[llvm] [VPlan] Create header phis once, after constructing VPlan0 (NFC). (PR #168291)

[via llvm-commits]

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@@ -8526,25 +8443,18 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(
   // Mapping from VPValues in the initial plan to their widened VPValues. Needed
   // temporarily to update created block masks.
   DenseMap<VPValue *, VPValue *> Old2New;
+
+  // Now process all other blocks and instructions.
   for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT)) {
     // Convert input VPInstructions to widened recipes.
     for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
-      auto *SingleDef = cast<VPSingleDefRecipe>(&R);
-      auto *UnderlyingValue = SingleDef->getUnderlyingValue();
-      // Skip recipes that do not need transforming, including canonical IV,
-      // wide canonical IV and VPInstructions without underlying values. The
-      // latter are added above for masking.
-      // FIXME: Migrate code relying on the underlying instruction from VPlan0
-      // to construct recipes below to not use the underlying instruction.
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ayalz wrote:

Worth retaining/updating these comments?

https://github.com/llvm/llvm-project/pull/168291