[FFmpeg-devel] [PATCH] WMA: use type punning and unroll loops in decode_exp_vlc()

[Måns Rullgård]

Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:

> On Tue, Sep 29, 2009 at 11:40:36AM +0100, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>> > On Tue, Sep 29, 2009 at 09:10:49AM +0100, M?ns Rullg?rd wrote:
>> >> Mans Rullgard <mans at mansr.com> writes:
>> >> 
>> >> > GCC does stupid things if these assignments are done using floats
>> >> > directly, so fill the runs using integer operations instead.  Also
>> >> > unroll the loops since the length is always a multiple of 4.
>> >> > ---
>> >> >  libavcodec/wmadec.c |   22 ++++++++++++++++------
>> >> >  1 files changed, 16 insertions(+), 6 deletions(-)
>> >> >
>> >> > +        iv = AV_RN32(ptab + last_exp);
>> >> 
>> >> I don't know what I was thinking when I wrote that.  I've changed it
>> >> to use a uint32_t pointer instead.
>> >
>> > float->uint32_t is ok
>> 
>> Those patches applied.
>
> I'd appreciate if you'd run make test before such extensive changes.
> Then you'd have noticed that n can be 0 in the loops you unrolled, which
> causes a crash.

Fixed.  The value can not be zero, or the old code was broken already.
However, it could apparently be a non-multiple of 4.  I must have
missed some place where those values are computed.

Always more fun complaining after the fact than reviewing patches,
isn't it?

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