[PATCH] D41463: [CodeGen] Add a new pass to sink Copy instructions after RA

[Sean Fertile via Phabricator via llvm-commits]

sfertile added a comment.

I've tested this out on Power with spec2006 and several open-source applications. With spec I saw a pretty similar increase in shrink wrapping opportunities (~11% with -O3 pgo+thinlto, ~7% with just -O3). I've noticed in some instances we do a lot of sinking without enabling new shrink-wrap opportunities though. For example with xalan stats showed we sunk about 4000 copies with this pass, but only enabled 5 new shrink-wrap opportunities and I see a consistent ~2% degradation with ref data.  My understanding was enabling more shrink-wrap candidates was the original motivation. Have you considered breaking this up into an analysis that collects what copies are sinkable, and then only sink if doing so is likely to make the block viable for shrink-wrapping?


https://reviews.llvm.org/D41463