[llvm] [AA] Improve precision for monotonic atomic load/store operations (PR #158169)

[Jin Huang via llvm-commits]

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@@ -457,8 +465,15 @@ ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
       return ModRefInfo::NoModRef;
   }
 
+  // At this point, the store's ordering is at most `Monotonic` (i.e.,
+  // Monotonic, Unordered, or non-atomic), and it aliases with `Loc`. The
+  // condition `isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered)` is
+  // true only for `Monotonic` stores.
+  if (isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered))
+    return ModRefInfo::ModRef;
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jinhuang1102 wrote:

I think both the if block and the code following it return ModRefInfo::ModRef. This makes the condition and the first return statement redundant. I remove this if condition to check if the Atomic ordering is stronger than unordered. Please let me know your comment (@nikic ). Thanks.

https://github.com/llvm/llvm-project/pull/158169