[gmx-users] Re: no altivec support found when compiling on macosx G5 gcc 3.3

Pim Schravendijk schraven at mpip-mainz.mpg.de
Tue Mar 23 16:45:01 CET 2004

I changed CFLAGS from -fast to "-O3 -faltivec" and now I don't get the 
warning anymore. 

Strange thing is that even before I did this the configure script noted 
that -faltivec is an accepted gcc option, but for some reason didn't 
enable it afterwards when compiling the altivec test program.

Nice result: Gflops for my system went up from 1.007 to 1.723 when
enabling altivec.

Another note, maybe it's useful for someone:

The -fast option didn't work anymore when enabling 
altivec, I got the following error:

../../include/ppc_altivec.h: In function `do_3_ctable_coul':
../../include/ppc_altivec.h:434: internal compiler error: in convert_move, 
at expr.c:592
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://developer.apple.com/bugreporter> for instructions.
make[3]: *** [inner_altivec.lo] Error 1
make[2]: *** [all-recursive] Error 1
make[1]: *** [all] Error 2
make: *** [all-recursive] Error 1

Since the man page and macintosh web site 
note that the -fast option is somewhat experimental, this might be a 
problem of the -fast optimization. Using just -O3 worked fine so this is 
not a major problem.

Greetings, Pim

Pim Schravendijk - PhD Student
Max Planck Institute for Polymer Research

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