[llvm] [AA] A conservative fix for atomic store instruction. (PR #155032)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Jin Huang (jinhuang1102)

<details>
<summary>Changes</summary>

The current atomic store check in function `AAResults::getModRefInfo` would compare to the `AtomicOrdering::Unordered` that mean any atomic store instruction will return `ModRefInfo::ModRef` without performing any further analysis on the memory location itself.

This PR raises the comparison form `Unordered` to `Monotonic`.


---
Full diff: https://github.com/llvm/llvm-project/pull/155032.diff


1 Files Affected:

- (modified) llvm/lib/Analysis/AliasAnalysis.cpp (+1-1) 


``````````diff
diff --git a/llvm/lib/Analysis/AliasAnalysis.cpp b/llvm/lib/Analysis/AliasAnalysis.cpp
index 3ec009ca4adde..b18ef88509b5c 100644
--- a/llvm/lib/Analysis/AliasAnalysis.cpp
+++ b/llvm/lib/Analysis/AliasAnalysis.cpp
@@ -439,7 +439,7 @@ ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
                                     const MemoryLocation &Loc,
                                     AAQueryInfo &AAQI) {
   // Be conservative in the face of atomic.
-  if (isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered))
+  if (isStrongerThan(S->getOrdering(), AtomicOrdering::Monotonic))
     return ModRefInfo::ModRef;
 
   if (Loc.Ptr) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/155032