Configuration advice, specifically for arm-cortex-a8

Bryan Hundven bryanhundven@gmail.com
Mon Feb 2 23:49:00 GMT 2015


Erik,

On Mon, Feb 2, 2015 at 2:48 PM, Erik Leunissen <elns@xs4all.nl> wrote:
> On 02/02/15 23:02, Erik Leunissen wrote:
>
>> ...
>> Whatever choice I make: the resulting toolchains fail if I invoke gcc
>> with the option:
>>
>>      -mfloat-abi=hard
>>
>
> Uhmmm, the error message is:
>
> /opt/toolchains/arm-none-linux-gnueabi/arm-none-linux-gnueabi/sysroot/usr/include/gnu/stubs.h:10:29:
> fatal error: gnu/stubs-hard.h: No such file or directory
>  # include <gnu/stubs-hard.h>
>                              ^
>
> So, where I suspected an intrinsic incompatibility amongst compiler options,
> it's merely a case of a missing file.
>
> However, I still don't understand why that file is not needed when using
> only -mfpu=neon

I'm guessing you are using the 1.20.0 release and not using
crosstool-NG from git?

We're getting close to doing a 1.20.1 release, and I know some
hard-float items have been fixed since 1.20.0.

     git clone https://github.com/crosstool-ng/crosstool-ng
     ./bootstrap
     ./configure ...--options...

Cheers,

-Bryan

>
> Greetings,
>
> Erik.
>
>
>
>>   However, the option
>>
>>      -mfpu=neon
>>
>> doesn't raise any errors.
>>
>> That surprises me. Doesn't "NEON floating-point accelerator" imply
>> hardware floating point? See also:
>>
>>
>>
>> http://www.eliteraspberries.com/blog/2013/09/cflags-for-numerical-computing-on-the-beaglebone-black.html)
>>
>>
>> What am I missing?
>>
>>
>> Case 2: the cpu
>> ===============
>> This is a arm-cortex-a8, specifically Sitara AM3358 ARM Cortex-A8.
>> What are the pro's and con's of configuring this in ct-ng (with the
>> option category "Target optimisations") and leaving it as configurable
>> at the gcc command line, using:
>>
>>      $prefix-gcc -march=armv7-a -mcpu=cortex-a8 -mtune=cortex-a8
>>
>>
>>
>> Thanks for sharing any insights,
>>
>> Erik Leunissen
>> --
>>
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>
>
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