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| author | Ovidiu Panait <ovpanait@gmail.com> | 2022-09-13 21:31:26 +0300 |
|---|---|---|
| committer | Tom Rini <trini@konsulko.com> | 2022-10-07 04:05:17 +0300 |
| commit | 181cbd4017305142eb26df0aa065b8bb95921f83 (patch) | |
| tree | 33a6ca7b87da1f7ac5c39e4166bc1e7d4611445b /doc/develop | |
| parent | a70c75cabae12a81d512b240d60413df294246eb (diff) | |
| download | u-boot-181cbd4017305142eb26df0aa065b8bb95921f83.tar.xz | |
common/board_f: remove XTRN_DECLARE_GLOBAL_DATA_PTR dead code
The XTRN_DECLARE_GLOBAL_DATA_PTR declarations in ppc code are permanently
commented out, so there are no users for this macro:
#if 1
#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r2")
#else /* We could use plain global data, but the resulting code is bigger */
#define XTRN_DECLARE_GLOBAL_DATA_PTR extern
#define DECLARE_GLOBAL_DATA_PTR XTRN_DECLARE_GLOBAL_DATA_PTR \
gd_t *gd
#endif
Remove all references to this macro, but add a documentation note regarding
the possibility of using plain global data for the GD pointer.
Signed-off-by: Ovidiu Panait <ovpanait@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Diffstat (limited to 'doc/develop')
| -rw-r--r-- | doc/develop/global_data.rst | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/doc/develop/global_data.rst b/doc/develop/global_data.rst index 2ac893de49..d143f27eed 100644 --- a/doc/develop/global_data.rst +++ b/doc/develop/global_data.rst @@ -36,6 +36,11 @@ On most architectures the global data pointer is stored in a register. The sandbox, x86_64, and Xtensa are notable exceptions. +Current implementation uses a register for the GD pointer because this results +in smaller code. However, using plain global data for the GD pointer would be +possible too (and simpler, as it does not require the reservation of a specific +register for it), but the resulting code is bigger. + Clang for ARM does not support assigning a global register. When using Clang gd is defined as an inline function using assembly code. This adds a few bytes to the code size. |