[MPlayer-dev-eng] ppc runtime-cpu-detection fails with gcc 3.3

[Alan Curry]

There's a bug in gcc 3.3:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13133

which prevents runtime CPU detection of altivec from working. If run on a
machine without altivec support, it dies with SIGILL because gcc has decided
to save all the altivec registers (along with floating point and others) in
the prologue. This bug is triggered by the presence of a call to [sig]setjmp
in the function.

It would be possible to rearrange the code in cpudetect.c to work around the
gcc 3.3 bug, but it's not easy - you have to have a SIGILL handler installed
before you can safely call a function that calls setjmp, but you have to have
a jmp_buf ready before your SIGILL handler can do anything useful, because
returning from the handler just causes the illegal instruction to be
retried. The only way I can think of to make it work is to forget the
handler, use a child process and let it die from the SIGILL.

And that's not the end of it. There are other places in mplayer that setjmp
is used, and they will all die with SIGILL on non-altivec-capable machines if
compiled with gcc-3.3 -mabi=altivec.

It looks to me like we should blacklist the combination of ppc,
runtime-cpu-detect, and gcc 3.3 in configure. Objections? Alternatives?
Comments?