On Friday 04 February 2005 10:13 am, Damian Kolkowski
<[EMAIL PROTECTED]> wrote:
> * Captain FantastiK <[EMAIL PROTECTED]> [2005-02-04 16:22]:
> > CFLAGS="-O3 -march=pentium4 -mcpu=i686 -fomit-frame-pointer -pipe
> > -ftracer"
>
> Use this instead:
> -O2 -march=pentium4 -formit-frame-pointer
>
> Yours CFLAGS are wrong, You need to use onlu one (mcpu or marcg), the
> last one are used.
That's incorrect.
-march=<arch> produces code that will only work on that architecture. For
example, it may use MMX, SSE, or 3dNow operations. It also includes the
optimizations performed by -mcpu=<arch>.
-mcpu=<cpu> (Previously -mtune=<cpu>) produces code that will work on any
architecture (within the limits of this gcc binary) but performs
instruction scheduling to optimize for a certain CPU.
For CFLAGS in make.conf, I suggest using both, just in case a certain
ebuild / makefile strips out -march, that way you still get the -mcpu
optimizations.
From "info gcc": (I have gcc 3.4.3 installed)
`-mtune=CPU-TYPE'
Tune to CPU-TYPE everything applicable about the generated code,
except for the ABI and the set of available instructions.
`-march=CPU-TYPE'
Generate instructions for the machine type CPU-TYPE. The choices
for CPU-TYPE are the same as for `-mtune'. Moreover, specifying
`-march=CPU-TYPE' implies `-mtune=CPU-TYPE'.
`-mcpu=CPU-TYPE'
A deprecated synonym for `-mtune'.
(Looks like I had -mtune and -mcpu backwards.)
--
Boyd Stephen Smith Jr.
[EMAIL PROTECTED]
ICQ: 514984 YM/AIM: DaTwinkDaddy
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