Re: [RFC][GCC, Multilib]Make GCC more easier for user to select and build extra libraries for ARM targets.

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Sun, 11 Sep 2011, Terry Guo wrote:

> This patch intends to implement a convenient interface for user to customize
> the final Multilibs according to their real requirements. There is no
> intention to override the default Multilib set, instead it only build
> "extra" libraries besides them. Specifically the extra Multilibs can be
> selected by user through a new configure option
> "--with-extra-multilibs=A-COMMA-SEPARATED-TARGET-LIST". For example if user
> want to build extra library for cortex-m0, cortex-m3 and cortex-m4, the
> configure option would be
> "--with-extra-multilibs=armv6s-m,armv7-m,armv7e-m".

This seems very similar to the --with-multilib-list option for SH and 
x86_64.  I think you should use the same name and share the same 
implementation as far as possible - certainly, you need to explain how 
what you have done compares to that option and justify differences.  If 
the difference is whether the multilibs add to or replace the default 
list, maybe allow "default," to appear in the argument to 
--with-multilib-list to indicate that the default list is added to rather 
than replaced.

> +@item --with-extra-multilibs=@var{list} @itemx 
> +--without-extra-multilibs Specify what extra multilibs to build besides 

You have @itemx on the wrong line here.

> Index: gcc/config/arm/t-armv7e-m
> ===================================================================
> --- gcc/config/arm/t-armv7e-m	(revision 0)
> +++ gcc/config/arm/t-armv7e-m	(revision 0)
> @@ -0,0 +1,16 @@
> +#Build below library for ARM armv7e-m architecture.
> +#  armv7e-m/     -mthumb -march=armv7e-m
> +
> +MULTILIB_OPTIONS      += march=armv7e-m
> +
> +MULTILIB_DIRNAMES     += armv7e-m
> +
> +MULTILIB_EXCEPTIONS   += march=armv7e-m*
> +MULTILIB_EXCEPTIONS   += marm*/march=armv7e-m*
> +MULTILIB_EXCEPTIONS   += mfloat-abi=hard/march=armv7e-m*
> +MULTILIB_EXCEPTIONS   += mthumb/mfloat-abi=hard/march=armv7e-m*
> +MULTILIB_EXCEPTIONS   += m*/march=armv7e-m/march*
> +
> +MULTILIB_MATCHES      += march?armv7e-m=mcpu?cortex-m4
> +
> +MULTILIB_OSDIRNAMES   += mthumb/march.armv7e-m=!armv7e-m

I don't think having such massive manually maintained files for each 
architecture is sustainable.  Note that when the SH configure option was 
enhanced

2009-04-17  Andrew Stubbs  <ams@codesourcery.com>

it *removed* a load of such files.

m68k/t-mlibs uses awk to process .def files to work out appropriate 
multilib settings in different cases.  That seems a much more sustainable 
way of producing these settings than entering them all manually.

-- 
Joseph S. Myers
joseph@codesourcery.com