/*

 * match.S -- optimized version of longest_match()

 * based on the similar work by Gilles Vollant, and Brian Raiter, written 1998

 *

 * This is free software; you can redistribute it and/or modify it

 * under the terms of the BSD License. Use by owners of Che Guevarra

 * parafernalia is prohibited, where possible, and highly discouraged

 * elsewhere.

 */

#ifndef NO_UNDERLINE

#	define	match_init	_match_init

#	define	longest_match	_longest_match

#endif

#define	scanend		ebx

#define	scanendw	bx

#define	chainlenwmask	edx /* high word: current chain len low word: s->wmask */

#define	curmatch	rsi

#define	curmatchd	esi

#define	windowbestlen	r8

#define	scanalign	r9

#define	scanalignd	r9d

#define	window		r10

#define	bestlen		r11

#define	bestlend	r11d

#define	scanstart	r12d

#define	scanstartw	r12w

#define scan		r13

#define nicematch	r14d

#define	limit		r15

#define	limitd		r15d

#define prev		rcx

/*

 * The 258 is a "magic number, not a parameter -- changing it

 * breaks the hell loose

 */

#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	LocalVarsSize	(112)

#define _chainlenwmask	( 8-LocalVarsSize)(%rsp)

#define _windowbestlen	(16-LocalVarsSize)(%rsp)

#define save_r14        (24-LocalVarsSize)(%rsp)

#define save_rsi        (32-LocalVarsSize)(%rsp)

#define save_rbx        (40-LocalVarsSize)(%rsp)

#define save_r12        (56-LocalVarsSize)(%rsp)

#define save_r13        (64-LocalVarsSize)(%rsp)

#define save_r15        (80-LocalVarsSize)(%rsp)

.globl	match_init, longest_match

/*

 * On AMD64 the first argument of a function (in our case -- the pointer to

 * deflate_state structure) is passed in %rdi, hence our offsets below are

 * all off of that.

 */

/* you can check the structure offset by running

#include <stdlib.h></stdlib.h>

#include <stdio.h></stdio.h>

#include "deflate.h"

void print_depl()

{

deflate_state ds;

deflate_state *s=&ds;

printf("size pointer=%u\n",(int)sizeof(void*));

printf("#define dsWSize         (%3u)(%%rdi)\n",(int)(((char*)&(s->w_size))-((char*)s)));

printf("#define dsWMask         (%3u)(%%rdi)\n",(int)(((char*)&(s->w_mask))-((char*)s)));

printf("#define dsWindow        (%3u)(%%rdi)\n",(int)(((char*)&(s->window))-((char*)s)));

printf("#define dsPrev          (%3u)(%%rdi)\n",(int)(((char*)&(s->prev))-((char*)s)));

printf("#define dsMatchLen      (%3u)(%%rdi)\n",(int)(((char*)&(s->match_length))-((char*)s)));

printf("#define dsPrevMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_match))-((char*)s)));

printf("#define dsStrStart      (%3u)(%%rdi)\n",(int)(((char*)&(s->strstart))-((char*)s)));

printf("#define dsMatchStart    (%3u)(%%rdi)\n",(int)(((char*)&(s->match_start))-((char*)s)));

printf("#define dsLookahead     (%3u)(%%rdi)\n",(int)(((char*)&(s->lookahead))-((char*)s)));

printf("#define dsPrevLen       (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_length))-((char*)s)));

printf("#define dsMaxChainLen   (%3u)(%%rdi)\n",(int)(((char*)&(s->max_chain_length))-((char*)s)));

printf("#define dsGoodMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->good_match))-((char*)s)));

printf("#define dsNiceMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->nice_match))-((char*)s)));

}

*/

/*

  to compile for XCode 3.2 on MacOSX x86_64

  - run "gcc -g -c -DXCODE_MAC_X64_STRUCTURE amd64-match.S"

 */

#ifndef CURRENT_LINX_XCODE_MAC_X64_STRUCTURE

#define dsWSize		( 68)(%rdi)

#define dsWMask		( 76)(%rdi)

#define dsWindow	( 80)(%rdi)

#define dsPrev		( 96)(%rdi)

#define dsMatchLen	(144)(%rdi)

#define dsPrevMatch	(148)(%rdi)

#define dsStrStart	(156)(%rdi)

#define dsMatchStart	(160)(%rdi)

#define dsLookahead	(164)(%rdi)

#define dsPrevLen	(168)(%rdi)

#define dsMaxChainLen	(172)(%rdi)

#define dsGoodMatch	(188)(%rdi)

#define dsNiceMatch	(192)(%rdi)

#else 

#ifndef STRUCT_OFFSET

#	define STRUCT_OFFSET	(0)

#endif

#define dsWSize		( 56 + STRUCT_OFFSET)(%rdi)

#define dsWMask		( 64 + STRUCT_OFFSET)(%rdi)

