cannam@89: /*
cannam@89:  * match.S -- optimized version of longest_match()
cannam@89:  * based on the similar work by Gilles Vollant, and Brian Raiter, written 1998
cannam@89:  *
cannam@89:  * This is free software; you can redistribute it and/or modify it
cannam@89:  * under the terms of the BSD License. Use by owners of Che Guevarra
cannam@89:  * parafernalia is prohibited, where possible, and highly discouraged
cannam@89:  * elsewhere.
cannam@89:  */
cannam@89: 
cannam@89: #ifndef NO_UNDERLINE
cannam@89: #	define	match_init	_match_init
cannam@89: #	define	longest_match	_longest_match
cannam@89: #endif
cannam@89: 
cannam@89: #define	scanend		ebx
cannam@89: #define	scanendw	bx
cannam@89: #define	chainlenwmask	edx /* high word: current chain len low word: s->wmask */
cannam@89: #define	curmatch	rsi
cannam@89: #define	curmatchd	esi
cannam@89: #define	windowbestlen	r8
cannam@89: #define	scanalign	r9
cannam@89: #define	scanalignd	r9d
cannam@89: #define	window		r10
cannam@89: #define	bestlen		r11
cannam@89: #define	bestlend	r11d
cannam@89: #define	scanstart	r12d
cannam@89: #define	scanstartw	r12w
cannam@89: #define scan		r13
cannam@89: #define nicematch	r14d
cannam@89: #define	limit		r15
cannam@89: #define	limitd		r15d
cannam@89: #define prev		rcx
cannam@89: 
cannam@89: /*
cannam@89:  * The 258 is a "magic number, not a parameter -- changing it
cannam@89:  * breaks the hell loose
cannam@89:  */
cannam@89: #define	MAX_MATCH	(258)
cannam@89: #define	MIN_MATCH	(3)
cannam@89: #define	MIN_LOOKAHEAD	(MAX_MATCH + MIN_MATCH + 1)
cannam@89: #define	MAX_MATCH_8	((MAX_MATCH + 7) & ~7)
cannam@89: 
cannam@89: /* stack frame offsets */
cannam@89: #define	LocalVarsSize	(112)
cannam@89: #define _chainlenwmask	( 8-LocalVarsSize)(%rsp)
cannam@89: #define _windowbestlen	(16-LocalVarsSize)(%rsp)
cannam@89: #define save_r14        (24-LocalVarsSize)(%rsp)
cannam@89: #define save_rsi        (32-LocalVarsSize)(%rsp)
cannam@89: #define save_rbx        (40-LocalVarsSize)(%rsp)
cannam@89: #define save_r12        (56-LocalVarsSize)(%rsp)
cannam@89: #define save_r13        (64-LocalVarsSize)(%rsp)
cannam@89: #define save_r15        (80-LocalVarsSize)(%rsp)
cannam@89: 
cannam@89: 
cannam@89: .globl	match_init, longest_match
cannam@89: 
cannam@89: /*
cannam@89:  * On AMD64 the first argument of a function (in our case -- the pointer to
cannam@89:  * deflate_state structure) is passed in %rdi, hence our offsets below are
cannam@89:  * all off of that.
