[llvm] [LoopVectorize] Improve algorithm for hoisting runtime checks (PR #73515)

[Nikita Popov via llvm-commits]

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@@ -346,7 +346,10 @@ void RuntimePointerChecking::tryToCreateDiffCheck(
     auto *SinkStartAR = cast<SCEVAddRecExpr>(SinkStartInt);
     const Loop *StartARLoop = SrcStartAR->getLoop();
     if (StartARLoop == SinkStartAR->getLoop() &&
-        StartARLoop == InnerLoop->getParentLoop()) {
+        StartARLoop == InnerLoop->getParentLoop() &&
+        !SE->isKnownPredicate(ICmpInst::ICMP_EQ,
+                              SrcStartAR->getStepRecurrence(*SE),
+                              SinkStartAR->getStepRecurrence(*SE))) {
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nikic wrote:

Yeah, SCEVs are uniqued, so a SCEV with the same args will have the same pointer. (Of course, it's possible that expressions are equal in ways that SCEV doesn't understand, but we'd consider that a canonicalization failure.)

https://github.com/llvm/llvm-project/pull/73515