[llvm] [VPlan] Add VPInstruction::StepVector and use it in VPWidenIntOrFpInductionRecipe (PR #129508)

[David Sherwood via llvm-commits]

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@@ -1094,6 +1093,12 @@ void VPInstructionWithType::execute(VPTransformState &State) {
     State.set(this, Cast, VPLane(0));
     break;
   }
+  case VPInstruction::StepVector: {
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david-arm wrote:

Do we need to add this to VPInstruction::computeCost?

https://github.com/llvm/llvm-project/pull/129508