Commit 8d9e5c6e authored by Miroslav Lichvar's avatar Miroslav Lichvar Committed by Erik de Castro Lopo
Browse files

Optimize FLAC__bitreader_read_rice_signed_block.


Signed-off-by: Erik de Castro Lopo's avatarErik de Castro Lopo <erikd@mega-nerd.com>
parent 7b37472a
......@@ -711,379 +711,144 @@ FLAC__bool FLAC__bitreader_read_rice_signed(FLAC__BitReader *br, int *val, unsig
}
/* this is by far the most heavily used reader call. it ain't pretty but it's fast */
/* a lot of the logic is copied, then adapted, from FLAC__bitreader_read_unary_unsigned() and FLAC__bitreader_read_raw_uint32() */
FLAC__bool FLAC__bitreader_read_rice_signed_block(FLAC__BitReader *br, int vals[], unsigned nvals, unsigned parameter)
/* OPT: possibly faster version for use with MSVC */
#ifdef _MSC_VER
{
unsigned i;
unsigned uval = 0;
unsigned bits; /* the # of binary LSBs left to read to finish a rice codeword */
/* try and get br->consumed_words and br->consumed_bits into register;
* must remember to flush them back to *br before calling other
* bitwriter functions that use them, and before returning */
register unsigned cwords;
register unsigned cbits;
* bitreader functions that use them, and before returning */
unsigned cwords, words, lsbs, msbs, x, y;
unsigned ucbits; /* keep track of the number of unconsumed bits in word */
uint32_t b;
int *val, *end;
FLAC__ASSERT(0 != br);
FLAC__ASSERT(0 != br->buffer);
/* WATCHOUT: code does not work with <32bit words; we can make things much faster with this assertion */
FLAC__ASSERT(FLAC__BITS_PER_WORD >= 32);
FLAC__ASSERT(parameter < 32);
/* the above two asserts also guarantee that the binary part never straddles more that 2 words, so we don't have to loop to read it */
if(nvals == 0)
return true;
cbits = br->consumed_bits;
cwords = br->consumed_words;
/* the above two asserts also guarantee that the binary part never straddles more than 2 words, so we don't have to loop to read it */
while(1) {
val = vals;
end = vals + nvals;
/* read unary part */
while(1) {
while(cwords < br->words) { /* if we've not consumed up to a partial tail word... */
uint32_t b = br->buffer[cwords] << cbits;
if(b) {
#if 0 /* slower, probably due to bad register allocation... */ && defined FLAC__CPU_IA32 && !defined FLAC__NO_ASM && FLAC__BITS_PER_WORD == 32
__asm {
bsr eax, b
not eax
and eax, 31
mov i, eax
}
#else
i = FLAC__clz_uint32(b);
#endif
uval += i;
bits = parameter;
i++;
cbits += i;
if(cbits == FLAC__BITS_PER_WORD) {
crc16_update_word_(br, br->buffer[cwords]);
cwords++;
cbits = 0;
}
goto break1;
}
else {
uval += FLAC__BITS_PER_WORD - cbits;
crc16_update_word_(br, br->buffer[cwords]);
cwords++;
cbits = 0;
/* didn't find stop bit yet, have to keep going... */
}
}
/* at this point we've eaten up all the whole words; have to try
* reading through any tail bytes before calling the read callback.
* this is a repeat of the above logic adjusted for the fact we
* don't have a whole word. note though if the client is feeding
* us data a byte at a time (unlikely), br->consumed_bits may not
* be zero.
*/
if(br->bytes*8 > cbits) {
const unsigned end = br->bytes * 8;
uint32_t b = (br->buffer[cwords] & (FLAC__WORD_ALL_ONES << (FLAC__BITS_PER_WORD-end))) << cbits;
if(b) {
i = FLAC__clz_uint32(b);
uval += i;
bits = parameter;
i++;
cbits += i;
FLAC__ASSERT(cbits < FLAC__BITS_PER_WORD);
goto break1;
}
else {
uval += end - cbits;
cbits = end;
FLAC__ASSERT(cbits < FLAC__BITS_PER_WORD);
/* didn't find stop bit yet, have to keep going... */
}
}
/* flush registers and read; bitreader_read_from_client_() does
* not touch br->consumed_bits at all but we still need to set
* it in case it fails and we have to return false.
