[llvm] r214336 - SimplifyCFG: Avoid miscompilations due to removed lifetime intrinsics.

[Rafael Espindola]

Author: rafael
Date: Wed Jul 30 16:04:00 2014
New Revision: 214336

URL: http://llvm.org/viewvc/llvm-project?rev=214336&view=rev
Log:
SimplifyCFG: Avoid miscompilations due to removed lifetime intrinsics.

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.

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=214336&r1=214335&r2=214336&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Wed Jul 30 16:04:00 2014
@@ -4008,7 +4008,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranc
     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;

Modified: llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll?rev=214336&r1=214335&r2=214336&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll Wed Jul 30 16:04:00 2014
@@ -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: