diff options
| author | Henrik Gramner <henrik@gramner.com> | 2016-12-25 20:24:59 +0100 |
|---|---|---|
| committer | Anton Khirnov <anton@khirnov.net> | 2017-01-09 13:21:12 +0100 |
| commit | 3cba1ad76d362c994fa98fb686e04e20826fb579 (patch) | |
| tree | e232a67af6e1b8dd2be2ff6bdff89cd8d066dad1 | |
| parent | e199a8099411d0992c3ed278287a81f1d791199c (diff) | |
x86inc: Avoid using eax/rax for storing the stack pointer
When allocating stack space with an alignment requirement that is larger
than the current stack alignment we need to store a copy of the original
stack pointer in order to be able to restore it later.
If we chose to use another register for this purpose we should not pick
eax/rax since it can be overwritten as a return value.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
| -rw-r--r-- | libavutil/x86/x86inc.asm | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/libavutil/x86/x86inc.asm b/libavutil/x86/x86inc.asm index dca1f78409..7941af304a 100644 --- a/libavutil/x86/x86inc.asm +++ b/libavutil/x86/x86inc.asm @@ -385,7 +385,14 @@ DECLARE_REG_TMP_SIZE 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14 %ifnum %1 %if %1 != 0 && required_stack_alignment > STACK_ALIGNMENT %if %1 > 0 + ; Reserve an additional register for storing the original stack pointer, but avoid using + ; eax/rax for this purpose since it can potentially get overwritten as a return value. %assign regs_used (regs_used + 1) + %if ARCH_X86_64 && regs_used == 7 + %assign regs_used 8 + %elif ARCH_X86_64 == 0 && regs_used == 1 + %assign regs_used 2 + %endif %endif %if ARCH_X86_64 && regs_used < 5 + UNIX64 * 3 ; Ensure that we don't clobber any registers containing arguments. For UNIX64 we also preserve r6 (rax) |