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

[David Sherwood via llvm-commits]

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@@ -1068,7 +1070,15 @@ class VPInstructionWithType : public VPInstruction {
     if (R->isScalarCast())
       return true;
     auto *VPI = dyn_cast<VPInstruction>(R);
-    return VPI && VPI->getOpcode() == VPInstruction::WideIVStep;
+    if (!VPI)
+      return false;
+    switch (VPI->getOpcode()) {
+    case VPInstruction::WideIVStep:
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david-arm wrote:

This patch isn't adding `VPInstruction::WideIVStep`. It feels like this should be done independently in a separate patch?

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