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Diffstat (limited to 'zlib/contrib/asm686/match.S')
| -rw-r--r-- | zlib/contrib/asm686/match.S | 357 |
1 files changed, 357 insertions, 0 deletions
diff --git a/zlib/contrib/asm686/match.S b/zlib/contrib/asm686/match.S new file mode 100644 index 00000000000..fa421092785 --- /dev/null +++ b/zlib/contrib/asm686/match.S @@ -0,0 +1,357 @@ +/* match.S -- x86 assembly version of the zlib longest_match() function. + * Optimized for the Intel 686 chips (PPro and later). + * + * Copyright (C) 1998, 2007 Brian Raiter <breadbox@muppetlabs.com> + * + * This software is provided 'as-is', without any express or implied + * warranty. In no event will the author be held liable for any damages + * arising from the use of this software. + * + * Permission is granted to anyone to use this software for any purpose, + * including commercial applications, and to alter it and redistribute it + * freely, subject to the following restrictions: + * + * 1. The origin of this software must not be misrepresented; you must not + * claim that you wrote the original software. If you use this software + * in a product, an acknowledgment in the product documentation would be + * appreciated but is not required. + * 2. Altered source versions must be plainly marked as such, and must not be + * misrepresented as being the original software. + * 3. This notice may not be removed or altered from any source distribution. + */ + +#ifndef NO_UNDERLINE +#define match_init _match_init +#define longest_match _longest_match +#endif + +#define MAX_MATCH (258) +#define MIN_MATCH (3) +#define MIN_LOOKAHEAD (MAX_MATCH + MIN_MATCH + 1) +#define MAX_MATCH_8 ((MAX_MATCH + 7) & ~7) + +/* stack frame offsets */ + +#define chainlenwmask 0 /* high word: current chain len */ + /* low word: s->wmask */ +#define window 4 /* local copy of s->window */ +#define windowbestlen 8 /* s->window + bestlen */ +#define scanstart 16 /* first two bytes of string */ +#define scanend 12 /* last two bytes of string */ +#define scanalign 20 /* dword-misalignment of string */ +#define nicematch 24 /* a good enough match size */ +#define bestlen 28 /* size of best match so far */ +#define scan 32 /* ptr to string wanting match */ + +#define LocalVarsSize (36) +/* saved ebx 36 */ +/* saved edi 40 */ +/* saved esi 44 */ +/* saved ebp 48 */ +/* return address 52 */ +#define deflatestate 56 /* the function arguments */ +#define curmatch 60 + +/* All the +zlib1222add offsets are due to the addition of fields + * in zlib in the deflate_state structure since the asm code was first written + * (if you compile with zlib 1.0.4 or older, use "zlib1222add equ (-4)"). + * (if you compile with zlib between 1.0.5 and 1.2.2.1, use "zlib1222add equ 0"). + * if you compile with zlib 1.2.2.2 or later , use "zlib1222add equ 8"). + */ + +#define zlib1222add (8) + +#define dsWSize (36+zlib1222add) +#define dsWMask (44+zlib1222add) +#define dsWindow (48+zlib1222add) +#define dsPrev (56+zlib1222add) +#define dsMatchLen (88+zlib1222add) +#define dsPrevMatch (92+zlib1222add) +#define dsStrStart (100+zlib1222add) +#define dsMatchStart (104+zlib1222add) +#define dsLookahead (108+zlib1222add) +#define dsPrevLen (112+zlib1222add) +#define dsMaxChainLen (116+zlib1222add) +#define dsGoodMatch (132+zlib1222add) +#define dsNiceMatch (136+zlib1222add) + + +.file "match.S" + +.globl match_init, longest_match + +.text + +/* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */ +.cfi_sections .debug_frame + +longest_match: + +.cfi_startproc +/* Save registers that the