[llvm] [clang-tools-extra] [clang] [VPlan] Add new VPUniformPerUFRecipe, use for step truncation. (PR #78113)

[Florian Hahn via cfe-commits]

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@@ -504,6 +504,15 @@ static VPValue *createScalarIVSteps(VPlan &Plan, const InductionDescriptor &ID,
     HeaderVPBB->insert(BaseIV->getDefiningRecipe(), IP);
   }
 
+  VPTypeAnalysis TypeInfo(SE.getContext());
+  if (TypeInfo.inferScalarType(BaseIV) != TypeInfo.inferScalarType(Step)) {
+    Step = new VPScalarCastRecipe(Instruction::Trunc, Step,
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fhahn wrote:

Yes, here the only use-case is `Trunc`, but the implementation of the recipe is intentionally kept generic for any cast where only the first lane is used, so it can be used directly in #76172


https://github.com/llvm/llvm-project/pull/78113