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[InstCombine] Preserve fast math flags when combining PHIs
Summary: When optimizing PHIs which have inputs floating point binary operators, we preserve all IR flags except the fast math flags. This change removes the logic which tracked some of the IR flags (no wrap, exact) and replaces it by doing an and on the IR flags of all inputs to the PHI - which will also handle the fast math flags. Reviewers: majnemer Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D19370 llvm-svn: 267139
This commit is contained in:
Silviu Baranga
parent
0102a446f7
commit
52b925e4c9
@ -35,15 +35,6 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
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Type *LHSType = LHSVal->getType();
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Type *RHSType = RHSVal->getType();
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bool isNUW = false, isNSW = false, isExact = false;
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if (OverflowingBinaryOperator *BO =
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dyn_cast<OverflowingBinaryOperator>(FirstInst)) {
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isNUW = BO->hasNoUnsignedWrap();
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isNSW = BO->hasNoSignedWrap();
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} else if (PossiblyExactOperator *PEO =
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dyn_cast<PossiblyExactOperator>(FirstInst))
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isExact = PEO->isExact();
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// Scan to see if all operands are the same opcode, and all have one use.
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for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
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Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
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@ -59,13 +50,6 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
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if (CI->getPredicate() != cast<CmpInst>(FirstInst)->getPredicate())
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return nullptr;
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if (isNUW)
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isNUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
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if (isNSW)
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isNSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
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if (isExact)
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isExact = cast<PossiblyExactOperator>(I)->isExact();
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// Keep track of which operand needs a phi node.
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if (I->getOperand(0) != LHSVal) LHSVal = nullptr;
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if (I->getOperand(1) != RHSVal) RHSVal = nullptr;
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@ -124,9 +108,12 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
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BinaryOperator *BinOp = cast<BinaryOperator>(FirstInst);
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BinaryOperator *NewBinOp =
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BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
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if (isNUW) NewBinOp->setHasNoUnsignedWrap();
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if (isNSW) NewBinOp->setHasNoSignedWrap();
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if (isExact) NewBinOp->setIsExact();
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NewBinOp->copyIRFlags(PN.getIncomingValue(0));
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for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i)
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NewBinOp->andIRFlags(PN.getIncomingValue(i));
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NewBinOp->setDebugLoc(FirstInst->getDebugLoc());
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return NewBinOp;
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}
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@ -497,7 +484,6 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
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// code size and simplifying code.
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Constant *ConstantOp = nullptr;
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Type *CastSrcTy = nullptr;
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bool isNUW = false, isNSW = false, isExact = false;
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if (isa<CastInst>(FirstInst)) {
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CastSrcTy = FirstInst->getOperand(0)->getType();
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@ -514,14 +500,6 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
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ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
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if (!ConstantOp)
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return FoldPHIArgBinOpIntoPHI(PN);
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if (OverflowingBinaryOperator *BO =
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dyn_cast<OverflowingBinaryOperator>(FirstInst)) {
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isNUW = BO->hasNoUnsignedWrap();
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isNSW = BO->hasNoSignedWrap();
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} else if (PossiblyExactOperator *PEO =
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dyn_cast<PossiblyExactOperator>(FirstInst))
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isExact = PEO->isExact();
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} else {
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return nullptr; // Cannot fold this operation.
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}
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@ -537,13 +515,6 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
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} else if (I->getOperand(1) != ConstantOp) {
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return nullptr;
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}
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if (isNUW)
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isNUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
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if (isNSW)
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isNSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
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if (isExact)
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isExact = cast<PossiblyExactOperator>(I)->isExact();
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}
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// Okay, they are all the same operation. Create a new PHI node of the
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@ -584,9 +555,11 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
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if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst)) {
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BinOp = BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
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if (isNUW) BinOp->setHasNoUnsignedWrap();
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if (isNSW) BinOp->setHasNoSignedWrap();
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if (isExact) BinOp->setIsExact();
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BinOp->copyIRFlags(PN.getIncomingValue(0));
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for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i)
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BinOp->andIRFlags(PN.getIncomingValue(i));
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BinOp->setDebugLoc(FirstInst->getDebugLoc());
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return BinOp;
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}
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89
test/Transforms/InstCombine/phi-preserve-ir-flags.ll
Normal file
89
test/Transforms/InstCombine/phi-preserve-ir-flags.ll
Normal file
@ -0,0 +1,89 @@
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; RUN: opt < %s -instcombine -S -o - | FileCheck %s
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target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
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; CHECK-LABEL: define float @func1(
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define float @func1(float %a, float %b, float %c, i1 %cond) {
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entry:
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br i1 %cond, label %cond.true, label %cond.false
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cond.true:
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%sub0 = fsub fast float %a, %b
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br label %cond.end
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cond.false:
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%sub1 = fsub fast float %a, %c
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br label %cond.end
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; The fast-math flags should always be transfered if possible.
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; CHECK-LABEL: cond.end
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; CHECK [[PHI:%[^ ]*]] = phi float [ %b, %cond.true ], [ %c, %cond.false ]
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; CHECK fsub fast float %a, [[PHI]]
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cond.end:
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%e = phi float [ %sub0, %cond.true ], [ %sub1, %cond.false ]
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ret float %e
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}
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; CHECK-LABEL: define float @func2(
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define float @func2(float %a, float %b, float %c, i1 %cond) {
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entry:
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br i1 %cond, label %cond.true, label %cond.false
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cond.true:
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%sub0 = fsub fast float %a, %b
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br label %cond.end
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cond.false:
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%sub1 = fsub float %a, %c
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br label %cond.end
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; The fast-math flags should always be transfered if possible.
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; CHECK-LABEL: cond.end
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; CHECK [[PHI:%[^ ]*]] = phi float [ %b, %cond.true ], [ %c, %cond.false ]
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; CHECK fsub float %a, [[PHI]]
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cond.end:
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%e = phi float [ %sub0, %cond.true ], [ %sub1, %cond.false ]
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ret float %e
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}
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; CHECK-LABEL: define float @func3(
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define float @func3(float %a, float %b, float %c, i1 %cond) {
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entry:
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br i1 %cond, label %cond.true, label %cond.false
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cond.true:
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%sub0 = fsub fast float %a, 2.0
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br label %cond.end
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cond.false:
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%sub1 = fsub fast float %b, 2.0
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br label %cond.end
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; CHECK-LABEL: cond.end
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; CHECK [[PHI:%[^ ]*]] = phi float [ %a, %cond.true ], [ %b, %cond.false ]
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; CHECK fadd fast float %a, [[PHI]]
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cond.end:
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%e = phi float [ %sub0, %cond.true ], [ %sub1, %cond.false ]
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ret float %e
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}
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; CHECK-LABEL: define float @func4(
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define float @func4(float %a, float %b, float %c, i1 %cond) {
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entry:
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br i1 %cond, label %cond.true, label %cond.false
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cond.true:
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%sub0 = fsub fast float %a, 2.0
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br label %cond.end
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cond.false:
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%sub1 = fsub float %b, 2.0
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br label %cond.end
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; CHECK-LABEL: cond.end
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; CHECK [[PHI:%[^ ]*]] = phi float [ %a, %cond.true ], [ %b, %cond.false ]
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; CHECK fadd float %a, [[PHI]]
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cond.end:
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%e = phi float [ %sub0, %cond.true ], [ %sub1, %cond.false ]
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ret float %e
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}
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