[llvm] [LV] Vectorize Epilogues for loops with small VF but high IC (PR #108190)

[Florian Hahn via llvm-commits]

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@@ -4719,6 +4733,14 @@ VectorizationFactor LoopVectorizationPlanner::selectEpilogueVectorizationFactor(
                "Trip count SCEV must be computable");
         RemainingIterations = SE.getURemExpr(
             TC, SE.getConstant(TCType, MainLoopVF.getKnownMinValue() * IC));
+        const APInt MaxRemainingIterations =
+            SE.getUnsignedRangeMax(RemainingIterations);
+        // Guard against huge trip counts.
+        if (MaxRemainingIterations.getActiveBits() <= 32) {
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fhahn wrote:

Hm, I would assume the max would always be `MainLoopVF.getKnownMinValue() * IC - 1` or less, if the trip count is known to be constant? Curios why this guard is needed?

https://github.com/llvm/llvm-project/pull/108190