chromium / chromium / src / 3484ae73788140327ff58665e03c3953be834b1d / . / third_party / zlib / fill_window_sse.c

/* | |

* Fill Window with SSE2-optimized hash shifting | |

* | |

* Copyright (C) 2013 Intel Corporation | |

* Authors: | |

* Arjan van de Ven <arjan@linux.intel.com> | |

* Jim Kukunas <james.t.kukunas@linux.intel.com> | |

* | |

* For conditions of distribution and use, see copyright notice in zlib.h | |

*/ | |

#include <immintrin.h> | |

#include "deflate.h" | |

#define UPDATE_HASH(s,h,i) \ | |

{\ | |

if (s->level < 6) { \ | |

h = (3483 * (s->window[i]) +\ | |

23081* (s->window[i+1]) +\ | |

6954 * (s->window[i+2]) +\ | |

20947* (s->window[i+3])) & s->hash_mask;\ | |

} else {\ | |

h = (25881* (s->window[i]) +\ | |

24674* (s->window[i+1]) +\ | |

25811* (s->window[i+2])) & s->hash_mask;\ | |

}\ | |

}\ | |

extern int deflate_read_buf OF((z_streamp strm, Bytef *buf, unsigned size)); | |

void fill_window_sse(deflate_state *s) | |

{ | |

const __m128i xmm_wsize = _mm_set1_epi16(s->w_size); | |

register unsigned n; | |

register Posf *p; | |

unsigned more; /* Amount of free space at the end of the window. */ | |

uInt wsize = s->w_size; | |

Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead"); | |

do { | |

more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); | |

/* Deal with !@#$% 64K limit: */ | |

if (sizeof(int) <= 2) { | |

if (more == 0 && s->strstart == 0 && s->lookahead == 0) { | |

more = wsize; | |

} else if (more == (unsigned)(-1)) { | |

/* Very unlikely, but possible on 16 bit machine if | |

* strstart == 0 && lookahead == 1 (input done a byte at time) | |

*/ | |

more--; | |

} | |

} | |

/* If the window is almost full and there is insufficient lookahead, | |

* move the upper half to the lower one to make room in the upper half. | |

*/ | |

if (s->strstart >= wsize+MAX_DIST(s)) { | |

zmemcpy(s->window, s->window+wsize, (unsigned)wsize); | |

s->match_start -= wsize; | |

s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ | |

s->block_start -= (long) wsize; | |

/* Slide the hash table (could be avoided with 32 bit values | |

at the expense of memory usage). We slide even when level == 0 | |

to keep the hash table consistent if we switch back to level > 0 | |

later. (Using level 0 permanently is not an optimal usage of | |

zlib, so we don't care about this pathological case.) | |

*/ | |

n = s->hash_size; | |

p = &s->head[n]; | |

p -= 8; | |

do { | |

__m128i value, result; | |

value = _mm_loadu_si128((__m128i *)p); | |

result = _mm_subs_epu16(value, xmm_wsize); | |

_mm_storeu_si128((__m128i *)p, result); | |

p -= 8; | |

n -= 8; | |

} while (n > 0); | |

n = wsize; | |

#ifndef FASTEST | |

p = &s->prev[n]; | |

p -= 8; | |

do { | |

__m128i value, result; | |

value = _mm_loadu_si128((__m128i *)p); | |

result = _mm_subs_epu16(value, xmm_wsize); | |

_mm_storeu_si128((__m128i *)p, result); | |

p -= 8; | |

n -= 8; | |

} while (n > 0); | |

#endif | |

more += wsize; | |

} | |

if (s->strm->avail_in == 0) break; | |

/* If there was no sliding: | |

* strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && | |

* more == window_size - lookahead - strstart | |

* => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) | |

* => more >= window_size - 2*WSIZE + 2 | |

* In the BIG_MEM or MMAP case (not yet supported), | |

* window_size == input_size + MIN_LOOKAHEAD && | |

* strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. | |

* Otherwise, window_size == 2*WSIZE so more >= 2. | |

* If there was sliding, more >= WSIZE. So in all cases, more >= 2. | |

*/ | |

Assert(more >= 2, "more < 2"); | |

n = deflate_read_buf(s->strm, | |

s->window + s->strstart + s->lookahead, | |

more); | |

s->lookahead += n; | |

/* Initialize the hash value now that we have some input: */ | |

if (s->lookahead >= MIN_MATCH) { | |

uInt str = s->strstart; | |

s->ins_h = s->window[str]; | |

if (str >= 1) | |

UPDATE_HASH(s, s->ins_h, str + 1 - (MIN_MATCH-1)); | |

#if MIN_MATCH != 3 | |

Call UPDATE_HASH() MIN_MATCH-3 more times | |

#endif | |

} | |

/* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, | |

* but this is not important since only literal bytes will be emitted. | |

*/ | |

} while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); | |

/* If the WIN_INIT bytes after the end of the current data have never been | |

* written, then zero those bytes in order to avoid memory check reports of | |

* the use of uninitialized (or uninitialised as Julian writes) bytes by | |

* the longest match routines. Update the high water mark for the next | |

* time through here. WIN_INIT is set to MAX_MATCH since the longest match | |

* routines allow scanning to strstart + MAX_MATCH, ignoring lookahead. | |

*/ | |

if (s->high_water < s->window_size) { | |

ulg curr = s->strstart + (ulg)(s->lookahead); | |

ulg init; | |

if (s->high_water < curr) { | |

/* Previous high water mark below current data -- zero WIN_INIT | |

* bytes or up to end of window, whichever is less. | |

*/ | |

init = s->window_size - curr; | |

if (init > WIN_INIT) | |

init = WIN_INIT; | |

zmemzero(s->window + curr, (unsigned)init); | |

s->high_water = curr + init; | |

} | |

else if (s->high_water < (ulg)curr + WIN_INIT) { | |

/* High water mark at or above current data, but below current data | |

* plus WIN_INIT -- zero out to current data plus WIN_INIT, or up | |

* to end of window, whichever is less. | |

*/ | |

init = (ulg)curr + WIN_INIT - s->high_water; | |

if (init > s->window_size - s->high_water) | |

init = s->window_size - s->high_water; | |

zmemzero(s->window + s->high_water, (unsigned)init); | |

s->high_water += init; | |

} | |

} | |

Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD, | |

"not enough room for search"); | |

} |