Sergey, thanks for the information:
I tried your gcc options on my ubuntu 14.4 (v4.8.4) and it is actually >> slightly faster: 10% on my fill ellipse test (450ms vs 490ms). >> > > I tested by your jmh test, and the difference became bigger on 1400 size. > Interesting; I will try too. > >> Do you know which gcc compiler and options are used to build JavaSE EA? >> > I guess that compiler options in makefile are the same. > > plus some default gcc options: > jdk8: > gcc (GCC) 4.3.0 20080428 (Red Hat-8) C compiler version 4.3.0-8) > > jdk9: > gcc-4.8.2 - OEL5.5 > However the gcc compiler are different: 4.3 vs 4.8.2 ! So it may be worth comparing their different optimization options; I guess somebody already looked at that ! > Moreover, the linux distrib may define default options. >> >> I will try to figure out all compiler options (command line + defaults) >> on my machine. >> > > It is not simple to find an option, which will help for everyone. Two > options suggested by me is a minimum number from -O3 to get the maximum > performance, both seems reasonable. Actually if I change the -O2 to > -O3(OPTIMIZATION := LOW =>> OPTIMIZATION := HIGHEST) performance became > worse. > It is often the case with O3, but your patch seems a good win with only 2 enabled options. > > What is your build environment ? >> > > Ubuntu 14.04 gcc 4.8.4 > I have the same and I got finally my gcc options: gcc -c -Q -O2 --help=common Here are the difference between O2 vs O3 with gcc 4.8.4: gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts diff /tmp/O2-opts /tmp/O3-opts | grep enabled *> -fgcse-after-reload [enabled]*> -finline-functions [enabled] > -fipa-cp-clone [enabled] > -fpredictive-commoning [enabled] > -ftree-loop-distribute-patterns [enabled] > -ftree-partial-pre [enabled] *> -ftree-vectorize [enabled]*> -funswitch-loops [enabled] > -fvect-cost-model [enabled] So we could evaluate some of these options and see what is the best compromise for libawt on gcc 4.8 ! Regards, Laurent
