[llvm] [VPlan] Introduce VPInstructionWithType, use instead of VPScalarCast(NFC) (PR #129706)

[via llvm-commits]

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@@ -1025,6 +1024,55 @@ class VPInstruction : public VPRecipeWithIRFlags,
   StringRef getName() const { return Name; }
 };
 
+/// A specialization of VPInstruction augmenting it with a dedicated result
+/// type, to be used when the opcode and operands of the VPInstruction don't
+/// directly determine the result type.
+class VPInstructionWithType : public VPInstruction {
+  /// Scalar result type produced by the recipe.
+  Type *ResultTy;
+
+  Value *generate(VPTransformState &State);
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ayalz wrote:

Document. May be a bit confusing being non-virtual nor override, worth a comment?

https://github.com/llvm/llvm-project/pull/129706