[U-Boot] [PATCH] ARM: compiler options cleanup - improve tool chain support

[Gaye Abdoulaye Walsimou <walsimou@walsimou.com>]

Wolfgang Denk wrote:
> For some time there have been repeated reports about build problems
> with some ARM (cross) tool chains.  Especially issues about
> (in)compatibility with the tool chain provided runtime support
> library libgcc.a caused to add and support a private implementation
> of such runtime support code in U-Boot.  A closer look at the code
> indicated that some of these issues are actually home-made.  This
> patch attempts to clean up some of the most obvious problems and make
> building of U-Boot with different tool chains easier:
>
> - Even though all ARM systems basicy used the same compiler options
>   to select a specific ABI from the tool chain, the code for this was
>   distributed over all cpu/*/config.mk files.  We move this one level
>   up into lib_arm/config.mk instead.
>
> - So far, we only checked if "-mapcs-32" was supported by the tool
>   chain; if yes, this was used, if not, "-mabi=apcs-gnu" was
>   selected, no matter if the tool chain actually understood this
>   option.  There was no support for EABI conformant tool chains.
>   This patch implements the following logic:
>
>   1) If the tool chain supports
> 	"-mabi=aapcs-linux -mno-thumb-interwork"
>      we use these options (EABI conformant tool chain).
>   2) Otherwise, we check first if
> 	"-mapcs-32"
>      is supported, and then check for
> 	"-mabi=apcs-gnu"
>      If one test succeeds, we use the first found option.
>   3) In case 2), we also test if "-mno-thumb-interwork", and use
>      this if the test succeeds. [For "-mabi=aapcs-linux" we set
>      "-mno-thumb-interwork" mandatorily.]
>
>   This way we use a similar logic for the compile options as the
>   Linux kenrel does.
>
> - Some EABI conformant tool chains cause external references to
>   utility functions like raise(); such functions are provided in the
>   new file lib_arm/eabi_compat.c
>
>   Note that lib_arm/config.mk gets parsed several times, so we must
>   make sure to add eabi_compat.o only once to the linker list.
>
> Signed-off-by: Wolfgang Denk <wd@denx.de>
> Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> Cc: Dirk Behme <dirk.behme@googlemail.com>
> Cc: Magnus Lilja <lilja.magnus@gmail.com>
> Cc: Tom Rix <Tom.Rix@windriver.com>
> Cc: Prafulla Wadaskar <prafulla@marvell.com>
> ---
>
> I have run a full "MAKEALL arm" for ELDK releases 3.1 (gcc 3.3.3),
> 3.1.1 (gcc 3.3.3), 4.1 (gcc 4.0.0) and 4.2 (gcc 4.2.2, both as "arm"
> [softfloat] and "armVFP" [VFP hardfloat]), and all of these both with
> USE_PRIVATE_LIBGCC=yes (i. e. using U-Boot internal libgcc
> replacement code) and without (i. e. using the tool chain provided
> standard libgcc instead).
>
> The ELDK fails to build the big-endian IXP boards, but this is a
> restriction of the ELDK, not a new issue introcued by this patch.
> Except of this, all build were succesful.
>
> Note 1: Please note that older tool chains (based on binutils versions
> older than 2.16) will have problems with the SORT_BY_ALIGNMENT()
> and SORT_BY_NAME() functions introduced to the linker scripts with
> commit f62fb99941c6. I'll soon submit a patch to fix this issue. Final
> tests are running right now.
>
> Note 2: Even though this is a bigger change, I consider it a bug fix
> and therefor tend to have it included into the upcoming release. Of
> course this requires sufficient test coverage and feedback. Please
> help!!
>
> Note 3: Most ARM systems also define this:
> PLATFORM_RELFLAGS +=$(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,))
> I guess this can be unified and moved to lib_arm/config.mk, too, but I
> would like to handle this in a separate, later patch. This makes
> testing (and bisecting) easier, and it is a non-critical problem.
>
>  
Tested-by: Gaye Abdoulaye Walsimou <walsimou@walsimou.com>