On Fri, Feb 15, 2019 at 3:30 AM Steve Ellcey <sell...@marvell.com> wrote: > > I have a question about SPEC CPU 2017 and what GCC can and cannot do > with -flto. As part of some SPEC analysis I am doing I found that with > -Ofast, ICC and GCC were not that far apart (especially spec int rate, > spec fp rate was a slightly larger difference). > > But when I added -ipo to the ICC command and -flto to the GCC command, > the difference got larger. In particular the 519.lbm_r was more than > twice as fast with ICC and -ipo, but -flto did not help GCC at all. > > There are other tests that also show this type of improvement with -ipo > like 538.imagick_r, 544.nab_r, 525.x264_r, 531.deepsjeng_r, and > 548.exchange2_r, but none are as dramatic as 519.lbm_r. Anyone have > any idea on what ICC is doing that GCC is missing? Is GCC just not > agressive enough with its inlining?
IIRC Jun did some investigation before? CCing. Thanks, bin > > Steve Ellcey > sell...@marvell.com
