[OpenJDK Rasterizer] Marlin #4

[Laurent Bourgès]

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
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