#define dsWindow	( 72 + STRUCT_OFFSET)(%rdi)

#define dsPrev		( 88 + STRUCT_OFFSET)(%rdi)

#define dsMatchLen	(136 + STRUCT_OFFSET)(%rdi)

#define dsPrevMatch	(140 + STRUCT_OFFSET)(%rdi)

#define dsStrStart	(148 + STRUCT_OFFSET)(%rdi)

#define dsMatchStart	(152 + STRUCT_OFFSET)(%rdi)

#define dsLookahead	(156 + STRUCT_OFFSET)(%rdi)

#define dsPrevLen	(160 + STRUCT_OFFSET)(%rdi)

#define dsMaxChainLen	(164 + STRUCT_OFFSET)(%rdi)

#define dsGoodMatch	(180 + STRUCT_OFFSET)(%rdi)

#define dsNiceMatch	(184 + STRUCT_OFFSET)(%rdi)

#endif

.text

/* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */

longest_match:

/*

 * Retrieve the function arguments. %curmatch will hold cur_match

 * throughout the entire function (passed via rsi on amd64).

 * rdi will hold the pointer to the deflate_state (first arg on amd64)

 */

		mov     %rsi, save_rsi

		mov     %rbx, save_rbx

		mov	%r12, save_r12

		mov     %r13, save_r13

		mov     %r14, save_r14

		mov     %r15, save_r15

/* uInt wmask = s->w_mask;						*/

/* unsigned chain_length = s->max_chain_length;				*/

/* if (s->prev_length >= s->good_match) {				*/

/*     chain_length >>= 2;						*/

/* }									*/

		movl	dsPrevLen, %eax

		movl	dsGoodMatch, %ebx

		cmpl	%ebx, %eax

		movl	dsWMask, %eax

		movl	dsMaxChainLen, %chainlenwmask

		jl	LastMatchGood

		shrl	$2, %chainlenwmask

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	%chainlenwmask

		shll	$16, %chainlenwmask

		orl	%eax, %chainlenwmask

/* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;	*/

		movl	dsNiceMatch, %eax

		movl	dsLookahead, %ebx

		cmpl	%eax, %ebx

		jl	LookaheadLess

		movl	%eax, %ebx

LookaheadLess:	movl	%ebx, %nicematch

/* register Bytef *scan = s->window + s->strstart;			*/

		mov	dsWindow, %window

		movl	dsStrStart, %limitd

		lea	(%limit, %window), %scan

/* Determine how many bytes the scan ptr is off from being		*/

/* dword-aligned.							*/

		mov	%scan, %scanalign

		negl	%scanalignd

		andl	$3, %scanalignd

/* IPos limit = s->strstart > (IPos)MAX_DIST(s) ?			*/

/*     s->strstart - (IPos)MAX_DIST(s) : NIL;				*/

		movl	dsWSize, %eax

		subl	$MIN_LOOKAHEAD, %eax

		xorl	%ecx, %ecx

		subl	%eax, %limitd

		cmovng	%ecx, %limitd

/* int best_len = s->prev_length;					*/

		movl	dsPrevLen, %bestlend

/* Store the sum of s->window + best_len in %windowbestlen locally, and in memory.	*/

		lea	(%window, %bestlen), %windowbestlen

		mov	%windowbestlen, _windowbestlen

/* register ush scan_start = *(ushf*)scan;				*/

/* register ush scan_end   = *(ushf*)(scan+best_len-1);			*/

/* Posf *prev = s->prev;						*/

		movzwl	(%scan), %scanstart

		movzwl	-1(%scan, %bestlen), %scanend

		mov	dsPrev, %prev

/* Jump into the main loop.						*/

		movl	%chainlenwmask, _chainlenwmask

		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.

 */

LookupLoop:

		andl	%chainlenwmask, %curmatchd

		movzwl	(%prev, %curmatch, 2), %curmatchd

		cmpl	%limitd, %curmatchd

		jbe	LeaveNow

		subl	$0x00010000, %chainlenwmask

		js	LeaveNow

LoopEntry:	cmpw	-1(%windowbestlen, %curmatch), %scanendw

		jne	LookupLoop

		cmpw	%scanstartw, (%window, %curmatch)

		jne	LookupLoop

/* Store the current value of chainlen.					*/

		movl	%chainlenwmask, _chainlenwmask

/* %scan is the string under scrutiny, and %prev 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).				*/

		mov	$(-MAX_MATCH_8), %rdx

		lea	(%curmatch, %window), %windowbestlen

		lea	MAX_MATCH_8(%windowbestlen, %scanalign), %windowbestlen

		lea	MAX_MATCH_8(%scan, %scanalign), %prev

/* the prefetching below makes very little difference... */

		prefetcht1	(%windowbestlen, %rdx)

		prefetcht1	(%prev, %rdx)

/*

 * Test the strings for equality, 8 bytes at a time. At the end,

 * adjust %rdx so that it is offset to the exact byte that mismatched.

