[llvm] [VPlan] Replicate VPScalarIVStepsRecipe by VF outside replicate regions. (PR #170053)

[via llvm-commits]

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@@ -150,7 +148,7 @@ void UnrollState::addStartIndexForScalarSteps(VPScalarIVStepsRecipe *Steps,
     StartIndex = Builder.createScalarCast(Instruction::SIToFP, StartIndex,
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ayalz wrote:

Curious to learn if this raises any issues. It will diverge treating scalable vs. fixed VF, but they already differ - the former represents only UF values, and seems clearer to fold expressions known to be constant when building.

https://github.com/llvm/llvm-project/pull/170053