[llvm] [VPlan] Support VPWidenPointerInductionRecipes with EVL tail folding (PR #152110)

[Florian Hahn via llvm-commits]

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@@ -2177,8 +2177,21 @@ static void transformRecipestoEVLRecipes(VPlan &Plan, VPValue &EVL) {
   assert(all_of(Plan.getVF().users(),
                 IsaPred<VPVectorEndPointerRecipe, VPScalarIVStepsRecipe,
                         VPWidenIntOrFpInductionRecipe>) &&
+         all_of(Plan.getVFxUF().users(),
+                [&Plan](VPUser *U) {
+                  // VFxUF users must either be VPWidenPointerInductionRecipe or
+                  // canonical IV increment.
+                  return match(U, m_c_Binary<Instruction::Add>(
+                                      m_Specific(Plan.getCanonicalIV()),
+                                      m_Specific(&Plan.getVFxUF()))) ||
+                         isa<VPWidenPointerInductionRecipe>(U);
+                }) &&
          "User of VF that we can't transform to EVL.");
   Plan.getVF().replaceAllUsesWith(&EVL);
+  Plan.getVFxUF().replaceUsesWithIf(&EVL, [](VPUser &U, unsigned Idx) {
+    // Don't replace the canonical IV increment.
----------------
fhahn wrote:

```suggestion
    // Only replace uses in VPWidenPointerInductionRecipe; the only other possible user is the increment of the canonical induction, which must not be updated.
```

>From the code it is not clear why this specifically would not repalce canonical IV increment. Might be good to clarify iin comment or split up the assert and move it just before here?

https://github.com/llvm/llvm-project/pull/152110