[PATCH] D84108: [SimplifyCFG][LoopRotate] SimplifyCFG: disable common instruction hoisting by default, enable late in pipeline

Fri Aug 21 08:29:04 PDT 2020

echristo added a comment.

In D84108#2229869 <https://reviews.llvm.org/D84108#2229869>, @dmgreen wrote:

>> I think you're still in scientific computing yes?
>
> Embedded computing actually. Low power Arm devices, but I'm always interested in all uses of Arm devices. I have been working in the vectorizer a lot lately, and a number of the benchmarks we usually run are DSP style codes, so quite similar to HPC.  But the improvements I saw included CPU's without any vectorization. Codesize was also flat in all, which I took as a good sign that the patch wasn't bad for general codegen.

We didn't see any codesize regression, but any scalar code with a hot loop started regressing fairly strongly. Particularly things like compression that were already hand vectorized a bit.

> The developer policy is quite clear when it comes to addressing regressions, but my vote would be for keeping the change :)

Understood.

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https://reviews.llvm.org/D84108