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

[Florian Hahn via llvm-commits]

================
@@ -883,6 +883,8 @@ class VPInstruction : public VPRecipeWithIRFlags,
     AnyOf,
     // Calculates the first active lane index of the vector predicate operand.
     FirstActiveLane,
+    // Creates a step vector starting from 0 with a step of 1.
----------------
fhahn wrote:

```suggestion
    // Creates a step vector starting from 0 with a step of 1 to the end value specified in the first operand.
```

It would probably be better to specify the end value/VF as operand?


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