[PATCH] D158332: [LV] Use IRBuilder to create and optimize middle-block compare.

Mon Aug 28 07:36:30 PDT 2023

Ayal accepted this revision.
Ayal added a comment.
This revision is now accepted and ready to land.

In D158332#4621170 <https://reviews.llvm.org/D158332#4621170>, @fhahn wrote:

> In D158332#4620180 <https://reviews.llvm.org/D158332#4620180>, @Ayal wrote:
>
>> Rather than have IRBuilder detect and optimize this implicitly at code-gen/ILV::completeLoopSkeleton() time, better do so explicitly at VPlan transform time, probably after VF and UF have been set, i.e., optimize the compare and conditional branch recipes into an unconditional branch recipe. Is the intent to do so as a subsequent patch? If so would be good to add a TODO to replace IRBuilder here; code-gen should ideally be straightforward.
>
> The immediate goal is to bring this code in line with how VPInstruction creates compares, so the diff for D150398 <https://reviews.llvm.org/D150398> is as small as possible.

Well, better avoid optimizing compares implicitly by VPInstruction's code-gen as well... but the goal is clear.

> Once we have the branch modeled in VPlan, we should simplify it there directly as well, but this  patch is a first step to get there, I added a TODO.

Thanks! Simplification is for both compare and branch.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D158332/new/

https://reviews.llvm.org/D158332