On Fri, Jun 07, 2002 at 09:55:39PM -0400, Ste wrote:
> Hey All,
> What seem to be the safest optimization flags these days for gcc 3? I
> haven't used optimizations since gcc 2.9.something where Bubble Bobble
> wouldn't display anything. But sound output sounds like garbage. are the
> optimizations for x86 systems in the makefile safe again? Are there
> other optimizations to use (in addition to -march? - does -march k6 work
> fully yet?) I really don't understand compilers that well and haven't
> found a web page with this info on it.
So far I've had good experiences with gcc-3.1 using the following CFLAGS
for general stuff:
-O2 -march=athlon-tbird -mmmx -m3dnow -fomit-frame-pointer
For xmame, I think I use -O3 and add -ffast-math -funroll-loops, and the
few things I've tried seem to work fine.
The only problematic flag I know of is -finline-limit=5000, which seems to
cause the same xmame crashes that -funroll-loops does for gcc-3.0.x.
If you want more details about options available in gcc-3.1 for x86
systems, check
http://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/i386-and-x86-64-Options.html#i386%20and%20x86-64%20Options
General optimizations are described at
http://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/Optimize-Options.html#Optimize%20Options
A lot of these are turned on by the various -O levels. To find out which,
you can compile a .c file like this:
gcc -S -fverbose-asm <filename>
and look at the resulting .s file.
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