[Buildroot] [PATCH v2] gcc: Build libgcc with BR2_TARGET_OPTIMIZATION flags
Alexey Brodkin
Alexey.Brodkin at synopsys.com
Wed Jan 31 10:33:09 UTC 2018
Hello,
On Thu, 2018-01-18 at 19:56 +0300, Alexey Brodkin wrote:
> libgcc gets built very early and what's more it is built not by
> "normal" cross gcc later found in "output/host/usr/bin" but by
> gcc's own bare-minimal version: output/build/host-gcc-xxx/build/./gcc/xgcc.
>
> Which in the end means BR2_TARGET_OPTIMIZATION is not applied to
> cross-compiler via toolchain wrapper.
>
> But given libgcc is an essential target executable we may want it to
> be built with the same "optimization" flags as all other libs and binaries.
>
> Technically this is doable with TARGET_ABI which is added to TARGET_CFLAGS
> but user cannot [or at least is not supposed to] modify TARGET_ABI as it
> is used for tunign for a particular platform.
>
> But still there might be a need to compile everything for tha target with
> a special compiler option and this change allows for that.
>
> For eaxmple ARC still doesn't have properly working link-time relaxation
> which requires us to compile everything properly from the beginning, otherwise
> we may face a situation when huge apps/libs like Qt5WebKit might fail to pass
> the final linkage because some symbols might be too far from each other as
> by default gcc will try to use shorter relocations. Solution is as simple as
> rebuild of everything with "-mlong-calls" so that all the symbols are
> compiled with full 32-bit relocations. And now only libgcc causes problems
> because it contains quite a few symbols used widely by other binaries like
> millicode, some math stuff etc.
>
> Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
> Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
> ---
>
> Changes v1 -> v2:
> * Strip quotes from BR2_TARGET_OPTIMIZATION
> Didn't notice a problem with 1 option in BR2_TARGET_OPTIMIZATION
> but if another one is added libgcc configuration fails because:
> CFLAGS_FOR_TARGET="-xxx "-yyy -zzz"" and thus
> /bin/sh: -zzz: command not found
Any comments on this one? If not please consider applying.
-Alexey
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