTMIN = INTMIN
|
|
HiOverflow = 1; // [INTMIN+1, overflow)
|
|
HiBound = APInt(); // e.g. X/INTMIN = 0 --> X > INTMIN
|
|
}
|
|
} else if (C.isStrictlyPositive()) { // (X / neg) op pos
|
|
// e.g. X/-5 op 3 --> [-19, -14)
|
|
HiBound = Prod + 1;
|
|
HiOverflow = LoOverflow = ProdOV ? -1 : 0;
|
|
if (!LoOverflow)
|
|
LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
|
|
} else { // (X / neg) op neg
|
|
LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
|
|
LoOverflow = HiOverflow = ProdOV;
|
|
if (!HiOverflow)
|
|
HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
|
|
}
|
|
|
|
// Dividing by a negative swaps the condition. LT <-> GT
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
}
|
|
|
|
Value *X = Div->getOperand(0);
|
|
switch (Pred) {
|
|
default: llvm_unreachable("Unhandled icmp opcode!");
|
|
case ICmpInst::ICMP_EQ:
|
|
if (LoOverflow && HiOverflow)
|
|
return replaceInstUsesWith(Cmp, Builder.getFalse());
|
|
if (HiOverflow)
|
|
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
|
|
ICmpInst::ICMP_UGE, X,
|
|
ConstantInt::get(Div->getType(), LoBound));
|
|
if (LoOverflow)
|
|
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
|
|
ICmpInst::ICMP_ULT, X,
|
|
ConstantInt::get(Div->getType(), HiBound));
|
|
return replaceInstUsesWith(
|
|
Cmp, insertRangeTest(X, LoBound, HiBound, DivIsSigned, true));
|
|
case ICmpInst::ICMP_NE:
|
|
if (LoOverflow && HiOverflow)
|
|
return replaceInstUsesWith(Cmp, Builder.getTrue());
|
|
if (HiOverflow)
|
|
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
|
|
ICmpInst::ICMP_ULT, X,
|
|
ConstantInt::get(Div->getType(), LoBound));
|
|
if (LoOverflow)
|
|
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
|
|
ICmpInst::ICMP_UGE, X,
|
|
ConstantInt::get(Div->getType(), HiBound));
|
|
return replaceInstUsesWith(Cmp,
|
|
insertRangeTest(X, LoBound, HiBound,
|
|
DivIsSigned, false));
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_SLT:
|
|
if (LoOverflow == +1) // Low bound is greater than input range.
|
|
return replaceInstUsesWith(Cmp, Builder.getTrue());
|
|
if (LoOverflow == -1) // Low bound is less than input range.
|
|
return replaceInstUsesWith(Cmp, Builder.getFalse());
|
|
return new ICmpInst(Pred, X, ConstantInt::get(Div->getType(), LoBound));
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_SGT:
|
|
if (HiOverflow == +1) // High bound greater than input range.
|
|
return replaceInstUsesWith(Cmp, Builder.getFalse());
|
|
if (HiOverflow == -1) // High bound less than input range.
|
|
return replaceInstUsesWith(Cmp, Builder.getTrue());
|
|
if (Pred == ICmpInst::ICMP_UGT)
|
|
return new ICmpInst(ICmpInst::ICMP_UGE, X,
|
|
ConstantInt::get(Div->getType(), HiBound));
|
|
return new ICmpInst(ICmpInst::ICMP_SGE, X,
|
|
ConstantInt::get(Div->getType(), HiBound));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (sub X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpSubConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Sub,
|
|
const APInt &C) {
|
|
Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
const APInt *C2;
|
|
APInt SubResult;
|
|
|
|
// icmp eq/ne (sub C, Y), C -> icmp eq/ne Y, 0
|
|
if (match(X, m_APInt(C2)) && *C2 == C && Cmp.isEquality())
|
|
return new ICmpInst(Cmp.getPredicate(), Y,
|
|
ConstantInt::get(Y->getType(), 0));
|
|
|
|
// (icmp P (sub nuw|nsw C2, Y), C) -> (icmp swap(P) Y, C2-C)
|
|
if (match(X, m_APInt(C2)) &&
|
|
((Cmp.isUnsigned() && Sub->hasNoUnsignedWrap()) ||
|
|
(Cmp.isSigned() && Sub->hasNoSignedWrap())) &&
|
|
!subWithOverflow(SubResult, *C2, C, Cmp.isSigned()))
|
|
return new ICmpInst(Cmp.getSwappedPredicate(), Y,
|
|
ConstantInt::get(Y->getType(), SubResult));
|
|
|
|
// The following transforms are only worth it if the only user of the subtract
|
|
// is the icmp.
|
|
if (!Sub->hasOneUse())
|
|
return nullptr;
|
|
|
|
if (Sub->hasNoSignedWrap()) {
|
|
// (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
|
|
if (Pred == ICmpInst::ICMP_SGT && C.isAllOnesValue())
|
|
return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
|
|
|
|
// (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
|
|
if (Pred == ICmpInst::ICMP_SGT && C.isNullValue())
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
|
|
|
|
// (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
|
|
if (Pred == ICmpInst::ICMP_SLT && C.isNullValue())
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
|
|
|
|
// (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
|
|
if (Pred == ICmpInst::ICMP_SLT && C.isOneValue())
|
|
return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
|
|
}
|
|
|
|
if (!match(X, m_APInt(C2)))
|
|
return nullptr;
|
|
|
|
// C2 - Y <u C -> (Y | (C - 1)) == C2
|
|
// iff (C2 & (C - 1)) == C - 1 and C is a power of 2
|
|
if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() &&
|
|
(*C2 & (C - 1)) == (C - 1))
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, C - 1), X);
|
|
|
|
// C2 - Y >u C -> (Y | C) != C2
|
|
// iff C2 & C == C and C + 1 is a power of 2
|
|
if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == C)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, C), X);
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp (add X, Y), C.
|
|
Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
|
|
BinaryOperator *Add,
|
|
const APInt &C) {
|
|
Value *Y = Add->getOperand(1);
|
|
const APInt *C2;
|
|
if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
|
|
return nullptr;
|
|
|
|
// Fold icmp pred (add X, C2), C.
|
|
Value *X = Add->getOperand(0);
|
|
Type *Ty = Add->getType();
|
|
CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
|
|
// If the add does not wrap, we can always adjust the compare by subtracting
|
|
// the constants. Equality comparisons are handled elsewhere. SGE/SLE/UGE/ULE
|
|
// are canonicalized to SGT/SLT/UGT/ULT.
|
|
if ((Add->hasNoSignedWrap() &&
|
|
(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) ||
|
|
(Add->hasNoUnsignedWrap() &&
|
|
(Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULT))) {
|
|
bool Overflow;
|
|
APInt NewC =
|
|
Cmp.isSigned() ? C.ssub_ov(*C2, Overflow) : C.usub_ov(*C2, Overflow);
|
|
// If there is overflow, the result must be true or false.
|
|
// TODO: Can we assert there is no overflow because InstSimplify always
|
|
// handles those cases?
|
|
if (!Overflow)
|
|
// icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
|
|
return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
|
|
}
|
|
|
|
auto CR = ConstantRange::makeExactICmpRegion(Pred, C).subtract(*C2);
|
|
const APInt &Upper = CR.getUpper();
|
|
const APInt &Lower = CR.getLower();
|
|
if (Cmp.isSigned()) {
|
|
if (Lower.isSignMask())
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
|
|
if (Upper.isSignMask())
|
|
return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
|
|
} else {
|
|
if (Lower.isMinValue())
|
|
return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
|
|
if (Upper.isMinValue())
|
|
return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
|
|
}
|
|
|
|
if (!Add->hasOneUse())
|
|
return nullptr;
|
|
|
|
// X+C <u C2 -> (X & -C2) == C
|
|
// iff C & (C2-1) == 0
|
|
// C2 is a power of 2
|
|
if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() && (*C2 & (C - 1)) == 0)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
|
|
ConstantExpr::getNeg(cast<Constant>(Y)));
|
|
|
|
// X+C >u C2 -> (X & ~C2) != C
|
|
// iff C & C2 == 0
|
|
// C2+1 is a power of 2
|
|
if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == 0)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~C),
|
|
ConstantExpr::getNeg(cast<Constant>(Y)));
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
bool InstCombinerImpl::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
|
|
Value *&RHS, ConstantInt *&Less,
|
|
ConstantInt *&Equal,
|
|
ConstantInt *&Greater) {
|
|
// TODO: Generalize this to work with other comparison idioms or ensure
|
|
// they get canonicalized into this form.
|
|
|
|
// select i1 (a == b),
|
|
// i32 Equal,
|
|
// i32 (select i1 (a < b), i32 Less, i32 Greater)
|
|
// where Equal, Less and Greater are placeholders for any three constants.
|
|
ICmpInst::Predicate PredA;
|
|
if (!match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) ||
|
|
!ICmpInst::isEquality(PredA))
|
|
return false;
|
|
Value *EqualVal = SI->getTrueValue();
|
|
Value *UnequalVal = SI->getFalseValue();
|
|
// We still can get non-canonical predicate here, so canonicalize.
|
|
if (PredA == ICmpInst::ICMP_NE)
|
|
std::swap(EqualVal, UnequalVal);
|
|
if (!match(EqualVal, m_ConstantInt(Equal)))
|
|
return false;
|
|
ICmpInst::Predicate PredB;
|
|
Value *LHS2, *RHS2;
|
|
if (!match(UnequalVal, m_Select(m_ICmp(PredB, m_Value(LHS2), m_Value(RHS2)),
|
|
m_ConstantInt(Less), m_ConstantInt(Greater))))
|
|
return false;
|
|
// We can get predicate mismatch here, so canonicalize if possible:
|
|
// First, ensure that 'LHS' match.
|
|
if (LHS2 != LHS) {
|
|
// x sgt y <--> y slt x
|
|
std::swap(LHS2, RHS2);
|
|
PredB = ICmpInst::getSwappedPredicate(PredB);
|
|
}
|
|
if (LHS2 != LHS)
|
|
return false;
|
|
// We also need to canonicalize 'RHS'.
|
|
if (PredB == ICmpInst::ICMP_SGT && isa<Constant>(RHS2)) {
|
|
// x sgt C-1 <--> x sge C <--> not(x slt C)
|
|
auto FlippedStrictness =
|
|
InstCombiner::getFlippedStrictnessPredicateAndConstant(
|
|
PredB, cast<Constant>(RHS2));
|
|
if (!FlippedStrictness)
|
|
return false;
|
|
assert(FlippedStrictness->first == ICmpInst::ICMP_SGE && "Sanity check");
|
|
RHS2 = FlippedStrictness->second;
|
|
// And kind-of perform the result swap.
|
|
std::swap(Less, Greater);
|
|
PredB = ICmpInst::ICMP_SLT;
|
|
}
|
|
return PredB == ICmpInst::ICMP_SLT && RHS == RHS2;
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::foldICmpSelectConstant(ICmpInst &Cmp,
|
|
SelectInst *Select,
|
|
ConstantInt *C) {
|
|
|
|
assert(C && "Cmp RHS should be a constant int!");
|
|
// If we're testing a constant value against the result of a three way
|
|
// comparison, the result can be expressed directly in terms of the
|
|
// original values being compared. Note: We could possibly be more
|
|
// aggressive here and remove the hasOneUse test. The original select is
|
|
// really likely to simplify or sink when we remove a test of the result.
|
|
Value *OrigLHS, *OrigRHS;
|
|
ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
|
|
if (Cmp.hasOneUse() &&
|
|
matchThreeWayIntCompare(Select, OrigLHS, OrigRHS, C1LessThan, C2Equal,
|
|
C3GreaterThan)) {
|
|
assert(C1LessThan && C2Equal && C3GreaterThan);
|
|
|
|
bool TrueWhenLessThan =
|
|
ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
|
|
->isAllOnesValue();
|
|
bool TrueWhenEqual =
|
|
ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
|
|
->isAllOnesValue();
|
|
bool TrueWhenGreaterThan =
|
|
ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
|
|
->isAllOnesValue();
|
|
|
|
// This generates the new instruction that will replace the original Cmp
|
|
// Instruction. Instead of enumerating the various combinations when
|
|
// TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
|
|
// false, we rely on chaining of ORs and future passes of InstCombine to
|
|
// simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
|
|
|
|
// When none of the three constants satisfy the predicate for the RHS (C),
|
|
// the entire original Cmp can be simplified to a false.
|
|
Value *Cond = Builder.getFalse();
|
|
if (TrueWhenLessThan)
|
|
Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT,
|
|
OrigLHS, OrigRHS));
|
|
if (TrueWhenEqual)
|
|
Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ,
|
|
OrigLHS, OrigRHS));
|
|
if (TrueWhenGreaterThan)
|
|
Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT,
|
|
OrigLHS, OrigRHS));
|
|
|
|
return replaceInstUsesWith(Cmp, Cond);
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
static Instruction *foldICmpBitCast(ICmpInst &Cmp,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
auto *Bitcast = dyn_cast<BitCastInst>(Cmp.getOperand(0));
|
|
if (!Bitcast)
|
|
return nullptr;
|
|
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *Op1 = Cmp.getOperand(1);
|
|
Value *BCSrcOp = Bitcast->getOperand(0);
|
|
|
|
// Make sure the bitcast doesn't change the number of vector elements.
|
|
if (Bitcast->getSrcTy()->getScalarSizeInBits() ==
|
|
Bitcast->getDestTy()->getScalarSizeInBits()) {
|
|
// Zero-equality and sign-bit checks are preserved through sitofp + bitcast.
|
|
Value *X;
|
|
if (match(BCSrcOp, m_SIToFP(m_Value(X)))) {
|
|
// icmp eq (bitcast (sitofp X)), 0 --> icmp eq X, 0
|
|
// icmp ne (bitcast (sitofp X)), 0 --> icmp ne X, 0
|
|
// icmp slt (bitcast (sitofp X)), 0 --> icmp slt X, 0
|
|
// icmp sgt (bitcast (sitofp X)), 0 --> icmp sgt X, 0
|
|
if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_SLT ||
|
|
Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT) &&
|
|
match(Op1, m_Zero()))
|
|
return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
|
|
|
|
// icmp slt (bitcast (sitofp X)), 1 --> icmp slt X, 1
|
|
if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_One()))
|
|
return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), 1));
|
|
|
|
// icmp sgt (bitcast (sitofp X)), -1 --> icmp sgt X, -1
|
|
if (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))
|
|
return new ICmpInst(Pred, X,
|
|
ConstantInt::getAllOnesValue(X->getType()));
|
|
}
|
|
|
|
// Zero-equality checks are preserved through unsigned floating-point casts:
|
|
// icmp eq (bitcast (uitofp X)), 0 --> icmp eq X, 0
|
|
// icmp ne (bitcast (uitofp X)), 0 --> icmp ne X, 0
|
|
if (match(BCSrcOp, m_UIToFP(m_Value(X))))
|
|
if (Cmp.isEquality() && match(Op1, m_Zero()))
|
|
return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
|
|
|
|
// If this is a sign-bit test of a bitcast of a casted FP value, eliminate
|
|
// the FP extend/truncate because that cast does not change the sign-bit.
|
|
// This is true for all standard IEEE-754 types and the X86 80-bit type.
|
|
// The sign-bit is always the most significant bit in those types.
|
|
const APInt *C;
|
|
bool TrueIfSigned;
|
|
if (match(Op1, m_APInt(C)) && Bitcast->hasOneUse() &&
|
|
InstCombiner::isSignBitCheck(Pred, *C, TrueIfSigned)) {
|
|
if (match(BCSrcOp, m_FPExt(m_Value(X))) ||
|
|
match(BCSrcOp, m_FPTrunc(m_Value(X)))) {
|
|
// (bitcast (fpext/fptrunc X)) to iX) < 0 --> (bitcast X to iY) < 0
|
|
// (bitcast (fpext/fptrunc X)) to iX) > -1 --> (bitcast X to iY) > -1
|
|
Type *XType = X->getType();
|
|
|
|
// We can't currently handle Power style floating point operations here.
|
|
if (!(XType->isPPC_FP128Ty() || BCSrcOp->getType()->isPPC_FP128Ty())) {
|
|
|
|
Type *NewType = Builder.getIntNTy(XType->getScalarSizeInBits());
|
|
if (auto *XVTy = dyn_cast<VectorType>(XType))
|
|
NewType = VectorType::get(NewType, XVTy->getElementCount());
|
|
Value *NewBitcast = Builder.CreateBitCast(X, NewType);
|
|
if (TrueIfSigned)
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, NewBitcast,
|
|
ConstantInt::getNullValue(NewType));
|
|
else
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, NewBitcast,
|
|
ConstantInt::getAllOnesValue(NewType));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Test to see if the operands of the icmp are casted versions of other
|
|
// values. If the ptr->ptr cast can be stripped off both arguments, do so.
|
|
if (Bitcast->getType()->isPointerTy() &&
|
|
(isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
|
|
// If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
|
|
// so eliminate it as well.
|
|
if (auto *BC2 = dyn_cast<BitCastInst>(Op1))
|
|
Op1 = BC2->getOperand(0);
|
|
|
|
Op1 = Builder.CreateBitCast(Op1, BCSrcOp->getType());
|
|
return new ICmpInst(Pred, BCSrcOp, Op1);
|
|
}
|
|
|
|
// Folding: icmp <pred> iN X, C
|
|
// where X = bitcast <M x iK> (shufflevector <M x iK> %vec, undef, SC)) to iN
|
|
// and C is a splat of a K-bit pattern
|
|
// and SC is a constant vector = <C', C', C', ..., C'>
|
|
// Into:
|
|
// %E = extractelement <M x iK> %vec, i32 C'
|
|
// icmp <pred> iK %E, trunc(C)
|
|
const APInt *C;
|
|
if (!match(Cmp.getOperand(1), m_APInt(C)) ||
|
|
!Bitcast->getType()->isIntegerTy() ||
|
|
!Bitcast->getSrcTy()->isIntOrIntVectorTy())
|
|
return nullptr;
|
|
|
|
Value *Vec;
|
|
ArrayRef<int> Mask;
|
|
if (match(BCSrcOp, m_Shuffle(m_Value(Vec), m_Undef(), m_Mask(Mask)))) {
|
|
// Check whether every element of Mask is the same constant
|
|
if (is_splat(Mask)) {
|
|
auto *VecTy = cast<VectorType>(BCSrcOp->getType());
|
|
auto *EltTy = cast<IntegerType>(VecTy->getElementType());
|
|
if (C->isSplat(EltTy->getBitWidth())) {
|
|
// Fold the icmp based on the value of C
|
|
// If C is M copies of an iK sized bit pattern,
|
|
// then:
|
|
// => %E = extractelement <N x iK> %vec, i32 Elem
|
|
// icmp <pred> iK %SplatVal, <pattern>
|
|
Value *Elem = Builder.getInt32(Mask[0]);
|
|
Value *Extract = Builder.CreateExtractElement(Vec, Elem);
|
|
Value *NewC = ConstantInt::get(EltTy, C->trunc(EltTy->getBitWidth()));
|
|
return new ICmpInst(Pred, Extract, NewC);
|
|
}
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// Try to fold integer comparisons with a constant operand: icmp Pred X, C
|
|
/// where X is some kind of instruction.
|
|
Instruction *InstCombinerImpl::foldICmpInstWithConstant(ICmpInst &Cmp) {
|
|
const APInt *C;
|
|
if (!match(Cmp.getOperand(1), m_APInt(C)))
|
|
return nullptr;
|
|
|
|
if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
|
|
switch (BO->getOpcode()) {
|
|
case Instruction::Xor:
|
|
if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::And:
|
|
if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::Or:
|
|
if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::Mul:
|
|
if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::Shl:
|
|
if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::SRem:
|
|
if (Instruction *I = foldICmpSRemConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::UDiv:
|
|
if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
|
|
return I;
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::SDiv:
|
|
if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::Sub:
|
|
if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
case Instruction::Add:
|
|
if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
|
|
return I;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
// TODO: These folds could be refactored to be part of the above calls.
