IBm XLC Compilter News? Rumors?

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alphap1us

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I don't know if anyone remebers but a few months ago IBM released a compiler for the G5 that was supposed to dramatically increase performance on G5s as well as G4's. I was really excited about this announcement but then I never heard anything else about it. Does anyone have any news or rumors about where this is currently used? Are any apps currently compiled with this thing?
 
In beta? I thought it was on sale for $499, with a 60-day evaluation version available?

This thing was supposed to be the better than sliced bread (which wouldn't be that great for a Mac, I'd admit), though I have to admit I haven't heard much about it.

Thanks for the reminder though, I want to give this a shot building an open-source app that so far has had lackluster performance on my G5 (this lackluster performance is the main reason why I was unable to convince the dept. to buy a fleet of them... grumble)
 
... I wonder whether xlcpp code will give worse results for G3 and G4 type processors than using GCC - and whether Apple's going to use the compiler at all...
 
The original results showed that xlc/xlcpp would improve performance for most PPC apps. NASA reported speed increases of 70% on G4 with one of their apps. Most independent benchmarks showed at least SOME improvement (one test I saw showed an average of 17% improvement) by using xlc on G4.

I assume that would apply to G3.

And XLC *does* have Altivec extensions.
 
GCC has support for Altivec too. The big question is, does it auto-vectorize the code, like the Intel C++ compiler does? That is what's going to give you big speed boost by letting the compiler automatically generate Altivec code where suitable.

From the page, it looks like it only supports the use of Altivec. At least it has binary compatibility with GCC, which is definitely a good thing.
 
GCC might auto vectorize some things but it's not much. To use Altivec you have to program your app to use it.
 
GCC doesn't auto vectorize. Not to my knowledge anyway, unless Apple changed it significantly. That's why they had to specifically create specialized C libraries that wrapped around the Altivec instructions so mortals wouldn't need to dive into assembly to use Altivec.

More at http://developer.apple.com/hardware/ve/ . There's no mention of GCC auto vectorizing code.

After some googling, I've found a page that is relevant. http://gcc.gnu.org/projects/tree-ssa/vectorization.html seems to suggest that they are planning to implement this feature in GCC, but its currently at planning stage. So who knows, in a few years we might have a decent optimizing compiler for free!
 
AFAIK, Apple uses GCC 4 for/with Tiger. Tests of XLC have been comparing to older GCC versions, I guess.
 
Yes, I know they will be using GCC 4. But that doesn't stop me from wishing :).

GCC 4 does improve on GCC 3.3 by a bit, but it isn't as dramatic an improvement as what XLC appears to provide. Nevertheless, Apple will still stick with GCC 4, mainly because that's what their tools are all built on and it would cost too much to switch to something else right now. While GCC isn't as good as XLC, it's still a pretty good compiler.
 
Well GCC 4 supports auto-vectorisation, so from what I read that makes a number of in-roads into it catching up with IBM's xLC.

However GCC is designed to be a generic fit to whatever platform it is run on, instead of xLC which is designed to take full advantage of the processor it's compiled for...

Plus, someone said to me that xLC does NOT compile for G3, so it would mean loss of compatibility with a large number of machines.
 
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