[MPlayer-users] configure and Cyrix C3

[Andre Majorel]

As of today, MPlayer HEAD does not build out of the box on
Cyrix/VIA C3 systems. It compiles, but the resulting binary
crashes with an "Illegal instruction" error.

configure (correctly) detects a 686 CPU and (incorrectly) passes
GCC the -march=i686 option. gcc -march=i686 produces code which
uses the CMOV instruction, which is missing on the C3. This is
true for all versions of GCC, as far as I know. Checked with 3.3.5
and 4.0.2.

I got it to work by

  - in config.mak,
    - setting TARGET_CPU to "c3",
    - in OPTFLAGS, replacing "-march=i686" by "-march=c3",
    - in OPTFLAGS, replacing "-mtune=i686" by "-mtune=486" (I'm
      told the 486 scheduling gives the best results with C3s).

  - In libavutil/common.h,
    - changing
        #if __CPU__ >= 686 && !defined(RUNTIME_CPUDETECT) 
      to
        #if 0

The "c3" arch was added in release 3.3 of GCC. With GCC 3.2 and
earlier, you have to use i386, i486 or i586 (either will do).

Thanks.

# cat /proc/cpuinfo
processor	: 0
vendor_id	: CentaurHauls
cpu family	: 6
model		: 7
model name	: VIA Ezra
stepping	: 8
cpu MHz		: 800.132
cache size	: 64 KB
fdiv_bug	: no
hlt_bug		: no
f00f_bug	: no
coma_bug	: no
fpu		: yes
fpu_exception	: yes
cpuid level	: 1
wp		: yes
flags		: fpu de tsc msr cx8 mtrr pge mmx 3dnow
bogomips	: 1603.45

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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