[PATCH] D35635: Optimize {s,u}{add,sub}.with.overflow on ARM

[Joel Galenson via Phabricator via llvm-commits]

jgalenson updated this revision to Diff 119716.
jgalenson added a comment.

>> Good idea. However, the ARMISD::BRCOND isn't combined until after saddo is lowered.
> 
> That shouldn't completely block all transforms; you could pattern-match the ARMISD nodes.  But I guess the patterns become a lot more complicated, so maybe not worth doing.

I'm not sure what you mean.  After the ARMISD::BRCOND is created, only a few unrelated instructions are matched before the saddo is transformed.  So without the reordering we've discussed, I don't see how this would help.  I'm probably missing something, but it sounds like it might well not be worth doing.


https://reviews.llvm.org/D35635

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMISelLowering.h
  test/CodeGen/ARM/su-addsub-overflow.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D35635.119716.patch
Type: text/x-patch
Size: 9050 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20171020/bf30f2c1/attachment.bin>