*/
br->consumed_bits = cbits;
br->consumed_words = cwords;
if(!bitreader_read_from_client_(br))
if(parameter == 0) {
while(val < end) {
/* read the unary MSBs and end bit */
if(!FLAC__bitreader_read_unary_unsigned(br, &msbs))
return false;
cwords = br->consumed_words;
}
break1:
/* read binary part */
FLAC__ASSERT(cwords <= br->words);
if(bits) {
while((br->words-cwords)*FLAC__BITS_PER_WORD + br->bytes*8 - cbits < bits) {
/* flush registers and read; bitreader_read_from_client_() does
* not touch br->consumed_bits at all but we still need to set
* it in case it fails and we have to return false.
*/
br->consumed_bits = cbits;
br->consumed_words = cwords;
if(!bitreader_read_from_client_(br))
return false;
cwords = br->consumed_words;
}
if(cwords < br->words) { /* if we've not consumed up to a partial tail word... */
if(cbits) {
/* this also works when consumed_bits==0, it's just a little slower than necessary for that case */
const unsigned n = FLAC__BITS_PER_WORD - cbits;
const uint32_t word = br->buffer[cwords];
if(bits < n) {
uval <<= bits;
uval |= (word & (FLAC__WORD_ALL_ONES >> cbits)) >> (n-bits);
cbits += bits;
goto break2;
}
uval <<= n;
uval |= word & (FLAC__WORD_ALL_ONES >> cbits);
bits -= n;
crc16_update_word_(br, word);
cwords++;
cbits = 0;
if(bits) { /* if there are still bits left to read, there have to be less than 32 so they will all be in the next word */
uval <<= bits;
uval |= (br->buffer[cwords] >> (FLAC__BITS_PER_WORD-bits));
cbits = bits;
}
goto break2;
}
else {
FLAC__ASSERT(bits < FLAC__BITS_PER_WORD);
uval <<= bits;
uval |= br->buffer[cwords] >> (FLAC__BITS_PER_WORD-bits);
cbits = bits;
goto break2;
}
}
else {
/* in this case we're starting our read at a partial tail word;
* the reader has guaranteed that we have at least 'bits' bits
* available to read, which makes this case simpler.
*/
uval <<= bits;
if(cbits) {
/* this also works when consumed_bits==0, it's just a little slower than necessary for that case */
FLAC__ASSERT(cbits + bits <= br->bytes*8);
uval |= (br->buffer[cwords] & (FLAC__WORD_ALL_ONES >> cbits)) >> (FLAC__BITS_PER_WORD-cbits-bits);
cbits += bits;
goto break2;
}
else {
uval |= br->buffer[cwords] >> (FLAC__BITS_PER_WORD-bits);
cbits += bits;
goto break2;
}
}
}
break2:
/* compose the value */
*vals = (int)(uval >> 1 ^ -(int)(uval & 1));
/* are we done? */
--nvals;
if(nvals == 0) {
br->consumed_bits = cbits;
br->consumed_words = cwords;
return true;
*val++ = (int)(msbs >> 1) ^ -(int)(msbs & 1);
}
uval = 0;
++vals;
return true;
}
}
#else
{
unsigned i;
unsigned uval = 0;
/* try and get br->consumed_words and br->consumed_bits into register;
* must remember to flush them back to *br before calling other
* bitwriter functions that use them, and before returning */
register unsigned cwords;
register unsigned cbits;
unsigned ucbits; /* keep track of the number of unconsumed bits in the buffer */
FLAC__ASSERT(parameter > 0);
FLAC__ASSERT(0 != br);
FLAC__ASSERT(0 != br->buffer);
/* WATCHOUT: code does not work with <32bit words; we can make things much faster with this assertion */
FLAC__ASSERT(FLAC__BITS_PER_WORD >= 32);
FLAC__ASSERT(parameter < 32);
/* the above two asserts also guarantee that the binary part never straddles more than 2 words, so we don't have to loop to read it */
cwords = br->consumed_words;
words = br->words;
if(nvals == 0)
