[SimplifyCFG] isSafeToSpeculateStore now ignores debug info

This patch fixes PR27615.

@llvm.dbg.value instructions no longer count towards the maximum number of
instructions to look back at in the instruction list when searching for a
store instruction. This should make the output consistent between debug and
non-debug build.

Patch by Henric Karlsson <henric.karlsson@ericsson.com>!

Differential Revision: http://reviews.llvm.org/D19912

llvm-svn: 268512

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6ac039d8a1a..6d347d624e2 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1448,10 +1448,14 @@ static Value *isSafeToSpeculateStore(Instruction *I, BasicBlock *BrBB,
   Value *StorePtr = StoreToHoist->getPointerOperand();
 
   // Look for a store to the same pointer in BrBB.
-  unsigned MaxNumInstToLookAt = 10;
+  unsigned MaxNumInstToLookAt = 9;
   for (BasicBlock::reverse_iterator RI = BrBB->rbegin(),
-       RE = BrBB->rend(); RI != RE && (--MaxNumInstToLookAt); ++RI) {
+       RE = BrBB->rend(); RI != RE && MaxNumInstToLookAt; ++RI) {
     Instruction *CurI = &*RI;
+    // Skip debug info.
+    if (isa<DbgInfoIntrinsic>(CurI))
+      continue;
+    --MaxNumInstToLookAt;
 
     // Could be calling an instruction that effects memory like free().
     if (CurI->mayHaveSideEffects() && !isa<StoreInst>(CurI))