[llvm] [VPlan] Use VPInstructionWithType for uniform casts. (PR #140623)

[via llvm-commits]

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@@ -1079,13 +1081,16 @@ void VPInstruction::print(raw_ostream &O, const Twine &Indent,
 
 void VPInstructionWithType::execute(VPTransformState &State) {
   State.setDebugLocFrom(getDebugLoc());
-  if (isScalarCast()) {
+  if (Instruction::isCast(getOpcode())) {
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ayalz wrote:

```suggestion
  if (Instruction::isCast(getOpcode())) {
    assert(isSingleScalar(this) && "VPInstructionWithType models casts of single scalars only");
```
before working with VPlan(0) only below?

https://github.com/llvm/llvm-project/pull/140623