return true;
/* if we've not consumed up to a partial tail word... */
if(cwords >= words) {
x = 0;
goto process_tail;
}
cbits = br->consumed_bits;
cwords = br->consumed_words;
ucbits = (br->words-cwords)*FLAC__BITS_PER_WORD + br->bytes*8 - cbits;
ucbits = FLAC__BITS_PER_WORD - br->consumed_bits;
b = br->buffer[cwords] << br->consumed_bits; /* keep unconsumed bits aligned to left */
while(1) {
while(val < end) {
/* read the unary MSBs and end bit */
x = y = FLAC__clz2_uint32(b);
if(x == FLAC__BITS_PER_WORD) {
x = ucbits;
do {
/* didn't find stop bit yet, have to keep going... */
crc16_update_word_(br, br->buffer[cwords++]);
if (cwords >= words)
goto incomplete_msbs;
b = br->buffer[cwords];
y = FLAC__clz2_uint32(b);
x += y;
} while(y == FLAC__BITS_PER_WORD);
}
b <<= y;
b <<= 1; /* account for stop bit */
ucbits = (ucbits - x - 1) % FLAC__BITS_PER_WORD;
msbs = x;
/* read the binary LSBs */
x = b >> (FLAC__BITS_PER_WORD - parameter);
if(parameter <= ucbits) {
ucbits -= parameter;
b <<= parameter;
} else {
/* there are still bits left to read, they will all be in the next word */
crc16_update_word_(br, br->buffer[cwords++]);
if (cwords >= words)
goto incomplete_lsbs;
b = br->buffer[cwords];
ucbits += FLAC__BITS_PER_WORD - parameter;
x |= b >> ucbits;
b <<= FLAC__BITS_PER_WORD - ucbits;
}
lsbs = x;
/* read unary part */
while(1) {
while(cwords < br->words) { /* if we've not consumed up to a partial tail word... */
uint32_t b = br->buffer[cwords] << cbits;
if(b) {
#if 0 /* is not discernably faster... */ && defined FLAC__CPU_IA32 && !defined FLAC__NO_ASM && FLAC__BITS_PER_WORD == 32 && defined __GNUC__
asm volatile (
"bsrl %1, %0;"
"notl %0;"
"andl $31, %0;"
: "=r"(i)
: "r"(b)
);
#else
i = FLAC__clz_uint32(b);
#endif
uval += i;
cbits += i;
cbits++; /* skip over stop bit */
if(cbits >= FLAC__BITS_PER_WORD) { /* faster way of testing if(cbits == FLAC__BITS_PER_WORD) */
crc16_update_word_(br, br->buffer[cwords]);
cwords++;
cbits = 0;
}
goto break1;
}
else {
uval += FLAC__BITS_PER_WORD - cbits;
crc16_update_word_(br, br->buffer[cwords]);
cwords++;
cbits = 0;
/* didn't find stop bit yet, have to keep going... */
}
}
/* at this point we've eaten up all the whole words; have to try
* reading through any tail bytes before calling the read callback.
* this is a repeat of the above logic adjusted for the fact we
* don't have a whole word. note though if the client is feeding
* us data a byte at a time (unlikely), br->consumed_bits may not
* be zero.
*/
if(br->bytes*8 > cbits) {
const unsigned end = br->bytes * 8;
uint32_t b = (br->buffer[cwords] & ~(FLAC__WORD_ALL_ONES >> end)) << cbits;
if(b) {
i = FLAC__clz_uint32(b);
uval += i;
cbits += i;
cbits++; /* skip over stop bit */
FLAC__ASSERT(cbits < FLAC__BITS_PER_WORD);
goto break1;
}
else {
uval += end - cbits;
cbits = end;
FLAC__ASSERT(cbits < FLAC__BITS_PER_WORD);
/* didn't find stop bit yet, have to keep going... */
}
/* compose the value */
x = (msbs << parameter) | lsbs;
*val++ = (int)(x >> 1) ^ -(int)(x & 1);
continue;
/* at this point we've eaten up all the whole words */
process_tail:
do {
if(0) {
incomplete_msbs:
br->consumed_bits = 0;
br->consumed_words = cwords;
}
/* flush registers and read; bitreader_read_from_client_() does
* not touch br->consumed_bits at all but we still need to set
* it in case it fails and we have to return false.
