[llvm] [LAA] Prepare to handle diff type sizes v2 (PR #161238)

[Ramkumar Ramachandra via llvm-commits]

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@@ -2108,19 +2106,41 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
   if (StrideAScaled == StrideBScaled)
     CommonStride = StrideAScaled;
 
-  // TODO: Historically, we didn't retry with runtime checks when (unscaled)
-  // strides were different but there is no inherent reason to.
-  if (!isa<SCEVConstant>(Dist))
-    ShouldRetryWithRuntimeChecks |= StrideAPtrInt == StrideBPtrInt;
-
   // If distance is a SCEVCouldNotCompute, return Unknown immediately.
   if (isa<SCEVCouldNotCompute>(Dist)) {
     LLVM_DEBUG(dbgs() << "LAA: Uncomputable distance.\n");
     return Dependence::Unknown;
   }
 
+  if (!isa<SCEVConstant>(Dist)) {
+    if (!LoopGuards)
+      LoopGuards.emplace(
+          ScalarEvolution::LoopGuards::collect(InnermostLoop, SE));
+    Dist = SE.applyLoopGuards(Dist, *LoopGuards);
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artagnon wrote:

Highly unintuitive, but it looks like there was a compile-time [improvement](https://llvm-compile-time-tracker.com/compare.php?from=ce70773cff2ab6b5d9b8d7a97ee62c75762a51d2&to=f4c295d2432ba2ce6d91650d4c1bee01b621146d&stat=instructions%3Au)?

https://github.com/llvm/llvm-project/pull/161238