Author Topic: Gcc 3.4  (Read 3071 times)

ThC

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Gcc 3.4
« on: December 12, 2004, 03:39:21 pm »
I've read recently that gcc 3.4 have a lot of extra optimisations for xscale arch (and some kind of enhanced software fpu for it) and even for the new "wireless mmx" enabled xscale cpus and was wondering why wouldn't we use it instead od 3.3.2 toolchain ... btw there might be some excellent reason but whhat are these ??
« Last Edit: December 12, 2004, 03:40:12 pm by ThC »
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lardman

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Gcc 3.4
« Reply #1 on: December 13, 2004, 05:33:26 am »
Depends who we is; we do use it in OpenEmbedded iirc.


Si
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ThC

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Gcc 3.4
« Reply #2 on: December 13, 2004, 02:27:02 pm »
right , "we" stands for pdaXrom users/developers as it seem to me the toolchain used is 3.3.4 (btw I may be wrong) ... btw I was thinking it was the same thing for other roms ...Maybe I should take a look at recent versions of OE/OZ
SL-C3000 - pdaXrom 1.1.0Beta1
SL-C860 - pdaXrom 1.1.0 RC8 (charging circuitry dead :( )
CF RamStar 512 Mb / Hitachi 4Gb microdrive (thanks to creative's muvo² :p)
SD Sandisk 1Gb / Viking 256 Mb
Linksys WCF13 CF wifi card

Anyone willing to donate for my work, please consider donate to pdaXrom and/or OE/OZ projects instead, I wouldn't have been able to do anything without them ...

Vit!

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Gcc 3.4
« Reply #3 on: March 02, 2005, 02:06:01 pm »
Quote
Depends who we is; we do use it in OpenEmbedded iirc.


Si
[div align=\"right\"][{POST_SNAPBACK}][/a][/div]

but XScale optimizations are disabled by default in OE!

I have feed with Opie build with optimizations inside OE. More info at [a href=\"http://mifki.ru/el-apps]http://mifki.ru/el-apps[/url]
« Last Edit: March 03, 2005, 05:35:29 am by Vit! »
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lardman

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Gcc 3.4
« Reply #4 on: March 02, 2005, 04:03:34 pm »
That's interesting. Presumably it wouldn't be too hard to enable the optimisations for those machines which have XScale processors (a matter of altering the machine's .conf file I assume).

How did you do this exactly? The wireless mmx extensions are for the C3000's processor if I'm not mistaken, these might have been excluded as I don't think any of the main developers/contributors has one of these to test with. I'd be interested to hear more about the c860 as I have a c750.

Have you performed any speed comparisons?


Si
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SL5500 OZ3.5.4 (Opie)
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Vit!

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« Reply #5 on: March 03, 2005, 04:50:18 am »
Yes, you are right. For example in h3900.conf (I'm not Zaurus owner, I use Linux on Ipaq H3970):

# not using tune-xscale so as to retain backwards compatibility
include conf/machine/tune-strongarm.conf

so here I changed to tune-xscale.conf

I haven't performed any comparisons yet. I simply was very surprised when saw that optimizations are specially disabled and re-enabled them. I'll look into more details about new optimization flags introduced in new gcc versions.
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Vit!

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« Reply #6 on: March 03, 2005, 04:58:59 am »
also, gcc accepts -mtune= -mcpu= -march= with "iwmmxt" parameter (all gives same internal results)
so you can easily turn on Wireless MMX optimizations by specifiing these parameters in tune-blabla.conf
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lardman

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Gcc 3.4
« Reply #7 on: March 03, 2005, 06:47:11 am »
Thanks for that, I'll take a look.

I suppose the backwards conpatibility thing is done simply to remove the need for 3 (?) different feeds for the different processor types.


Si
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SL5500 OZ3.5.4 (Opie)
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Vit!

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« Reply #8 on: March 03, 2005, 07:01:57 am »
maybe.. but imho we must use all advangates of having source codes and one of them is to make highly optimized builds..
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lardman

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Gcc 3.4
« Reply #9 on: March 03, 2005, 09:12:13 am »
I quite agree.

Next time I'm on IRC I'll ask whether/when the plan is to move over to processor specific builds.


Si
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SL5500 OZ3.5.4 (Opie)
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Mickeyl

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Gcc 3.4
« Reply #10 on: March 03, 2005, 09:52:36 am »
As you can see in conf/machine/tune-strongarm.conf, we already tune everything for xscale (-mtune=xscale), but we don't allow the gcc to use the few arm5 specific constructs, which would have a bad impact on arm4 performance.

Our gcc experts have found that using march=armv5te wouldn't give much of a benefit - especially not compared to the need of having to build more feeds. So unless someone comes up with some packages / benchmarks which proof something different, it'll stay that way.
« Last Edit: March 03, 2005, 09:53:24 am by Mickeyl »
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