*/
br->consumed_bits = cbits;
br->consumed_words = cwords;
if(!bitreader_read_from_client_(br))
/* read the unary MSBs and end bit */
if(!FLAC__bitreader_read_unary_unsigned(br, &msbs))
return false;
cwords = br->consumed_words;
ucbits = (br->words-cwords)*FLAC__BITS_PER_WORD + br->bytes*8 - cbits + uval;
/* + uval to offset our count by the # of unary bits already
* consumed before the read, because we will add these back
* in all at once at break1
*/
}
break1:
ucbits -= uval;
ucbits--; /* account for stop bit */
/* read binary part */
FLAC__ASSERT(cwords <= br->words);
if(parameter) {
while(ucbits < parameter) {
/* flush registers and read; bitreader_read_from_client_() does
* not touch br->consumed_bits at all but we still need to set
* it in case it fails and we have to return false.
*/
br->consumed_bits = cbits;
msbs += x;
x = ucbits = 0;
if(0) {
incomplete_lsbs:
br->consumed_bits = 0;
br->consumed_words = cwords;
if(!bitreader_read_from_client_(br))
return false;
cwords = br->consumed_words;
ucbits = (br->words-cwords)*FLAC__BITS_PER_WORD + br->bytes*8 - cbits;
}
if(cwords < br->words) { /* if we've not consumed up to a partial tail word... */
if(cbits) {
/* this also works when consumed_bits==0, it's just slower than necessary for that case */
const unsigned n = FLAC__BITS_PER_WORD - cbits;
const uint32_t word = br->buffer[cwords];
if(parameter < n) {
uval <<= parameter;
uval |= (word & (FLAC__WORD_ALL_ONES >> cbits)) >> (n-parameter);
cbits += parameter;
}
else {
uval <<= n;
uval |= word & (FLAC__WORD_ALL_ONES >> cbits);
crc16_update_word_(br, word);
cwords++;
cbits = parameter - n;
if(cbits) { /* parameter > n, i.e. if there are still bits left to read, there have to be less than 32 so they will all be in the next word */
uval <<= cbits;
uval |= (br->buffer[cwords] >> (FLAC__BITS_PER_WORD-cbits));
}
}
}
else {
cbits = parameter;
uval <<= parameter;
uval |= br->buffer[cwords] >> (FLAC__BITS_PER_WORD-cbits);
}
}
else {
/* in this case we're starting our read at a partial tail word;
* the reader has guaranteed that we have at least 'parameter'
* bits available to read, which makes this case simpler.
*/
uval <<= parameter;
if(cbits) {
/* this also works when consumed_bits==0, it's just a little slower than necessary for that case */
FLAC__ASSERT(cbits + parameter <= br->bytes*8);
uval |= (br->buffer[cwords] & (FLAC__WORD_ALL_ONES >> cbits)) >> (FLAC__BITS_PER_WORD-cbits-parameter);
cbits += parameter;
}
else {
cbits = parameter;
uval |= br->buffer[cwords] >> (FLAC__BITS_PER_WORD-cbits);
}
}
}
ucbits -= parameter;
/* compose the value */
*vals = (int)(uval >> 1 ^ -(int)(uval & 1));
/* read the binary LSBs */
if(!FLAC__bitreader_read_raw_uint32(br, &lsbs, parameter - ucbits))
return false;
lsbs = x | lsbs;
/* are we done? */
--nvals;
if(nvals == 0) {
br->consumed_bits = cbits;
br->consumed_words = cwords;
return true;
}
/* compose the value */
x = (msbs << parameter) | lsbs;
*val++ = (int)(x >> 1) ^ -(int)(x & 1);
x = 0;
uval = 0;
++vals;
cwords = br->consumed_words;
words = br->words;
ucbits = FLAC__BITS_PER_WORD - br->consumed_bits;
b = br->buffer[cwords] << br->consumed_bits;
} while(cwords >= words && val < end);
}
if(ucbits == 0 && cwords < words) {
/* don't leave the head word with no unconsumed bits */
crc16_update_word_(br, br->buffer[cwords++]);
ucbits = FLAC__BITS_PER_WORD;
}
br->consumed_bits = FLAC__BITS_PER_WORD - ucbits;
br->consumed_words = cwords;
return true;
}
#endif
#if 0 /* UNUSED */
FLAC__bool FLAC__bitreader_read_golomb_signed(FLAC__BitReader *br, int *val, unsigned parameter)
......
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