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doc: global data pointer on x86, x86_64 

On x86 the global data pointer is stored in register fs.
On x86_64 no register is used for the global data pointer.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Heinrich Schuchardt 2020-10-15 07:40:57 +02:00
parent c206702155
commit b2107a4b77
1 changed files with 3 additions and 1 deletions
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doc/develop/global_data.rst
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@ -33,8 +33,10 @@ On most architectures the global data pointer is stored in a register.
+------------+----------+
| SuperH | r13 |
+------------+----------+
| x86 32bit | fs |
+------------+----------+
The sandbox, x86, and Xtensa are notable exceptions.
The sandbox, x86_64, and Xtensa are notable exceptions.
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