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452 lines
12 KiB
452 lines
12 KiB
/* |
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* match.S -- optimized version of longest_match() |
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* based on the similar work by Gilles Vollant, and Brian Raiter, written 1998 |
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* |
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* This is free software; you can redistribute it and/or modify it |
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* under the terms of the BSD License. Use by owners of Che Guevarra |
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* parafernalia is prohibited, where possible, and highly discouraged |
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* elsewhere. |
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*/ |
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#ifndef NO_UNDERLINE |
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# define match_init _match_init |
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# define longest_match _longest_match |
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#endif |
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#define scanend ebx |
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#define scanendw bx |
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#define chainlenwmask edx /* high word: current chain len low word: s->wmask */ |
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#define curmatch rsi |
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#define curmatchd esi |
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#define windowbestlen r8 |
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#define scanalign r9 |
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#define scanalignd r9d |
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#define window r10 |
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#define bestlen r11 |
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#define bestlend r11d |
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#define scanstart r12d |
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#define scanstartw r12w |
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#define scan r13 |
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#define nicematch r14d |
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#define limit r15 |
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#define limitd r15d |
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#define prev rcx |
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/* |
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* The 258 is a "magic number, not a parameter -- changing it |
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* breaks the hell loose |
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*/ |
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#define MAX_MATCH (258) |
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#define MIN_MATCH (3) |
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#define MIN_LOOKAHEAD (MAX_MATCH + MIN_MATCH + 1) |
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#define MAX_MATCH_8 ((MAX_MATCH + 7) & ~7) |
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/* stack frame offsets */ |
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#define LocalVarsSize (112) |
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#define _chainlenwmask ( 8-LocalVarsSize)(%rsp) |
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#define _windowbestlen (16-LocalVarsSize)(%rsp) |
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#define save_r14 (24-LocalVarsSize)(%rsp) |
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#define save_rsi (32-LocalVarsSize)(%rsp) |
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#define save_rbx (40-LocalVarsSize)(%rsp) |
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#define save_r12 (56-LocalVarsSize)(%rsp) |
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#define save_r13 (64-LocalVarsSize)(%rsp) |
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#define save_r15 (80-LocalVarsSize)(%rsp) |
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.globl match_init, longest_match |
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/* |
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* On AMD64 the first argument of a function (in our case -- the pointer to |
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* deflate_state structure) is passed in %rdi, hence our offsets below are |
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* all off of that. |
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*/ |
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/* you can check the structure offset by running |
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#include <stdlib.h> |
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#include <stdio.h> |
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#include "deflate.h" |
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void print_depl() |
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{ |
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deflate_state ds; |
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deflate_state *s=&ds; |
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printf("size pointer=%u\n",(int)sizeof(void*)); |
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printf("#define dsWSize (%3u)(%%rdi)\n",(int)(((char*)&(s->w_size))-((char*)s))); |
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printf("#define dsWMask (%3u)(%%rdi)\n",(int)(((char*)&(s->w_mask))-((char*)s))); |
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printf("#define dsWindow (%3u)(%%rdi)\n",(int)(((char*)&(s->window))-((char*)s))); |
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printf("#define dsPrev (%3u)(%%rdi)\n",(int)(((char*)&(s->prev))-((char*)s))); |
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printf("#define dsMatchLen (%3u)(%%rdi)\n",(int)(((char*)&(s->match_length))-((char*)s))); |
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printf("#define dsPrevMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_match))-((char*)s))); |
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printf("#define dsStrStart (%3u)(%%rdi)\n",(int)(((char*)&(s->strstart))-((char*)s))); |
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printf("#define dsMatchStart (%3u)(%%rdi)\n",(int)(((char*)&(s->match_start))-((char*)s))); |
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printf("#define dsLookahead (%3u)(%%rdi)\n",(int)(((char*)&(s->lookahead))-((char*)s))); |
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printf("#define dsPrevLen (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_length))-((char*)s))); |
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printf("#define dsMaxChainLen (%3u)(%%rdi)\n",(int)(((char*)&(s->max_chain_length))-((char*)s))); |
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printf("#define dsGoodMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->good_match))-((char*)s))); |
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printf("#define dsNiceMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->nice_match))-((char*)s))); |
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} |
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*/ |
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/* |
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to compile for XCode 3.2 on MacOSX x86_64 |
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- run "gcc -g -c -DXCODE_MAC_X64_STRUCTURE amd64-match.S" |
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*/ |
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#ifndef CURRENT_LINX_XCODE_MAC_X64_STRUCTURE |
