--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/zlib/contrib/asm586/match.S	Sun Feb 07 18:27:48 2010 +0900
@@ -0,0 +1,364 @@
+/* match.s -- Pentium-optimized version of longest_match()
+ * Written for zlib 1.1.2
+ * Copyright (C) 1998 Brian Raiter <breadbox@muppetlabs.com>
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License.
+ */
+
+#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	wmask			0	/* local copy of s->wmask	*/
+#define	window			4	/* local copy of s->window	*/
+#define	windowbestlen		8	/* s->window + bestlen		*/
+#define	chainlenscanend		12	/* high word: current chain len	*/
+					/* low word: last bytes sought	*/
+#define	scanstart		16	/* first 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
+
+/* Offsets for fields in the deflate_state structure. These numbers
+ * are calculated from the definition of deflate_state, with the
+ * assumption that the compiler will dword-align the fields. (Thus,
+ * changing the definition of deflate_state could easily cause this
+ * program to crash horribly, without so much as a warning at
+ * compile time. Sigh.)
+ */
+
+/* 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) */
+
+longest_match:
+
+/* Save registers that the compiler may be using, and adjust %esp to	*/
+/* make room for our stack frame.					*/
+
+		pushl	%ebp
+		pushl	%edi
+		pushl	%esi
+		pushl	%ebx
+		subl	$LocalVarsSize, %esp
+
+/* 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
+
+/* 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:
+
+/* 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	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 scanend	*/
+/* scanend value, which it will always accompany.			*/
+
+		decl	%ebx
+		shll	$16, %ebx
+
+/* 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);			*/
+
+		movw	(%edi), %bx
+		movw	%bx, scanstart(%esp)
+		movw	-1(%edi,%eax), %bx
+		movl	%ebx, chainlenscanend(%esp)
+
+/* Posf *prev = s->prev;						*/
+/* uInt wmask = s->w_mask;						*/
+
+		movl	dsPrev(%edx), %edi
+		movl	dsWMask(%edx), %edx
+		mov	%edx, wmask(%esp)
+
+/* Jump into the main loop.						*/
+
+		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 = chainlenscanend - i.e., ((chainlen << 16) | scanend)
+ * %ecx = curmatch
+ * %edx = curmatch & wmask
+ * %esi = windowbestlen - i.e., (window + bestlen)
+ * %edi = prev
+ * %ebp = limit
+ *
+ * Two optimization notes on the choice of instructions:
+ *
+ * The first instruction uses a 16-bit address, which costs an extra,
+ * unpairable cycle. This is cheaper than doing a 32-bit access and
+ * zeroing the high word, due to the 3-cycle misalignment penalty which
+ * would occur half the time. This also turns out to be cheaper than
+ * doing two separate 8-bit accesses, as the memory is so rarely in the
+ * L1 cache.
+ *
+ * The window buffer, however, apparently spends a lot of time in the
+ * cache, and so it is faster to retrieve the word at the end of the
+ * match string with two 8-bit loads. The instructions that test the
+ * word at the beginning of the match string, however, are executed
+ * much less frequently, and there it was cheaper to use 16-bit
+ * instructions, which avoided the necessity of saving off and
+ * subsequently reloading one of the other registers.
+ */
+LookupLoop:
+							/* 1 U & V  */
+		movw	(%edi,%edx,2), %cx		/* 2 U pipe */
+		movl	wmask(%esp), %edx		/* 2 V pipe */
+		cmpl	%ebp, %ecx			/* 3 U pipe */
+		jbe	LeaveNow			/* 3 V pipe */
+		subl	$0x00010000, %ebx		/* 4 U pipe */
+		js	LeaveNow			/* 4 V pipe */
+LoopEntry:	movb	-1(%esi,%ecx), %al		/* 5 U pipe */
+		andl	%ecx, %edx			/* 5 V pipe */
+		cmpb	%bl, %al			/* 6 U pipe */
+		jnz	LookupLoop			/* 6 V pipe */
+		movb	(%esi,%ecx), %ah
+		cmpb	%bh, %ah
+		jnz	LookupLoop
+		movl	window(%esp), %eax
+		movw	(%eax,%ecx), %ax
+		cmpw	scanstart(%esp), %ax
+		jnz	LookupLoop
+
+/* Store the current value of chainlen.					*/
+
+		movl	%ebx, chainlenscanend(%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
+		movl	(%edi,%edx), %ebx
+		xorl	%ebx, %eax
+		jnz	LeaveLoopCmps
+		movl	4(%esi,%edx), %eax
+		movl	4(%edi,%edx), %ebx
+		xorl	%ebx, %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	chainlenscanend(%esp), %ebx
+		movl	windowbestlen(%esp), %esi
+		movl	dsPrev(%edx), %edi
+		movl	wmask(%esp), %edx
+		andl	%ecx, %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)
+		movl	chainlenscanend(%esp), %ebx
+		movw	-1(%edi,%eax), %bx
+		movl	dsPrev(%edx), %edi
+		movl	%ebx, chainlenscanend(%esp)
+		movl	wmask(%esp), %edx
+		andl	%ecx, %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
+		popl	%ebx
+		popl	%esi
+		popl	%edi
+		popl	%ebp
+match_init:	ret