|
|
if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
|
|
return I;
|
|
}
|
|
|
|
// Match against CmpInst LHS being instructions other than binary operators.
|
|
|
|
if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
|
|
// For now, we only support constant integers while folding the
|
|
// ICMP(SELECT)) pattern. We can extend this to support vector of integers
|
|
// similar to the cases handled by binary ops above.
|
|
if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
|
|
if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
|
|
return I;
|
|
}
|
|
|
|
if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
|
|
if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
|
|
return I;
|
|
}
|
|
|
|
if (auto *II = dyn_cast<IntrinsicInst>(Cmp.getOperand(0)))
|
|
if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, II, *C))
|
|
return I;
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold an icmp equality instruction with binary operator LHS and constant RHS:
|
|
/// icmp eq/ne BO, C.
|
|
Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
|
|
ICmpInst &Cmp, BinaryOperator *BO, const APInt &C) {
|
|
// TODO: Some of these folds could work with arbitrary constants, but this
|
|
// function is limited to scalar and vector splat constants.
|
|
if (!Cmp.isEquality())
|
|
return nullptr;
|
|
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
|
|
Constant *RHS = cast<Constant>(Cmp.getOperand(1));
|
|
Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
|
|
|
|
switch (BO->getOpcode()) {
|
|
case Instruction::SRem:
|
|
// If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
|
|
if (C.isNullValue() && BO->hasOneUse()) {
|
|
const APInt *BOC;
|
|
if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
|
|
Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
|
|
return new ICmpInst(Pred, NewRem,
|
|
Constant::getNullValue(BO->getType()));
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::Add: {
|
|
// Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
|
|
if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
|
|
if (BO->hasOneUse())
|
|
return new ICmpInst(Pred, BOp0, ConstantExpr::getSub(RHS, BOC));
|
|
} else if (C.isNullValue()) {
|
|
// Replace ((add A, B) != 0) with (A != -B) if A or B is
|
|
// efficiently invertible, or if the add has just this one use.
|
|
if (Value *NegVal = dyn_castNegVal(BOp1))
|
|
return new ICmpInst(Pred, BOp0, NegVal);
|
|
if (Value *NegVal = dyn_castNegVal(BOp0))
|
|
return new ICmpInst(Pred, NegVal, BOp1);
|
|
if (BO->hasOneUse()) {
|
|
Value *Neg = Builder.CreateNeg(BOp1);
|
|
Neg->takeName(BO);
|
|
return new ICmpInst(Pred, BOp0, Neg);
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Xor:
|
|
if (BO->hasOneUse()) {
|
|
if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
|
|
// For the xor case, we can xor two constants together, eliminating
|
|
// the explicit xor.
|
|
return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
|
|
} else if (C.isNullValue()) {
|
|
// Replace ((xor A, B) != 0) with (A != B)
|
|
return new ICmpInst(Pred, BOp0, BOp1);
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::Sub:
|
|
if (BO->hasOneUse()) {
|
|
// Only check for constant LHS here, as constant RHS will be canonicalized
|
|
// to add and use the fold above.
|
|
if (Constant *BOC = dyn_cast<Constant>(BOp0)) {
|
|
// Replace ((sub BOC, B) != C) with (B != BOC-C).
|
|
return new ICmpInst(Pred, BOp1, ConstantExpr::getSub(BOC, RHS));
|
|
} else if (C.isNullValue()) {
|
|
// Replace ((sub A, B) != 0) with (A != B).
|
|
return new ICmpInst(Pred, BOp0, BOp1);
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::Or: {
|
|
const APInt *BOC;
|
|
if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
|
|
// Comparing if all bits outside of a constant mask are set?
|
|
// Replace (X | C) == -1 with (X & ~C) == ~C.
|
|
// This removes the -1 constant.
|
|
Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
|
|
Value *And = Builder.CreateAnd(BOp0, NotBOC);
|
|
return new ICmpInst(Pred, And, NotBOC);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::And: {
|
|
const APInt *BOC;
|
|
if (match(BOp1, m_APInt(BOC))) {
|
|
// If we have ((X & C) == C), turn it into ((X & C) != 0).
|
|
if (C == *BOC && C.isPowerOf2())
|
|
return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
|
|
BO, Constant::getNullValue(RHS->getType()));
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::UDiv:
|
|
if (C.isNullValue()) {
|
|
// (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
|
|
auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
|
|
return new ICmpInst(NewPred, BOp1, BOp0);
|
|
}
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold an equality icmp with LLVM intrinsic and constant operand.
|
|
Instruction *InstCombinerImpl::foldICmpEqIntrinsicWithConstant(
|
|
ICmpInst &Cmp, IntrinsicInst *II, const APInt &C) {
|
|
Type *Ty = II->getType();
|
|
unsigned BitWidth = C.getBitWidth();
|
|
switch (II->getIntrinsicID()) {
|
|
case Intrinsic::abs:
|
|
// abs(A) == 0 -> A == 0
|
|
// abs(A) == INT_MIN -> A == INT_MIN
|
|
if (C.isNullValue() || C.isMinSignedValue())
|
|
return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
|
|
ConstantInt::get(Ty, C));
|
|
break;
|
|
|
|
case Intrinsic::bswap:
|
|
// bswap(A) == C -> A == bswap(C)
|
|
return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
|
|
ConstantInt::get(Ty, C.byteSwap()));
|
|
|
|
case Intrinsic::ctlz:
|
|
case Intrinsic::cttz: {
|
|
// ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
|
|
if (C == BitWidth)
|
|
return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
|
|
ConstantInt::getNullValue(Ty));
|
|
|
|
// ctz(A) == C -> A & Mask1 == Mask2, where Mask2 only has bit C set
|
|
// and Mask1 has bits 0..C+1 set. Similar for ctl, but for high bits.
|
|
// Limit to one use to ensure we don't increase instruction count.
|
|
unsigned Num = C.getLimitedValue(BitWidth);
|
|
if (Num != BitWidth && II->hasOneUse()) {
|
|
bool IsTrailing = II->getIntrinsicID() == Intrinsic::cttz;
|
|
APInt Mask1 = IsTrailing ? APInt::getLowBitsSet(BitWidth, Num + 1)
|
|
: APInt::getHighBitsSet(BitWidth, Num + 1);
|
|
APInt Mask2 = IsTrailing
|
|
? APInt::getOneBitSet(BitWidth, Num)
|
|
: APInt::getOneBitSet(BitWidth, BitWidth - Num - 1);
|
|
return new ICmpInst(Cmp.getPredicate(),
|
|
Builder.CreateAnd(II->getArgOperand(0), Mask1),
|
|
ConstantInt::get(Ty, Mask2));
|
|
}
|
|
break;
|
|
}
|
|
|
|
case Intrinsic::ctpop: {
|
|
// popcount(A) == 0 -> A == 0 and likewise for !=
|
|
// popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
|
|
bool IsZero = C.isNullValue();
|
|
if (IsZero || C == BitWidth)
|
|
return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
|
|
IsZero ? Constant::getNullValue(Ty) : Constant::getAllOnesValue(Ty));
|
|
|
|
break;
|
|
}
|
|
|
|
case Intrinsic::uadd_sat: {
|
|
// uadd.sat(a, b) == 0 -> (a | b) == 0
|
|
if (C.isNullValue()) {
|
|
Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1));
|
|
return new ICmpInst(Cmp.getPredicate(), Or, Constant::getNullValue(Ty));
|
|
}
|
|
break;
|
|
}
|
|
|
|
case Intrinsic::usub_sat: {
|
|
// usub.sat(a, b) == 0 -> a <= b
|
|
if (C.isNullValue()) {
|
|
ICmpInst::Predicate NewPred = Cmp.getPredicate() == ICmpInst::ICMP_EQ
|
|
? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
|
|
return new ICmpInst(NewPred, II->getArgOperand(0), II->getArgOperand(1));
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
|
|
Instruction *InstCombinerImpl::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
|
|
IntrinsicInst *II,
|
|
const APInt &C) {
|
|
if (Cmp.isEquality())
|
|
return foldICmpEqIntrinsicWithConstant(Cmp, II, C);
|
|
|
|
Type *Ty = II->getType();
|
|
unsigned BitWidth = C.getBitWidth();
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
switch (II->getIntrinsicID()) {
|
|
case Intrinsic::ctpop: {
|
|
// (ctpop X > BitWidth - 1) --> X == -1
|
|
Value *X = II->getArgOperand(0);
|
|
if (C == BitWidth - 1 && Pred == ICmpInst::ICMP_UGT)
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ, X,
|
|
ConstantInt::getAllOnesValue(Ty));
|
|
// (ctpop X < BitWidth) --> X != -1
|
|
if (C == BitWidth && Pred == ICmpInst::ICMP_ULT)
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_NE, X,
|
|
ConstantInt::getAllOnesValue(Ty));
|
|
break;
|
|
}
|
|
case Intrinsic::ctlz: {
|
|
// ctlz(0bXXXXXXXX) > 3 -> 0bXXXXXXXX < 0b00010000
|
|
if (Pred == ICmpInst::ICMP_UGT && C.ult(BitWidth)) {
|
|
unsigned Num = C.getLimitedValue();
|
|
APInt Limit = APInt::getOneBitSet(BitWidth, BitWidth - Num - 1);
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_ULT,
|
|
II->getArgOperand(0), ConstantInt::get(Ty, Limit));
|
|
}
|
|
|
|
// ctlz(0bXXXXXXXX) < 3 -> 0bXXXXXXXX > 0b00011111
|
|
if (Pred == ICmpInst::ICMP_ULT && C.uge(1) && C.ule(BitWidth)) {
|
|
unsigned Num = C.getLimitedValue();
|
|
APInt Limit = APInt::getLowBitsSet(BitWidth, BitWidth - Num);
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_UGT,
|
|
II->getArgOperand(0), ConstantInt::get(Ty, Limit));
|
|
}
|
|
break;
|
|
}
|
|
case Intrinsic::cttz: {
|
|
// Limit to one use to ensure we don't increase instruction count.
|
|
if (!II->hasOneUse())
|
|
return nullptr;
|
|
|
|
// cttz(0bXXXXXXXX) > 3 -> 0bXXXXXXXX & 0b00001111 == 0
|
|
if (Pred == ICmpInst::ICMP_UGT && C.ult(BitWidth)) {
|
|
APInt Mask = APInt::getLowBitsSet(BitWidth, C.getLimitedValue() + 1);
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ,
|
|
Builder.CreateAnd(II->getArgOperand(0), Mask),
|
|
ConstantInt::getNullValue(Ty));
|
|
}
|
|
|
|
// cttz(0bXXXXXXXX) < 3 -> 0bXXXXXXXX & 0b00000111 != 0
|
|
if (Pred == ICmpInst::ICMP_ULT && C.uge(1) && C.ule(BitWidth)) {
|
|
APInt Mask = APInt::getLowBitsSet(BitWidth, C.getLimitedValue());
|
|
return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_NE,
|
|
Builder.CreateAnd(II->getArgOperand(0), Mask),
|
|
ConstantInt::getNullValue(Ty));
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Handle icmp with constant (but not simple integer constant) RHS.
|
|
Instruction *InstCombinerImpl::foldICmpInstWithConstantNotInt(ICmpInst &I) {
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
Constant *RHSC = dyn_cast<Constant>(Op1);
|
|
Instruction *LHSI = dyn_cast<Instruction>(Op0);
|
|
if (!RHSC || !LHSI)
|
|
return nullptr;
|
|
|
|
switch (LHSI->getOpcode()) {
|
|
case Instruction::GetElementPtr:
|
|
// icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
|
|
if (RHSC->isNullValue() &&
|
|
cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
|
|
return new ICmpInst(
|
|
I.getPredicate(), LHSI->getOperand(0),
|
|
Constant::getNullValue(LHSI->getOperand(0)->getType()));
|
|
break;
|
|
case Instruction::PHI:
|
|
// Only fold icmp into the PHI if the phi and icmp are in the same
|
|
// block. If in the same block, we're encouraging jump threading. If
|
|
// not, we are just pessimizing the code by making an i1 phi.
|
|
if (LHSI->getParent() == I.getParent())
|
|
if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
|
|
return NV;
|
|
break;
|
|
case Instruction::Select: {
|
|
// If either operand of the select is a constant, we can fold the
|
|
// comparison into the select arms, which will cause one to be
|
|
// constant folded and the select turned into a bitwise or.
|
|
Value *Op1 = nullptr, *Op2 = nullptr;
|
|
ConstantInt *CI = nullptr;
|
|
if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
|
|
Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
|
|
CI = dyn_cast<ConstantInt>(Op1);
|
|
}
|
|
if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
|
|
Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
|
|
CI = dyn_cast<ConstantInt>(Op2);
|
|
}
|
|
|
|
// We only want to perform this transformation if it will not lead to
|
|
// additional code. This is true if either both sides of the select
|
|
// fold to a constant (in which case the icmp is replaced with a select
|
|
// which will usually simplify) or this is the only user of the
|
|
// select (in which case we are trading a select+icmp for a simpler
|
|
// select+icmp) or all uses of the select can be replaced based on
|
|
// dominance information ("Global cases").
|
|
bool Transform = false;
|
|
if (Op1 && Op2)
|
|
Transform = true;
|
|
else if (Op1 || Op2) {
|
|
// Local case
|
|
if (LHSI->hasOneUse())
|
|
Transform = true;
|
|
// Global cases
|
|
else if (CI && !CI->isZero())
|
|
// When Op1 is constant try replacing select with second operand.
|
|
// Otherwise Op2 is constant and try replacing select with first
|
|
// operand.
|
|
Transform =
|
|
replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
|
|
}
|
|
if (Transform) {
|
|
if (!Op1)
|
|
Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
|
|
I.getName());
|
|
if (!Op2)
|
|
Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
|
|
I.getName());
|
|
return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::IntToPtr:
|
|
// icmp pred inttoptr(X), null -> icmp pred X, 0
|
|
if (RHSC->isNullValue() &&
|
|
DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
|
|
return new ICmpInst(
|
|
I.getPredicate(), LHSI->getOperand(0),
|
|
Constant::getNullValue(LHSI->getOperand(0)->getType()));
|
|
break;
|
|
|
|
case Instruction::Load:
|
|
// Try to optimize things like "A[i] > 4" to index computations.
|
|
if (GetElementPtrInst *GEP =
|
|
dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
|
|
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
|
|
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
|
|
!cast<LoadInst>(LHSI)->isVolatile())
|
|
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
|
|
return Res;
|
|
}
|
|
break;
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Some comparisons can be simplified.
|
|
/// In this case, we are looking for comparisons that look like
|
|
/// a check for a lossy truncation.
|
|
/// Folds:
|
|
/// icmp SrcPred (x & Mask), x to icmp DstPred x, Mask
|
|
/// Where Mask is some pattern that produces all-ones in low bits:
|
|
/// (-1 >> y)
|
|
/// ((-1 << y) >> y) <- non-canonical, has extra uses
|
|
/// ~(-1 << y)
|
|
/// ((1 << y) + (-1)) <- non-canonical, has extra uses
|
|
/// The Mask can be a constant, too.
|
|
/// For some predicates, the operands are commutative.
|
|
/// For others, x can only be on a specific side.
|
|
static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
ICmpInst::Predicate SrcPred;
|
|
Value *X, *M, *Y;
|
|
auto m_VariableMask = m_CombineOr(
|
|
m_CombineOr(m_Not(m_Shl(m_AllOnes(), m_Value())),
|
|
m_Add(m_Shl(m_One(), m_Value()), m_AllOnes())),
|
|
m_CombineOr(m_LShr(m_AllOnes(), m_Value()),
|
|
m_LShr(m_Shl(m_AllOnes(), m_Value(Y)), m_Deferred(Y))));
|
|
auto m_Mask = m_CombineOr(m_VariableMask, m_LowBitMask());
|
|
if (!match(&I, m_c_ICmp(SrcPred,
|
|
m_c_And(m_CombineAnd(m_Mask, m_Value(M)), m_Value(X)),
|
|
m_Deferred(X))))
|
|
return nullptr;
|
|
|
|
ICmpInst::Predicate DstPred;
|
|
switch (SrcPred) {
|
|
case ICmpInst::Predicate::ICMP_EQ:
|
|
// x & (-1 >> y) == x -> x u<= (-1 >> y)
|
|
DstPred = ICmpInst::Predicate::ICMP_ULE;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_NE:
|
|
// x & (-1 >> y) != x -> x u> (-1 >> y)
|
|
DstPred = ICmpInst::Predicate::ICMP_UGT;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_ULT:
|
|
// x & (-1 >> y) u< x -> x u> (-1 >> y)
|
|
// x u> x & (-1 >> y) -> x u> (-1 >> y)
|
|
DstPred = ICmpInst::Predicate::ICMP_UGT;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_UGE:
|
|
// x & (-1 >> y) u>= x -> x u<= (-1 >> y)
|
|
// x u<= x & (-1 >> y) -> x u<= (-1 >> y)
|
|
DstPred = ICmpInst::Predicate::ICMP_ULE;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_SLT:
|
|
// x & (-1 >> y) s< x -> x s> (-1 >> y)
|
|
// x s> x & (-1 >> y) -> x s> (-1 >> y)
|
|
if (!match(M, m_Constant())) // Can not do this fold with non-constant.
|
|
return nullptr;
|
|
if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
|
|
return nullptr;
|
|
DstPred = ICmpInst::Predicate::ICMP_SGT;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_SGE:
|
|
// x & (-1 >> y) s>= x -> x s<= (-1 >> y)
|
|
// x s<= x & (-1 >> y) -> x s<= (-1 >> y)
|
|
if (!match(M, m_Constant())) // Can not do this fold with non-constant.
|
|
return nullptr;
|
|
if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
|
|
return nullptr;
|
|
DstPred = ICmpInst::Predicate::ICMP_SLE;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_SGT:
|
|
case ICmpInst::Predicate::ICMP_SLE:
|
|
return nullptr;
|
|
case ICmpInst::Predicate::ICMP_UGT:
|
|
case ICmpInst::Predicate::ICMP_ULE:
|
|
llvm_unreachable("Instsimplify took care of commut. variant");
|
|
break;
|
|
default:
|
|
llvm_unreachable("All possible folds are handled.");
|
|
}
|
|
|
|
// The mask value may be a vector constant that has undefined elements. But it
|
|
// may not be safe to propagate those undefs into the new compare, so replace
|
|
// those elements by copying an existing, defined, and safe scalar constant.
|
|
Type *OpTy = M->getType();
|
|
auto *VecC = dyn_cast<Constant>(M);
|
|
auto *OpVTy = dyn_cast<FixedVectorType>(OpTy);
|
|
if (OpVTy && VecC && VecC->containsUndefOrPoisonElement()) {
|
|
Constant *SafeReplacementConstant = nullptr;
|
|
for (unsigned i = 0, e = OpVTy->getNumElements(); i != e; ++i) {
|
|
if (!isa<UndefValue>(VecC->getAggregateElement(i))) {
|
|
SafeReplacementConstant = VecC->getAggregateElement(i);
|
|
break;
|
|
}
|
|
}
|
|
assert(SafeReplacementConstant && "Failed to find undef replacement");
|
|
M = Constant::replaceUndefsWith(VecC, SafeReplacementConstant);
|
|
}
|
|
|
|
return Builder.CreateICmp(DstPred, X, M);
|
|
}
|
|
|
|
/// Some comparisons can be simplified.
|
|
/// In this case, we are looking for comparisons that look like
|
|
/// a check for a lossy signed truncation.
|
|
/// Folds: (MaskedBits is a constant.)
