[PATCH] D91857: [ARM] Remove dead mov's in preheader of tail predicated loops

[Dave Green via Phabricator via llvm-commits]

dmgreen added inline comments.


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Comment at: llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp:793
+  // If we converted the LoopStart to a t2DoLoopStartTP, we can also remove any
+  // extra instructions in the preheader, which often includes a now unused MOV.
+  if (Start->getOpcode() == ARM::t2DoLoopStartTP && Preheader &&
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samtebbs wrote:
> Is it guaranteed that these extra instructions are unused (and so it's ok to remove them without any extra RDA checks)?
I am hoping that is what TryRemove will do. It checks for things like corrupting IT blocks too.

I'm not super confident about this code late-backend dead code removal not causing some problems, but hope it's at least as sane as the existing checks. I have not seen any problems so far at least.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91857/new/

https://reviews.llvm.org/D91857