[uClibc] 603e performance

Marc Leeman marc.leeman at barco.com
Fri Aug 20 14:04:04 UTC 2004


> The only thing I can think of that may be influencing coDEC efficiency
> is compiler support for SSE/MMX etc..

The 82xx processors don't have Altivec IIRC.

It's not really decoding on the powerpc itself, it's 'just' stripping
off the headers. Since a lot of the streams have no payload indication;
this involves a lot of byte shifting, byte swapping, comparing and
branching...

The -mcpu=603e and altivec options were the first ones I checked. I am
currently at

CFLAGS="-O3 -Winline -Wall -fPIC -mcpu=603e -mtune=603e -mstrict-align
-mno-longcall" 

but no real improvement at all (incremental addition of these options).

Could having the kernel compiled with the other compiler have such a
decremental effect? These two seem to be relatively independent from
each other to me.

Ah one other thing. I noticed when compiling that isdigit() is
implicitly defined, but the functionality of the program is fine
(uclibc). man isdigit showed me to include ctype.h, but then the program
failed. I think a macro must be defined in the uclibc counterpart of
ctype.h which behaves badly. Just leaving out the inclusion of ctype.h
'solves' the problem for me... It's in combination of a slightly
modified version if inet_aton I used it.

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