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#define dsWSize ( 68)(%rdi) |
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#define dsWMask ( 76)(%rdi) |
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#define dsWindow ( 80)(%rdi) |
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#define dsPrev ( 96)(%rdi) |
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#define dsMatchLen (144)(%rdi) |
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#define dsPrevMatch (148)(%rdi) |
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#define dsStrStart (156)(%rdi) |
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#define dsMatchStart (160)(%rdi) |
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#define dsLookahead (164)(%rdi) |
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#define dsPrevLen (168)(%rdi) |
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#define dsMaxChainLen (172)(%rdi) |
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#define dsGoodMatch (188)(%rdi) |
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#define dsNiceMatch (192)(%rdi) |
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#else |
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#ifndef STRUCT_OFFSET |
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# define STRUCT_OFFSET (0) |
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#endif |
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#define dsWSize ( 56 + STRUCT_OFFSET)(%rdi) |
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#define dsWMask ( 64 + STRUCT_OFFSET)(%rdi) |
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#define dsWindow ( 72 + STRUCT_OFFSET)(%rdi) |
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#define dsPrev ( 88 + STRUCT_OFFSET)(%rdi) |
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#define dsMatchLen (136 + STRUCT_OFFSET)(%rdi) |
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#define dsPrevMatch (140 + STRUCT_OFFSET)(%rdi) |
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#define dsStrStart (148 + STRUCT_OFFSET)(%rdi) |
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#define dsMatchStart (152 + STRUCT_OFFSET)(%rdi) |
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#define dsLookahead (156 + STRUCT_OFFSET)(%rdi) |
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#define dsPrevLen (160 + STRUCT_OFFSET)(%rdi) |
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#define dsMaxChainLen (164 + STRUCT_OFFSET)(%rdi) |
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#define dsGoodMatch (180 + STRUCT_OFFSET)(%rdi) |
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#define dsNiceMatch (184 + STRUCT_OFFSET)(%rdi) |
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#endif |
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.text |
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/* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */ |
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longest_match: |
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/* |
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* Retrieve the function arguments. %curmatch will hold cur_match |
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* throughout the entire function (passed via rsi on amd64). |
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* rdi will hold the pointer to the deflate_state (first arg on amd64) |
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*/ |
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mov %rsi, save_rsi |
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mov %rbx, save_rbx |
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mov %r12, save_r12 |
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mov %r13, save_r13 |
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mov %r14, save_r14 |
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mov %r15, save_r15 |
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/* uInt wmask = s->w_mask; */ |
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/* unsigned chain_length = s->max_chain_length; */ |
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/* if (s->prev_length >= s->good_match) { */ |
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/* chain_length >>= 2; */ |
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/* } */ |
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movl dsPrevLen, %eax |
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movl dsGoodMatch, %ebx |
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cmpl %ebx, %eax |
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movl dsWMask, %eax |
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movl dsMaxChainLen, %chainlenwmask |
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jl LastMatchGood |
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shrl $2, %chainlenwmask |
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LastMatchGood: |
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/* chainlen is decremented once beforehand so that the function can */ |
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/* use the sign flag instead of the zero flag for the exit test. */ |
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/* It is then shifted into the high word, to make room for the wmask */ |
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/* value, which it will always accompany. */ |
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decl %chainlenwmask |
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shll $16, %chainlenwmask |
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orl %eax, %chainlenwmask |
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/* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; */ |
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movl dsNiceMatch, %eax |
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movl dsLookahead, %ebx |
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cmpl %eax, %ebx |
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jl LookaheadLess |
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movl %eax, %ebx |
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LookaheadLess: movl %ebx, %nicematch |
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/* register Bytef *scan = s->window + s->strstart; */ |
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mov dsWindow, %window |
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movl dsStrStart, %limitd |
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lea (%limit, %window), %scan |
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/* Determine how many bytes the scan ptr is off from being */ |
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/* dword-aligned. */ |
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mov %scan, %scanalign |
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negl %scanalignd |
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andl $3, %scanalignd |
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/* IPos limit = s->strstart > (IPos)MAX_DIST(s) ? */ |
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/* s->strstart - (IPos)MAX_DIST(s) : NIL; */ |
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movl dsWSize, %eax |
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subl $MIN_LOOKAHEAD, %eax |
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xorl %ecx, %ecx |
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subl %eax, %limitd |
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cmovng %ecx, %limitd |
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/* int best_len = s->prev_length; */ |
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movl dsPrevLen, %bestlend |
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/* Store the sum of s->window + best_len in %windowbestlen locally, and in memory. */ |
