[PATCH] D156671: [AMDGPU][SIInsertWaitcnts] Initialize the WaitcntBrackets for non-kernel functions

Mon Jul 31 06:07:41 PDT 2023

foad added a comment.

In D156671#4546620 <https://reviews.llvm.org/D156671#4546620>, @jmmartinez wrote:

> In D156671#4546409 <https://reviews.llvm.org/D156671#4546409>, @foad wrote:
>
>> Please explain what this is for. Is it a bug fix? Do you have a test that shows the intended effect?
>
> Hello,
>
> The test that best depicts the issue is amd.endpgm.ll <https://reviews.llvm.org/differential/changeset/?ref=4373291>.
>
> In this test there is a `test1` non-kernel function that inmediately does a call to `@llvm.amdgcn.endpgm`. On GFX11, I'd expect a `s_sendmsg` instruction before the `s_endpgm` for that function.
>
> `SIInsertWaitcnt` inserts an `s_sendmsg` before each `s_endpgm` if the `VS_CNT` score is not 0 and if there is any pending scratch store operation; but when `SIInsertWaitcnt` initializes the `WaitcntBrackets` object for any function (entry or not) all the counters are set to 0.

Thanks for the explanation. A simpler implementation of this would just set VS_CNT to its max value, not all the counters.

//However// you can only insert the `s_sendmsg sendmsg(MSG_DEALLOC_VGPRS)` if there are //**no**// pending scratch stores (see D153295 <https://reviews.llvm.org/D153295>) so I don't think this patch is acceptable.

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