compiler may be using, and adjust %esp to */ +/* make room for our stack frame. */ + + pushl %ebp + .cfi_def_cfa_offset 8 + .cfi_offset ebp, -8 + pushl %edi + .cfi_def_cfa_offset 12 + pushl %esi + .cfi_def_cfa_offset 16 + pushl %ebx + .cfi_def_cfa_offset 20 + subl $LocalVarsSize, %esp + .cfi_def_cfa_offset LocalVarsSize+20 + +/* Retrieve the function arguments. %ecx will hold cur_match */ +/* throughout the entire function. %edx will hold the pointer to the */ +/* deflate_state structure during the function's setup (before */ +/* entering the main loop). */ + + movl deflatestate(%esp), %edx + movl curmatch(%esp), %ecx + +/* uInt wmask = s->w_mask; */ +/* unsigned chain_length = s->max_chain_length; */ +/* if (s->prev_length >= s->good_match) { */ +/* chain_length >>= 2; */ +/* } */ + + movl dsPrevLen(%edx), %eax + movl dsGoodMatch(%edx), %ebx + cmpl %ebx, %eax + movl dsWMask(%edx), %eax + movl dsMaxChainLen(%edx), %ebx + jl LastMatchGood + shrl $2, %ebx +LastMatchGood: + +/* chainlen is decremented once beforehand so that the function can */ +/* use the sign flag instead of the zero flag for the exit test. */ +/* It is then shifted into the high word, to make room for the wmask */ +/* value, which it will always accompany. */ + + decl %ebx + shll $16, %ebx + orl %eax, %ebx + movl %ebx, chainlenwmask(%esp) + +/* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; */ + + movl dsNiceMatch(%edx), %eax + movl dsLookahead(%edx), %ebx + cmpl %eax, %ebx + jl LookaheadLess + movl %eax, %ebx +LookaheadLess: movl %ebx, nicematch(%esp) + +/* register Bytef *scan = s->window + s->strstart; */ + + movl dsWindow(%edx), %esi + movl %esi, window(%esp) + movl dsStrStart(%edx), %ebp + lea (%esi,%ebp), %edi + movl %edi, scan(%esp) + +/* Determine how many bytes the scan ptr is off from being */ +/* dword-aligned. */ + + movl %edi, %eax + negl %eax + andl $3, %eax + movl %eax, scanalign(%esp) + +/* IPos limit = s->strstart > (IPos)MAX_DIST(s) ? */ +/* s->strstart - (IPos)MAX_DIST(s) : NIL; */ + + movl dsWSize(%edx), %eax + subl $MIN_LOOKAHEAD, %eax + subl %eax, %ebp + jg LimitPositive + xorl %ebp, %ebp +LimitPositive: + +/* int best_len = s->prev_length; */ + + movl dsPrevLen(%edx), %eax + movl %eax, bestlen(%esp) + +/* Store the sum of s->window + best_len in %esi locally, and in %esi. */ + + addl %eax, %esi + movl %esi, windowbestlen(%esp) + +/* register ush scan_start = *(ushf*)scan; */ +/* register ush scan_end = *(ushf*)(scan+best_len-1); */ +/* Posf *prev = s->prev; */ + + movzwl (%edi), %ebx + movl %ebx, scanstart(%esp) + movzwl -1(%edi,%eax), %ebx + movl %ebx, scanend(%esp) + movl dsPrev(%edx), %edi + +/* Jump into the main loop. */ + + movl chainlenwmask(%esp), %edx + jmp LoopEntry + +.balign 16 + +/* do { + * match = s->window + cur_match; + * if (*(ushf*)(match+best_len-1) != scan_end || + * *(ushf*)match != scan_start) continue; + * [...] + * } while ((cur_match = prev[cur_match & wmask]) > limit + * && --chain_length != 0); + * + * Here is the inner loop of the function. The function will spend the + * majority of its time in this loop, and majority of that time will + * be spent in the first ten instructions. + * + * Within this loop: + * %ebx = scanend + * %ecx = curmatch + * %edx = chainlenwmask - i.e., ((chainlen << 16) | wmask) + * %esi = windowbestlen - i.e., (window + bestlen) + * %edi = prev + * %ebp = limit + */ +LookupLoop: + andl %edx, %ecx + movzwl (%edi,%ecx,2), %ecx + cmpl %ebp, %ecx + jbe LeaveNow + subl $0x00010000, %edx + js LeaveNow +LoopEntry: movzwl -1(%esi,%ecx), %eax + cmpl %ebx, %eax + jnz