[llvm] [LV] codegen for tail-folded epilogue loop (PR #208764)

[David Sherwood via llvm-commits]

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@@ -7562,7 +7646,7 @@ static SmallVector<Instruction *> preparePlanForEpilogueVectorLoop(
   auto *Increment = vputils::findCanonicalIVIncrement(Plan);
   assert(Increment && "Must have a canonical IV increment at this point");
   IV->replaceUsesWithIf(Add, [Add, Increment](VPUser &U, unsigned) {
-    return &U != Add && &U != Increment;
+    return &U != Add && &U != Increment && !isa<VPWidenCanonicalIVRecipe>(&U);
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david-arm wrote:

Might be worth adding a comment explaining why this is needed. Also, it looks like this is fixing an existing bug - could it be committed separately?

https://github.com/llvm/llvm-project/pull/208764