[PATCH] Get rid of the ARM variant choice in the menuconfig

Yann E. MORIN yann.morin.1998 at anciens.enib.fr
Wed Apr 8 21:11:08 UTC 2009


Mike,
All,

On Wednesday 08 April 2009 01:45:57 Mike Frysinger wrote:
> iirc, it is possible to build a toolchain that supports both big and little 
> endian simultaneously.  i believe the code sorcery guys do this.  i would 
> leave this option in for now until we can completely remove it from the build 
> system ...

On one hand, either we fully trust the compiler, or we do not trust it at
all. 

On the other hand, there are processors that can work in both endianness,
even on the same board (eg. the Linksys NSLU2 is such a board that can be
set to either endianness by software). Having a single, bi-endian compiler
thus makes sense.

I admit that keeping endianness as being selectable in menuconfig is not a
bad idea per se, but we must be carefull at where we put the border line.

As this patch is ARM-only, two questions about the ARM cleanup:

First, I left the "Use BX" knob in place, because I do not fully understand
all the implications it has. BX is an ARM insn that allows Branching and
eXchange, that is conditionnally switch from ARM to Thumb (or the other way
around) and branch to the specified offset or address. Can't we detect at
compile time if both ARM and Thumb are available (*), and use BX if so, or
just use MOV if not?

Second, gcc defines the macro __ARM_EABI__ iff compiling for EABI. The only
place where this is used is in libc/sysdeps/linux/arm/Makefile.arch
Maybe we should have the mackefile check by itself. What do you think?

I'm preparing a new patchset I'll send a bit later.

Regards,
Yann E. MORIN.

(*) Check for a combination of the macros __THUMB_INTERWORK__ , __arm__ ,
    __thumb__ and __thumb2__ .

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +0/33 662376056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| --==< ^_^ >==-- `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
`------------------------------^-------^------------------^--------------------'



More information about the uClibc mailing list