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x86inc: Preserve arguments when allocating stack space 

When allocating stack space with a larger alignment than the known stack
alignment a temporary register is used for storing the stack pointer.
Ensure that this isn't one of the registers used for passing arguments.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
Henrik Gramner 2016-01-21 00:05:15 +01:00 committed by Anton Khirnov
parent 715eb7ca24
commit 91ed050f42
1 changed files with 5 additions and 2 deletions
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7
libavutil/x86/x86inc.asm
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@ -386,8 +386,11 @@ DECLARE_REG_TMP_SIZE 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14
%if %1 != 0 && required_stack_alignment > STACK_ALIGNMENT
%if %1 > 0
%assign regs_used (regs_used + 1)
%elif ARCH_X86_64 && regs_used == num_args && num_args <= 4 + UNIX64 * 2
%warning "Stack pointer will overwrite register argument"
%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)
; since it's used as a hidden argument in vararg functions to specify the number of vector registers used.
%assign regs_used 5 + UNIX64 * 3
%endif
%endif
%endif