 *

 * 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 -- unrolling it, for example, makes no difference.

 */

#undef USE_SSE	/* works, but is 6-7% slower, than non-SSE... */

LoopCmps:

#ifdef USE_SSE

		/* Preload the SSE registers */

		movdqu	  (%windowbestlen, %rdx), %xmm1

		movdqu	  (%prev, %rdx), %xmm2

		pcmpeqb	%xmm2, %xmm1

		movdqu	16(%windowbestlen, %rdx), %xmm3

		movdqu	16(%prev, %rdx), %xmm4

		pcmpeqb	%xmm4, %xmm3

		movdqu	32(%windowbestlen, %rdx), %xmm5

		movdqu	32(%prev, %rdx), %xmm6

		pcmpeqb	%xmm6, %xmm5

		movdqu	48(%windowbestlen, %rdx), %xmm7

		movdqu	48(%prev, %rdx), %xmm8

		pcmpeqb	%xmm8, %xmm7

		/* Check the comparisions' results */

		pmovmskb %xmm1, %rax

		notw	%ax

		bsfw	%ax, %ax

		jnz	LeaveLoopCmps

		/* this is the only iteration of the loop with a possibility of having

		   incremented rdx by 0x108 (each loop iteration add 16*4 = 0x40 

		   and (0x40*4)+8=0x108 */

		add	$8, %rdx

		jz LenMaximum

		add	$8, %rdx

		pmovmskb %xmm3, %rax

		notw	%ax

		bsfw	%ax, %ax

		jnz	LeaveLoopCmps

		add	$16, %rdx

		pmovmskb %xmm5, %rax

		notw	%ax

		bsfw	%ax, %ax

		jnz	LeaveLoopCmps

		add	$16, %rdx

		pmovmskb %xmm7, %rax

		notw	%ax

		bsfw	%ax, %ax

		jnz	LeaveLoopCmps

		add	$16, %rdx

		jmp	LoopCmps

LeaveLoopCmps:	add	%rax, %rdx

#else

		mov	(%windowbestlen, %rdx), %rax

		xor	(%prev, %rdx), %rax

		jnz	LeaveLoopCmps

		mov	8(%windowbestlen, %rdx), %rax

		xor	8(%prev, %rdx), %rax

		jnz	LeaveLoopCmps8

		mov	16(%windowbestlen, %rdx), %rax

		xor	16(%prev, %rdx), %rax

		jnz	LeaveLoopCmps16

		add	$24, %rdx

		jnz	LoopCmps

		jmp	LenMaximum

#	if 0

/*

 * This three-liner is tantalizingly simple, but bsf is a slow instruction,

 * and the complicated alternative down below is quite a bit faster. Sad...

 */

LeaveLoopCmps:	bsf	%rax, %rax /* find the first non-zero bit */

		shrl	$3, %eax /* divide by 8 to get the byte */

		add	%rax, %rdx

#	else

LeaveLoopCmps16:

		add	$8, %rdx

LeaveLoopCmps8:

		add	$8, %rdx

LeaveLoopCmps:	testl   $0xFFFFFFFF, %eax /* Check the first 4 bytes */

		jnz     Check16

		add     $4, %rdx

		shr     $32, %rax

Check16:        testw   $0xFFFF, %ax

		jnz     LenLower

		add	$2, %rdx

		shrl	$16, %eax

LenLower:	subb	$1, %al

		adc	$0, %rdx

#	endif

#endif

/* 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	(%prev, %rdx), %rax

		sub	%scan, %rax

		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.		*/

		cmpl	%bestlend, %eax

		jg	LongerMatch

		mov	_windowbestlen, %windowbestlen

		mov	dsPrev, %prev

		movl	_chainlenwmask, %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	%eax, %bestlend

		movl	%curmatchd, dsMatchStart

		cmpl	%nicematch, %eax

		jge	LeaveNow

		lea	(%window, %bestlen), %windowbestlen

		mov	%windowbestlen, _windowbestlen

		movzwl	-1(%scan, %rax), %scanend

		mov	dsPrev, %prev

		movl	_chainlenwmask, %chainlenwmask

		jmp	LookupLoop

/* Accept the current string, with the maximum possible length.		*/

LenMaximum:

		movl	$MAX_MATCH, %bestlend

		movl	%curmatchd, dsMatchStart

/* if ((uInt)best_len <= s->lookahead) return (uInt)best_len;		*/

/* return s->lookahead;							*/

LeaveNow:

		movl	dsLookahead, %eax

		cmpl	%eax, %bestlend

		cmovngl	%bestlend, %eax

LookaheadRet:

/* Restore the registers and return from whence we came.			*/

	mov	save_rsi, %rsi

	mov	save_rbx, %rbx

	mov	save_r12, %r12

	mov	save_r13, %r13

	mov	save_r14, %r14

	mov	save_r15, %r15

	ret

match_init:	ret