[PATCH] D96643: [AMDGPU] Limit memory scope for scratch, LDS and GDS

Mon Feb 15 11:00:17 PST 2021

rampitec added inline comments.

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Comment at: llvm/test/CodeGen/AMDGPU/memory-legalizer-local-agent.ll:726
 ; GFX10-WGP-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX10-WGP-NEXT:    s_waitcnt_vscnt null, 0x0
 ; GFX10-WGP-NEXT:    buffer_gl0_inv
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t-tye wrote:
> t-tye wrote:
> > rampitec wrote:
> > > Looks like it is sill insufficient.
> > In WGP mode it is still necessary to synchronize across CUs, hence the need to wait/invalidate for VMEM when at workgroup scope. Basically, the scope limited to workgroup has to do the equivalent of agent scope.
> > 
> > In CU more this is not necessary and so this waitcnt vscnt /gl0 invalidate is not present as seen in line 738-739.
> But this does demonstrate that simply treating WGP mode as agent scope is conservatively correct, but not optimal. I will look to see if can be improved further.
I do not see it in the memory model for GFX10. There is no reference that vmem counter is needed in WGP mode.

Repository:
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  https://reviews.llvm.org/D96643/new/

https://reviews.llvm.org/D96643