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452 lines
12 KiB
ArmAsm
452 lines
12 KiB
ArmAsm
/*
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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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