[llvm] [VPlan] Introduce VPSingleDefRecipe. (PR #77023)

[via llvm-commits]

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@@ -412,16 +412,16 @@ void VPlanTransforms::removeRedundantInductionCasts(VPlan &Plan) {
     auto &Casts = IV->getInductionDescriptor().getCastInsts();
     VPValue *FindMyCast = IV;
     for (Instruction *IRCast : reverse(Casts)) {
-      VPRecipeBase *FoundUserCast = nullptr;
+      VPSingleDefRecipe *FoundUserCast = nullptr;
       for (auto *U : FindMyCast->users()) {
-        auto *UserCast = cast<VPRecipeBase>(U);
-        if (UserCast->getNumDefinedValues() == 1 &&
-            UserCast->getVPSingleValue()->getUnderlyingValue() == IRCast) {
+        auto *UserCast = dyn_cast<VPSingleDefRecipe>(U);
+        if (UserCast && UserCast->getNumDefinedValues() == 1 &&
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ayalz wrote:

```suggestion
        if (UserCast &&
```

https://github.com/llvm/llvm-project/pull/77023