[FFmpeg-devel] [PATCH] Fix ff_imdct_calc_sse() on gcc-4.6.

[Måns Rullgård]

Alex Converse <alex.converse at gmail.com> writes:

> 2011/1/30 M?ns Rullg?rd <mans at mansr.com>:
>> Alex Converse <alex.converse at gmail.com> writes:
>>
>>> On Sun, Jan 30, 2011 at 2:13 AM, Reimar D?ffinger
>>> <Reimar.Doeffinger at gmx.de> wrote:
>>>> On Sun, Jan 30, 2011 at 01:22:05AM -0800, Alex Converse wrote:
>>>>> On Sun, Jan 30, 2011 at 1:08 AM, Alex Converse <alex.converse at gmail.com> wrote:
>>>>> >
>>>>> > Gcc 4.6 only preserves the first value when using a vector with an "m"
>>>>> > constraint.
>>>>> > ---
>>>>> > ?libavcodec/x86/fft_sse.c | ? ?4 ++--
>>>>> > ?1 files changed, 2 insertions(+), 2 deletions(-)
>>>>> >
>>>>> >
>>>>>
>>>>> oops this generates an extra indirection. Those of you who like to
>>>>> defend inline asm, please step up and make some suggestions.
>>>>
>>>> Use what would be your _only_ option (conceptually, not in implementation
>>>> of course) if you didn't use inline asm:
>>>> MANGLE and change DECLARE_ALIGNED to DECLARE_ASM_CONST
>>>> There's also the option of a gcc bug report, I have some doubts that is
>>>> a valid optimization (though there are constraints to make gcc load
>>>> directly into a xmm register, but both that and the current code have
>>>> needlessly unpredictable performance).
>>
>> The optimisation is valid, the constraint is wrong.
>>
>>> With MANGLE this time.
>>>
>>> From 51a872ff818bbb0071ab1649d104afcea48546c9 Mon Sep 17 00:00:00 2001
>>> From: Alex Converse <alex.converse at gmail.com>
>>> Date: Sun, 30 Jan 2011 01:04:41 -0800
>>> Subject: [PATCH 1/2] Fix ff_imdct_calc_sse() on gcc-4.6.
>>> MIME-Version: 1.0
>>> Content-Type: multipart/mixed; boundary="------------1"
>>>
>>> This is a multi-part message in MIME format.
>>> --------------1
>>> Content-Type: text/plain; charset=UTF-8; format=fixed
>>> Content-Transfer-Encoding: 8bit
>>
>> Please try to avoid sending attached patches in this format.
>
> What's wrong with this format and how do I make my tools avoid it?

All the multipart mime stuff is a little distracting when sent as an
attachment (vs with git send-email).  You must have set some flag to
make format-patch produce this style.  It's no big deal though.

-- 
M?ns Rullg?rd
mans at mansr.com