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| author | Marek Behún <marek.behun@nic.cz> | 2021-05-20 13:24:10 +0200 |
|---|---|---|
| committer | Tom Rini <trini@konsulko.com> | 2021-05-24 14:21:30 -0400 |
| commit | 86c5e21013d5efd895de9905a19893b4403e4642 (patch) | |
| tree | 826e54e219b261f6d282c5f42d126276bc5af191 /arch/arm/include | |
| parent | 82b63e95410ebca0bbfd343ce163299a44a2d932 (diff) | |
| download | u-boot-86c5e21013d5efd895de9905a19893b4403e4642.zip u-boot-86c5e21013d5efd895de9905a19893b4403e4642.tar.gz u-boot-86c5e21013d5efd895de9905a19893b4403e4642.tar.bz2 | |
ARM: make gd a function call for LTO and set via set_gd()
On ARM, the gd pointer is stored in registers r9 / x18. For this the
-ffixed-r9 / -ffixed-x18 flag is used when compiling, but using global
register variables causes errors when building with LTO, and these
errors are very difficult to overcome.
Richard Biener says [1]:
Note that global register vars shouldn't be used with LTO and if they
are restricted to just a few compilation units the recommended fix is
to build those CUs without -flto.
We cannot do this for U-Boot since all CUs use -ffixed-reg flag.
It seems that with LTO we could in fact store the gd pointer differently
and gain performance or size benefit by allowing the compiler to use
r9 / x18. But this would need more work.
So for now, when building with LTO, go the clang way, and instead of
declaring gd a global register variable, we make it a function call via
macro.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68384
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'arch/arm/include')
| -rw-r--r-- | arch/arm/include/asm/global_data.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h index bb82efa..2aff1c4 100644 --- a/arch/arm/include/asm/global_data.h +++ b/arch/arm/include/asm/global_data.h @@ -91,7 +91,7 @@ struct arch_global_data { #include <asm-generic/global_data.h> -#ifdef __clang__ +#if defined(__clang__) || defined(CONFIG_LTO) #define DECLARE_GLOBAL_DATA_PTR #define gd get_gd() |