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lea (%window, %bestlen), %windowbestlen |
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mov %windowbestlen, _windowbestlen |
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/* register ush scan_start = *(ushf*)scan; */ |
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/* register ush scan_end = *(ushf*)(scan+best_len-1); */ |
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/* Posf *prev = s->prev; */ |
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movzwl (%scan), %scanstart |
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movzwl -1(%scan, %bestlen), %scanend |
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mov dsPrev, %prev |
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/* Jump into the main loop. */ |
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movl %chainlenwmask, _chainlenwmask |
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jmp LoopEntry |
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.balign 16 |
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/* do { |
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* match = s->window + cur_match; |
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* if (*(ushf*)(match+best_len-1) != scan_end || |
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* *(ushf*)match != scan_start) continue; |
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* [...] |
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* } while ((cur_match = prev[cur_match & wmask]) > limit |
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* && --chain_length != 0); |
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* |
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* Here is the inner loop of the function. The function will spend the |
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* majority of its time in this loop, and majority of that time will |
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* be spent in the first ten instructions. |
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*/ |
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LookupLoop: |
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andl %chainlenwmask, %curmatchd |
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movzwl (%prev, %curmatch, 2), %curmatchd |
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cmpl %limitd, %curmatchd |
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jbe LeaveNow |
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subl $0x00010000, %chainlenwmask |
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js LeaveNow |
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LoopEntry: cmpw -1(%windowbestlen, %curmatch), %scanendw |
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jne LookupLoop |
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cmpw %scanstartw, (%window, %curmatch) |
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jne LookupLoop |
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/* Store the current value of chainlen. */ |
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movl %chainlenwmask, _chainlenwmask |
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/* %scan is the string under scrutiny, and %prev to the string we */ |
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/* are hoping to match it up with. In actuality, %esi and %edi are */ |
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/* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is */ |
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/* initialized to -(MAX_MATCH_8 - scanalign). */ |
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mov $(-MAX_MATCH_8), %rdx |
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lea (%curmatch, %window), %windowbestlen |
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lea MAX_MATCH_8(%windowbestlen, %scanalign), %windowbestlen |
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lea MAX_MATCH_8(%scan, %scanalign), %prev |
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/* the prefetching below makes very little difference... */ |
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prefetcht1 (%windowbestlen, %rdx) |
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prefetcht1 (%prev, %rdx) |
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/* |
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* Test the strings for equality, 8 bytes at a time. At the end, |
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* adjust %rdx so that it is offset to the exact byte that mismatched. |
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* |
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* It should be confessed that this loop usually does not represent |
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* much of the total running time. Replacing it with a more |
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* straightforward "rep cmpsb" would not drastically degrade |
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* performance -- unrolling it, for example, makes no difference. |
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*/ |
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#undef USE_SSE /* works, but is 6-7% slower, than non-SSE... */ |
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LoopCmps: |
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#ifdef USE_SSE |
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/* Preload the SSE registers */ |
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movdqu (%windowbestlen, %rdx), %xmm1 |
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movdqu (%prev, %rdx), %xmm2 |
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pcmpeqb %xmm2, %xmm1 |
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movdqu 16(%windowbestlen, %rdx), %xmm3 |
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movdqu 16(%prev, %rdx), %xmm4 |
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pcmpeqb %xmm4, %xmm3 |
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movdqu 32(%windowbestlen, %rdx), %xmm5 |
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movdqu 32(%prev, %rdx), %xmm6 |
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pcmpeqb %xmm6, %xmm5 |
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movdqu 48(%windowbestlen, %rdx), %xmm7 |
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movdqu 48(%prev, %rdx), %xmm8 |
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pcmpeqb %xmm8, %xmm7 |
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/* Check the comparisions' results */ |
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pmovmskb %xmm1, %rax |
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notw %ax |
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bsfw %ax, %ax |
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jnz LeaveLoopCmps |
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/* this is the only iteration of the loop with a possibility of having |
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incremented rdx by 0x108 (each loop iteration add 16*4 = 0x40 |
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and (0x40*4)+8=0x108 */ |
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add $8, %rdx |
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jz LenMaximum |
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add $8, %rdx |
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pmovmskb %xmm3, %rax |
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notw %ax |
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bsfw %ax, %ax |
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jnz LeaveLoopCmps |
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add $16, %rdx |
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pmovmskb %xmm5, %rax |
