--- /dev/null
+/* 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
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