[PATCH] D137483: [NFC][PowerPC] Add NFC fixes to PPCInstrinfo.cpp when getting the defined machine instruction.

[ChenZheng via Phabricator via llvm-commits]

shchenz added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCInstrInfo.cpp:3394
+        } else
+          DefMI = nullptr;
       }
----------------
amyk wrote:
> shchenz wrote:
> > If `OpNoForForwarding` is not changed, then the reassigned `DefMI` will not be used. Do you find any issue for this?
> Thanks for your comment. I believe if `OpNoForForwarding` remains as `~0U` like it is in the beginning in this case, then we did not end up finding a valid operand in pre-SSA form.
> 
> I realize that we also anticipate that `DefMI` would be null as at the end we have, 
> ```
> return OpNoForForwarding == ~0U ? nullptr : DefMI;
> ```
> Which will indicate that we’ll return a null `DefMI` if `OpNoForForwarding` doesn’t end up getting updated.
> 
> Thus, I don’t believe this is an issue, but please do let me know if I have misunderstood your question.
I think the change here (reassigning `DefMI` to nullptr) does not make any functionality change, right? And it makes the code more complicated(at least now one basic block is added), so I was wondering about the benefit about this change.


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https://reviews.llvm.org/D137483