Re: How to get GCC on par with ICC?

[Steve Ellcey <sellcey@cavium.com>]

On Thu, 2018-06-07 at 12:01 +0200, Richard Biener wrote:
> 
> When we do our own comparisons of GCC vs. ICC on benchmarks
> like SPEC CPU 2006/2017 ICC doesn't have a big lead over GCC
> (in fact it even trails in some benchmarks) unless you get to
> "SPEC tricks" like data structure re-organization optimizations that
> probably never apply in practice on real-world code (and people
> should fix such things at the source level being pointed at them
> via actually profiling their codes).

Richard,

I was wondering if you have any more details about these comparisions
you have done that you can share?  Compiler versions, options used,
hardware, etc  Also, were there any tests that stood out in terms of
icc outperforming GCC?

I did a compare of SPEC 2017 rate using GCC 8.* (pre release) and
a recent ICC (2018.0.128?) on my desktop (Xeon CPU E5-1650 v4).
I used '-xHost -O3' for icc and '-march=native -mtune=native -O3'
for gcc.

The int rate numbers (running 1 copy only) were not too bad, GCC was
only about 2% slower and only 525.x264_r seemed way slower with GCC.
The fp rate numbers (again only 1 copy) showed a larger difference, 
around 20%.  521.wrf_r was more than twice as slow when compiled with
GCC instead of ICC and 503.bwaves_r and 510.parest_r also showed
significant slowdowns when compiled with GCC vs. ICC.

Steve Ellcey
sellcey@cavium.com