[llvm] [VPlan] Create header phi recipes after initial scalar optimizations. (PR #200920)

[Florian Hahn via llvm-commits]

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@@ -962,6 +966,9 @@ bool VPlanTransforms::createHeaderPhiRecipes(
   if (!tryToSinkOrHoistRecurrenceUsers(HeaderVPBB, VPDT))
     return false;
 
+  if (range_size(HeaderVPBB->phis()) !=
+      range_size(Plan.getScalarPreheader()->phis()))
+    return true;
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fhahn wrote:

I added a brief comment; a header phi now may be removed/simplified early, in which case we need to skip the renaming, as we can't map header phi to scalar phi any longer. This just skips the IR naming for cases that should not really happen in practice (those phis would be cleaned up earlier)

https://github.com/llvm/llvm-project/pull/200920