Re: PPC cflags

"Nick Smith" writes:
  |
  | >>
  | >> CFLAGS="-O3 -mcpu=G3 -maltivec -mabi=altivec
  | >> -fno-strict-aliasing -pipe"
  | >
  | > Does the G3 have altivec extensions?  I thought that they didn't
  | > show up till
  | > the G4.
  | man dont tell me that! i was going with what the guy said and
  | have almost completed the entire bootstrap with those cflags! i
  | hope your wrong.....(no offense of course)



It's at this stage that Id like to re-suggest that we consider
collecting a table of cflags and put in in the install or ppc docs.
Something like table with a sample line from /proc/cpuinfo and then
the stable and risky CFLAGS settings.



For my G5 (no bogomips entry?):
  CFLAGS="-O2 -mcpu=G5 -pipe -maltivec -mabi=altivec -fno-strict-aliasing -mpowerpc-gfxopt -mmultiple -mstring"


For my 800Mhz G3 laptop (1589.24 bogomips by the way:):
  CFLAGS="-O2 -pipe -mcpu=750 -mpowerpc-gfxopt -mmultiple -mstring"



A while ago I was md5sum'ing some iso images and I noticed my G5
was _WAY_ slower than my G3 laptop and it was because Id dropped
the mcpu=G5 setting from my G5 CFLAGS. I realise that md5sum'ing is a
special case, but small changes can make a massive change.

Even if the idea is too hard for gentoo as a whole, would it be
possible for gentoo-ppc?


Ive suggested it a few times in posts like:

  http://forums.gentoo.org/viewtopic-t-166999-highlight-.html

but everyone seems to say that its too hard :-/ or that there are too
many combos to track (which I dont quite get, I mean gentoo runs on
what, a couple of hundred cpu variations? Wouldnt the pain that this 
solves be worth it? :)

I mean developers and iso releasers must work this stuff out.... :)
But I guess it would be harder in that one would need to collect the info
for cpu model and gcc version or maybe 'gentoo/portage version' too.

Id comment that once we had the data, creating a script on the install
disk wouldnt be hard, but Im sure that would take away a little more
of the 'hacker' spirit of the whole install process :-)


cheers,
cam

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