|
|
/// ((%x << MaskedBits) a>> MaskedBits) SrcPred %x
|
|
/// Into:
|
|
/// (add %x, (1 << (KeptBits-1))) DstPred (1 << KeptBits)
|
|
/// Where KeptBits = bitwidth(%x) - MaskedBits
|
|
static Value *
|
|
foldICmpWithTruncSignExtendedVal(ICmpInst &I,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
ICmpInst::Predicate SrcPred;
|
|
Value *X;
|
|
const APInt *C0, *C1; // FIXME: non-splats, potentially with undef.
|
|
// We are ok with 'shl' having multiple uses, but 'ashr' must be one-use.
|
|
if (!match(&I, m_c_ICmp(SrcPred,
|
|
m_OneUse(m_AShr(m_Shl(m_Value(X), m_APInt(C0)),
|
|
m_APInt(C1))),
|
|
m_Deferred(X))))
|
|
return nullptr;
|
|
|
|
// Potential handling of non-splats: for each element:
|
|
// * if both are undef, replace with constant 0.
|
|
// Because (1<<0) is OK and is 1, and ((1<<0)>>1) is also OK and is 0.
|
|
// * if both are not undef, and are different, bailout.
|
|
// * else, only one is undef, then pick the non-undef one.
|
|
|
|
// The shift amount must be equal.
|
|
if (*C0 != *C1)
|
|
return nullptr;
|
|
const APInt &MaskedBits = *C0;
|
|
assert(MaskedBits != 0 && "shift by zero should be folded away already.");
|
|
|
|
ICmpInst::Predicate DstPred;
|
|
switch (SrcPred) {
|
|
case ICmpInst::Predicate::ICMP_EQ:
|
|
// ((%x << MaskedBits) a>> MaskedBits) == %x
|
|
// =>
|
|
// (add %x, (1 << (KeptBits-1))) u< (1 << KeptBits)
|
|
DstPred = ICmpInst::Predicate::ICMP_ULT;
|
|
break;
|
|
case ICmpInst::Predicate::ICMP_NE:
|
|
// ((%x << MaskedBits) a>> MaskedBits) != %x
|
|
// =>
|
|
// (add %x, (1 << (KeptBits-1))) u>= (1 << KeptBits)
|
|
DstPred = ICmpInst::Predicate::ICMP_UGE;
|
|
break;
|
|
// FIXME: are more folds possible?
|
|
default:
|
|
return nullptr;
|
|
}
|
|
|
|
auto *XType = X->getType();
|
|
const unsigned XBitWidth = XType->getScalarSizeInBits();
|
|
const APInt BitWidth = APInt(XBitWidth, XBitWidth);
|
|
assert(BitWidth.ugt(MaskedBits) && "shifts should leave some bits untouched");
|
|
|
|
// KeptBits = bitwidth(%x) - MaskedBits
|
|
const APInt KeptBits = BitWidth - MaskedBits;
|
|
assert(KeptBits.ugt(0) && KeptBits.ult(BitWidth) && "unreachable");
|
|
// ICmpCst = (1 << KeptBits)
|
|
const APInt ICmpCst = APInt(XBitWidth, 1).shl(KeptBits);
|
|
assert(ICmpCst.isPowerOf2());
|
|
// AddCst = (1 << (KeptBits-1))
|
|
const APInt AddCst = ICmpCst.lshr(1);
|
|
assert(AddCst.ult(ICmpCst) && AddCst.isPowerOf2());
|
|
|
|
// T0 = add %x, AddCst
|
|
Value *T0 = Builder.CreateAdd(X, ConstantInt::get(XType, AddCst));
|
|
// T1 = T0 DstPred ICmpCst
|
|
Value *T1 = Builder.CreateICmp(DstPred, T0, ConstantInt::get(XType, ICmpCst));
|
|
|
|
return T1;
|
|
}
|
|
|
|
// Given pattern:
|
|
// icmp eq/ne (and ((x shift Q), (y oppositeshift K))), 0
|
|
// we should move shifts to the same hand of 'and', i.e. rewrite as
|
|
// icmp eq/ne (and (x shift (Q+K)), y), 0 iff (Q+K) u< bitwidth(x)
|
|
// We are only interested in opposite logical shifts here.
|
|
// One of the shifts can be truncated.
|
|
// If we can, we want to end up creating 'lshr' shift.
|
|
static Value *
|
|
foldShiftIntoShiftInAnotherHandOfAndInICmp(ICmpInst &I, const SimplifyQuery SQ,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
if (!I.isEquality() || !match(I.getOperand(1), m_Zero()) ||
|
|
!I.getOperand(0)->hasOneUse())
|
|
return nullptr;
|
|
|
|
auto m_AnyLogicalShift = m_LogicalShift(m_Value(), m_Value());
|
|
|
|
// Look for an 'and' of two logical shifts, one of which may be truncated.
|
|
// We use m_TruncOrSelf() on the RHS to correctly handle commutative case.
|
|
Instruction *XShift, *MaybeTruncation, *YShift;
|
|
if (!match(
|
|
I.getOperand(0),
|
|
m_c_And(m_CombineAnd(m_AnyLogicalShift, m_Instruction(XShift)),
|
|
m_CombineAnd(m_TruncOrSelf(m_CombineAnd(
|
|
m_AnyLogicalShift, m_Instruction(YShift))),
|
|
m_Instruction(MaybeTruncation)))))
|
|
return nullptr;
|
|
|
|
// We potentially looked past 'trunc', but only when matching YShift,
|
|
// therefore YShift must have the widest type.
|
|
Instruction *WidestShift = YShift;
|
|
// Therefore XShift must have the shallowest type.
|
|
// Or they both have identical types if there was no truncation.
|
|
Instruction *NarrowestShift = XShift;
|
|
|
|
Type *WidestTy = WidestShift->getType();
|
|
Type *NarrowestTy = NarrowestShift->getType();
|
|
assert(NarrowestTy == I.getOperand(0)->getType() &&
|
|
"We did not look past any shifts while matching XShift though.");
|
|
bool HadTrunc = WidestTy != I.getOperand(0)->getType();
|
|
|
|
// If YShift is a 'lshr', swap the shifts around.
|
|
if (match(YShift, m_LShr(m_Value(), m_Value())))
|
|
std::swap(XShift, YShift);
|
|
|
|
// The shifts must be in opposite directions.
|
|
auto XShiftOpcode = XShift->getOpcode();
|
|
if (XShiftOpcode == YShift->getOpcode())
|
|
return nullptr; // Do not care about same-direction shifts here.
|
|
|
|
Value *X, *XShAmt, *Y, *YShAmt;
|
|
match(XShift, m_BinOp(m_Value(X), m_ZExtOrSelf(m_Value(XShAmt))));
|
|
match(YShift, m_BinOp(m_Value(Y), m_ZExtOrSelf(m_Value(YShAmt))));
|
|
|
|
// If one of the values being shifted is a constant, then we will end with
|
|
// and+icmp, and [zext+]shift instrs will be constant-folded. If they are not,
|
|
// however, we will need to ensure that we won't increase instruction count.
|
|
if (!isa<Constant>(X) && !isa<Constant>(Y)) {
|
|
// At least one of the hands of the 'and' should be one-use shift.
|
|
if (!match(I.getOperand(0),
|
|
m_c_And(m_OneUse(m_AnyLogicalShift), m_Value())))
|
|
return nullptr;
|
|
if (HadTrunc) {
|
|
// Due to the 'trunc', we will need to widen X. For that either the old
|
|
// 'trunc' or the shift amt in the non-truncated shift should be one-use.
|
|
if (!MaybeTruncation->hasOneUse() &&
|
|
!NarrowestShift->getOperand(1)->hasOneUse())
|
|
return nullptr;
|
|
}
|
|
}
|
|
|
|
// We have two shift amounts from two different shifts. The types of those
|
|
// shift amounts may not match. If that's the case let's bailout now.
|
|
if (XShAmt->getType() != YShAmt->getType())
|
|
return nullptr;
|
|
|
|
// As input, we have the following pattern:
|
|
// icmp eq/ne (and ((x shift Q), (y oppositeshift K))), 0
|
|
// We want to rewrite that as:
|
|
// icmp eq/ne (and (x shift (Q+K)), y), 0 iff (Q+K) u< bitwidth(x)
|
|
// While we know that originally (Q+K) would not overflow
|
|
// (because 2 * (N-1) u<= iN -1), we have looked past extensions of
|
|
// shift amounts. so it may now overflow in smaller bitwidth.
|
|
// To ensure that does not happen, we need to ensure that the total maximal
|
|
// shift amount is still representable in that smaller bit width.
|
|
unsigned MaximalPossibleTotalShiftAmount =
|
|
(WidestTy->getScalarSizeInBits() - 1) +
|
|
(NarrowestTy->getScalarSizeInBits() - 1);
|
|
APInt MaximalRepresentableShiftAmount =
|
|
APInt::getAllOnesValue(XShAmt->getType()->getScalarSizeInBits());
|
|
if (MaximalRepresentableShiftAmount.ult(MaximalPossibleTotalShiftAmount))
|
|
return nullptr;
|
|
|
|
// Can we fold (XShAmt+YShAmt) ?
|
|
auto *NewShAmt = dyn_cast_or_null<Constant>(
|
|
SimplifyAddInst(XShAmt, YShAmt, /*isNSW=*/false,
|
|
/*isNUW=*/false, SQ.getWithInstruction(&I)));
|
|
if (!NewShAmt)
|
|
return nullptr;
|
|
NewShAmt = ConstantExpr::getZExtOrBitCast(NewShAmt, WidestTy);
|
|
unsigned WidestBitWidth = WidestTy->getScalarSizeInBits();
|
|
|
|
// Is the new shift amount smaller than the bit width?
|
|
// FIXME: could also rely on ConstantRange.
|
|
if (!match(NewShAmt,
|
|
m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_ULT,
|
|
APInt(WidestBitWidth, WidestBitWidth))))
|
|
return nullptr;
|
|
|
|
// An extra legality check is needed if we had trunc-of-lshr.
|
|
if (HadTrunc && match(WidestShift, m_LShr(m_Value(), m_Value()))) {
|
|
auto CanFold = [NewShAmt, WidestBitWidth, NarrowestShift, SQ,
|
|
WidestShift]() {
|
|
// It isn't obvious whether it's worth it to analyze non-constants here.
|
|
// Also, let's basically give up on non-splat cases, pessimizing vectors.
|
|
// If *any* of these preconditions matches we can perform the fold.
|
|
Constant *NewShAmtSplat = NewShAmt->getType()->isVectorTy()
|
|
? NewShAmt->getSplatValue()
|
|
: NewShAmt;
|
|
// If it's edge-case shift (by 0 or by WidestBitWidth-1) we can fold.
|
|
if (NewShAmtSplat &&
|
|
(NewShAmtSplat->isNullValue() ||
|
|
NewShAmtSplat->getUniqueInteger() == WidestBitWidth - 1))
|
|
return true;
|
|
// We consider *min* leading zeros so a single outlier
|
|
// blocks the transform as opposed to allowing it.
|
|
if (auto *C = dyn_cast<Constant>(NarrowestShift->getOperand(0))) {
|
|
KnownBits Known = computeKnownBits(C, SQ.DL);
|
|
unsigned MinLeadZero = Known.countMinLeadingZeros();
|
|
// If the value being shifted has at most lowest bit set we can fold.
|
|
unsigned MaxActiveBits = Known.getBitWidth() - MinLeadZero;
|
|
if (MaxActiveBits <= 1)
|
|
return true;
|
|
// Precondition: NewShAmt u<= countLeadingZeros(C)
|
|
if (NewShAmtSplat && NewShAmtSplat->getUniqueInteger().ule(MinLeadZero))
|
|
return true;
|
|
}
|
|
if (auto *C = dyn_cast<Constant>(WidestShift->getOperand(0))) {
|
|
KnownBits Known = computeKnownBits(C, SQ.DL);
|
|
unsigned MinLeadZero = Known.countMinLeadingZeros();
|
|
// If the value being shifted has at most lowest bit set we can fold.
|
|
unsigned MaxActiveBits = Known.getBitWidth() - MinLeadZero;
|
|
if (MaxActiveBits <= 1)
|
|
return true;
|
|
// Precondition: ((WidestBitWidth-1)-NewShAmt) u<= countLeadingZeros(C)
|
|
if (NewShAmtSplat) {
|
|
APInt AdjNewShAmt =
|
|
(WidestBitWidth - 1) - NewShAmtSplat->getUniqueInteger();
|
|
if (AdjNewShAmt.ule(MinLeadZero))
|
|
return true;
|
|
}
|
|
}
|
|
return false; // Can't tell if it's ok.
|
|
};
|
|
if (!CanFold())
|
|
return nullptr;
|
|
}
|
|
|
|
// All good, we can do this fold.
|
|
X = Builder.CreateZExt(X, WidestTy);
|
|
Y = Builder.CreateZExt(Y, WidestTy);
|
|
// The shift is the same that was for X.
|
|
Value *T0 = XShiftOpcode == Instruction::BinaryOps::LShr
|
|
? Builder.CreateLShr(X, NewShAmt)
|
|
: Builder.CreateShl(X, NewShAmt);
|
|
Value *T1 = Builder.CreateAnd(T0, Y);
|
|
return Builder.CreateICmp(I.getPredicate(), T1,
|
|
Constant::getNullValue(WidestTy));
|
|
}
|
|
|
|
/// Fold
|
|
/// (-1 u/ x) u< y
|
|
/// ((x * y) u/ x) != y
|
|
/// to
|
|
/// @llvm.umul.with.overflow(x, y) plus extraction of overflow bit
|
|
/// Note that the comparison is commutative, while inverted (u>=, ==) predicate
|
|
/// will mean that we are looking for the opposite answer.
|
|
Value *InstCombinerImpl::foldUnsignedMultiplicationOverflowCheck(ICmpInst &I) {
|
|
ICmpInst::Predicate Pred;
|
|
Value *X, *Y;
|
|
Instruction *Mul;
|
|
bool NeedNegation;
|
|
// Look for: (-1 u/ x) u</u>= y
|
|
if (!I.isEquality() &&
|
|
match(&I, m_c_ICmp(Pred, m_OneUse(m_UDiv(m_AllOnes(), m_Value(X))),
|
|
m_Value(Y)))) {
|
|
Mul = nullptr;
|
|
|
|
// Are we checking that overflow does not happen, or does happen?
|
|
switch (Pred) {
|
|
case ICmpInst::Predicate::ICMP_ULT:
|
|
NeedNegation = false;
|
|
break; // OK
|
|
case ICmpInst::Predicate::ICMP_UGE:
|
|
NeedNegation = true;
|
|
break; // OK
|
|
default:
|
|
return nullptr; // Wrong predicate.
|
|
}
|
|
} else // Look for: ((x * y) u/ x) !=/== y
|
|
if (I.isEquality() &&
|
|
match(&I, m_c_ICmp(Pred, m_Value(Y),
|
|
m_OneUse(m_UDiv(m_CombineAnd(m_c_Mul(m_Deferred(Y),
|
|
m_Value(X)),
|
|
m_Instruction(Mul)),
|
|
m_Deferred(X)))))) {
|
|
NeedNegation = Pred == ICmpInst::Predicate::ICMP_EQ;
|
|
} else
|
|
return nullptr;
|
|
|
|
BuilderTy::InsertPointGuard Guard(Builder);
|
|
// If the pattern included (x * y), we'll want to insert new instructions
|
|
// right before that original multiplication so that we can replace it.
|
|
bool MulHadOtherUses = Mul && !Mul->hasOneUse();
|
|
if (MulHadOtherUses)
|
|
Builder.SetInsertPoint(Mul);
|
|
|
|
Function *F = Intrinsic::getDeclaration(
|
|
I.getModule(), Intrinsic::umul_with_overflow, X->getType());
|
|
CallInst *Call = Builder.CreateCall(F, {X, Y}, "umul");
|
|
|
|
// If the multiplication was used elsewhere, to ensure that we don't leave
|
|
// "duplicate" instructions, replace uses of that original multiplication
|
|
// with the multiplication result from the with.overflow intrinsic.
|
|
if (MulHadOtherUses)
|
|
replaceInstUsesWith(*Mul, Builder.CreateExtractValue(Call, 0, "umul.val"));
|
|
|
|
Value *Res = Builder.CreateExtractValue(Call, 1, "umul.ov");
|
|
if (NeedNegation) // This technically increases instruction count.
|
|
Res = Builder.CreateNot(Res, "umul.not.ov");
|
|
|
|
// If we replaced the mul, erase it. Do this after all uses of Builder,
|
|
// as the mul is used as insertion point.
|
|
if (MulHadOtherUses)
|
|
eraseInstFromFunction(*Mul);
|
|
|
|
return Res;
|
|
}
|
|
|
|
static Instruction *foldICmpXNegX(ICmpInst &I) {
|
|
CmpInst::Predicate Pred;
|
|
Value *X;
|
|
if (!match(&I, m_c_ICmp(Pred, m_NSWNeg(m_Value(X)), m_Deferred(X))))
|
|
return nullptr;
|
|
|
|
if (ICmpInst::isSigned(Pred))
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
else if (ICmpInst::isUnsigned(Pred))
|
|
Pred = ICmpInst::getSignedPredicate(Pred);
|
|
// else for equality-comparisons just keep the predicate.
|
|
|
|
return ICmpInst::Create(Instruction::ICmp, Pred, X,
|
|
Constant::getNullValue(X->getType()), I.getName());
|
|
}
|
|
|
|
/// Try to fold icmp (binop), X or icmp X, (binop).
|
|
/// TODO: A large part of this logic is duplicated in InstSimplify's
|
|
/// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
|
|
/// duplication.
|
|
Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
|
|
const SimplifyQuery &SQ) {
|
|
const SimplifyQuery Q = SQ.getWithInstruction(&I);
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
|
|
// Special logic for binary operators.
|
|
BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
|
|
BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
|
|
if (!BO0 && !BO1)
|
|
return nullptr;
|
|
|
|
if (Instruction *NewICmp = foldICmpXNegX(I))
|
|
return NewICmp;
|
|
|
|
const CmpInst::Predicate Pred = I.getPredicate();
|
|
Value *X;
|
|
|
|
// Convert add-with-unsigned-overflow comparisons into a 'not' with compare.
|
|
// (Op1 + X) u</u>= Op1 --> ~Op1 u</u>= X
|
|
if (match(Op0, m_OneUse(m_c_Add(m_Specific(Op1), m_Value(X)))) &&
|
|
(Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE))
|
|
return new ICmpInst(Pred, Builder.CreateNot(Op1), X);
|
|
// Op0 u>/u<= (Op0 + X) --> X u>/u<= ~Op0
|
|
if (match(Op1, m_OneUse(m_c_Add(m_Specific(Op0), m_Value(X)))) &&
|
|
(Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULE))
|
|
return new ICmpInst(Pred, X, Builder.CreateNot(Op0));
|
|
|
|
bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
|
|
if (BO0 && isa<OverflowingBinaryOperator>(BO0))
|
|
NoOp0WrapProblem =
|
|
ICmpInst::isEquality(Pred) ||
|
|
(CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
|
|
(CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
|
|
if (BO1 && isa<OverflowingBinaryOperator>(BO1))
|
|
NoOp1WrapProblem =
|
|
ICmpInst::isEquality(Pred) ||
|
|
(CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
|
|
(CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
|
|
|
|
// Analyze the case when either Op0 or Op1 is an add instruction.
|
|
// Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
|
|
Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
|
|
if (BO0 && BO0->getOpcode() == Instruction::Add) {
|
|
A = BO0->getOperand(0);
|
|
B = BO0->getOperand(1);
|
|
}
|
|
if (BO1 && BO1->getOpcode() == Instruction::Add) {
|
|
C = BO1->getOperand(0);
|
|
D = BO1->getOperand(1);
|
|
}
|
|
|
|
// icmp (A+B), A -> icmp B, 0 for equalities or if there is no overflow.
