https://llvm.org/bugs/show_bug.cgi?id=27615
Bug ID: 27615
Summary: SimplifyCFG::isSafeToSpeculateStore produce different
result with debug intrinsic
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Transformation Utilities
Assignee: unassignedb...@nondot.org
Reporter: henric.karls...@ericsson.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 16297
--> https://llvm.org/bugs/attachment.cgi?id=16297&action=edit
Test case that shows diff in output
Depending on if you have @llvm.dbg.value present or not the output from
isSafeToSpeculateStore will in some cases be different.
Right now the method checks a fixed number of instructions back, but those
instructions include the dbg values.
One possible fix could be to just ignore dbg values:
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp
b/lib/Transforms/Utils/SimplifyCFG.cpp
index 1c27bc6..32b68de 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1449,9 +1449,14 @@ static Value *isSafeToSpeculateStore(Instruction *I,
BasicBlock *BrBB,
// Look for a store to the same pointer in BrBB.
unsigned MaxNumInstToLookAt = 10;
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))
return nullptr;
--
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