[x265] ASM crash in r6706

[Steve Borho]

On Wed, Apr 16, 2014 at 12:28 PM, Jason Garrett-Glaser <jason at x264.com> wrote:
>> x264 manually aligns their stack (see x264_stack_align())
>
> Note that this is because we don't require gcc's
> force_arg_align_stack_pointer intrinsic (added in 4.2). The stack
> isn't guaranteed to be aligned on thread entry or library entry on
> x86_32, so even if gcc is told to keep stack alignment, it can only
> keep stack alignment relative to the entry point, hence we have to
> manually align the entry point.
>
> Note that this is important even if you don't use x264asm, because
> using alignment intrinsics on stack-allocated arrays does not work if
> the entry point hasn't been aligned.
>
> x264asm's stack alignment /should/ align relative to the values being
> pushed onto the stack -- if it isn't, something's probably very wrong.
> I'm going to assume it's not broken, since it's used for a good bit of
> ffmpeg and x264 code, but if it is broken, poke the x264 mailing list
> with assembly code and the (wrong) assembled output.

Would it be appropriate to simply add "-mpreferred-stack-boundary=4"
for x86_32 compiles if GCC is new enough to support it, or set
HAVE_ALIGNED_STACK=0 if it is too old?

-- 
Steve Borho