[PATCH] D69661: [AMDGPU] Fix vccz after v_readlane/v_readfirstlane to vcc_lo/hi

[Jay Foad via Phabricator via llvm-commits]

foad marked an inline comment as done.
foad added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp:1415
+        VCCZCorrect = false;
+      else if (Inst.definesRegister(AMDGPU::VCC))
+        VCCZCorrect = true;
----------------
arsenm wrote:
> Can you just check modifiesRegister(VCC) instead of trying all the subregs?
I don't think that would let me distinguish this instruction (which writes to vcc_lo and corrupts vccz) from a "normal" write to vcc, would it?
```
$vcc_hi = V_READFIRSTLANE_B32 killed $vgpr0, implicit $exec, implicit-def $vcc
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69661/new/

https://reviews.llvm.org/D69661