[PATCH] D40047: AMDGPU/GCN: Remove xnack from 801 and 810

[Tony Tye via Phabricator via llvm-commits]

t-tye added a comment.

In https://reviews.llvm.org/D40047#925599, @tstellar wrote:

> Does this change break backwards compatibility with the gfx801 target?  If so, which ROCm version will I need to use with these changes?


It changes the default setting for XNACK which may break backwards compatibility depending whether the runtime sets the hardware to XNACK replay. I do not believe gfx801 has ever been fully working as there are still known bugs in OpenCL conformance related to XNACK support.

Not sure if graphics enables XNACK replay as all buffers may be pinned.

One possibility, now that all APUs have distinct GFX names if https://reviews.llvm.org/D40051 is accepted, would be to default the target feature of XNACK to enabled for APUs. However, it is harder to know how to handle dGPU as each runtime may choose a different setting of XNACK for the same target, depending on if buffers are transferred/pinned. In other words the setting of XNACK is not directly dependent on the target name. So always defaulting to disabled seems a cleaner, then each runtime can decide if it wants to enable XNACK and use the -mxnack option (or cc1 equivalent).


https://reviews.llvm.org/D40047