Hi,
On Fri, Dec 7, 2012 at 2:01 PM, Måns Rullgård <m...@mansr.com> wrote:
> "Ronald S. Bultje" <rsbul...@gmail.com> writes:
>> On Fri, Dec 7, 2012 at 1:01 PM, Måns Rullgård <m...@mansr.com> wrote:
>>> "Ronald S. Bultje" <rsbul...@gmail.com> writes:
>>>
>>>> + %if mmsize <= 16 && HAVE_ALIGNED_STACK
>>>
>>> How much overhead would it be to drop HAVE_ALIGNED_STACK entirely?
>>
>> Well, for now, we still have a ton of functions that don't use the
>> cglobal-method of allocating stack. I only ported h264/vp8 loopfilter,
>> nothing else.
>>
>> But anyway, more generally, it's 4-5 instructions per function. For
>> typical functions with an inner loop, that's negligible, but for a
>> select small set of functions, it may be significant.
>
> The remaining functions are ff_h264_idct8_add(4)_10_{sse2,avx},
> ff_hadamard8_diff(16)_{sse2,ssse3}, and something in swscale.
lavr also.
> Besides, does anyone still use 32-bit where performance is that
> critical?
This is used for YMM (e.g. avx float) stack alignment (to 32-byte)
also, so it will affect 64-bit also. My personal point of view is that
the code to take advantage of an actual feature of the compiler/system
(alignment) is there. I don't see why we'd remove it.
Ronald
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