[PATCH] D39906: [InstCombine] Allowing GEP Instructions with loop Invariant operands to combine

Thu Mar 8 13:26:14 PST 2018

sebpop added a comment.

The motivation behind this patch is that it brings up the performance
of gzip deflate by 10%: this pattern occurs in the hot spot of
longest_match() in zlib.

To answer Eli's question, here are the performance numbers
for the spec2000 int with and without the patch on A72 firefly:
a positive value is a speedup percent, a negative value is a slowdown percent

164.gzip .1000
175.vpr -1.5400
176.gcc -.5200
177.mesa .6200
179.art 2.1500
181.mcf -.7100
183.equake 1.2800
186.crafty .5400
188.ammp -.8700
197.parser .0400
252.eon .4700
253.perlbmk .7200
254.gap -.8300
255.vortex -.3400
256.bzip2 -.0400
300.twolf .4800

I will update the patch with all corrections asked in previous comments.

https://reviews.llvm.org/D39906