[OpenJDK Rasterizer] Marlin #4

[Sergey Bylokhov]

Hi, Laurent.
Can you please check the next patch:
==========
diff -r 8a61c000a194 make/lib/Awt2dLibraries.gmk
--- a/make/lib/Awt2dLibraries.gmk	Tue Dec 20 09:52:14 2016 -0800
+++ b/make/lib/Awt2dLibraries.gmk	Wed Dec 21 17:33:36 2016 +0300
@@ -222,6 +222,7 @@
 # applies to debug builds.
 ifeq ($(TOOLCHAIN_TYPE), gcc)
   BUILD_LIBAWT_debug_mem.c_CFLAGS := -w
+  LIBAWT_CFLAGS += -fgcse-after-reload
 endif
 
 $(eval $(call SetupNativeCompilation,BUILD_LIBAWT, \
==========

It seems that this is the simplest version which produce the good performance results and safe enough to be integrated. On my system(Ubuntu gcc5.4) it will speedup default rasterizer from 8.400 to 6.200 ms/op +- 20%. Default rasterizer in OracleJDK 8u112 has 6.500.
Fix does not affect the the public jdk9.(which is build by RE on gcc 4.9.2), seems gcc 4.9.2 produce good results w/ and w/o this option.


> 
> We should also be wary of compiler options that are a win on one processor family and a loss on another.  Anything that schedules instructions may be specific to a particular generation of CPUs, for instance.  Or for i5 vs i7 vs M(obile)...
> 
> 			...jim
> 
> On 10/2/15 9:10 AM, Laurent Bourgès wrote:
>> 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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