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have instcombine preserve nsw/nuw/exact when sinking 

common operations through a phi. 

llvm-svn: 125790
This commit is contained in:
Chris Lattner 2011-02-17 23:01:49 +00:00
parent 99827e861f
commit a8fed47eed
2 changed files with 71 additions and 11 deletions
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64
llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
View File

@ -31,22 +31,37 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
const Type *LHSType = LHSVal->getType();
const Type *RHSType = RHSVal->getType();
bool isNUW = false, isNSW = false, isExact = false;
if (OverflowingBinaryOperator *BO =
dyn_cast<OverflowingBinaryOperator>(FirstInst)) {
isNUW = BO->hasNoUnsignedWrap();
isNSW = BO->hasNoSignedWrap();
} else if (PossiblyExactOperator *PEO =
dyn_cast<PossiblyExactOperator>(FirstInst))
isExact = PEO->isExact();
// Scan to see if all operands are the same opcode, and all have one use.
for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
if (!I || I->getOpcode() != Opc || !I->hasOneUse() ||
// Verify type of the LHS matches so we don't fold cmp's of different
// types or GEP's with different index types.
// types.
I->getOperand(0)->getType() != LHSType ||
I->getOperand(1)->getType() != RHSType)
return 0;
// If they are CmpInst instructions, check their predicates
if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
if (cast<CmpInst>(I)->getPredicate() !=
cast<CmpInst>(FirstInst)->getPredicate())
if (CmpInst *CI = dyn_cast<CmpInst>(I))
if (CI->getPredicate() != cast<CmpInst>(FirstInst)->getPredicate())
return 0;
if (isNUW)
isNUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
if (isNSW)
isNSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
if (isExact)
isExact = cast<PossiblyExactOperator>(I)->isExact();
// Keep track of which operand needs a phi node.
if (I->getOperand(0) != LHSVal) LHSVal = 0;
if (I->getOperand(1) != RHSVal) RHSVal = 0;
@ -97,11 +112,17 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
}
}
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
CmpInst *CIOp = cast<CmpInst>(FirstInst);
return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
LHSVal, RHSVal);
if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
LHSVal, RHSVal);
BinaryOperator *BinOp = cast<BinaryOperator>(FirstInst);
BinaryOperator *NewBinOp =
BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
if (isNUW) NewBinOp->setHasNoUnsignedWrap();
if (isNSW) NewBinOp->setHasNoSignedWrap();
if (isExact) NewBinOp->setIsExact();
return NewBinOp;
}
Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
@ -373,6 +394,7 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
// code size and simplifying code.
Constant *ConstantOp = 0;
const Type *CastSrcTy = 0;
bool isNUW = false, isNSW = false, isExact = false;
if (isa<CastInst>(FirstInst)) {
CastSrcTy = FirstInst->getOperand(0)->getType();
@ -389,6 +411,14 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
if (ConstantOp == 0)
return FoldPHIArgBinOpIntoPHI(PN);
if (OverflowingBinaryOperator *BO =
dyn_cast<OverflowingBinaryOperator>(FirstInst)) {
isNUW = BO->hasNoUnsignedWrap();
isNSW = BO->hasNoSignedWrap();
} else if (PossiblyExactOperator *PEO =
dyn_cast<PossiblyExactOperator>(FirstInst))
isExact = PEO->isExact();
} else {
return 0; // Cannot fold this operation.
}
@ -404,6 +434,13 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
} else if (I->getOperand(1) != ConstantOp) {
return 0;
}
if (isNUW)
isNUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
if (isNSW)
isNSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
if (isExact)
isExact = cast<PossiblyExactOperator>(I)->isExact();
}
// Okay, they are all the same operation. Create a new PHI node of the
@ -438,8 +475,13 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
if (CastInst *FirstCI = dyn_cast<CastInst>(FirstInst))
return CastInst::Create(FirstCI->getOpcode(), PhiVal, PN.getType());
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst)) {
BinOp = BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
if (isNUW) BinOp->setHasNoUnsignedWrap();
if (isNSW) BinOp->setHasNoSignedWrap();
if (isExact) BinOp->setIsExact();
return BinOp;
}
CmpInst *CIOp = cast<CmpInst>(FirstInst);
return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),

18
llvm/test/Transforms/InstCombine/phi.ll
View File

@ -526,3 +526,21 @@ Exit: ; preds = %Loop
; CHECK-NEXT: ret i32 %B
}
define i32 @test24(i32 %A, i1 %cond) {
BB0:
%X = add nuw nsw i32 %A, 1
br i1 %cond, label %BB1, label %BB2
BB1:
%Y = add nuw i32 %A, 1
br label %BB2
BB2:
%C = phi i32 [ %X, %BB0 ], [ %Y, %BB1 ]
ret i32 %C
; CHECK: @test24
; CHECK-NOT: phi
; CHECK: BB2:
; CHECK-NEXT: %C = add nuw i32 %A, 1
; CHECK-NEXT: ret i32 %C
}