[Buildroot] [PATCHv2 1/2] toolchain: add coldfire support

[Waldemar Brodkorb]

Hi Thomas,
Thomas Petazzoni wrote,

> Hello,
> 
> On Fri, 29 Apr 2016 19:51:23 +0200, Waldemar Brodkorb wrote:
> 
> > +config BR2_GCC_TARGET_ARCH
> > +	default "m68k"		if BR2_m68k_m68k
> > +	default "cf"		if BR2_m68k_cf
> 
> This change looks wrong. I've started testing m68k with external
> toolchains, and m68k or cf are not valid -march= values. From the gcc
> documentation:
> 
> '-march=ARCH'
>      Generate code for a specific M680x0 or ColdFire instruction set
>      architecture.  Permissible values of ARCH for M680x0 architectures
>      are: '68000', '68010', '68020', '68030', '68040', '68060' and
>      'cpu32'.  ColdFire architectures are selected according to
>      Freescale's ISA classification and the permissible values are:
>      'isaa', 'isaaplus', 'isab' and 'isac'.
> 
>      GCC defines a macro '__mcfARCH__' whenever it is generating code
>      for a ColdFire target.  The ARCH in this macro is one of the
>      '-march' arguments given above.
> 
>      When used together, '-march' and '-mtune' select code that runs on
>      a family of similar processors but that is optimized for a
>      particular microarchitecture.
> 
> So indeed, gcc complains with:
> 
> m68k-linux-gcc.br_real: error: unrecognized argument in option '-march=m68k'
> m68k-linux-gcc.br_real: note: valid arguments to '-march=' are: 68000 68010 68020 68030 68040 68060 cpu32 isaa isaaplus isab isac
> m68k-linux-gcc.br_real: error: unrecognized argument in option '-march=m68k'
> m68k-linux-gcc.br_real: note: valid arguments to '-march=' are: 68000 68010 68020 68030 68040 68060 cpu32 isaa isaaplus isab isac
> m68k-linux-gcc.br_real: error: unrecognized argument in option '-march=m68k'
> m68k-linux-gcc.br_real: note: valid arguments to '-march=' are: 68000 68010 68020 68030 68040 68060 cpu32 isaa isaaplus isab isac
> 
> You can reproduce with:
> 
> BR2_m68k=y
> BR2_TOOLCHAIN_EXTERNAL=y
> BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
> BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-m68k-68040-full-2016.05-2-g5dabb45.tar.bz2"
> BR2_TOOLCHAIN_EXTERNAL_GCC_4_9=y
> BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_5=y
> BR2_TOOLCHAIN_EXTERNAL_LOCALE=y
> # BR2_TOOLCHAIN_EXTERNAL_HAS_THREADS_DEBUG is not set
> # BR2_TOOLCHAIN_EXTERNAL_HAS_THREADS_NPTL is not set
> BR2_TOOLCHAIN_EXTERNAL_INET_RPC=y
> BR2_TOOLCHAIN_EXTERNAL_CXX=y
> BR2_INIT_NONE=y
> BR2_SYSTEM_BIN_SH_NONE=y
> # BR2_PACKAGE_BUSYBOX is not set
> # BR2_TARGET_ROOTFS_TAR is not set
> 
> Where did this change came from? Do you really need those values passed
> as --with-arch when configuring gcc?

The change was added when we enabled coldfire support.
Unfortunately at this time, I didn't know the complete mechanism inside
buildroot. With the blackfin toolchain patches I learned the
external/internal stuff and how the wrapper is used.

--with-arch for cf/m68k is again a special thing in GCC to decide
which kind of multilibs for libgcc are build, either the m68k
variants or the coldfire variants. But the -march options are
different, so that BR2_GCC_TARGET_ARCH can't be used for the
wrapper.

But we have luck here, we can just remove the BR2_GCC_TARGET_ARCH
entries.

best regards
 Waldemar