This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

GCC missing -flto optimizations? SPEC lbm benchmark


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?

Steve Ellcey
sellcey@marvell.com

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]