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Subject: Re: IBM G4/G5 Compiler

Author: Vincent Diepeveen

Date: 07:29:13 08/30/03

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On August 29, 2003 at 23:48:12, Matthew Hull wrote:

>On August 29, 2003 at 10:04:26, Rick Bischoff wrote:
>
>>Hi all,
>>
>>As you may or may not know, IBM has released their C/C++/Fortran compiler for
>>Mac OS X.  Here are some results from running said compiler against GCC with
>>various optimizations-- Tom's simple chess program (TSCP) is used (i.e., the
>>bench command).  The machine was my G4 tower (dual 867 w 1 GB Ram):
>>
>>GCC - "gcc *.c -o tscp_gcc0" produces
>>Trial NPS Score
>>1 44101 0.181
>>2 43977 0.181
>>3 45197 0.186
>>
>>IBM - "xlc *.c -o tscp_ibm0":
>>4 54253 0.223
>>5 54387 0.224
>>6 54424 0.224
>>
>>GCC - "gcc -O *.c -o tscp_gcc1":
>>7 113632 0.467
>>8 113609 0.467
>>9 113797 0.468
>>
>>IBM - "xlc -O *.c -o tscp_ibm1"
>>10 138769 0.571
>>11 138769 0.571
>>12 138560 0.570
>>
>>GCC - "gcc -O2 *.c -o tscp_gcc2"
>>13 121156 0.498
>>14 120811 0.497
>>15 121076 0.498
>>
>>IBM -O2 not tested as man page says it is equivalent to -O
>>
>>GCC - "gcc -O3 *.c -o tscp_gcc3"
>>16 119448 0.491
>>17 119734 0.492
>>18 120414 0.495
>>
>>IBM - "xlc -O3 *.c -o tscp_ibm3"
>>19 150939 0.621
>>20 150815 0.620
>>21 149994 0.617
>>
>>IBM - "xlc -O4 *.c -o tscp_ibm4"
>>22 167613 0.689
>>23 167868 0.690
>>24 168330 0.692
>>
>>IBM - "xlc -O5 *.c -o tscp_ibm5"
>>25 168691 0.694
>>26 168451 0.693
>>27 168536 0.693
>>
>>Executable size
>>gcc0 47076
>>gcc1 38948
>>gcc2 38948
>>gcc3 38948
>>ibm0 47164
>>ibm1 43068
>>ibm3 51260
>>ibm4 71468
>>ibm5 104500
>>
>>(I ran diff on the gcc executables of the same size and it assures me they are
>>different! That is somewhat unusual?)
>>
>>Anyway, it looks like the IBM compiler is a sure win over GCC if you are running
>>TSCP :-) I haven't been able to get Crafty to compile cleanly wih it yet, when I
>>do I will post an update.  If you know of any other compiler flags for GCC or
>>the IBM compiler let me know and I will test those too.
>
>What about the -mcpu or -march switches.  Are those set automatically?

and compiling using PGO also and options like:

# gebruiken om profile info te verzamelen voor betere optimalisatie op k7
CFLAGS   = -fprofile-arcs -O3 -march=athlon -mcpu=athlon -frename-registers -DUN
IXPII -fno-gcse -foptimize-register-move -fif-conversion
# te gebruiken om profile informatie te gebruiken bij optimalisatie k7
#CFLAGS    = -O3 -march=athlon -mcpu=athlon -fbranch-probabilities -frename-regi
sters -DUNIXPII -fno-gcse -foptimize-register-move -fif-conversion

Most persons do not know a thing about compiling with GCC.

doesn't take away that it is likely that the ibm compiler is going to be faster
at G5 than gcc.

>MH
>
>
>>
>>Rick



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