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SimplifyCFG: Avoid miscompilations due to removed lifetime intrinsics.

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The lifetime intrinsics need some work in order to make it clear which
optimizations are or are not valid.

For now dropping this optimization avoids a miscompilation.

Patch by Björn Steinbrink.

llvm-svn: 214336
This commit is contained in:
Rafael Espindola 2014-07-30 21:04:00 +00:00
parent e81540b210
commit d0d1fa9454
2 changed files with 4 additions and 4 deletions
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2
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -4008,7 +4008,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){
return true;
// If the Terminator is the only non-phi instruction, simplify the block.
BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime();
BasicBlock::iterator I = BB->getFirstNonPHIOrDbg();
if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
TryToSimplifyUncondBranchFromEmptyBlock(BB))
return true;

6
test/Transforms/SimplifyCFG/lifetime.ll
View File

@ -1,11 +1,11 @@
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; Test that a lifetime intrinsic doesn't prevent us from simplifying this.
; Test that a lifetime intrinsic isn't removed because that would change semantics
; CHECK: foo
; CHECK: entry:
; CHECK-NOT: bb0:
; CHECK-NOT: bb1:
; CHECK: bb0:
; CHECK: bb1:
; CHECK: ret
define void @foo(i1 %x) {
entry: