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what's wrong with -mcpu=arm946e-s on gcc4

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Offline matc

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what's wrong with -mcpu=arm946e-s on gcc4
« on: 07 / July / 2011, 16:09:40 »
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Hi,

the makefile say

Code: [Select]
        # TODO should be -mcpu, but breaks things ATM
        CFLAGS+=-mtune=arm946e-s

But after looking on the forum I am not able to found what's the problem.

Trying it with 4.5.2 seems to works.

What's the problem with this options ?

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Offline reyalp

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #1 on: 07 / July / 2011, 21:41:16 »
I think we had configuration issues with GCC/toolchain which prevented it from building correctly, see  http://chdk.setepontos.com/index.php?topic=2500.msg24326#msg24326

Don't forget what the H stands for.

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Offline matc

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #2 on: 08 / July / 2011, 16:25:01 »
I think we had configuration issues with GCC/toolchain which prevented it from building correctly, see  http://chdk.setepontos.com/index.php?topic=2500.msg24326#msg24326

Thanks for the link. But what's strange is that the fix shouldn't be hard. It was proposed 2 years ago.
Seems nobody care about this ?

That weird because -mcpu=arm946e-s should improve performance.

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Offline Lebeau

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #3 on: 08 / July / 2011, 21:23:27 »
Matc ! That's a pertinent and interesting question !

I made some searches because I am interested, but not enough experienced in gcc, arm and all. Here are my modest found.
http://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html
http://gcc.gnu.org/wiki/Software_floating_point
http://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html
http://www.jhauser.us/arithmetic/SoftFloat.html
http://lists.busybox.net/pipermail/buildroot/2011-May/043192.html

I donT know if they are pertinent but, I am motivated :)


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Offline reyalp

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #4 on: 09 / July / 2011, 00:21:55 »
Thanks for the link. But what's strange is that the fix shouldn't be hard. It was proposed 2 years ago.
Seems nobody care about this ?
The existing setup works. I have better things to do than spend days playing lotto with gcc and binutils configurations for some marginal performance gain. It would be nice but it's not a high priority.

Maybe I'm missing it, but I don't see a clear solution in that thread.
Don't forget what the H stands for.

Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #5 on: 09 / July / 2011, 02:11:55 »
The existing setup works. I have better things to do than spend days playing lotto with gcc and binutils configurations for some marginal performance gain. It would be nice but it's not a high priority.

Maybe I'm missing it, but I don't see a clear solution in that thread.
Yup - if its not broken - don't fix it.  We have a lot of other things to worry about before this.


Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #6 on: 09 / July / 2011, 03:57:06 »
Yup - if its not broken - don't fix it.  We have a lot of other things to worry about before this.
It should give a decent memory saving, which is something we can definitely use.  I'm not against someone working on this, it's just not near the top of my personal list ;)
Don't forget what the H stands for.

Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #7 on: 09 / July / 2011, 05:29:45 »

It should give a decent memory saving, which is something we can definitely use. 

I thought extended memory was the solution for that ?


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Offline reyalp

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Re: what's wrong with -mcpu=arm946e-s on gcc4
« Reply #8 on: 09 / July / 2011, 15:45:53 »
I thought extended memory was the solution for that ?
Maybe. The current implementation is very hacky, not clear it will work everywhere. Plus, no matter where you put it, it's taking away memory from the camera.
Don't forget what the H stands for.

 

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