[llvm] [SLP][NFC]Fix non-determinism in pointers comparison, NFC (PR #210216)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/210216.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+13-8) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 6698395bf963b..93af803644a60 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -24660,9 +24660,10 @@ bool BoUpSLP::isCoveredByExistingVersionCheck(BasicBlock *BB,
   const Value *Base2 = getUnderlyingObject(Ptr2);
   if (Base1 == Base2)
     return false;
-  if (Base2 < Base1)
-    std::swap(Base1, Base2);
-  return It->second.contains({Base1, Base2});
+  // The recorded pairs keep their discovery order (see
+  // recordRuntimeAliasCheck), so accept either orientation.
+  return It->second.contains({Base1, Base2}) ||
+         It->second.contains({Base2, Base1});
 }
 
 /// Returns true if \p BB's body already contains vector instructions, e.g.
@@ -24702,16 +24703,20 @@ bool BoUpSLP::recordRuntimeAliasCheck(BasicBlock *BB, Instruction *Inst1,
   // Only a single block can be versioned per attempt.
   if (RTChecks.BB && RTChecks.BB != BB)
     return false;
-  // Normalize the pair order so duplicate checks collapse.
-  if (Base2 < Base1)
-    std::swap(Base1, Base2);
+  // A base-object pair is unordered: (Base1, Base2) and (Base2, Base1) are the
+  // same check. Keep it in discovery (program) order and drop the reverse as a
+  // duplicate, rather than ordering by pointer value, which would make the
+  // emitted checks depend on allocation addresses.
   auto Pair = std::make_pair(Base1, Base2);
+  bool Present = RTChecks.BasePairs.contains(Pair) ||
+                 RTChecks.BasePairs.contains({Base2, Base1});
   // After the checks have been validated and bounded, do not introduce new
   // pairs.
   if (RTChecksFinalized)
-    return RTChecks.BasePairs.contains(Pair);
+    return Present;
   RTChecks.BB = BB;
-  RTChecks.BasePairs.insert(Pair);
+  if (!Present)
+    RTChecks.BasePairs.insert(Pair);
   return true;
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/210216