|
|
// icmp (A+B), B -> icmp A, 0 for equalities or if there is no overflow.
|
|
if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
|
|
return new ICmpInst(Pred, A == Op1 ? B : A,
|
|
Constant::getNullValue(Op1->getType()));
|
|
|
|
// icmp C, (C+D) -> icmp 0, D for equalities or if there is no overflow.
|
|
// icmp D, (C+D) -> icmp 0, C for equalities or if there is no overflow.
|
|
if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
|
|
return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
|
|
C == Op0 ? D : C);
|
|
|
|
// icmp (A+B), (A+D) -> icmp B, D for equalities or if there is no overflow.
|
|
if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
|
|
NoOp1WrapProblem) {
|
|
// Determine Y and Z in the form icmp (X+Y), (X+Z).
|
|
Value *Y, *Z;
|
|
if (A == C) {
|
|
// C + B == C + D -> B == D
|
|
Y = B;
|
|
Z = D;
|
|
} else if (A == D) {
|
|
// D + B == C + D -> B == C
|
|
Y = B;
|
|
Z = C;
|
|
} else if (B == C) {
|
|
// A + C == C + D -> A == D
|
|
Y = A;
|
|
Z = D;
|
|
} else {
|
|
assert(B == D);
|
|
// A + D == C + D -> A == C
|
|
Y = A;
|
|
Z = C;
|
|
}
|
|
return new ICmpInst(Pred, Y, Z);
|
|
}
|
|
|
|
// icmp slt (A + -1), Op1 -> icmp sle A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
|
|
match(B, m_AllOnes()))
|
|
return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
|
|
|
|
// icmp sge (A + -1), Op1 -> icmp sgt A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
|
|
match(B, m_AllOnes()))
|
|
return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
|
|
|
|
// icmp sle (A + 1), Op1 -> icmp slt A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
|
|
|
|
// icmp sgt (A + 1), Op1 -> icmp sge A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
|
|
|
|
// icmp sgt Op0, (C + -1) -> icmp sge Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
|
|
match(D, m_AllOnes()))
|
|
return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
|
|
|
|
// icmp sle Op0, (C + -1) -> icmp slt Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
|
|
match(D, m_AllOnes()))
|
|
return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
|
|
|
|
// icmp sge Op0, (C + 1) -> icmp sgt Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
|
|
|
|
// icmp slt Op0, (C + 1) -> icmp sle Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
|
|
|
|
// TODO: The subtraction-related identities shown below also hold, but
|
|
// canonicalization from (X -nuw 1) to (X + -1) means that the combinations
|
|
// wouldn't happen even if they were implemented.
|
|
//
|
|
// icmp ult (A - 1), Op1 -> icmp ule A, Op1
|
|
// icmp uge (A - 1), Op1 -> icmp ugt A, Op1
|
|
// icmp ugt Op0, (C - 1) -> icmp uge Op0, C
|
|
// icmp ule Op0, (C - 1) -> icmp ult Op0, C
|
|
|
|
// icmp ule (A + 1), Op0 -> icmp ult A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
|
|
|
|
// icmp ugt (A + 1), Op0 -> icmp uge A, Op1
|
|
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
|
|
|
|
// icmp uge Op0, (C + 1) -> icmp ugt Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
|
|
|
|
// icmp ult Op0, (C + 1) -> icmp ule Op0, C
|
|
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
|
|
return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
|
|
|
|
// if C1 has greater magnitude than C2:
|
|
// icmp (A + C1), (C + C2) -> icmp (A + C3), C
|
|
// s.t. C3 = C1 - C2
|
|
//
|
|
// if C2 has greater magnitude than C1:
|
|
// icmp (A + C1), (C + C2) -> icmp A, (C + C3)
|
|
// s.t. C3 = C2 - C1
|
|
if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
|
|
(BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
|
|
if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
|
|
if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
|
|
const APInt &AP1 = C1->getValue();
|
|
const APInt &AP2 = C2->getValue();
|
|
if (AP1.isNegative() == AP2.isNegative()) {
|
|
APInt AP1Abs = C1->getValue().abs();
|
|
APInt AP2Abs = C2->getValue().abs();
|
|
if (AP1Abs.uge(AP2Abs)) {
|
|
ConstantInt *C3 = Builder.getInt(AP1 - AP2);
|
|
Value *NewAdd = Builder.CreateNSWAdd(A, C3);
|
|
return new ICmpInst(Pred, NewAdd, C);
|
|
} else {
|
|
ConstantInt *C3 = Builder.getInt(AP2 - AP1);
|
|
Value *NewAdd = Builder.CreateNSWAdd(C, C3);
|
|
return new ICmpInst(Pred, A, NewAdd);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Analyze the case when either Op0 or Op1 is a sub instruction.
|
|
// Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
|
|
A = nullptr;
|
|
B = nullptr;
|
|
C = nullptr;
|
|
D = nullptr;
|
|
if (BO0 && BO0->getOpcode() == Instruction::Sub) {
|
|
A = BO0->getOperand(0);
|
|
B = BO0->getOperand(1);
|
|
}
|
|
if (BO1 && BO1->getOpcode() == Instruction::Sub) {
|
|
C = BO1->getOperand(0);
|
|
D = BO1->getOperand(1);
|
|
}
|
|
|
|
// icmp (A-B), A -> icmp 0, B for equalities or if there is no overflow.
|
|
if (A == Op1 && NoOp0WrapProblem)
|
|
return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
|
|
// icmp C, (C-D) -> icmp D, 0 for equalities or if there is no overflow.
|
|
if (C == Op0 && NoOp1WrapProblem)
|
|
return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
|
|
|
|
// Convert sub-with-unsigned-overflow comparisons into a comparison of args.
|
|
// (A - B) u>/u<= A --> B u>/u<= A
|
|
if (A == Op1 && (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULE))
|
|
return new ICmpInst(Pred, B, A);
|
|
// C u</u>= (C - D) --> C u</u>= D
|
|
if (C == Op0 && (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE))
|
|
return new ICmpInst(Pred, C, D);
|
|
// (A - B) u>=/u< A --> B u>/u<= A iff B != 0
|
|
if (A == Op1 && (Pred == ICmpInst::ICMP_UGE || Pred == ICmpInst::ICMP_ULT) &&
|
|
isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
|
|
return new ICmpInst(CmpInst::getFlippedStrictnessPredicate(Pred), B, A);
|
|
// C u<=/u> (C - D) --> C u</u>= D iff B != 0
|
|
if (C == Op0 && (Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_UGT) &&
|
|
isKnownNonZero(D, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
|
|
return new ICmpInst(CmpInst::getFlippedStrictnessPredicate(Pred), C, D);
|
|
|
|
// icmp (A-B), (C-B) -> icmp A, C for equalities or if there is no overflow.
|
|
if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem)
|
|
return new ICmpInst(Pred, A, C);
|
|
|
|
// icmp (A-B), (A-D) -> icmp D, B for equalities or if there is no overflow.
|
|
if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem)
|
|
return new ICmpInst(Pred, D, B);
|
|
|
|
// icmp (0-X) < cst --> x > -cst
|
|
if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
|
|
Value *X;
|
|
if (match(BO0, m_Neg(m_Value(X))))
|
|
if (Constant *RHSC = dyn_cast<Constant>(Op1))
|
|
if (RHSC->isNotMinSignedValue())
|
|
return new ICmpInst(I.getSwappedPredicate(), X,
|
|
ConstantExpr::getNeg(RHSC));
|
|
}
|
|
|
|
{
|
|
// Try to remove shared constant multiplier from equality comparison:
|
|
// X * C == Y * C (with no overflowing/aliasing) --> X == Y
|
|
Value *X, *Y;
|
|
const APInt *C;
|
|
if (match(Op0, m_Mul(m_Value(X), m_APInt(C))) && *C != 0 &&
|
|
match(Op1, m_Mul(m_Value(Y), m_SpecificInt(*C))) && I.isEquality())
|
|
if (!C->countTrailingZeros() ||
|
|
(BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap()) ||
|
|
(BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap()))
|
|
return new ICmpInst(Pred, X, Y);
|
|
}
|
|
|
|
BinaryOperator *SRem = nullptr;
|
|
// icmp (srem X, Y), Y
|
|
if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
|
|
SRem = BO0;
|
|
// icmp Y, (srem X, Y)
|
|
else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
|
|
Op0 == BO1->getOperand(1))
|
|
SRem = BO1;
|
|
if (SRem) {
|
|
// We don't check hasOneUse to avoid increasing register pressure because
|
|
// the value we use is the same value this instruction was already using.
|
|
switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
|
|
default:
|
|
break;
|
|
case ICmpInst::ICMP_EQ:
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
case ICmpInst::ICMP_NE:
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_SGE:
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
|
|
Constant::getAllOnesValue(SRem->getType()));
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_SLE:
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
|
|
Constant::getNullValue(SRem->getType()));
|
|
}
|
|
}
|
|
|
|
if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
|
|
BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
|
|
switch (BO0->getOpcode()) {
|
|
default:
|
|
break;
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::Xor: {
|
|
if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
|
|
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
|
|
|
|
const APInt *C;
|
|
if (match(BO0->getOperand(1), m_APInt(C))) {
|
|
// icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
|
|
if (C->isSignMask()) {
|
|
ICmpInst::Predicate NewPred = I.getFlippedSignednessPredicate();
|
|
return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
|
|
}
|
|
|
|
// icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
|
|
if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
|
|
ICmpInst::Predicate NewPred = I.getFlippedSignednessPredicate();
|
|
NewPred = I.getSwappedPredicate(NewPred);
|
|
return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Mul: {
|
|
if (!I.isEquality())
|
|
break;
|
|
|
|
const APInt *C;
|
|
if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
|
|
!C->isOneValue()) {
|
|
// icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
|
|
// Mask = -1 >> count-trailing-zeros(C).
|
|
if (unsigned TZs = C->countTrailingZeros()) {
|
|
Constant *Mask = ConstantInt::get(
|
|
BO0->getType(),
|
|
APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
|
|
Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
|
|
Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
|
|
return new ICmpInst(Pred, And1, And2);
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::UDiv:
|
|
case Instruction::LShr:
|
|
if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
|
|
break;
|
|
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
|
|
|
|
case Instruction::SDiv:
|
|
if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
|
|
break;
|
|
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
|
|
|
|
case Instruction::AShr:
|
|
if (!BO0->isExact() || !BO1->isExact())
|
|
break;
|
|
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
|
|
|
|
case Instruction::Shl: {
|
|
bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
|
|
bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
|
|
if (!NUW && !NSW)
|
|
break;
|
|
if (!NSW && I.isSigned())
|
|
break;
|
|
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
|
|
}
|
|
}
|
|
}
|
|
|
|
if (BO0) {
|
|
// Transform A & (L - 1) `ult` L --> L != 0
|
|
auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
|
|
auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
|
|
|
|
if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
|
|
auto *Zero = Constant::getNullValue(BO0->getType());
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
|
|
}
|
|
}
|
|
|
|
if (Value *V = foldUnsignedMultiplicationOverflowCheck(I))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
if (Value *V = foldICmpWithLowBitMaskedVal(I, Builder))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
if (Value *V = foldICmpWithTruncSignExtendedVal(I, Builder))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
if (Value *V = foldShiftIntoShiftInAnotherHandOfAndInICmp(I, SQ, Builder))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Fold icmp Pred min|max(X, Y), X.
|
|
static Instruction *foldICmpWithMinMax(ICmpInst &Cmp) {
|
|
ICmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *Op0 = Cmp.getOperand(0);
|
|
Value *X = Cmp.getOperand(1);
|
|
|
|
// Canonicalize minimum or maximum operand to LHS of the icmp.
|
|
if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
|
|
match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
|
|
match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
|
|
match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
|
|
std::swap(Op0, X);
|
|
Pred = Cmp.getSwappedPredicate();
|
|
}
|
|
|
|
Value *Y;
|
|
if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
|
|
// smin(X, Y) == X --> X s<= Y
|
|
// smin(X, Y) s>= X --> X s<= Y
|
|
if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
|
|
return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
|
|
|
|
// smin(X, Y) != X --> X s> Y
|
|
// smin(X, Y) s< X --> X s> Y
|
|
if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
|
|
|
|
// These cases should be handled in InstSimplify:
|
|
// smin(X, Y) s<= X --> true
|
|
// smin(X, Y) s> X --> false
|
|
return nullptr;
|
|
}
|
|
|
|
if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
|
|
// smax(X, Y) == X --> X s>= Y
|
|
// smax(X, Y) s<= X --> X s>= Y
|
|
if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
|
|
return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
|
|
|
|
// smax(X, Y) != X --> X s< Y
|
|
// smax(X, Y) s> X --> X s< Y
|
|
if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
|
|
|
|
// These cases should be handled in InstSimplify:
|
|
// smax(X, Y) s>= X --> true
|
|
// smax(X, Y) s< X --> false
|
|
return nullptr;
|
|
}
|
|
|
|
if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
|
|
// umin(X, Y) == X --> X u<= Y
|
|
// umin(X, Y) u>= X --> X u<= Y
|
|
if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
|
|
return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
|
|
|
|
// umin(X, Y) != X --> X u> Y
|
|
// umin(X, Y) u< X --> X u> Y
|
|
if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
|
|
return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
|
|
|
|
// These cases should be handled in InstSimplify:
|
|
// umin(X, Y) u<= X --> true
|
|
// umin(X, Y) u> X --> false
|
|
return nullptr;
|
|
}
|
|
|
|
if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
|
|
// umax(X, Y) == X --> X u>= Y
|
|
// umax(X, Y) u<= X --> X u>= Y
|
|
if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
|
|
return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
|
|
|
|
// umax(X, Y) != X --> X u< Y
|
|
// umax(X, Y) u> X --> X u< Y
|
|
if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
|
|
return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
|
|
|
|
// These cases should be handled in InstSimplify:
|
|
// umax(X, Y) u>= X --> true
|
|
// umax(X, Y) u< X --> false
|
|
return nullptr;
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::foldICmpEquality(ICmpInst &I) {
|
|
if (!I.isEquality())
|
|
return nullptr;
|
|
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
const CmpInst::Predicate Pred = I.getPredicate();
|
|
Value *A, *B, *C, *D;
|
|
if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
|
|
if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
|
|
Value *OtherVal = A == Op1 ? B : A;
|
|
return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
|
|
}
|
|
|
|
if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
|
|
// A^c1 == C^c2 --> A == C^(c1^c2)
|
|
ConstantInt *C1, *C2;
|
|
if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
|
|
Op1->hasOneUse()) {
|
|
Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
|
|
Value *Xor = Builder.CreateXor(C, NC);
|
|
return new ICmpInst(Pred, A, Xor);
|
|
}
|
|
|
|
// A^B == A^D -> B == D
|
|
if (A == C)
|
|
return new ICmpInst(Pred, B, D);
|
|
if (A == D)
|
|
return new ICmpInst(Pred, B, C);
|
|
if (B == C)
|
|
return new ICmpInst(Pred, A, D);
|
|
if (B == D)
|
|
return new ICmpInst(Pred, A, C);
|
|
}
|
|
}
|
|
|
|
if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
|
|
// A == (A^B) -> B == 0
|
|
Value *OtherVal = A == Op0 ? B : A;
|
|
return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
|
|
}
|
|
|
|
// (X&Z) == (Y&Z) -> (X^Y) & Z == 0
|
|
if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
|
|
match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
|
|
Value *X = nullptr, *Y = nullptr, *Z = nullptr;
|
|
|
|
if (A == C) {
|
|
X = B;
|
|
Y = D;
|
|
Z = A;
|
|
} else if (A == D) {
|
|
X = B;
|
|
Y = C;
|
|
Z = A;
|
|
} else if (B == C) {
|
|
X = A;
|
|
Y = D;
|
|
Z = B;
|
|
} else if (B == D) {
|
|
X = A;
|
|
Y = C;
|
|
Z = B;
|
|
}
|
|
|
|
if (X) { // Build (X^Y) & Z
|
|
Op1 = Builder.CreateXor(X, Y);
|
|
Op1 = Builder.CreateAnd(Op1, Z);
|
|
return new ICmpInst(Pred, Op1, Constant::getNullValue(Op1->getType()));
|
|
}
|
|
}
|
|
|
|
// Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
|
|
// and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
|
|
ConstantInt *Cst1;
|
|
if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
|
|
match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
|
|
(Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
|
|
match(Op1, m_ZExt(m_Value(A))))) {
|
|
APInt Pow2 = Cst1->getValue() + 1;
|
|
if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
|
|
Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
|
|
return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
|
|
}
|
|
|
|
// (A >> C) == (B >> C) --> (A^B) u< (1 << C)
|
|
// For lshr and ashr pairs.
|
|
if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
|
|
match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
|
|
(match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
|
|
match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
|
|
unsigned TypeBits = Cst1->getBitWidth();
|
|
unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
|
|
if (ShAmt < TypeBits && ShAmt != 0) {
|
|
ICmpInst::Predicate NewPred =
|
|
Pred == ICmpInst::ICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
|
|
Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
|
|
APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
|
|
return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
|
|
}
|
|
}
|
|
|
|
// (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
|
|
if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
|
|
match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
|
|
unsigned TypeBits = Cst1->getBitWidth();
|
|
unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
|
|
if (ShAmt < TypeBits && ShAmt != 0) {
|
|
Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
|
|
APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
|
|
Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
|
|
I.getName() + ".mask");
|
|
return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
|
|
}
|
|
}
|
|
|
|
// Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
|
|
// "icmp (and X, mask), cst"
|
|
uint64_t ShAmt = 0;
|
|
if (Op0->hasOneUse() &&
|
|
match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
|
|
match(Op1, m_ConstantInt(Cst1)) &&
|
|
// Only do this when A has multiple uses. This is most important to do
|
|
// when it exposes other optimizations.
|
|
!A->hasOneUse()) {
|
|
unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
|
|
|
|
if (ShAmt < ASize) {
|
|
APInt MaskV =
|
|
APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits());
|
|
MaskV <<= ShAmt;
|
|
|
|
APInt CmpV = Cst1->getValue().zext(ASize);
|
|
CmpV <<= ShAmt;
|
|
|
|
Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
|
|
return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
|
|
}
|
|
}
|
|
|
|
// If both operands are byte-swapped or bit-reversed, just compare the
|
|
// original values.
|
|
// TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
|
|
// and handle more intrinsics.
|
|
if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
|
|
(match(Op0, m_BitReverse(m_Value(A))) &&
|
|
match(Op1, m_BitReverse(m_Value(B)))))
|
|
return new ICmpInst(Pred, A, B);
|
|
|
|
// Canonicalize checking for a power-of-2-or-zero value:
|
|
// (A & (A-1)) == 0 --> ctpop(A) < 2 (two commuted variants)
|
|
// ((A-1) & A) != 0 --> ctpop(A) > 1 (two commuted variants)
|
|
if (!match(Op0, m_OneUse(m_c_And(m_Add(m_Value(A), m_AllOnes()),
|
|
m_Deferred(A)))) ||
|
|
!match(Op1, m_ZeroInt()))
|
|
A = nullptr;
|
|
|
|
// (A & -A) == A --> ctpop(A) < 2 (four commuted variants)
|
|
// (-A & A) != A --> ctpop(A) > 1 (four commuted variants)
|
|
if (match(Op0, m_OneUse(m_c_And(m_Neg(m_Specific(Op1)), m_Specific(Op1)))))
|
|
A = Op1;
|
|
else if (match(Op1,
|
|
m_OneUse(m_c_And(m_Neg(m_Specific(Op0)), m_Specific(Op0)))))
|
|
A = Op0;
|
|
|
|
if (A) {
|
|
Type *Ty = A->getType();
|
|
CallInst *CtPop = Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, A);
|
|
return Pred == ICmpInst::ICMP_EQ
|
|
? new ICmpInst(ICmpInst::ICMP_ULT, CtPop, ConstantInt::get(Ty, 2))
|
|
: new ICmpInst(ICmpInst::ICMP_UGT, CtPop, ConstantInt::get(Ty, 1));
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
assert(isa<CastInst>(ICmp.getOperand(0)) && "Expected cast for operand 0");
|
|
auto *CastOp0 = cast<CastInst>(ICmp.getOperand(0));
|
|
Value *X;
|
|
if (!match(CastOp0, m_ZExtOrSExt(m_Value(X))))
|
|
return nullptr;
|
|
|
|
bool IsSignedExt = CastOp0->getOpcode() == Instruction::SExt;
|
|
bool IsSignedCmp = ICmp.isSigned();
|
|
if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
|
|
// If the signedness of the two casts doesn't agree (i.e. one is a sext
|
|
// and the other is a zext), then we can't handle this.
