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

[David Sherwood via llvm-commits]

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@@ -177,8 +177,11 @@ class VPBuilder {
                               Type *ResultTy,
                               std::optional<FastMathFlags> FMFs = {},
                               DebugLoc DL = {}, const Twine &Name = "") {
-    return tryInsertInstruction(new VPInstructionWithType(
-        Opcode, Operands, ResultTy, FMFs.value_or(FastMathFlags()), DL, Name));
+    if (FMFs)
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david-arm wrote:

Oh is this only exercised in this patch? Perhaps I'm missing something, but it wasn't obvious to me that this change was required. What breaks if you revert this change here?

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