[llvm] [VPlan] Delay adding canonical IV increment. (PR #82270)

[via llvm-commits]

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@@ -9471,6 +9465,15 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   if (!VPlanTransforms::adjustFixedOrderRecurrences(*Plan, Builder))
     return nullptr;
 
+  // Don't use getDecisionAndClampRange here, because we don't know the UF
+  // so this function is better to be conservative, rather than to split
+  // it up into different VPlans.
+  // TODO: Consider using getDecisionAndClampRange here to split up VPlans.
+  bool IVUpdateMayOverflow = false;
+  for (ElementCount VF : Range)
+    IVUpdateMayOverflow |= !isIndvarOverflowCheckKnownFalse(&CM, VF);
+
+  TailFoldingStyle Style = CM.getTailFoldingStyle(IVUpdateMayOverflow);
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ayalz wrote:

This is moved here from earlier in tryToBuildVPlanWithVPRecipes(), so this information is still computed conservatively at this stage.

https://github.com/llvm/llvm-project/pull/82270