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notw %ax |
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bsfw %ax, %ax |
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jnz LeaveLoopCmps |
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add $16, %rdx |
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pmovmskb %xmm7, %rax |
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notw %ax |
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bsfw %ax, %ax |
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jnz LeaveLoopCmps |
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add $16, %rdx |
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jmp LoopCmps |
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LeaveLoopCmps: add %rax, %rdx |
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#else |
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mov (%windowbestlen, %rdx), %rax |
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xor (%prev, %rdx), %rax |
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jnz LeaveLoopCmps |
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mov 8(%windowbestlen, %rdx), %rax |
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xor 8(%prev, %rdx), %rax |
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jnz LeaveLoopCmps8 |
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mov 16(%windowbestlen, %rdx), %rax |
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xor 16(%prev, %rdx), %rax |
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jnz LeaveLoopCmps16 |
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add $24, %rdx |
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jnz LoopCmps |
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jmp LenMaximum |
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# if 0 |
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/* |
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* This three-liner is tantalizingly simple, but bsf is a slow instruction, |
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* and the complicated alternative down below is quite a bit faster. Sad... |
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*/ |
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LeaveLoopCmps: bsf %rax, %rax /* find the first non-zero bit */ |
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shrl $3, %eax /* divide by 8 to get the byte */ |
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add %rax, %rdx |
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# else |
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LeaveLoopCmps16: |
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add $8, %rdx |
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LeaveLoopCmps8: |
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add $8, %rdx |
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LeaveLoopCmps: testl $0xFFFFFFFF, %eax /* Check the first 4 bytes */ |
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jnz Check16 |
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add $4, %rdx |
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shr $32, %rax |
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Check16: testw $0xFFFF, %ax |
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jnz LenLower |
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add $2, %rdx |
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shrl $16, %eax |
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LenLower: subb $1, %al |
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adc $0, %rdx |
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# endif |
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#endif |
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/* Calculate the length of the match. If it is longer than MAX_MATCH, */ |
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/* then automatically accept it as the best possible match and leave. */ |
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lea (%prev, %rdx), %rax |
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sub %scan, %rax |
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cmpl $MAX_MATCH, %eax |
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jge LenMaximum |
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/* If the length of the match is not longer than the best match we */ |
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/* have so far, then forget it and return to the lookup loop. */ |
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cmpl %bestlend, %eax |
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jg LongerMatch |
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mov _windowbestlen, %windowbestlen |
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mov dsPrev, %prev |
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movl _chainlenwmask, %edx |
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jmp LookupLoop |
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/* s->match_start = cur_match; */ |
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/* best_len = len; */ |
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/* if (len >= nice_match) break; */ |
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/* scan_end = *(ushf*)(scan+best_len-1); */ |
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LongerMatch: |
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movl %eax, %bestlend |
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movl %curmatchd, dsMatchStart |
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cmpl %nicematch, %eax |
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jge LeaveNow |
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lea (%window, %bestlen), %windowbestlen |
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mov %windowbestlen, _windowbestlen |
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movzwl -1(%scan, %rax), %scanend |
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mov dsPrev, %prev |
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movl _chainlenwmask, %chainlenwmask |
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jmp LookupLoop |
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/* Accept the current string, with the maximum possible length. */ |
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LenMaximum: |
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movl $MAX_MATCH, %bestlend |
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movl %curmatchd, dsMatchStart |
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/* if ((uInt)best_len <= s->lookahead) return (uInt)best_len; */ |
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/* return s->lookahead; */ |
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LeaveNow: |
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movl dsLookahead, %eax |
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cmpl %eax, %bestlend |
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cmovngl %bestlend, %eax |
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LookaheadRet: |
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/* Restore the registers and return from whence we came. */ |
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mov save_rsi, %rsi |
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mov save_rbx, %rbx |
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mov save_r12, %r12 |
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mov save_r13, %r13 |
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mov save_r14, %r14 |
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mov save_r15, %r15 |
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ret |
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match_init: ret
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