LookupLoop + movl window(%esp), %eax + movzwl (%eax,%ecx), %eax + cmpl scanstart(%esp), %eax + jnz LookupLoop + +/* Store the current value of chainlen. */ + + movl %edx, chainlenwmask(%esp) + +/* Point %edi to the string under scrutiny, and %esi to the string we */ +/* are hoping to match it up with. In actuality, %esi and %edi are */ +/* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is */ +/* initialized to -(MAX_MATCH_8 - scanalign). */ + + movl window(%esp), %esi + movl scan(%esp), %edi + addl %ecx, %esi + movl scanalign(%esp), %eax + movl $(-MAX_MATCH_8), %edx + lea MAX_MATCH_8(%edi,%eax), %edi + lea MAX_MATCH_8(%esi,%eax), %esi + +/* Test the strings for equality, 8 bytes at a time. At the end, + * adjust %edx so that it is offset to the exact byte that mismatched. + * + * We already know at this point that the first three bytes of the + * strings match each other, and they can be safely passed over before + * starting the compare loop. So what this code does is skip over 0-3 + * bytes, as much as necessary in order to dword-align the %edi + * pointer. (%esi will still be misaligned three times out of four.) + * + * It should be confessed that this loop usually does not represent + * much of the total running time. Replacing it with a more + * straightforward "rep cmpsb" would not drastically degrade + * performance. + */ +LoopCmps: + movl (%esi,%edx), %eax + xorl (%edi,%edx), %eax + jnz LeaveLoopCmps + movl 4(%esi,%edx), %eax + xorl 4(%edi,%edx), %eax + jnz LeaveLoopCmps4 + addl $8, %edx + jnz LoopCmps + jmp LenMaximum +LeaveLoopCmps4: addl $4, %edx +LeaveLoopCmps: testl $0x0000FFFF, %eax + jnz LenLower + addl $2, %edx + shrl $16, %eax +LenLower: subb $1, %al + adcl $0, %edx + +/* Calculate the length of the match. If it is longer than MAX_MATCH, */ +/* then automatically accept it as the best possible match and leave. */ + + lea (%edi,%edx), %eax + movl scan(%esp), %edi + subl %edi, %eax + cmpl $MAX_MATCH, %eax + jge LenMaximum + +/* If the length of the match is not longer than the best match we */ +/* have so far, then forget it and return to the lookup loop. */ + + movl deflatestate(%esp), %edx + movl bestlen(%esp), %ebx + cmpl %ebx, %eax + jg LongerMatch + movl windowbestlen(%esp), %esi + movl dsPrev(%edx), %edi + movl scanend(%esp), %ebx + movl chainlenwmask(%esp), %edx + jmp LookupLoop + +/* s->match_start = cur_match; */ +/* best_len = len; */ +/* if (len >= nice_match) break; */ +/* scan_end = *(ushf*)(scan+best_len-1); */ + +LongerMatch: movl nicematch(%esp), %ebx + movl %eax, bestlen(%esp) + movl %ecx, dsMatchStart(%edx) + cmpl %ebx, %eax + jge LeaveNow + movl window(%esp), %esi + addl %eax, %esi + movl %esi, windowbestlen(%esp) + movzwl -1(%edi,%eax), %ebx + movl dsPrev(%edx), %edi + movl %ebx, scanend(%esp) + movl chainlenwmask(%esp), %edx + jmp LookupLoop + +/* Accept the current string, with the maximum possible length. */ + +LenMaximum: movl deflatestate(%esp), %edx + movl $MAX_MATCH, bestlen(%esp) + movl %ecx, dsMatchStart(%edx) + +/* if ((uInt)best_len <= s->lookahead) return (uInt)best_len; */ +/* return s->lookahead; */ + +LeaveNow: + movl deflatestate(%esp), %edx + movl bestlen(%esp), %ebx + movl dsLookahead(%edx), %eax + cmpl %eax, %ebx + jg LookaheadRet + movl %ebx, %eax +LookaheadRet: + +/* Restore the stack and return from whence we came. */ + + addl $LocalVarsSize, %esp + .cfi_def_cfa_offset 20 + popl %ebx + .cfi_def_cfa_offset 16 + popl %esi + .cfi_def_cfa_offset 12 + popl %edi + .cfi_def_cfa_offset 8 + popl %ebp + .cfi_def_cfa_offset 4 +.cfi_endproc +match_init: ret |