From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 30 Jul 2014 21:04:00 +0000 (+0000)
Subject: SimplifyCFG: Avoid miscompilations due to removed lifetime intrinsics.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7fef5a3d1907c813712fcb2a44d8187a65ba08cd;p=oota-llvm.git

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214336 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 24bb63bb60a..1c62559739f 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -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;
diff --git a/test/Transforms/SimplifyCFG/lifetime.ll b/test/Transforms/SimplifyCFG/lifetime.ll
index b7942217253..7c66be52950 100644
--- a/test/Transforms/SimplifyCFG/lifetime.ll
+++ b/test/Transforms/SimplifyCFG/lifetime.ll
@@ -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: