[PATCH] D90334: [AMDGPU] Fix inserting combined s_nop in bundles

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added inline comments.


================
Comment at: llvm/test/CodeGen/AMDGPU/llvm.amdgcn.ds.gws.sema.p.ll:14
 ; LOOP-NEXT: s_setreg_imm32_b32 hwreg(HW_REG_TRAPSTS, 8, 1), 0
-; GFX8-NEXT: s_nop 0
 ; LOOP-NEXT: ds_gws_sema_p gds
----------------
rampitec wrote:
> kerbowa wrote:
> > rampitec wrote:
> > > rampitec wrote:
> > > > Is this expected?
> > > According to GCNHazardRecognizer::checkRFEHazards() it needs 1 waitstate.
> > I don't think this is an RFE hazard.
> Hm... Right, there is no rfe here...
OK, it was inserted by checkReadM0Hazards(). There is a def and use of m0, but it seem to incorrectly process BOUNDLE itself. There shall be 1 waitstate between def and use of m0. PreEmitNoopsCommon() returns 1 from checkReadM0Hazards(), and the IR is:


```
bb.0 (%ir-block.0):
  successors: %bb.1(0x80000000); %bb.1(100.00%)

  $m0 = S_MOV_B32 0

bb.1:
; predecessors: %bb.1, %bb.0
  successors: %bb.1(0x40000000), %bb.2(0x40000000); %bb.1(50.00%), %bb.2(50.00%)

  S_SETREG_IMM32_B32 0, 515, implicit-def $mode, implicit $mode
  BUNDLE implicit $m0, implicit $exec {
    DS_GWS_SEMA_V 0, -1, implicit $m0, implicit $exec :: (store 4 into custom "GWSResource")
    S_WAITCNT 0
  }
  renamable $sgpr0 = S_GETREG_B32 515
  S_CMP_LG_U32 killed renamable $sgpr0, 0, implicit-def $scc
  S_CBRANCH_SCC1 %bb.1, implicit killed $scc
```

There is def of m0 in bb.0, but it is really expired by the GWS operation.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D90334/new/

https://reviews.llvm.org/D90334