Re: G4 Upgrade
On Thu, Mar 28, 2002 at 10:12:37AM -0500, Brian Victor wrote:
> 1) Does the G4 have any advantage in linux over a G3? Last I knew, gcc
> didn't compile for Altivec, though I thought I recalled hearing that Apple
> was merging their Altivec compiling code. (OT - can anyone tell me how I'd
> be able to code to take advantage of Altivec if gcc *did* compile for it?)
There are a few applications that have Altivec speedups, mainly
the ones where it significantly helps performance, such as MPEG
decoders.
There's a gcc patch floating around for 2.95.4 that will convert
Altivec intrinsics (basically macros) into Altivec instructions
and schedule them nicely. Unfortuantely, the resulting gcc is
buggy as hell, and the only thing I use it for is to schedule
instructions which I then convert to inline assembly. This is
probably the patch that will be merged. I assume the result will
be a lot less buggy.
I would be really impressed if the GCC patches could take ordinary
C code, find intrinsic parallelism, and write Altivec instructions
for that. That would be cool, but I don't think GCC is
architecturally capable of that (yet).
One of my pet projects is a SIMD library that has speedups for a
number of functions that are common in image processing, codecs,
and audio processing. It's currently only a local project, but
it's already usable and will be released soon. This should enable
a lot of acceleration in many computationally intensive apps.
dave...
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