https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11488
Matt Turner <mattst88 at gmail dot com> changed:
What |Removed |Added
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CC| |mattst88 at gmail dot com
--- Comment #11 from Matt Turner <mattst88 at gmail dot com> ---
(In reply to Steven Bosscher from comment #10)
> Someone should try with -fsched-pressure...
On alpha with gcc-5.3.0:
% gcc -O2 -mbwx idct3.c && time ./a.out
./a.out 1.72s user 0.00s system 99% cpu 1.721 total
% gcc -O2 -fno-schedule-insns -mbwx idct3.c && time ./a.out
./a.out 0.96s user 0.01s system 99% cpu 0.970 total
% gcc -O2 -fsched-pressure -mbwx idct3.c && time ./a.out
./a.out 1.01s user 0.00s system 99% cpu 1.016 total
(-mbwx is needed, otherwise -fsched-pressure/-fno-schedule-insns doesn't show
any benefit)
So it looks like -fsched-pressure helps significantly, but not quite as much as
-fno-schedule-insns.