|
|
// TODO: This is too strict. We can handle some predicates (equality?).
|
|
if (CastOp0->getOpcode() != CastOp1->getOpcode())
|
|
return nullptr;
|
|
|
|
// Not an extension from the same type?
|
|
Value *Y = CastOp1->getOperand(0);
|
|
Type *XTy = X->getType(), *YTy = Y->getType();
|
|
if (XTy != YTy) {
|
|
// One of the casts must have one use because we are creating a new cast.
|
|
if (!CastOp0->hasOneUse() && !CastOp1->hasOneUse())
|
|
return nullptr;
|
|
// Extend the narrower operand to the type of the wider operand.
|
|
if (XTy->getScalarSizeInBits() < YTy->getScalarSizeInBits())
|
|
X = Builder.CreateCast(CastOp0->getOpcode(), X, YTy);
|
|
else if (YTy->getScalarSizeInBits() < XTy->getScalarSizeInBits())
|
|
Y = Builder.CreateCast(CastOp0->getOpcode(), Y, XTy);
|
|
else
|
|
return nullptr;
|
|
}
|
|
|
|
// (zext X) == (zext Y) --> X == Y
|
|
// (sext X) == (sext Y) --> X == Y
|
|
if (ICmp.isEquality())
|
|
return new ICmpInst(ICmp.getPredicate(), X, Y);
|
|
|
|
// A signed comparison of sign extended values simplifies into a
|
|
// signed comparison.
|
|
if (IsSignedCmp && IsSignedExt)
|
|
return new ICmpInst(ICmp.getPredicate(), X, Y);
|
|
|
|
// The other three cases all fold into an unsigned comparison.
|
|
return new ICmpInst(ICmp.getUnsignedPredicate(), X, Y);
|
|
}
|
|
|
|
// Below here, we are only folding a compare with constant.
|
|
auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
|
|
if (!C)
|
|
return nullptr;
|
|
|
|
// Compute the constant that would happen if we truncated to SrcTy then
|
|
// re-extended to DestTy.
|
|
Type *SrcTy = CastOp0->getSrcTy();
|
|
Type *DestTy = CastOp0->getDestTy();
|
|
Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
|
|
Constant *Res2 = ConstantExpr::getCast(CastOp0->getOpcode(), Res1, DestTy);
|
|
|
|
// If the re-extended constant didn't change...
|
|
if (Res2 == C) {
|
|
if (ICmp.isEquality())
|
|
return new ICmpInst(ICmp.getPredicate(), X, Res1);
|
|
|
|
// A signed comparison of sign extended values simplifies into a
|
|
// signed comparison.
|
|
if (IsSignedExt && IsSignedCmp)
|
|
return new ICmpInst(ICmp.getPredicate(), X, Res1);
|
|
|
|
// The other three cases all fold into an unsigned comparison.
|
|
return new ICmpInst(ICmp.getUnsignedPredicate(), X, Res1);
|
|
}
|
|
|
|
// The re-extended constant changed, partly changed (in the case of a vector),
|
|
// or could not be determined to be equal (in the case of a constant
|
|
// expression), so the constant cannot be represented in the shorter type.
|
|
// All the cases that fold to true or false will have already been handled
|
|
// by SimplifyICmpInst, so only deal with the tricky case.
|
|
if (IsSignedCmp || !IsSignedExt || !isa<ConstantInt>(C))
|
|
return nullptr;
|
|
|
|
// Is source op positive?
|
|
// icmp ult (sext X), C --> icmp sgt X, -1
|
|
if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
|
|
return new ICmpInst(CmpInst::ICMP_SGT, X, Constant::getAllOnesValue(SrcTy));
|
|
|
|
// Is source op negative?
|
|
// icmp ugt (sext X), C --> icmp slt X, 0
|
|
assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
|
|
return new ICmpInst(CmpInst::ICMP_SLT, X, Constant::getNullValue(SrcTy));
|
|
}
|
|
|
|
/// Handle icmp (cast x), (cast or constant).
|
|
Instruction *InstCombinerImpl::foldICmpWithCastOp(ICmpInst &ICmp) {
|
|
auto *CastOp0 = dyn_cast<CastInst>(ICmp.getOperand(0));
|
|
if (!CastOp0)
|
|
return nullptr;
|
|
if (!isa<Constant>(ICmp.getOperand(1)) && !isa<CastInst>(ICmp.getOperand(1)))
|
|
return nullptr;
|
|
|
|
Value *Op0Src = CastOp0->getOperand(0);
|
|
Type *SrcTy = CastOp0->getSrcTy();
|
|
Type *DestTy = CastOp0->getDestTy();
|
|
|
|
// Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
|
|
// integer type is the same size as the pointer type.
|
|
auto CompatibleSizes = [&](Type *SrcTy, Type *DestTy) {
|
|
if (isa<VectorType>(SrcTy)) {
|
|
SrcTy = cast<VectorType>(SrcTy)->getElementType();
|
|
DestTy = cast<VectorType>(DestTy)->getElementType();
|
|
}
|
|
return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
|
|
};
|
|
if (CastOp0->getOpcode() == Instruction::PtrToInt &&
|
|
CompatibleSizes(SrcTy, DestTy)) {
|
|
Value *NewOp1 = nullptr;
|
|
if (auto *PtrToIntOp1 = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
|
|
Value *PtrSrc = PtrToIntOp1->getOperand(0);
|
|
if (PtrSrc->getType()->getPointerAddressSpace() ==
|
|
Op0Src->getType()->getPointerAddressSpace()) {
|
|
NewOp1 = PtrToIntOp1->getOperand(0);
|
|
// If the pointer types don't match, insert a bitcast.
|
|
if (Op0Src->getType() != NewOp1->getType())
|
|
NewOp1 = Builder.CreateBitCast(NewOp1, Op0Src->getType());
|
|
}
|
|
} else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
|
|
NewOp1 = ConstantExpr::getIntToPtr(RHSC, SrcTy);
|
|
}
|
|
|
|
if (NewOp1)
|
|
return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
|
|
}
|
|
|
|
return foldICmpWithZextOrSext(ICmp, Builder);
|
|
}
|
|
|
|
static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {
|
|
switch (BinaryOp) {
|
|
default:
|
|
llvm_unreachable("Unsupported binary op");
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
return match(RHS, m_Zero());
|
|
case Instruction::Mul:
|
|
return match(RHS, m_One());
|
|
}
|
|
}
|
|
|
|
OverflowResult
|
|
InstCombinerImpl::computeOverflow(Instruction::BinaryOps BinaryOp,
|
|
bool IsSigned, Value *LHS, Value *RHS,
|
|
Instruction *CxtI) const {
|
|
switch (BinaryOp) {
|
|
default:
|
|
llvm_unreachable("Unsupported binary op");
|
|
case Instruction::Add:
|
|
if (IsSigned)
|
|
return computeOverflowForSignedAdd(LHS, RHS, CxtI);
|
|
else
|
|
return computeOverflowForUnsignedAdd(LHS, RHS, CxtI);
|
|
case Instruction::Sub:
|
|
if (IsSigned)
|
|
return computeOverflowForSignedSub(LHS, RHS, CxtI);
|
|
else
|
|
return computeOverflowForUnsignedSub(LHS, RHS, CxtI);
|
|
case Instruction::Mul:
|
|
if (IsSigned)
|
|
return computeOverflowForSignedMul(LHS, RHS, CxtI);
|
|
else
|
|
return computeOverflowForUnsignedMul(LHS, RHS, CxtI);
|
|
}
|
|
}
|
|
|
|
bool InstCombinerImpl::OptimizeOverflowCheck(Instruction::BinaryOps BinaryOp,
|
|
bool IsSigned, Value *LHS,
|
|
Value *RHS, Instruction &OrigI,
|
|
Value *&Result,
|
|
Constant *&Overflow) {
|
|
if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
|
|
std::swap(LHS, RHS);
|
|
|
|
// If the overflow check was an add followed by a compare, the insertion point
|
|
// may be pointing to the compare. We want to insert the new instructions
|
|
// before the add in case there are uses of the add between the add and the
|
|
// compare.
|
|
Builder.SetInsertPoint(&OrigI);
|
|
|
|
Type *OverflowTy = Type::getInt1Ty(LHS->getContext());
|
|
if (auto *LHSTy = dyn_cast<VectorType>(LHS->getType()))
|
|
OverflowTy = VectorType::get(OverflowTy, LHSTy->getElementCount());
|
|
|
|
if (isNeutralValue(BinaryOp, RHS)) {
|
|
Result = LHS;
|
|
Overflow = ConstantInt::getFalse(OverflowTy);
|
|
return true;
|
|
}
|
|
|
|
switch (computeOverflow(BinaryOp, IsSigned, LHS, RHS, &OrigI)) {
|
|
case OverflowResult::MayOverflow:
|
|
return false;
|
|
case OverflowResult::AlwaysOverflowsLow:
|
|
case OverflowResult::AlwaysOverflowsHigh:
|
|
Result = Builder.CreateBinOp(BinaryOp, LHS, RHS);
|
|
Result->takeName(&OrigI);
|
|
Overflow = ConstantInt::getTrue(OverflowTy);
|
|
return true;
|
|
case OverflowResult::NeverOverflows:
|
|
Result = Builder.CreateBinOp(BinaryOp, LHS, RHS);
|
|
Result->takeName(&OrigI);
|
|
Overflow = ConstantInt::getFalse(OverflowTy);
|
|
if (auto *Inst = dyn_cast<Instruction>(Result)) {
|
|
if (IsSigned)
|
|
Inst->setHasNoSignedWrap();
|
|
else
|
|
Inst->setHasNoUnsignedWrap();
|
|
}
|
|
return true;
|
|
}
|
|
|
|
llvm_unreachable("Unexpected overflow result");
|
|
}
|
|
|
|
/// Recognize and process idiom involving test for multiplication
|
|
/// overflow.
|
|
///
|
|
/// The caller has matched a pattern of the form:
|
|
/// I = cmp u (mul(zext A, zext B), V
|
|
/// The function checks if this is a test for overflow and if so replaces
|
|
/// multiplication with call to 'mul.with.overflow' intrinsic.
|
|
///
|
|
/// \param I Compare instruction.
|
|
/// \param MulVal Result of 'mult' instruction. It is one of the arguments of
|
|
/// the compare instruction. Must be of integer type.
|
|
/// \param OtherVal The other argument of compare instruction.
|
|
/// \returns Instruction which must replace the compare instruction, NULL if no
|
|
/// replacement required.
|
|
static Instruction *processUMulZExtIdiom(ICmpInst &I, Value *MulVal,
|
|
Value *OtherVal,
|
|
InstCombinerImpl &IC) {
|
|
// Don't bother doing this transformation for pointers, don't do it for
|
|
// vectors.
|
|
if (!isa<IntegerType>(MulVal->getType()))
|
|
return nullptr;
|
|
|
|
assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
|
|
assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
|
|
auto *MulInstr = dyn_cast<Instruction>(MulVal);
|
|
if (!MulInstr)
|
|
return nullptr;
|
|
assert(MulInstr->getOpcode() == Instruction::Mul);
|
|
|
|
auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
|
|
*RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
|
|
assert(LHS->getOpcode() == Instruction::ZExt);
|
|
assert(RHS->getOpcode() == Instruction::ZExt);
|
|
Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
|
|
|
|
// Calculate type and width of the result produced by mul.with.overflow.
|
|
Type *TyA = A->getType(), *TyB = B->getType();
|
|
unsigned WidthA = TyA->getPrimitiveSizeInBits(),
|
|
WidthB = TyB->getPrimitiveSizeInBits();
|
|
unsigned MulWidth;
|
|
Type *MulType;
|
|
if (WidthB > WidthA) {
|
|
MulWidth = WidthB;
|
|
MulType = TyB;
|
|
} else {
|
|
MulWidth = WidthA;
|
|
MulType = TyA;
|
|
}
|
|
|
|
// In order to replace the original mul with a narrower mul.with.overflow,
|
|
// all uses must ignore upper bits of the product. The number of used low
|
|
// bits must be not greater than the width of mul.with.overflow.
|
|
if (MulVal->hasNUsesOrMore(2))
|
|
for (User *U : MulVal->users()) {
|
|
if (U == &I)
|
|
continue;
|
|
if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
|
|
// Check if truncation ignores bits above MulWidth.
|
|
unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
|
|
if (TruncWidth > MulWidth)
|
|
return nullptr;
|
|
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
|
|
// Check if AND ignores bits above MulWidth.
|
|
if (BO->getOpcode() != Instruction::And)
|
|
return nullptr;
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
|
|
const APInt &CVal = CI->getValue();
|
|
if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
|
|
return nullptr;
|
|
} else {
|
|
// In this case we could have the operand of the binary operation
|
|
// being defined in another block, and performing the replacement
|
|
// could break the dominance relation.
|
|
return nullptr;
|
|
}
|
|
} else {
|
|
// Other uses prohibit this transformation.
|
|
return nullptr;
|
|
}
|
|
}
|
|
|
|
// Recognize patterns
|
|
switch (I.getPredicate()) {
|
|
case ICmpInst::ICMP_EQ:
|
|
case ICmpInst::ICMP_NE:
|
|
// Recognize pattern:
|
|
// mulval = mul(zext A, zext B)
|
|
// cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
|
|
ConstantInt *CI;
|
|
Value *ValToMask;
|
|
if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
|
|
if (ValToMask != MulVal)
|
|
return nullptr;
|
|
const APInt &CVal = CI->getValue() + 1;
|
|
if (CVal.isPowerOf2()) {
|
|
unsigned MaskWidth = CVal.logBase2();
|
|
if (MaskWidth == MulWidth)
|
|
break; // Recognized
|
|
}
|
|
}
|
|
return nullptr;
|
|
|
|
case ICmpInst::ICMP_UGT:
|
|
// Recognize pattern:
|
|
// mulval = mul(zext A, zext B)
|
|
// cmp ugt mulval, max
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
|
|
APInt MaxVal = APInt::getMaxValue(MulWidth);
|
|
MaxVal = MaxVal.zext(CI->getBitWidth());
|
|
if (MaxVal.eq(CI->getValue()))
|
|
break; // Recognized
|
|
}
|
|
return nullptr;
|
|
|
|
case ICmpInst::ICMP_UGE:
|
|
// Recognize pattern:
|
|
// mulval = mul(zext A, zext B)
|
|
// cmp uge mulval, max+1
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
|
|
APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
|
|
if (MaxVal.eq(CI->getValue()))
|
|
break; // Recognized
|
|
}
|
|
return nullptr;
|
|
|
|
case ICmpInst::ICMP_ULE:
|
|
// Recognize pattern:
|
|
// mulval = mul(zext A, zext B)
|
|
// cmp ule mulval, max
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
|
|
APInt MaxVal = APInt::getMaxValue(MulWidth);
|
|
MaxVal = MaxVal.zext(CI->getBitWidth());
|
|
if (MaxVal.eq(CI->getValue()))
|
|
break; // Recognized
|
|
}
|
|
return nullptr;
|
|
|
|
case ICmpInst::ICMP_ULT:
|
|
// Recognize pattern:
|
|
// mulval = mul(zext A, zext B)
|
|
// cmp ule mulval, max + 1
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
|
|
APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
|
|
if (MaxVal.eq(CI->getValue()))
|
|
break; // Recognized
|
|
}
|
|
return nullptr;
|
|
|
|
default:
|
|
return nullptr;
|
|
}
|
|
|
|
InstCombiner::BuilderTy &Builder = IC.Builder;
|
|
Builder.SetInsertPoint(MulInstr);
|
|
|
|
// Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
|
|
Value *MulA = A, *MulB = B;
|
|
if (WidthA < MulWidth)
|
|
MulA = Builder.CreateZExt(A, MulType);
|
|
if (WidthB < MulWidth)
|
|
MulB = Builder.CreateZExt(B, MulType);
|
|
Function *F = Intrinsic::getDeclaration(
|
|
I.getModule(), Intrinsic::umul_with_overflow, MulType);
|
|
CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
|
|
IC.addToWorklist(MulInstr);
|
|
|
|
// If there are uses of mul result other than the comparison, we know that
|
|
// they are truncation or binary AND. Change them to use result of
|
|
// mul.with.overflow and adjust properly mask/size.
|
|
if (MulVal->hasNUsesOrMore(2)) {
|
|
Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
|
|
for (User *U : make_early_inc_range(MulVal->users())) {
|
|
if (U == &I || U == OtherVal)
|
|
continue;
|
|
if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
|
|
if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
|
|
IC.replaceInstUsesWith(*TI, Mul);
|
|
else
|
|
TI->setOperand(0, Mul);
|
|
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
|
|
assert(BO->getOpcode() == Instruction::And);
|
|
// Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
|
|
ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
|
|
APInt ShortMask = CI->getValue().trunc(MulWidth);
|
|
Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
|
|
Value *Zext = Builder.CreateZExt(ShortAnd, BO->getType());
|
|
IC.replaceInstUsesWith(*BO, Zext);
|
|
} else {
|
|
llvm_unreachable("Unexpected Binary operation");
|
|
}
|
|
IC.addToWorklist(cast<Instruction>(U));
|
|
}
|
|
}
|
|
if (isa<Instruction>(OtherVal))
|
|
IC.addToWorklist(cast<Instruction>(OtherVal));
|
|
|
|
// The original icmp gets replaced with the overflow value, maybe inverted
|
|
// depending on predicate.
|
|
bool Inverse = false;
|
|
switch (I.getPredicate()) {
|
|
case ICmpInst::ICMP_NE:
|
|
break;
|
|
case ICmpInst::ICMP_EQ:
|
|
Inverse = true;
|
|
break;
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_UGE:
|
|
if (I.getOperand(0) == MulVal)
|
|
break;
|
|
Inverse = true;
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_ULE:
|
|
if (I.getOperand(1) == MulVal)
|
|
break;
|
|
Inverse = true;
|
|
break;
|
|
default:
|
|
llvm_unreachable("Unexpected predicate");
|
|
}
|
|
if (Inverse) {
|
|
Value *Res = Builder.CreateExtractValue(Call, 1);
|
|
return BinaryOperator::CreateNot(Res);
|
|
}
|
|
|
|
return ExtractValueInst::Create(Call, 1);
|
|
}
|
|
|
|
/// When performing a comparison against a constant, it is possible that not all
|
|
/// the bits in the LHS are demanded. This helper method computes the mask that
|
|
/// IS demanded.
|
|
static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
|
|
const APInt *RHS;
|
|
if (!match(I.getOperand(1), m_APInt(RHS)))
|
|
return APInt::getAllOnesValue(BitWidth);
|
|
|
|
// If this is a normal comparison, it demands all bits. If it is a sign bit
|
|
// comparison, it only demands the sign bit.
