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Convert VP8LFastLog2 to fixed point

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The lossless encoding speed-ups are:
- up to 1% with default parameters
- up to 4% in cruncher mode: -q 100 -m 6

Change-Id: Id92d4bad0b0a2c28c8aa9ff5280eea5717017f30
This commit is contained in:
Vincent Rabaud
2024-06-26 15:21:55 +02:00
parent c4af79d053
commit 0a9f1c19f8
5 changed files with 154 additions and 81 deletions
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18
src/dsp/lossless_enc_mips32.c
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@ -53,18 +53,18 @@ static float FastSLog2Slow_MIPS32(uint32_t v) {
// (v % y) = (v % 2^log_cnt) = v & (2^log_cnt - 1)
correction = (23 * (v & (y - 1))) >> 4;
return v_f * (kLog2Table[temp] + log_cnt) + correction;
return v_f * (kLog2fTable[temp] + log_cnt) + correction;
} else {
return (float)(LOG_2_RECIPROCAL * v * log((double)v));
}
}
static float FastLog2Slow_MIPS32(uint32_t v) {
static uint32_t FastLog2Slow_MIPS32(uint32_t v) {
assert(v >= LOG_LOOKUP_IDX_MAX);
if (v < APPROX_LOG_WITH_CORRECTION_MAX) {
uint32_t log_cnt, y;
const int c24 = 24;
double log_2;
uint32_t log_2;
uint32_t temp;
__asm__ volatile(
@ -78,17 +78,17 @@ static float FastLog2Slow_MIPS32(uint32_t v) {
: [c24]"r"(c24), [v]"r"(v)
);
log_2 = kLog2Table[temp] + log_cnt;
log_2 = kLog2Table[temp] + (log_cnt << LOG_2_PRECISION_BITS);
if (v >= APPROX_LOG_MAX) {
// Since the division is still expensive, add this correction factor only
// for large values of 'v'.
const uint32_t correction = (23 * (v & (y - 1))) >> 4;
log_2 += (double)correction / v;
const uint64_t correction =
(uint64_t)LOG_2_RECIPROCAL_FIXED * (v & (y - 1));
log_2 += (uint32_t)DivRound(correction, v);
}
return (float)log_2;
return log_2;
} else {
return (float)(LOG_2_RECIPROCAL * log((double)v));
return (uint32_t)(LOG_2_RECIPROCAL_FIXED_DOUBLE * log((double)v) + .5);
}
}