Brent Baude - Latest comments on Semi-optimized PS3 stages

In response to: Semi-optimized PS3 stages

Fallen- [Visitor] — Sat, 22 Sep 2007 15:26:21 +0000

Hello, I have my PS3 with Gentoo now :D and I want to optimize CFLAGS to install other things like Gnome.Should I replace mcpu=cell or do I leave mcpu=970? on:
http://gentoo-wiki.com/Safe_Cflags#Cell_Broadband_Engine_.28Playstation_3.29
the recommendation is cell.

Thank you for your help! Best regards.

In response to: Semi-optimized PS3 stages

popper [Visitor] — Sat, 18 Aug 2007 05:16:54 +0000

hi brent.

just a passing thought as you bring up
the flags.

i was rereading http://forum.beyond3d.com/showthread.php?s=7c9350bc2751cdda0bb5aee91b329bf7&p=893620#post893620 again and remembered about
using -funroll-loops to increase speed.

also, while i assume noones yet
replaced any core PPC linux code with
Altivec routines?, perhaps its time
to see if some optimisations can be found.

it seems such a waste to have the
Altivec chip sat there (almost) idle
taking up power and not being used in
any of the current core OS code.

markos's freevec still seems unused
anywere obvious in any part of the PPC OS codebase, and yet freevec is full of
tested code that works for most app
speed options....

he implyed it could be used to replace
or supliment lots of core code and get
a massive speed boost, such a shame
noone seems to have tryed to run tests
to see if it can boost the PS3 effort.

for readers, that thread was good for test code
code and otpimisations to try.
-----------------

-O0: some basic and minimum optimization
-O2: strong, low-level optimization that benefits most programs
-O3: intense, low-level optimization analysis with basic loop optimization

--------------

i think gcc4 still has broken -03 and still produces slower code than the old ones, but i may be wrong or was it just 4.0.3

In response to: Semi-optimized PS3 stages

Brent BAUDE [Member] — Sun, 29 Jul 2007 22:01:19 +0000

In my humble opinion, optimized can be a result of several different things. I would not consider -0-anything the only way to optimize. The passing of the 970 flags was what my original announcement was referring to. Prior to then, as I mentioned in the post, the CFLAGS were not getting set properly in the various stages as they were built, specifically in stage3.

Just for reference, we're working to become more gcc-4.3 savy so that we can actually begin to pass the "cell" mcpu for increased optimization. My hope is that will make things a little more interesting.

In response to: Semi-optimized PS3 stages

Stroller [Visitor] — Fri, 13 Jul 2007 22:08:37 +0000

Hi there,

Is -O2 really optimal for the PS3? I have little experience of optimising CFLAGS but considering the PS3 doesn't have so much RAM, might -Os be better? Do you know if anyone has done any tests?

Stroller.