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Lifetime intrinsics on undef are dead.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136722 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-08-02 21:19:27 +00:00
parent 11066fb937
commit 3e69c13c30
2 changed files with 19 additions and 4 deletions
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12
lib/Transforms/Utils/Local.cpp
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@ -229,10 +229,10 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) {
// We don't want debug info removed by anything this general, unless
// debug info is empty.
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
if (DDI->getAddress())
if (DDI->getAddress())
return false;
return true;
}
}
if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
if (DVI->getValue())
return false;
@ -243,10 +243,16 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) {
// Special case intrinsics that "may have side effects" but can be deleted
// when dead.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Safe to delete llvm.stacksave if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave)
return true;
// Lifetime intrinsics are dead when their right-hand is undef.
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end)
return isa<UndefValue>(II->getArgOperand(1));
}
return false;
}

11
test/Transforms/InstCombine/deadcode.ll
View File

@ -1,5 +1,5 @@
; RUN: opt < %s -instcombine -S | grep {ret i32 %A}
; RUN: opt < %s -die -S | not grep call.*llvm.stacksave
; RUN: opt < %s -die -S | not grep call.*llvm
define i32 @test(i32 %A) {
%X = or i1 false, false
@ -22,3 +22,12 @@ define i32* @test2(i32 %width) {
declare i8* @llvm.stacksave()
declare void @llvm.lifetime.start(i64, i8*)
declare void @llvm.lifetime.end(i64, i8*)
define void @test3() {
call void @llvm.lifetime.start(i64 -1, i8* undef)
call void @llvm.lifetime.end(i64 -1, i8* undef)
ret void
}