|
|
bool UnusedBit;
|
|
if (InstCombiner::isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
|
|
return APInt::getSignMask(BitWidth);
|
|
|
|
switch (I.getPredicate()) {
|
|
// For a UGT comparison, we don't care about any bits that
|
|
// correspond to the trailing ones of the comparand. The value of these
|
|
// bits doesn't impact the outcome of the comparison, because any value
|
|
// greater than the RHS must differ in a bit higher than these due to carry.
|
|
case ICmpInst::ICMP_UGT:
|
|
return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
|
|
|
|
// Similarly, for a ULT comparison, we don't care about the trailing zeros.
|
|
// Any value less than the RHS must differ in a higher bit because of carries.
|
|
case ICmpInst::ICMP_ULT:
|
|
return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
|
|
|
|
default:
|
|
return APInt::getAllOnesValue(BitWidth);
|
|
}
|
|
}
|
|
|
|
/// Check if the order of \p Op0 and \p Op1 as operands in an ICmpInst
|
|
/// should be swapped.
|
|
/// The decision is based on how many times these two operands are reused
|
|
/// as subtract operands and their positions in those instructions.
|
|
/// The rationale is that several architectures use the same instruction for
|
|
/// both subtract and cmp. Thus, it is better if the order of those operands
|
|
/// match.
|
|
/// \return true if Op0 and Op1 should be swapped.
|
|
static bool swapMayExposeCSEOpportunities(const Value *Op0, const Value *Op1) {
|
|
// Filter out pointer values as those cannot appear directly in subtract.
|
|
// FIXME: we may want to go through inttoptrs or bitcasts.
|
|
if (Op0->getType()->isPointerTy())
|
|
return false;
|
|
// If a subtract already has the same operands as a compare, swapping would be
|
|
// bad. If a subtract has the same operands as a compare but in reverse order,
|
|
// then swapping is good.
|
|
int GoodToSwap = 0;
|
|
for (const User *U : Op0->users()) {
|
|
if (match(U, m_Sub(m_Specific(Op1), m_Specific(Op0))))
|
|
GoodToSwap++;
|
|
else if (match(U, m_Sub(m_Specific(Op0), m_Specific(Op1))))
|
|
GoodToSwap--;
|
|
}
|
|
return GoodToSwap > 0;
|
|
}
|
|
|
|
/// Check that one use is in the same block as the definition and all
|
|
/// other uses are in blocks dominated by a given block.
|
|
///
|
|
/// \param DI Definition
|
|
/// \param UI Use
|
|
/// \param DB Block that must dominate all uses of \p DI outside
|
|
/// the parent block
|
|
/// \return true when \p UI is the only use of \p DI in the parent block
|
|
/// and all other uses of \p DI are in blocks dominated by \p DB.
|
|
///
|
|
bool InstCombinerImpl::dominatesAllUses(const Instruction *DI,
|
|
const Instruction *UI,
|
|
const BasicBlock *DB) const {
|
|
assert(DI && UI && "Instruction not defined\n");
|
|
// Ignore incomplete definitions.
|
|
if (!DI->getParent())
|
|
return false;
|
|
// DI and UI must be in the same block.
|
|
if (DI->getParent() != UI->getParent())
|
|
return false;
|
|
// Protect from self-referencing blocks.
|
|
if (DI->getParent() == DB)
|
|
return false;
|
|
for (const User *U : DI->users()) {
|
|
auto *Usr = cast<Instruction>(U);
|
|
if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Return true when the instruction sequence within a block is select-cmp-br.
|
|
static bool isChainSelectCmpBranch(const SelectInst *SI) {
|
|
const BasicBlock *BB = SI->getParent();
|
|
if (!BB)
|
|
return false;
|
|
auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
|
|
if (!BI || BI->getNumSuccessors() != 2)
|
|
return false;
|
|
auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
|
|
if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
/// True when a select result is replaced by one of its operands
|
|
/// in select-icmp sequence. This will eventually result in the elimination
|
|
/// of the select.
|
|
///
|
|
/// \param SI Select instruction
|
|
/// \param Icmp Compare instruction
|
|
/// \param SIOpd Operand that replaces the select
|
|
///
|
|
/// Notes:
|
|
/// - The replacement is global and requires dominator information
|
|
/// - The caller is responsible for the actual replacement
|
|
///
|
|
/// Example:
|
|
///
|
|
/// entry:
|
|
/// %4 = select i1 %3, %C* %0, %C* null
|
|
/// %5 = icmp eq %C* %4, null
|
|
/// br i1 %5, label %9, label %7
|
|
/// ...
|
|
/// ; <label>:7 ; preds = %entry
|
|
/// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
|
|
/// ...
|
|
///
|
|
/// can be transformed to
|
|
///
|
|
/// %5 = icmp eq %C* %0, null
|
|
/// %6 = select i1 %3, i1 %5, i1 true
|
|
/// br i1 %6, label %9, label %7
|
|
/// ...
|
|
/// ; <label>:7 ; preds = %entry
|
|
/// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
|
|
///
|
|
/// Similar when the first operand of the select is a constant or/and
|
|
/// the compare is for not equal rather than equal.
|
|
///
|
|
/// NOTE: The function is only called when the select and compare constants
|
|
/// are equal, the optimization can work only for EQ predicates. This is not a
|
|
/// major restriction since a NE compare should be 'normalized' to an equal
|
|
/// compare, which usually happens in the combiner and test case
|
|
/// select-cmp-br.ll checks for it.
|
|
bool InstCombinerImpl::replacedSelectWithOperand(SelectInst *SI,
|
|
const ICmpInst *Icmp,
|
|
const unsigned SIOpd) {
|
|
assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
|
|
if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
|
|
BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
|
|
// The check for the single predecessor is not the best that can be
|
|
// done. But it protects efficiently against cases like when SI's
|
|
// home block has two successors, Succ and Succ1, and Succ1 predecessor
|
|
// of Succ. Then SI can't be replaced by SIOpd because the use that gets
|
|
// replaced can be reached on either path. So the uniqueness check
|
|
// guarantees that the path all uses of SI (outside SI's parent) are on
|
|
// is disjoint from all other paths out of SI. But that information
|
|
// is more expensive to compute, and the trade-off here is in favor
|
|
// of compile-time. It should also be noticed that we check for a single
|
|
// predecessor and not only uniqueness. This to handle the situation when
|
|
// Succ and Succ1 points to the same basic block.
|
|
if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
|
|
NumSel++;
|
|
SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Try to fold the comparison based on range information we can get by checking
|
|
/// whether bits are known to be zero or one in the inputs.
|
|
Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
Type *Ty = Op0->getType();
|
|
ICmpInst::Predicate Pred = I.getPredicate();
|
|
|
|
// Get scalar or pointer size.
|
|
unsigned BitWidth = Ty->isIntOrIntVectorTy()
|
|
? Ty->getScalarSizeInBits()
|
|
: DL.getPointerTypeSizeInBits(Ty->getScalarType());
|
|
|
|
if (!BitWidth)
|
|
return nullptr;
|
|
|
|
KnownBits Op0Known(BitWidth);
|
|
KnownBits Op1Known(BitWidth);
|
|
|
|
if (SimplifyDemandedBits(&I, 0,
|
|
getDemandedBitsLHSMask(I, BitWidth),
|
|
Op0Known, 0))
|
|
return &I;
|
|
|
|
if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
|
|
Op1Known, 0))
|
|
return &I;
|
|
|
|
// Given the known and unknown bits, compute a range that the LHS could be
|
|
// in. Compute the Min, Max and RHS values based on the known bits. For the
|
|
// EQ and NE we use unsigned values.
|
|
APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
|
|
APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
|
|
if (I.isSigned()) {
|
|
Op0Min = Op0Known.getSignedMinValue();
|
|
Op0Max = Op0Known.getSignedMaxValue();
|
|
Op1Min = Op1Known.getSignedMinValue();
|
|
Op1Max = Op1Known.getSignedMaxValue();
|
|
} else {
|
|
Op0Min = Op0Known.getMinValue();
|
|
Op0Max = Op0Known.getMaxValue();
|
|
Op1Min = Op1Known.getMinValue();
|
|
Op1Max = Op1Known.getMaxValue();
|
|
}
|
|
|
|
// If Min and Max are known to be the same, then SimplifyDemandedBits figured
|
|
// out that the LHS or RHS is a constant. Constant fold this now, so that
|
|
// code below can assume that Min != Max.
|
|
if (!isa<Constant>(Op0) && Op0Min == Op0Max)
|
|
return new ICmpInst(Pred, ConstantExpr::getIntegerValue(Ty, Op0Min), Op1);
|
|
if (!isa<Constant>(Op1) && Op1Min == Op1Max)
|
|
return new ICmpInst(Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Min));
|
|
|
|
// Based on the range information we know about the LHS, see if we can
|
|
// simplify this comparison. For example, (x&4) < 8 is always true.
|
|
switch (Pred) {
|
|
default:
|
|
llvm_unreachable("Unknown icmp opcode!");
|
|
case ICmpInst::ICMP_EQ:
|
|
case ICmpInst::ICMP_NE: {
|
|
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
|
|
return replaceInstUsesWith(
|
|
I, ConstantInt::getBool(I.getType(), Pred == CmpInst::ICMP_NE));
|
|
|
|
// If all bits are known zero except for one, then we know at most one bit
|
|
// is set. If the comparison is against zero, then this is a check to see if
|
|
// *that* bit is set.
|
|
APInt Op0KnownZeroInverted = ~Op0Known.Zero;
|
|
if (Op1Known.isZero()) {
|
|
// If the LHS is an AND with the same constant, look through it.
|
|
Value *LHS = nullptr;
|
|
const APInt *LHSC;
|
|
if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
|
|
*LHSC != Op0KnownZeroInverted)
|
|
LHS = Op0;
|
|
|
|
Value *X;
|
|
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
|
|
APInt ValToCheck = Op0KnownZeroInverted;
|
|
Type *XTy = X->getType();
|
|
if (ValToCheck.isPowerOf2()) {
|
|
// ((1 << X) & 8) == 0 -> X != 3
|
|
// ((1 << X) & 8) != 0 -> X == 3
|
|
auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
|
|
auto NewPred = ICmpInst::getInversePredicate(Pred);
|
|
return new ICmpInst(NewPred, X, CmpC);
|
|
} else if ((++ValToCheck).isPowerOf2()) {
|
|
// ((1 << X) & 7) == 0 -> X >= 3
|
|
// ((1 << X) & 7) != 0 -> X < 3
|
|
auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
|
|
auto NewPred =
|
|
Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGE : CmpInst::ICMP_ULT;
|
|
return new ICmpInst(NewPred, X, CmpC);
|
|
}
|
|
}
|
|
|
|
// Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
|
|
const APInt *CI;
|
|
if (Op0KnownZeroInverted.isOneValue() &&
|
|
match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
|
|
// ((8 >>u X) & 1) == 0 -> X != 3
|
|
// ((8 >>u X) & 1) != 0 -> X == 3
|
|
unsigned CmpVal = CI->countTrailingZeros();
|
|
auto NewPred = ICmpInst::getInversePredicate(Pred);
|
|
return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_ULT: {
|
|
if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
|
|
|
|
const APInt *CmpC;
|
|
if (match(Op1, m_APInt(CmpC))) {
|
|
// A <u C -> A == C-1 if min(A)+1 == C
|
|
if (*CmpC == Op0Min + 1)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
|
|
ConstantInt::get(Op1->getType(), *CmpC - 1));
|
|
// X <u C --> X == 0, if the number of zero bits in the bottom of X
|
|
// exceeds the log2 of C.
|
|
if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
|
|
Constant::getNullValue(Op1->getType()));
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_UGT: {
|
|
if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
|
|
|
|
const APInt *CmpC;
|
|
if (match(Op1, m_APInt(CmpC))) {
|
|
// A >u C -> A == C+1 if max(a)-1 == C
|
|
if (*CmpC == Op0Max - 1)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
|
|
ConstantInt::get(Op1->getType(), *CmpC + 1));
|
|
// X >u C --> X != 0, if the number of zero bits in the bottom of X
|
|
// exceeds the log2 of C.
|
|
if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op0,
|
|
Constant::getNullValue(Op1->getType()));
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_SLT: {
|
|
if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
|
|
const APInt *CmpC;
|
|
if (match(Op1, m_APInt(CmpC))) {
|
|
if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
|
|
ConstantInt::get(Op1->getType(), *CmpC - 1));
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_SGT: {
|
|
if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
|
|
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
|
|
const APInt *CmpC;
|
|
if (match(Op1, m_APInt(CmpC))) {
|
|
if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
|
|
ConstantInt::get(Op1->getType(), *CmpC + 1));
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_SGE:
|
|
assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
|
|
if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
|
|
if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
|
|
if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
|
|
break;
|
|
case ICmpInst::ICMP_ULE:
|
|
assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
|
|
if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
|
|
if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
|
|
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
|
|
if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
|
|
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
|
|
break;
|
|
}
|
|
|
|
// Turn a signed comparison into an unsigned one if both operands are known to
|
|
// have the same sign.
|
|
if (I.isSigned() &&
|
|
((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
|
|
(Op0Known.One.isNegative() && Op1Known.One.isNegative())))
|
|
return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
llvm::Optional<std::pair<CmpInst::Predicate, Constant *>>
|
|
InstCombiner::getFlippedStrictnessPredicateAndConstant(CmpInst::Predicate Pred,
|
|
Constant *C) {
|
|
assert(ICmpInst::isRelational(Pred) && ICmpInst::isIntPredicate(Pred) &&
|
|
"Only for relational integer predicates.");
|
|
|
|
Type *Type = C->getType();
|
|
bool IsSigned = ICmpInst::isSigned(Pred);
|
|
|
|
CmpInst::Predicate UnsignedPred = ICmpInst::getUnsignedPredicate(Pred);
|
|
bool WillIncrement =
|
|
UnsignedPred == ICmpInst::ICMP_ULE || UnsignedPred == ICmpInst::ICMP_UGT;
|
|
|
|
// Check if the constant operand can be safely incremented/decremented
|
|
// without overflowing/underflowing.
|
|
auto ConstantIsOk = [WillIncrement, IsSigned](ConstantInt *C) {
|
|
return WillIncrement ? !C->isMaxValue(IsSigned) : !C->isMinValue(IsSigned);
|
|
};
|
|
|
|
Constant *SafeReplacementConstant = nullptr;
|
|
if (auto *CI = dyn_cast<ConstantInt>(C)) {
|
|
// Bail out if the constant can't be safely incremented/decremented.
|
|
if (!ConstantIsOk(CI))
|
|
return llvm::None;
|
|
} else if (auto *FVTy = dyn_cast<FixedVectorType>(Type)) {
|
|
unsigned NumElts = FVTy->getNumElements();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
Constant *Elt = C->getAggregateElement(i);
|
|
if (!Elt)
|
|
return llvm::None;
|
|
|
|
if (isa<UndefValue>(Elt))
|
|
continue;
|
|
|
|
// Bail out if we can't determine if this constant is min/max or if we
|
|
// know that this constant is min/max.
|
|
auto *CI = dyn_cast<ConstantInt>(Elt);
|
|
if (!CI || !ConstantIsOk(CI))
|
|
return llvm::None;
|
|
|
|
if (!SafeReplacementConstant)
|
|
SafeReplacementConstant = CI;
|
|
}
|
|
} else {
|
|
// ConstantExpr?
|
|
return llvm::None;
|
|
}
|
|
|
|
// It may not be safe to change a compare predicate in the presence of
|
|
// undefined elements, so replace those elements with the first safe constant
|
|
// that we found.
|
|
// TODO: in case of poison, it is safe; let's replace undefs only.
|
|
if (C->containsUndefOrPoisonElement()) {
|
|
assert(SafeReplacementConstant && "Replacement constant not set");
|
|
C = Constant::replaceUndefsWith(C, SafeReplacementConstant);
|
|
}
|
|
|
|
CmpInst::Predicate NewPred = CmpInst::getFlippedStrictnessPredicate(Pred);
|
|
|
|
// Increment or decrement the constant.
|
|
Constant *OneOrNegOne = ConstantInt::get(Type, WillIncrement ? 1 : -1, true);
|
|
Constant *NewC = ConstantExpr::getAdd(C, OneOrNegOne);
|
|
|
|
return std::make_pair(NewPred, NewC);
|
|
}
|
|
|
|
/// If we have an icmp le or icmp ge instruction with a constant operand, turn
|
|
/// it into the appropriate icmp lt or icmp gt instruction. This transform
|
|
/// allows them to be folded in visitICmpInst.
|
|
static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I) {
|
|
ICmpInst::Predicate Pred = I.getPredicate();
|
|
if (ICmpInst::isEquality(Pred) || !ICmpInst::isIntPredicate(Pred) ||
|
|
InstCombiner::isCanonicalPredicate(Pred))
|
|
return nullptr;
|
|
|
|
Value *Op0 = I.getOperand(0);
|
|
Value *Op1 = I.getOperand(1);
|
|
auto *Op1C = dyn_cast<Constant>(Op1);
|
|
if (!Op1C)
|
|
return nullptr;
|
|
|
|
auto FlippedStrictness =
|
|
InstCombiner::getFlippedStrictnessPredicateAndConstant(Pred, Op1C);
|
|
if (!FlippedStrictness)
|
|
return nullptr;
|
|
|
|
return new ICmpInst(FlippedStrictness->first, Op0, FlippedStrictness->second);
|
|
}
|
|
|
|
/// If we have a comparison with a non-canonical predicate, if we can update
|
|
/// all the users, invert the predicate and adjust all the users.
|
|
CmpInst *InstCombinerImpl::canonicalizeICmpPredicate(CmpInst &I) {
|
|
// Is the predicate already canonical?
|
|
CmpInst::Predicate Pred = I.getPredicate();
|
|
if (InstCombiner::isCanonicalPredicate(Pred))
|
|
return nullptr;
|
|
|
|
// Can all users be adjusted to predicate inversion?
|
|
if (!InstCombiner::canFreelyInvertAllUsersOf(&I, /*IgnoredUser=*/nullptr))
|
|
return nullptr;
|
|
|
|
// Ok, we can canonicalize comparison!
|
|
// Let's first invert the comparison's predicate.
|
|
I.setPredicate(CmpInst::getInversePredicate(Pred));
|
|
I.setName(I.getName() + ".not");
|
|
|
|
// And, adapt users.
|
|
freelyInvertAllUsersOf(&I);
|
|
|
|
return &I;
|
|
}
|
|
|
|
/// Integer compare with boolean values can always be turned into bitwise ops.
|
|
static Instruction *canonicalizeICmpBool(ICmpInst &I,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
Value *A = I.getOperand(0), *B = I.getOperand(1);
|
|
assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
|
|
|
|
// A boolean compared to true/false can be simplified to Op0/true/false in
|
|
// 14 out of the 20 (10 predicates * 2 constants) possible combinations.
|
|
// Cases not handled by InstSimplify are always 'not' of Op0.
