[llvm-dev] llvm-mca for in-order CPUs (was Re: LLVM Weekly - #375, March 8th 2021) (original) (raw)

Andrew Savonichev via llvm-dev llvm-dev at lists.llvm.org
Tue Mar 9 08:33:21 PST 2021

Hi Jay,

Jay Foad writes:

On Mon, 8 Mar 2021 at 18:33, LLVM Weekly <list at llvmweekly.org> wrote:

* The llvm-mca static performance analysis tool now support in-order CPUs such as the Arm Cortex-A55. d791695. Thanks for doing this! I am very interested in using it for the AMDGPU target.

So far the feature was only tested for ARM in-order CPUs, so it will be great if you can try it for the AMDGPU target!

Have you given any thought to targets with MicroOpBufferSize=1? I understand that these are also "in order". I found that I could get some tests running with these changes: https://reviews.llvm.org/differential/diff/329308/

But I am really shooting in the dark here. I don't have a good understanding of the difference between MicroOpBufferSize=0 and 1, and I am not even sure which setting is really best for AMDGPU.

Frankly, I don't know what is the difference between MicroOpBufferSize=0 and 1. We should probably treat them the same for MCA, so your changes look good.

-- Andrew

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