[PATCH] D120544: [AMDGPU] Omit unnecessary waitcnt before barriers

[Austin Kerbow via Phabricator via llvm-commits]

kerbowa added a comment.

In D120544#3487040 <https://reviews.llvm.org/D120544#3487040>, @mareko wrote:

> We are going to insert amdgcn.s.waitcnt instead of a fence because fences wait for memory stores, which we don't want.

Without this patch, the compiler will wait for everything, so I'm not sure how you will be differentiating between loads and stores.

> What does the release fence add? Waiting for only LDS or everything?

It depends on the scope of the fence and the HW. See: https://llvm.org/docs/AMDGPUUsage.html#amdgpu-amdhsa-memory-model


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