Hi,
2011/12/15 Måns Rullgård <[email protected]>
> >> @@ -230,7 +263,12 @@ static inline int get_bits_count(const
> GetBitContext
> >> *s) {
> >> > static inline void skip_bits_long(GetBitContext *s, int n){
> >> > OPEN_READER(re, s);
> >> > re_bit_count += n;
> >> > +#if UNCHECKED_BITSTREAM_READER
> >> > re_buffer_ptr += re_bit_count>>5;
> >> > +#else
> >> > + re_buffer_ptr = (re_bit_count >> 5) < (const uint32_t *)
> s->buffer_end - re_buffer_ptr ?
> >> > + re_buffer_ptr + (re_bit_count >> 5) : (const
> uint32_t *) s->buffer_end;
> >> > +#endif
> >>
> >> This is again guaranteed to fall within the padding region, so whatever
> >> variant gives better code is OK to use here.
> >
> > gcc messes up and does 4 more instructions. Fortunately it's not terribly
> > important, but I'll stick to this:
> >
> > [..]
> > re_buffer_ptr += re_bit_count>>5;
> > + #if !UNCHECKED_BITSTREAM_READER
> > + re_buffer_ptr = FFMIN(re_buffer_ptr, s->buffer_end);
> > + #endif
>
> Gah, I'm stupid. This is skip_bits_long(), which can be called with any
> value. It must protect against overflow.
>
No you're actually right, but differently; re_bit_count is never >31.
> > +#if UNCHECKED_BITSTREAM_READER
> > # define SKIP_COUNTER(name, gb, num) name##_index += (num)
> > +#else
> > +# define SKIP_COUNTER(name, gb, num) name##_index =
> FFMIN((gb)->size_in_bits, \
> > +
> name##_index + num)
> > +#endif
>
> Those lines are awfully long. Please do something about that, e.g. like
> this:
>
> # define SKIP_COUNTER(name, gb, num) \
> name##_index = FFMIN((gb)->size_in_bits, name##_index + num)
>
Will fix and resend.
Ronald
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