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WMA: use type punning and unroll loops in decode_exp_vlc()

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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.

Originally committed as revision 20077 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Måns Rullgård 2009-09-29 10:38:30 +00:00
parent c0d1463da7
commit ff00b94e9d
1 changed files with 16 additions and 6 deletions
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22
libavcodec/wmadec.c
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@ -315,21 +315,27 @@ static int decode_exp_vlc(WMACodecContext *s, int ch)
{
int last_exp, n, code;
const uint16_t *ptr;
float v, *q, max_scale, *q_end;
float v, max_scale;
uint32_t *q, *q_end, iv;
const float *ptab = pow_tab + 60;
const uint32_t *iptab = (const uint32_t*)ptab;
ptr = s->exponent_bands[s->frame_len_bits - s->block_len_bits];
q = s->exponents[ch];
q = (uint32_t *)s->exponents[ch];
q_end = q + s->block_len;
max_scale = 0;
if (s->version == 1) {
last_exp = get_bits(&s->gb, 5) + 10;
v = ptab[last_exp];
iv = iptab[last_exp];
max_scale = v;
n = *ptr++;
do {
*q++ = v;
} while (--n);
*q++ = iv;
*q++ = iv;
*q++ = iv;
*q++ = iv;
} while (n -= 4);
}else
last_exp = 36;
@ -342,12 +348,16 @@ static int decode_exp_vlc(WMACodecContext *s, int ch)
if ((unsigned)last_exp + 60 > FF_ARRAY_ELEMS(pow_tab))
return -1;
v = ptab[last_exp];
iv = iptab[last_exp];
if (v > max_scale)
max_scale = v;
n = *ptr++;
do {
*q++ = v;
} while (--n);
*q++ = iv;
*q++ = iv;
*q++ = iv;
*q++ = iv;
} while (n -= 4);
}
s->max_exponent[ch] = max_scale;
return 0;