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[GVN] Intersect the IR flags when CSE'ing two instructions

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We performed a simple, but incomplete, intersection when it came time to
CSE instructions.  It didn't handle, for example, the 'exact' flag.

This fixes PR23922.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240595 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2015-06-24 21:52:25 +00:00
parent e40e848767
commit 12bb40b2ab
2 changed files with 17 additions and 7 deletions
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10
lib/Transforms/Scalar/GVN.cpp
View File

@ -1783,13 +1783,9 @@ static void patchReplacementInstruction(Instruction *I, Value *Repl) {
// being replaced.
BinaryOperator *Op = dyn_cast<BinaryOperator>(I);
BinaryOperator *ReplOp = dyn_cast<BinaryOperator>(Repl);
if (Op && ReplOp && isa<OverflowingBinaryOperator>(Op) &&
isa<OverflowingBinaryOperator>(ReplOp)) {
if (ReplOp->hasNoSignedWrap() && !Op->hasNoSignedWrap())
ReplOp->setHasNoSignedWrap(false);
if (ReplOp->hasNoUnsignedWrap() && !Op->hasNoUnsignedWrap())
ReplOp->setHasNoUnsignedWrap(false);
}
if (Op && ReplOp)
ReplOp->andIRFlags(Op);
if (Instruction *ReplInst = dyn_cast<Instruction>(Repl)) {
// FIXME: If both the original and replacement value are part of the
// same control-flow region (meaning that the execution of one

14
test/Transforms/GVN/pr12979.ll
View File

@ -77,3 +77,17 @@ define i32 @test7(i32 %x, i32 %y) {
%foo = add i32 %add1, %add2
ret i32 %foo
}
declare void @mumble(i2, i2)
define void @test8(i2 %x) {
; CHECK-LABEL: @test8(
; CHECK: %[[ashr:.*]] = ashr i2 %x, 1
; CHECK-NEXT: call void @mumble(i2 %[[ashr]], i2 %[[ashr]])
; CHECK-NEXT: ret void
%ashr0 = ashr exact i2 %x, 1
%ashr1 = ashr i2 %x, 1
call void @mumble(i2 %ashr0, i2 %ashr1)
ret void
}