[SDL] CPU specific build flags for OS X Universal Binaries

[E. Wing]

So I think we're close to getting the Universal Binaries finished. The
tricky part has been figuring how to maintain 10.2 compatibility in
this whole process. I think we're finally past this (pending on some
final 10.2 test results).


One thing I still need help with is what build flags should I be
defining to enable CPU specific optimizations like Altivec or SSE/MMX?
I know how to pass architecture specific flags in Xcode, but I don't
know what actual flags (if any) I need to use for SDL.

Currently, for PowerPC I think I need -DGCC_ALTIVEC
-DUSE_ALTIVEC_BLITTERS. Are there any others? And I'm not sure what
flags (if any) I need for Intel. Also, does additional code need to be
included in the Xcode project for x86? (The Xcode project seems to
omit non-Mac code.) Currently, the x86 side compiles without any
flags, but I don't know if it gets any SSE capabilities by default.

Thanks,
Eric