|
|
if (match(B, m_Zero())) {
|
|
switch (I.getPredicate()) {
|
|
case CmpInst::ICMP_EQ: // A == 0 -> !A
|
|
case CmpInst::ICMP_ULE: // A <=u 0 -> !A
|
|
case CmpInst::ICMP_SGE: // A >=s 0 -> !A
|
|
return BinaryOperator::CreateNot(A);
|
|
default:
|
|
llvm_unreachable("ICmp i1 X, C not simplified as expected.");
|
|
}
|
|
} else if (match(B, m_One())) {
|
|
switch (I.getPredicate()) {
|
|
case CmpInst::ICMP_NE: // A != 1 -> !A
|
|
case CmpInst::ICMP_ULT: // A <u 1 -> !A
|
|
case CmpInst::ICMP_SGT: // A >s -1 -> !A
|
|
return BinaryOperator::CreateNot(A);
|
|
default:
|
|
llvm_unreachable("ICmp i1 X, C not simplified as expected.");
|
|
}
|
|
}
|
|
|
|
switch (I.getPredicate()) {
|
|
default:
|
|
llvm_unreachable("Invalid icmp instruction!");
|
|
case ICmpInst::ICMP_EQ:
|
|
// icmp eq i1 A, B -> ~(A ^ B)
|
|
return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
|
|
|
|
case ICmpInst::ICMP_NE:
|
|
// icmp ne i1 A, B -> A ^ B
|
|
return BinaryOperator::CreateXor(A, B);
|
|
|
|
case ICmpInst::ICMP_UGT:
|
|
// icmp ugt -> icmp ult
|
|
std::swap(A, B);
|
|
LLVM_FALLTHROUGH;
|
|
case ICmpInst::ICMP_ULT:
|
|
// icmp ult i1 A, B -> ~A & B
|
|
return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
|
|
|
|
case ICmpInst::ICMP_SGT:
|
|
// icmp sgt -> icmp slt
|
|
std::swap(A, B);
|
|
LLVM_FALLTHROUGH;
|
|
case ICmpInst::ICMP_SLT:
|
|
// icmp slt i1 A, B -> A & ~B
|
|
return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
|
|
|
|
case ICmpInst::ICMP_UGE:
|
|
// icmp uge -> icmp ule
|
|
std::swap(A, B);
|
|
LLVM_FALLTHROUGH;
|
|
case ICmpInst::ICMP_ULE:
|
|
// icmp ule i1 A, B -> ~A | B
|
|
return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
|
|
|
|
case ICmpInst::ICMP_SGE:
|
|
// icmp sge -> icmp sle
|
|
std::swap(A, B);
|
|
LLVM_FALLTHROUGH;
|
|
case ICmpInst::ICMP_SLE:
|
|
// icmp sle i1 A, B -> A | ~B
|
|
return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
|
|
}
|
|
}
|
|
|
|
// Transform pattern like:
|
|
// (1 << Y) u<= X or ~(-1 << Y) u< X or ((1 << Y)+(-1)) u< X
|
|
// (1 << Y) u> X or ~(-1 << Y) u>= X or ((1 << Y)+(-1)) u>= X
|
|
// Into:
|
|
// (X l>> Y) != 0
|
|
// (X l>> Y) == 0
|
|
static Instruction *foldICmpWithHighBitMask(ICmpInst &Cmp,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
ICmpInst::Predicate Pred, NewPred;
|
|
Value *X, *Y;
|
|
if (match(&Cmp,
|
|
m_c_ICmp(Pred, m_OneUse(m_Shl(m_One(), m_Value(Y))), m_Value(X)))) {
|
|
switch (Pred) {
|
|
case ICmpInst::ICMP_ULE:
|
|
NewPred = ICmpInst::ICMP_NE;
|
|
break;
|
|
case ICmpInst::ICMP_UGT:
|
|
NewPred = ICmpInst::ICMP_EQ;
|
|
break;
|
|
default:
|
|
return nullptr;
|
|
}
|
|
} else if (match(&Cmp, m_c_ICmp(Pred,
|
|
m_OneUse(m_CombineOr(
|
|
m_Not(m_Shl(m_AllOnes(), m_Value(Y))),
|
|
m_Add(m_Shl(m_One(), m_Value(Y)),
|
|
m_AllOnes()))),
|
|
m_Value(X)))) {
|
|
// The variant with 'add' is not canonical, (the variant with 'not' is)
|
|
// we only get it because it has extra uses, and can't be canonicalized,
|
|
|
|
switch (Pred) {
|
|
case ICmpInst::ICMP_ULT:
|
|
NewPred = ICmpInst::ICMP_NE;
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
NewPred = ICmpInst::ICMP_EQ;
|
|
break;
|
|
default:
|
|
return nullptr;
|
|
}
|
|
} else
|
|
return nullptr;
|
|
|
|
Value *NewX = Builder.CreateLShr(X, Y, X->getName() + ".highbits");
|
|
Constant *Zero = Constant::getNullValue(NewX->getType());
|
|
return CmpInst::Create(Instruction::ICmp, NewPred, NewX, Zero);
|
|
}
|
|
|
|
static Instruction *foldVectorCmp(CmpInst &Cmp,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
const CmpInst::Predicate Pred = Cmp.getPredicate();
|
|
Value *LHS = Cmp.getOperand(0), *RHS = Cmp.getOperand(1);
|
|
Value *V1, *V2;
|
|
ArrayRef<int> M;
|
|
if (!match(LHS, m_Shuffle(m_Value(V1), m_Undef(), m_Mask(M))))
|
|
return nullptr;
|
|
|
|
// If both arguments of the cmp are shuffles that use the same mask and
|
|
// shuffle within a single vector, move the shuffle after the cmp:
|
|
// cmp (shuffle V1, M), (shuffle V2, M) --> shuffle (cmp V1, V2), M
|
|
Type *V1Ty = V1->getType();
|
|
if (match(RHS, m_Shuffle(m_Value(V2), m_Undef(), m_SpecificMask(M))) &&
|
|
V1Ty == V2->getType() && (LHS->hasOneUse() || RHS->hasOneUse())) {
|
|
Value *NewCmp = Builder.CreateCmp(Pred, V1, V2);
|
|
return new ShuffleVectorInst(NewCmp, UndefValue::get(NewCmp->getType()), M);
|
|
}
|
|
|
|
// Try to canonicalize compare with splatted operand and splat constant.
|
|
// TODO: We could generalize this for more than splats. See/use the code in
|
|
// InstCombiner::foldVectorBinop().
|
|
Constant *C;
|
|
if (!LHS->hasOneUse() || !match(RHS, m_Constant(C)))
|
|
return nullptr;
|
|
|
|
// Length-changing splats are ok, so adjust the constants as needed:
|
|
// cmp (shuffle V1, M), C --> shuffle (cmp V1, C'), M
|
|
Constant *ScalarC = C->getSplatValue(/* AllowUndefs */ true);
|
|
int MaskSplatIndex;
|
|
if (ScalarC && match(M, m_SplatOrUndefMask(MaskSplatIndex))) {
|
|
// We allow undefs in matching, but this transform removes those for safety.
|
|
// Demanded elements analysis should be able to recover some/all of that.
|
|
C = ConstantVector::getSplat(cast<VectorType>(V1Ty)->getElementCount(),
|
|
ScalarC);
|
|
SmallVector<int, 8> NewM(M.size(), MaskSplatIndex);
|
|
Value *NewCmp = Builder.CreateCmp(Pred, V1, C);
|
|
return new ShuffleVectorInst(NewCmp, UndefValue::get(NewCmp->getType()),
|
|
NewM);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
// extract(uadd.with.overflow(A, B), 0) ult A
|
|
// -> extract(uadd.with.overflow(A, B), 1)
|
|
static Instruction *foldICmpOfUAddOv(ICmpInst &I) {
|
|
CmpInst::Predicate Pred = I.getPredicate();
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
|
|
Value *UAddOv;
|
|
Value *A, *B;
|
|
auto UAddOvResultPat = m_ExtractValue<0>(
|
|
m_Intrinsic<Intrinsic::uadd_with_overflow>(m_Value(A), m_Value(B)));
|
|
if (match(Op0, UAddOvResultPat) &&
|
|
((Pred == ICmpInst::ICMP_ULT && (Op1 == A || Op1 == B)) ||
|
|
(Pred == ICmpInst::ICMP_EQ && match(Op1, m_ZeroInt()) &&
|
|
(match(A, m_One()) || match(B, m_One()))) ||
|
|
(Pred == ICmpInst::ICMP_NE && match(Op1, m_AllOnes()) &&
|
|
(match(A, m_AllOnes()) || match(B, m_AllOnes())))))
|
|
// extract(uadd.with.overflow(A, B), 0) < A
|
|
// extract(uadd.with.overflow(A, 1), 0) == 0
|
|
// extract(uadd.with.overflow(A, -1), 0) != -1
|
|
UAddOv = cast<ExtractValueInst>(Op0)->getAggregateOperand();
|
|
else if (match(Op1, UAddOvResultPat) &&
|
|
Pred == ICmpInst::ICMP_UGT && (Op0 == A || Op0 == B))
|
|
// A > extract(uadd.with.overflow(A, B), 0)
|
|
UAddOv = cast<ExtractValueInst>(Op1)->getAggregateOperand();
|
|
else
|
|
return nullptr;
|
|
|
|
return ExtractValueInst::Create(UAddOv, 1);
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
|
|
bool Changed = false;
|
|
const SimplifyQuery Q = SQ.getWithInstruction(&I);
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
unsigned Op0Cplxity = getComplexity(Op0);
|
|
unsigned Op1Cplxity = getComplexity(Op1);
|
|
|
|
/// Orders the operands of the compare so that they are listed from most
|
|
/// complex to least complex. This puts constants before unary operators,
|
|
/// before binary operators.
|
|
if (Op0Cplxity < Op1Cplxity ||
|
|
(Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
|
|
I.swapOperands();
|
|
std::swap(Op0, Op1);
|
|
Changed = true;
|
|
}
|
|
|
|
if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, Q))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
// Comparing -val or val with non-zero is the same as just comparing val
|
|
// ie, abs(val) != 0 -> val != 0
|
|
if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
|
|
Value *Cond, *SelectTrue, *SelectFalse;
|
|
if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
|
|
m_Value(SelectFalse)))) {
|
|
if (Value *V = dyn_castNegVal(SelectTrue)) {
|
|
if (V == SelectFalse)
|
|
return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
|
|
}
|
|
else if (Value *V = dyn_castNegVal(SelectFalse)) {
|
|
if (V == SelectTrue)
|
|
return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (Op0->getType()->isIntOrIntVectorTy(1))
|
|
if (Instruction *Res = canonicalizeICmpBool(I, Builder))
|
|
return Res;
|
|
|
|
if (Instruction *Res = canonicalizeCmpWithConstant(I))
|
|
return Res;
|
|
|
|
if (Instruction *Res = canonicalizeICmpPredicate(I))
|
|
return Res;
|
|
|
|
if (Instruction *Res = foldICmpWithConstant(I))
|
|
return Res;
|
|
|
|
if (Instruction *Res = foldICmpWithDominatingICmp(I))
|
|
return Res;
|
|
|
|
if (Instruction *Res = foldICmpBinOp(I, Q))
|
|
return Res;
|
|
|
|
if (Instruction *Res = foldICmpUsingKnownBits(I))
|
|
return Res;
|
|
|
|
// Test if the ICmpInst instruction is used exclusively by a select as
|
|
// part of a minimum or maximum operation. If so, refrain from doing
|
|
// any other folding. This helps out other analyses which understand
|
|
// non-obfuscated minimum and maximum idioms, such as ScalarEvolution
|
|
// and CodeGen. And in this case, at least one of the comparison
|
|
// operands has at least one user besides the compare (the select),
|
|
// which would often largely negate the benefit of folding anyway.
|
|
//
|
|
// Do the same for the other patterns recognized by matchSelectPattern.
|
|
if (I.hasOneUse())
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
|
|
Value *A, *B;
|
|
SelectPatternResult SPR = matchSelectPattern(SI, A, B);
|
|
if (SPR.Flavor != SPF_UNKNOWN)
|
|
return nullptr;
|
|
}
|
|
|
|
// Do this after checking for min/max to prevent infinite looping.
|
|
if (Instruction *Res = foldICmpWithZero(I))
|
|
return Res;
|
|
|
|
// FIXME: We only do this after checking for min/max to prevent infinite
|
|
// looping caused by a reverse canonicalization of these patterns for min/max.
|
|
// FIXME: The organization of folds is a mess. These would naturally go into
|
|
// canonicalizeCmpWithConstant(), but we can't move all of the above folds
|
|
// down here after the min/max restriction.
|
|
ICmpInst::Predicate Pred = I.getPredicate();
|
|
const APInt *C;
|
|
if (match(Op1, m_APInt(C))) {
|
|
// For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
|
|
if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
|
|
Constant *Zero = Constant::getNullValue(Op0->getType());
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
|
|
}
|
|
|
|
// For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
|
|
if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
|
|
Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
|
|
return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
|
|
}
|
|
}
|
|
|
|
if (Instruction *Res = foldICmpInstWithConstant(I))
|
|
return Res;
|
|
|
|
// Try to match comparison as a sign bit test. Intentionally do this after
|
|
// foldICmpInstWithConstant() to potentially let other folds to happen first.
|
|
if (Instruction *New = foldSignBitTest(I))
|
|
return New;
|
|
|
|
if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
|
|
return Res;
|
|
|
|
// If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
|
|
if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
|
|
if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
|
|
return NI;
|
|
if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
|
|
if (Instruction *NI = foldGEPICmp(GEP, Op0,
|
|
ICmpInst::getSwappedPredicate(I.getPredicate()), I))
|
|
return NI;
|
|
|
|
// Try to optimize equality comparisons against alloca-based pointers.
|
|
if (Op0->getType()->isPointerTy() && I.isEquality()) {
|
|
assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
|
|
if (auto *Alloca = dyn_cast<AllocaInst>(getUnderlyingObject(Op0)))
|
|
if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
|
|
return New;
|
|
if (auto *Alloca = dyn_cast<AllocaInst>(getUnderlyingObject(Op1)))
|
|
if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
|
|
return New;
|
|
}
|
|
|
|
if (Instruction *Res = foldICmpBitCast(I, Builder))
|
|
return Res;
|
|
|
|
// TODO: Hoist this above the min/max bailout.
|
|
if (Instruction *R = foldICmpWithCastOp(I))
|
|
return R;
|
|
|
|
if (Instruction *Res = foldICmpWithMinMax(I))
|
|
return Res;
|
|
|
|
{
|
|
Value *A, *B;
|
|
// Transform (A & ~B) == 0 --> (A & B) != 0
|
|
// and (A & ~B) != 0 --> (A & B) == 0
|
|
// if A is a power of 2.
|
|
if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
|
|
match(Op1, m_Zero()) &&
|
|
isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
|
|
return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
|
|
Op1);
|
|
|
|
// ~X < ~Y --> Y < X
|
|
// ~X < C --> X > ~C
|
|
if (match(Op0, m_Not(m_Value(A)))) {
|
|
if (match(Op1, m_Not(m_Value(B))))
|
|
return new ICmpInst(I.getPredicate(), B, A);
|
|
|
|
const APInt *C;
|
|
if (match(Op1, m_APInt(C)))
|
|
return new ICmpInst(I.getSwappedPredicate(), A,
|
|
ConstantInt::get(Op1->getType(), ~(*C)));
|
|
}
|
|
|
|
Instruction *AddI = nullptr;
|
|
if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
|
|
m_Instruction(AddI))) &&
|
|
isa<IntegerType>(A->getType())) {
|
|
Value *Result;
|
|
Constant *Overflow;
|
|
// m_UAddWithOverflow can match patterns that do not include an explicit
|
|
// "add" instruction, so check the opcode of the matched op.
|
|
if (AddI->getOpcode() == Instruction::Add &&
|
|
OptimizeOverflowCheck(Instruction::Add, /*Signed*/ false, A, B, *AddI,
|
|
Result, Overflow)) {
|
|
replaceInstUsesWith(*AddI, Result);
|
|
eraseInstFromFunction(*AddI);
|
|
return replaceInstUsesWith(I, Overflow);
|
|
}
|
|
}
|
|
|
|
// (zext a) * (zext b) --> llvm.umul.with.overflow.
|
|
if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
|
|
if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
|
|
return R;
|
|
}
|
|
if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
|
|
if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
|
|
return R;
|
|
}
|
|
}
|
|
|
|
if (Instruction *Res = foldICmpEquality(I))
|
|
return Res;
|
|
|
|
if (Instruction *Res = foldICmpOfUAddOv(I))
|
|
return Res;
|
|
|
|
// The 'cmpxchg' instruction returns an aggregate containing the old value and
|
|
// an i1 which indicates whether or not we successfully did the swap.
|
|
//
|
|
// Replace comparisons between the old value and the expected value with the
|
|
// indicator that 'cmpxchg' returns.
|
|
//
|
|
// N.B. This transform is only valid when the 'cmpxchg' is not permitted to
|
|
// spuriously fail. In those cases, the old value may equal the expected
|
|
// value but it is possible for the swap to not occur.
|
|
if (I.getPredicate() == ICmpInst::ICMP_EQ)
|
|
if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
|
|
if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
|
|
if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
|
|
!ACXI->isWeak())
|
|
return ExtractValueInst::Create(ACXI, 1);
|
|
|
|
{
|
|
Value *X;
|
|
const APInt *C;
|
|
// icmp X+Cst, X
|
|
if (match(Op0, m_Add(m_Value(X), m_APInt(C))) && Op1 == X)
|
|
return foldICmpAddOpConst(X, *C, I.getPredicate());
|
|
|
|
// icmp X, X+Cst
|
|
if (match(Op1, m_Add(m_Value(X), m_APInt(C))) && Op0 == X)
|
|
return foldICmpAddOpConst(X, *C, I.getSwappedPredicate());
|
|
}
|
|
|
|
if (Instruction *Res = foldICmpWithHighBitMask(I, Builder))
|
|
return Res;
|
|
|
|
if (I.getType()->isVectorTy())
|
|
if (Instruction *Res = foldVectorCmp(I, Builder))
|
|
return Res;
|
|
|
|
return Changed ? &I : nullptr;
|
|
}
|
|
|
|
/// Fold fcmp ([us]itofp x, cst) if possible.
|
|
Instruction *InstCombinerImpl::foldFCmpIntToFPConst(FCmpInst &I,
|
|
Instruction *LHSI,
|
|
Constant *RHSC) {
|
|
if (!isa<ConstantFP>(RHSC)) return nullptr;
|
|
const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
|
|
|
|
// Get the width of the mantissa. We don't want to hack on conversions that
|
|
// might lose information from the integer, e.g. "i64 -> float"
|
|
int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
|
|
if (MantissaWidth == -1) return nullptr; // Unknown.
|
|
|
|
IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
|
|
|
|
bool LHSUnsigned = isa<UIToFPInst>(LHSI);
|
|
|
|
if (I.isEquality()) {
|
|
FCmpInst::Predicate P = I.getPredicate();
|
|
bool IsExact = false;
|
|
APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
|
|
RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
|
|
|
|
// If the floating point constant isn't an integer value, we know if we will
|
|
// ever compare equal / not equal to it.
|
|
if (!IsExact) {
|
|
// TODO: Can never be -0.0 and other non-representable values
|
|
APFloat RHSRoundInt(RHS);
|
|
RHSRoundInt.roundToIntegral(APFloat::rmNearestTiesToEven);
|
|
if (RHS != RHSRoundInt) {
|
|
if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
|
|
assert(P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE);
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
}
|
|
}
|
|
|
|
// TODO: If the constant is exactly representable, is it always OK to do
|
|
// equality compares as integer?
|
|
}
|
|
|
|
// Check to see that the input is converted from an integer type that is small
|
|
// enough that preserves all bits. TODO: check here for "known" sign bits.
|
|
// This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
|
|
unsigned InputSize = IntTy->getScalarSizeInBits();
|
|
|
|
// Following test does NOT adjust InputSize downwards for signed inputs,
|
|
// because the most negative value still requires all the mantissa bits
|
|
// to distinguish it from one less than that value.
|
|
if ((int)InputSize > MantissaWidth) {
|
|
// Conversion would lose accuracy. Check if loss can impact comparison.
|
|
int Exp = ilogb(RHS);
|
|
if (Exp == APFloat::IEK_Inf) {
|
|
int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
|
|
if (MaxExponent < (int)InputSize - !LHSUnsigned)
|
|
// Conversion could create infinity.
|
|
return nullptr;
|
|
} else {
|
|
// Note that if RHS is zero or NaN, then Exp is negative
|
|
// and first condition is trivially false.
|
|
if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
|
|
// Conversion could affect comparison.
