[PATCH] D63958: [SDAG] commute setcc operands to match a subtract

Mon Jul 1 08:29:22 PDT 2019

spatel added a comment.

In D63958#1564460 <https://reviews.llvm.org/D63958#1564460>, @RKSimon wrote:

> Apart from the Lanai code (which like @spatel I know very little about) everything LGTM

I'm not finding any docs for this target other than the code in LLVM itself. Discussion about whether this target should be included in LLVM from when it first appeared in trunk:
http://lists.llvm.org/pipermail/llvm-dev/2016-February/095118.html

>From commit activity, maybe only @jpienaar can say what is happening on that target?

FWIW, there's a more involved version of this transform already in IR (in instcombine although that seems misplaced to me) - see "swapMayExposeCSEOpportunities()".

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https://reviews.llvm.org/D63958