[llvm] [VPlan] First step towards VPlan cost modeling (LegacyCM in CostCtx) (PR #92555)

[via llvm-commits]

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@@ -908,8 +908,13 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
         unsigned ExtOpcode = match(R.getOperand(0), m_SExt(m_VPValue()))
                                  ? Instruction::SExt
                                  : Instruction::ZExt;
-        auto *VPC =
-            new VPWidenCastRecipe(Instruction::CastOps(ExtOpcode), A, TruncTy);
+        VPSingleDefRecipe *VPC;
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ayalz wrote:

Worth a comment that `UnderlyingExt`, having distinct return type, is recorded only to support legacy cost computation?

https://github.com/llvm/llvm-project/pull/92555