[PATCH] D64393: [AMDGPU] Fix DPP combiner check for exec modification

[Jay Foad via Phabricator via llvm-commits]

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


================
Comment at: llvm/lib/Target/AMDGPU/SIInstrInfo.cpp:6159
+    }
+
     if (I->modifiesRegister(AMDGPU::EXEC, TRI))
----------------
vpykhtin wrote:
> foad wrote:
> > vpykhtin wrote:
> > > vpykhtin wrote:
> > > > Now I recall why I used the set originally - to detect use instruction fast. Matt, is there other way to detect whether the instruction use a register without scanning its operands?
> > > and without scanning whether an instruction is in the use list for a register.
> > We have to scan the operands of every instruction anyway, in order to test `I->modifiesRegister(AMDGPU::EXEC, TRI)`. Your original code did that too.
> Good point. BTW you can probably use readsRegister instead of the loop.
`readsRegister` doesn't appear to ignore debug operands.


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