|
|
return nullptr;
|
|
}
|
|
}
|
|
|
|
// Otherwise, we can potentially simplify the comparison. We know that it
|
|
// will always come through as an integer value and we know the constant is
|
|
// not a NAN (it would have been previously simplified).
|
|
assert(!RHS.isNaN() && "NaN comparison not already folded!");
|
|
|
|
ICmpInst::Predicate Pred;
|
|
switch (I.getPredicate()) {
|
|
default: llvm_unreachable("Unexpected predicate!");
|
|
case FCmpInst::FCMP_UEQ:
|
|
case FCmpInst::FCMP_OEQ:
|
|
Pred = ICmpInst::ICMP_EQ;
|
|
break;
|
|
case FCmpInst::FCMP_UGT:
|
|
case FCmpInst::FCMP_OGT:
|
|
Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
|
|
break;
|
|
case FCmpInst::FCMP_UGE:
|
|
case FCmpInst::FCMP_OGE:
|
|
Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
|
|
break;
|
|
case FCmpInst::FCMP_ULT:
|
|
case FCmpInst::FCMP_OLT:
|
|
Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
|
|
break;
|
|
case FCmpInst::FCMP_ULE:
|
|
case FCmpInst::FCMP_OLE:
|
|
Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
|
|
break;
|
|
case FCmpInst::FCMP_UNE:
|
|
case FCmpInst::FCMP_ONE:
|
|
Pred = ICmpInst::ICMP_NE;
|
|
break;
|
|
case FCmpInst::FCMP_ORD:
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
case FCmpInst::FCMP_UNO:
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
}
|
|
|
|
// Now we know that the APFloat is a normal number, zero or inf.
|
|
|
|
// See if the FP constant is too large for the integer. For example,
|
|
// comparing an i8 to 300.0.
|
|
unsigned IntWidth = IntTy->getScalarSizeInBits();
|
|
|
|
if (!LHSUnsigned) {
|
|
// If the RHS value is > SignedMax, fold the comparison. This handles +INF
|
|
// and large values.
|
|
APFloat SMax(RHS.getSemantics());
|
|
SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
|
|
APFloat::rmNearestTiesToEven);
|
|
if (SMax < RHS) { // smax < 13123.0
|
|
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
|
|
Pred == ICmpInst::ICMP_SLE)
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
}
|
|
} else {
|
|
// If the RHS value is > UnsignedMax, fold the comparison. This handles
|
|
// +INF and large values.
|
|
APFloat UMax(RHS.getSemantics());
|
|
UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
|
|
APFloat::rmNearestTiesToEven);
|
|
if (UMax < RHS) { // umax < 13123.0
|
|
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
|
|
Pred == ICmpInst::ICMP_ULE)
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
}
|
|
}
|
|
|
|
if (!LHSUnsigned) {
|
|
// See if the RHS value is < SignedMin.
|
|
APFloat SMin(RHS.getSemantics());
|
|
SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
|
|
APFloat::rmNearestTiesToEven);
|
|
if (SMin > RHS) { // smin > 12312.0
|
|
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
|
|
Pred == ICmpInst::ICMP_SGE)
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
}
|
|
} else {
|
|
// See if the RHS value is < UnsignedMin.
|
|
APFloat UMin(RHS.getSemantics());
|
|
UMin.convertFromAPInt(APInt::getMinValue(IntWidth), false,
|
|
APFloat::rmNearestTiesToEven);
|
|
if (UMin > RHS) { // umin > 12312.0
|
|
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
|
|
Pred == ICmpInst::ICMP_UGE)
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
}
|
|
}
|
|
|
|
// Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
|
|
// [0, UMAX], but it may still be fractional. See if it is fractional by
|
|
// casting the FP value to the integer value and back, checking for equality.
|
|
// Don't do this for zero, because -0.0 is not fractional.
|
|
Constant *RHSInt = LHSUnsigned
|
|
? ConstantExpr::getFPToUI(RHSC, IntTy)
|
|
: ConstantExpr::getFPToSI(RHSC, IntTy);
|
|
if (!RHS.isZero()) {
|
|
bool Equal = LHSUnsigned
|
|
? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
|
|
: ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
|
|
if (!Equal) {
|
|
// If we had a comparison against a fractional value, we have to adjust
|
|
// the compare predicate and sometimes the value. RHSC is rounded towards
|
|
// zero at this point.
|
|
switch (Pred) {
|
|
default: llvm_unreachable("Unexpected integer comparison!");
|
|
case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
case ICmpInst::ICMP_ULE:
|
|
// (float)int <= 4.4 --> int <= 4
|
|
// (float)int <= -4.4 --> false
|
|
if (RHS.isNegative())
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
// (float)int <= 4.4 --> int <= 4
|
|
// (float)int <= -4.4 --> int < -4
|
|
if (RHS.isNegative())
|
|
Pred = ICmpInst::ICMP_SLT;
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
// (float)int < -4.4 --> false
|
|
// (float)int < 4.4 --> int <= 4
|
|
if (RHS.isNegative())
|
|
return replaceInstUsesWith(I, Builder.getFalse());
|
|
Pred = ICmpInst::ICMP_ULE;
|
|
break;
|
|
case ICmpInst::ICMP_SLT:
|
|
// (float)int < -4.4 --> int < -4
|
|
// (float)int < 4.4 --> int <= 4
|
|
if (!RHS.isNegative())
|
|
Pred = ICmpInst::ICMP_SLE;
|
|
break;
|
|
case ICmpInst::ICMP_UGT:
|
|
// (float)int > 4.4 --> int > 4
|
|
// (float)int > -4.4 --> true
|
|
if (RHS.isNegative())
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
break;
|
|
case ICmpInst::ICMP_SGT:
|
|
// (float)int > 4.4 --> int > 4
|
|
// (float)int > -4.4 --> int >= -4
|
|
if (RHS.isNegative())
|
|
Pred = ICmpInst::ICMP_SGE;
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
// (float)int >= -4.4 --> true
|
|
// (float)int >= 4.4 --> int > 4
|
|
if (RHS.isNegative())
|
|
return replaceInstUsesWith(I, Builder.getTrue());
|
|
Pred = ICmpInst::ICMP_UGT;
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
// (float)int >= -4.4 --> int >= -4
|
|
// (float)int >= 4.4 --> int > 4
|
|
if (!RHS.isNegative())
|
|
Pred = ICmpInst::ICMP_SGT;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Lower this FP comparison into an appropriate integer version of the
|
|
// comparison.
|
|
return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
|
|
}
|
|
|
|
/// Fold (C / X) < 0.0 --> X < 0.0 if possible. Swap predicate if necessary.
|
|
static Instruction *foldFCmpReciprocalAndZero(FCmpInst &I, Instruction *LHSI,
|
|
Constant *RHSC) {
|
|
// When C is not 0.0 and infinities are not allowed:
|
|
// (C / X) < 0.0 is a sign-bit test of X
|
|
// (C / X) < 0.0 --> X < 0.0 (if C is positive)
|
|
// (C / X) < 0.0 --> X > 0.0 (if C is negative, swap the predicate)
|
|
//
|
|
// Proof:
|
|
// Multiply (C / X) < 0.0 by X * X / C.
|
|
// - X is non zero, if it is the flag 'ninf' is violated.
|
|
// - C defines the sign of X * X * C. Thus it also defines whether to swap
|
|
// the predicate. C is also non zero by definition.
|
|
//
|
|
// Thus X * X / C is non zero and the transformation is valid. [qed]
|
|
|
|
FCmpInst::Predicate Pred = I.getPredicate();
|
|
|
|
// Check that predicates are valid.
|
|
if ((Pred != FCmpInst::FCMP_OGT) && (Pred != FCmpInst::FCMP_OLT) &&
|
|
(Pred != FCmpInst::FCMP_OGE) && (Pred != FCmpInst::FCMP_OLE))
|
|
return nullptr;
|
|
|
|
// Check that RHS operand is zero.
|
|
if (!match(RHSC, m_AnyZeroFP()))
|
|
return nullptr;
|
|
|
|
// Check fastmath flags ('ninf').
|
|
if (!LHSI->hasNoInfs() || !I.hasNoInfs())
|
|
return nullptr;
|
|
|
|
// Check the properties of the dividend. It must not be zero to avoid a
|
|
// division by zero (see Proof).
|
|
const APFloat *C;
|
|
if (!match(LHSI->getOperand(0), m_APFloat(C)))
|
|
return nullptr;
|
|
|
|
if (C->isZero())
|
|
return nullptr;
|
|
|
|
// Get swapped predicate if necessary.
|
|
if (C->isNegative())
|
|
Pred = I.getSwappedPredicate();
|
|
|
|
return new FCmpInst(Pred, LHSI->getOperand(1), RHSC, "", &I);
|
|
}
|
|
|
|
/// Optimize fabs(X) compared with zero.
|
|
static Instruction *foldFabsWithFcmpZero(FCmpInst &I, InstCombinerImpl &IC) {
|
|
Value *X;
|
|
if (!match(I.getOperand(0), m_FAbs(m_Value(X))) ||
|
|
!match(I.getOperand(1), m_PosZeroFP()))
|
|
return nullptr;
|
|
|
|
auto replacePredAndOp0 = [&IC](FCmpInst *I, FCmpInst::Predicate P, Value *X) {
|
|
I->setPredicate(P);
|
|
return IC.replaceOperand(*I, 0, X);
|
|
};
|
|
|
|
switch (I.getPredicate()) {
|
|
case FCmpInst::FCMP_UGE:
|
|
case FCmpInst::FCMP_OLT:
|
|
// fabs(X) >= 0.0 --> true
|
|
// fabs(X) < 0.0 --> false
|
|
llvm_unreachable("fcmp should have simplified");
|
|
|
|
case FCmpInst::FCMP_OGT:
|
|
// fabs(X) > 0.0 --> X != 0.0
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_ONE, X);
|
|
|
|
case FCmpInst::FCMP_UGT:
|
|
// fabs(X) u> 0.0 --> X u!= 0.0
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_UNE, X);
|
|
|
|
case FCmpInst::FCMP_OLE:
|
|
// fabs(X) <= 0.0 --> X == 0.0
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_OEQ, X);
|
|
|
|
case FCmpInst::FCMP_ULE:
|
|
// fabs(X) u<= 0.0 --> X u== 0.0
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_UEQ, X);
|
|
|
|
case FCmpInst::FCMP_OGE:
|
|
// fabs(X) >= 0.0 --> !isnan(X)
|
|
assert(!I.hasNoNaNs() && "fcmp should have simplified");
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_ORD, X);
|
|
|
|
case FCmpInst::FCMP_ULT:
|
|
// fabs(X) u< 0.0 --> isnan(X)
|
|
assert(!I.hasNoNaNs() && "fcmp should have simplified");
|
|
return replacePredAndOp0(&I, FCmpInst::FCMP_UNO, X);
|
|
|
|
case FCmpInst::FCMP_OEQ:
|
|
case FCmpInst::FCMP_UEQ:
|
|
case FCmpInst::FCMP_ONE:
|
|
case FCmpInst::FCMP_UNE:
|
|
case FCmpInst::FCMP_ORD:
|
|
case FCmpInst::FCMP_UNO:
|
|
// Look through the fabs() because it doesn't change anything but the sign.
|
|
// fabs(X) == 0.0 --> X == 0.0,
|
|
// fabs(X) != 0.0 --> X != 0.0
|
|
// isnan(fabs(X)) --> isnan(X)
|
|
// !isnan(fabs(X) --> !isnan(X)
|
|
return replacePredAndOp0(&I, I.getPredicate(), X);
|
|
|
|
default:
|
|
return nullptr;
|
|
}
|
|
}
|
|
|
|
Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
|
|
bool Changed = false;
|
|
|
|
/// Orders the operands of the compare so that they are listed from most
|
|
/// complex to least complex. This puts constants before unary operators,
|
|
/// before binary operators.
|
|
if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
|
|
I.swapOperands();
|
|
Changed = true;
|
|
}
|
|
|
|
const CmpInst::Predicate Pred = I.getPredicate();
|
|
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
|
if (Value *V = SimplifyFCmpInst(Pred, Op0, Op1, I.getFastMathFlags(),
|
|
SQ.getWithInstruction(&I)))
|
|
return replaceInstUsesWith(I, V);
|
|
|
|
// Simplify 'fcmp pred X, X'
|
|
Type *OpType = Op0->getType();
|
|
assert(OpType == Op1->getType() && "fcmp with different-typed operands?");
|
|
if (Op0 == Op1) {
|
|
switch (Pred) {
|
|
default: break;
|
|
case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
|
|
case FCmpInst::FCMP_ULT: // True if unordered or less than
|
|
case FCmpInst::FCMP_UGT: // True if unordered or greater than
|
|
case FCmpInst::FCMP_UNE: // True if unordered or not equal
|
|
// Canonicalize these to be 'fcmp uno %X, 0.0'.
|
|
I.setPredicate(FCmpInst::FCMP_UNO);
|
|
I.setOperand(1, Constant::getNullValue(OpType));
|
|
return &I;
|
|
|
|
case FCmpInst::FCMP_ORD: // True if ordered (no nans)
|
|
case FCmpInst::FCMP_OEQ: // True if ordered and equal
|
|
case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
|
|
case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
|
|
// Canonicalize these to be 'fcmp ord %X, 0.0'.
|
|
I.setPredicate(FCmpInst::FCMP_ORD);
|
|
I.setOperand(1, Constant::getNullValue(OpType));
|
|
return &I;
|
|
}
|
|
}
|
|
|
|
// If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
|
|
// then canonicalize the operand to 0.0.
|
|
if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
|
|
if (!match(Op0, m_PosZeroFP()) && isKnownNeverNaN(Op0, &TLI))
|
|
return replaceOperand(I, 0, ConstantFP::getNullValue(OpType));
|
|
|
|
if (!match(Op1, m_PosZeroFP()) && isKnownNeverNaN(Op1, &TLI))
|
|
return replaceOperand(I, 1, ConstantFP::getNullValue(OpType));
|
|
}
|
|
|
|
// fcmp pred (fneg X), (fneg Y) -> fcmp swap(pred) X, Y
|
|
Value *X, *Y;
|
|
if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
|
|
return new FCmpInst(I.getSwappedPredicate(), X, Y, "", &I);
|
|
|
|
// Test if the FCmpInst instruction is used exclusively by a select as
|
|
// part of a minimum or maximum operation. If so, refrain from doing
|
|
// any other folding. This helps out other analyses which understand
|
|
// non-obfuscated minimum and maximum idioms, such as ScalarEvolution
|
|
// and CodeGen. And in this case, at least one of the comparison
|
|
// operands has at least one user besides the compare (the select),
|
|
// which would often largely negate the benefit of folding anyway.
|
|
if (I.hasOneUse())
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
|
|
Value *A, *B;
|
|
SelectPatternResult SPR = matchSelectPattern(SI, A, B);
|
|
if (SPR.Flavor != SPF_UNKNOWN)
|
|
return nullptr;
|
|
}
|
|
|
|
// The sign of 0.0 is ignored by fcmp, so canonicalize to +0.0:
|
|
// fcmp Pred X, -0.0 --> fcmp Pred X, 0.0
|
|
if (match(Op1, m_AnyZeroFP()) && !match(Op1, m_PosZeroFP()))
|
|
return replaceOperand(I, 1, ConstantFP::getNullValue(OpType));
|
|
|
|
// Handle fcmp with instruction LHS and constant RHS.
|
|
Instruction *LHSI;
|
|
Constant *RHSC;
|
|
if (match(Op0, m_Instruction(LHSI)) && match(Op1, m_Constant(RHSC))) {
|
|
switch (LHSI->getOpcode()) {
|
|
case Instruction::PHI:
|
|
// Only fold fcmp into the PHI if the phi and fcmp are in the same
|
|
// block. If in the same block, we're encouraging jump threading. If
|
|
// not, we are just pessimizing the code by making an i1 phi.
|
|
if (LHSI->getParent() == I.getParent())
|
|
if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
|
|
return NV;
|
|
break;
|
|
case Instruction::SIToFP:
|
|
case Instruction::UIToFP:
|
|
if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
|
|
return NV;
|
|
break;
|
|
case Instruction::FDiv:
|
|
if (Instruction *NV = foldFCmpReciprocalAndZero(I, LHSI, RHSC))
|
|
return NV;
|
|
break;
|
|
case Instruction::Load:
|
|
if (auto *GEP = dyn_cast<GetElementPtrInst>(LHSI->getOperand(0)))
|
|
if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
|
|
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
|
|
!cast<LoadInst>(LHSI)->isVolatile())
|
|
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
|
|
return Res;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (Instruction *R = foldFabsWithFcmpZero(I, *this))
|
|
return R;
|
|
|
|
if (match(Op0, m_FNeg(m_Value(X)))) {
|
|
// fcmp pred (fneg X), C --> fcmp swap(pred) X, -C
|
|
Constant *C;
|
|
if (match(Op1, m_Constant(C))) {
|
|
Constant *NegC = ConstantExpr::getFNeg(C);
|
|
return new FCmpInst(I.getSwappedPredicate(), X, NegC, "", &I);
|
|
}
|
|
}
|
|
|
|
if (match(Op0, m_FPExt(m_Value(X)))) {
|
|
// fcmp (fpext X), (fpext Y) -> fcmp X, Y
|
|
if (match(Op1, m_FPExt(m_Value(Y))) && X->getType() == Y->getType())
|
|
return new FCmpInst(Pred, X, Y, "", &I);
|
|
|
|
// fcmp (fpext X), C -> fcmp X, (fptrunc C) if fptrunc is lossless
|
|
const APFloat *C;
|
|
if (match(Op1, m_APFloat(C))) {
|
|
const fltSemantics &FPSem =
|
|
X->getType()->getScalarType()->getFltSemantics();
|
|
bool Lossy;
|
|
APFloat TruncC = *C;
|
|
TruncC.convert(FPSem, APFloat::rmNearestTiesToEven, &Lossy);
|
|
|
|
// Avoid lossy conversions and denormals.
|
|
// Zero is a special case that's OK to convert.
|
|
APFloat Fabs = TruncC;
|
|
Fabs.clearSign();
|
|
if (!Lossy &&
|
|
(!(Fabs < APFloat::getSmallestNormalized(FPSem)) || Fabs.isZero())) {
|
|
Constant *NewC = ConstantFP::get(X->getType(), TruncC);
|
|
return new FCmpInst(Pred, X, NewC, "", &I);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Convert a sign-bit test of an FP value into a cast and integer compare.
|
|
// TODO: Simplify if the copysign constant is 0.0 or NaN.
|
|
// TODO: Handle non-zero compare constants.
|
|
// TODO: Handle other predicates.
|
|
const APFloat *C;
|
|
if (match(Op0, m_OneUse(m_Intrinsic<Intrinsic::copysign>(m_APFloat(C),
|
|
m_Value(X)))) &&
|
|
match(Op1, m_AnyZeroFP()) && !C->isZero() && !C->isNaN()) {
|
|
Type *IntType = Builder.getIntNTy(X->getType()->getScalarSizeInBits());
|
|
if (auto *VecTy = dyn_cast<VectorType>(OpType))
|
|
IntType = VectorType::get(IntType, VecTy->getElementCount());
|
|
|
|
// copysign(non-zero constant, X) < 0.0 --> (bitcast X) < 0
|
|
if (Pred == FCmpInst::FCMP_OLT) {
|
|
Value *IntX = Builder.CreateBitCast(X, IntType);
|
|
return new ICmpInst(ICmpInst::ICMP_SLT, IntX,
|
|
ConstantInt::getNullValue(IntType));
|
|
}
|
|
}
|
|
|
|
if (I.getType()->isVectorTy())
|
|
if (Instruction *Res = foldVectorCmp(I, Builder))
|
|
return Res;
|
|
|
|
return Changed ? &I : nullptr;
|
|
}
|