Re: scripts: add support for overriding the arch name in the tuple

["Yann E. MORIN" <yann dot morin dot 1998 at free dot fr>]

Willy, All,

On Sunday 20 January 2013 Willy Tarreau wrote:
> it sometimes happens that I need to build toolchains for several variants
> of a CPU and I want to have the variant name in the arch tuple. In fact,
> this is very similar to what is done with i386/i486/i586/i686, all of them
> being variants of the x86 arch family.
> 
> On arm, we commonly see armv5/armv6/armv7 and with v7 there are two common
> cpus which are cortex a8 and a9.
> 
> So I'm used to build my toolchains with a prefix which is 'armv5te',
> 'armv7a8', 'armv7a9' etc...
> 
> For this I wrote the small patch below for ct-ng-1.15.3, which still works
> with 1.17.0.
> 
> On one of my machines, the toolchain directory looks like this, which is
> quite convenient to use :
> 
>   arm-gcc43_glibc29-linux-gnueabi/
>   arm-gcc44_glibc29-linux-gnueabi/
>   arm-gcc45_glibc29-linux-gnueabi/
>   armv7a8-gcc43_glibc29-linux-gnueabi/
>   armv7a9-gcc44_glibc29-linux-gnueabi/
>   armv7a9-gcc47_glibc29-linux-gnueabi/
>   armv7a9-gcc47_glibc29-linux-gnueabihf/

How do you managfed to have a '*-gnueabihf' with crosstool-NG?
Last I tested, gcc broke because it did not recognise it as an EABI
variant, and would not include the EABI file in gcc/config/arm/ .

Even with a bit of patching, I ended up in a few hiccups here and there,
so that's why ct-ng does not set the tuple to '*-gnueabihf' for now for
ARM hard-float ABI.

>   i386-gcc34_glibc23-linux-gnu/
>   x86_64-gcc34_glibc23-linux-gnu/
> 
> Hoping someone finds the patch useful.

A few comments:
  - missing SoB line
  - provide a more terse commit-log, eg something like:
    ---8<---
    arch: provide a arch-override for the tuple

    For some architectures, it is legit to have an alternate value in the
    'architecture' part of the tuple. For example:
        armv5te-*
        armv7a8-*

    Besides, some packages expect the tuple to reflect the arch variant
    (eg. openMPI) to detect the variant's capabilities (eg. atomic
    primitives).

    We already have this for x86 (i[3456]86-*), but it is not possible
    for other archs.

    This patch provides an overide mechanism

    Signed-off-by: You you@there
    ---8<---
    
> diff -urN ./config/target.in ./config/target.in
> --- ./config/target.in.orig	2012-07-17 22:39:55.000000000 +0200
> +++ ./config/target.in	2012-07-27 12:02:08.682588639 +0200
> @@ -5,6 +5,17 @@
>  config ARCH
>      string
>  
> +config ARCH_OVERRIDE
> +    string
> +    prompt "Arch name to use in the resulting tuple instead of ${CT_ARCH}"
> +    help
> +      Some architectures have multiple variants and being able to specify
> +      the variant instead of the arch is quite convenient. This is commonly
> +      seen for instance when "armv5tel-" is used as a prefix instead of the
> +      more generic "arm-", or with "alphaev6-" instead of "alpha-".
> +
> +      If you're not sure about what this is, leave it blank.
> +

I think we should not allow the user to completely overide the arch-part.
We should just allow for appending to the arch-part. This would be added
to the default tuple, and would not create symlinks as the two other
options currently do, so it would be possible to install more than one
toolchain in the same place, as the default tuples would all be different
(maybe that's what I did not completely explain during our private
exchange).

Thus, CT_TARGET_ARCH_SUFFIX="v5te" would give a tuple starting with
"armv5te-".

IMHO, giving the user the ability to completely overide the arch-part is
opening the door to complete mayhem. I'm a bit uneasy with that.

[--SNIP--]
> diff -urN ./scripts/functions ./scripts/functions
> --- ./scripts/functions.orig	2012-07-17 22:39:55.000000000 +0200
> +++ ./scripts/functions	2012-07-27 11:57:19.903088370 +0200
> @@ -982,7 +982,7 @@
>      esac
>  
>      # Build the default architecture tuple part
> -    CT_TARGET_ARCH="${CT_ARCH}"
> +    CT_TARGET_ARCH="${CT_ARCH_OVERRIDE:-${CT_ARCH}}"

Here, we'd have:
    CT_TARGET_ARCH="${CT_ARCH}${CT_TARGET_ARCH_SUFFIX}"

And similar for the architectures. Which would ensure the default tuple
will include this arch-part suffix.

Regards,
Yann E. MORIN.

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