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[InstCombine] Make sure we preserve fast math flags when folding fp instructions into phi nodes 

Summary: I noticed in the select folding code that we copied fast math flags, but did not do the same for the similar handling in phi nodes. This patch fixes that to do the same thing as select

Reviewers: spatel, davide, majnemer, hfinkel

Reviewed By: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31690

llvm-svn: 299838
This commit is contained in:
Craig Topper 2017-04-10 07:00:10 +00:00
parent d8840d7b10
commit 838d13e7ee
2 changed files with 29 additions and 2 deletions
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8
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -937,11 +937,15 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
Constant *C = cast<Constant>(I.getOperand(1)); Constant *C = cast<Constant>(I.getOperand(1));
for (unsigned i = 0; i != NumPHIValues; ++i) { for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV = nullptr; Value *InV = nullptr;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = ConstantExpr::get(I.getOpcode(), InC, C); InV = ConstantExpr::get(I.getOpcode(), InC, C);
else } else {
InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(),
PN->getIncomingValue(i), C, "phitmp"); PN->getIncomingValue(i), C, "phitmp");
auto *FPInst = dyn_cast<Instruction>(InV);
if (FPInst && isa<FPMathOperator>(FPInst))
FPInst->copyFastMathFlags(&I);
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i)); NewPN->addIncoming(InV, PN->getIncomingBlock(i));
} }
} else { } else {

23
llvm/test/Transforms/InstCombine/fast-math.ll
View File

@ -831,3 +831,26 @@ define fp128 @min4(fp128 %a, fp128 %b) {
; CHECK-NEXT: select {{.*}} fp128 %a, fp128 %b ; CHECK-NEXT: select {{.*}} fp128 %a, fp128 %b
; CHECK-NEXT: ret ; CHECK-NEXT: ret
} }
define float @test55(i1 %which, float %a) {
; CHECK-LABEL: @test55(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[WHICH:%.*]], label [[FINAL:%.*]], label [[DELAY:%.*]]
; CHECK: delay:
; CHECK-NEXT: [[PHITMP:%.*]] = fadd fast float [[A:%.*]], 1.000000e+00
; CHECK-NEXT: br label [[FINAL]]
; CHECK: final:
; CHECK-NEXT: [[A:%.*]] = phi float [ 3.000000e+00, [[ENTRY:%.*]] ], [ [[PHITMP]], [[DELAY]] ]
; CHECK-NEXT: ret float [[A]]
;
entry:
br i1 %which, label %final, label %delay
delay:
br label %final
final:
%A = phi float [ 2.0, %entry ], [ %a, %delay ]
%value = fadd fast float %A, 1.0
ret float %value
}