cannam@89:  */
cannam@89: 
cannam@89: /* you can check the structure offset by running
cannam@89: 
cannam@89: #include <stdlib.h>
cannam@89: #include <stdio.h>
cannam@89: #include "deflate.h"
cannam@89: 
cannam@89: void print_depl()
cannam@89: {
cannam@89: deflate_state ds;
cannam@89: deflate_state *s=&ds;
cannam@89: printf("size pointer=%u\n",(int)sizeof(void*));
cannam@89: 
cannam@89: printf("#define dsWSize         (%3u)(%%rdi)\n",(int)(((char*)&(s->w_size))-((char*)s)));
cannam@89: printf("#define dsWMask         (%3u)(%%rdi)\n",(int)(((char*)&(s->w_mask))-((char*)s)));
cannam@89: printf("#define dsWindow        (%3u)(%%rdi)\n",(int)(((char*)&(s->window))-((char*)s)));
cannam@89: printf("#define dsPrev          (%3u)(%%rdi)\n",(int)(((char*)&(s->prev))-((char*)s)));
cannam@89: printf("#define dsMatchLen      (%3u)(%%rdi)\n",(int)(((char*)&(s->match_length))-((char*)s)));
cannam@89: printf("#define dsPrevMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_match))-((char*)s)));
cannam@89: printf("#define dsStrStart      (%3u)(%%rdi)\n",(int)(((char*)&(s->strstart))-((char*)s)));
cannam@89: printf("#define dsMatchStart    (%3u)(%%rdi)\n",(int)(((char*)&(s->match_start))-((char*)s)));
cannam@89: printf("#define dsLookahead     (%3u)(%%rdi)\n",(int)(((char*)&(s->lookahead))-((char*)s)));
cannam@89: printf("#define dsPrevLen       (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_length))-((char*)s)));
cannam@89: printf("#define dsMaxChainLen   (%3u)(%%rdi)\n",(int)(((char*)&(s->max_chain_length))-((char*)s)));
cannam@89: printf("#define dsGoodMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->good_match))-((char*)s)));
cannam@89: printf("#define dsNiceMatch     (%3u)(%%rdi)\n",(int)(((char*)&(s->nice_match))-((char*)s)));
cannam@89: }
cannam@89: 
cannam@89: */
cannam@89: 
cannam@89: 
cannam@89: /*
cannam@89:   to compile for XCode 3.2 on MacOSX x86_64
cannam@89:   - run "gcc -g -c -DXCODE_MAC_X64_STRUCTURE amd64-match.S"
cannam@89:  */
cannam@89: 
cannam@89: 
cannam@89: #ifndef CURRENT_LINX_XCODE_MAC_X64_STRUCTURE
cannam@89: #define dsWSize		( 68)(%rdi)
cannam@89: #define dsWMask		( 76)(%rdi)
cannam@89: #define dsWindow	( 80)(%rdi)
cannam@89: #define dsPrev		( 96)(%rdi)
cannam@89: #define dsMatchLen	(144)(%rdi)
cannam@89: #define dsPrevMatch	(148)(%rdi)
cannam@89: #define dsStrStart	(156)(%rdi)
cannam@89: #define dsMatchStart	(160)(%rdi)
cannam@89: #define dsLookahead	(164)(%rdi)
cannam@89: #define dsPrevLen	(168)(%rdi)
cannam@89: #define dsMaxChainLen	(172)(%rdi)
cannam@89: #define dsGoodMatch	(188)(%rdi)
cannam@89: #define dsNiceMatch	(192)(%rdi)
cannam@89: 
cannam@89: #else 
cannam@89: 
cannam@89: #ifndef STRUCT_OFFSET
cannam@89: #	define STRUCT_OFFSET	(0)
cannam@89: #endif
cannam@89: 
cannam@89: 
cannam@89: #define dsWSize		( 56 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsWMask		( 64 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsWindow	( 72 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsPrev		( 88 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsMatchLen	(136 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsPrevMatch	(140 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsStrStart	(148 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsMatchStart	(152 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsLookahead	(156 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsPrevLen	(160 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsMaxChainLen	(164 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsGoodMatch	(180 + STRUCT_OFFSET)(%rdi)
cannam@89: #define dsNiceMatch	(184 + STRUCT_OFFSET)(%rdi)
cannam@89: 
cannam@89: #endif
cannam@89: 
cannam@89: 
cannam@89: 
cannam@89: 
cannam@89: .text
cannam@89: 
cannam@89: /* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */
cannam@89: 
cannam@89: longest_match:
cannam@89: /*
cannam@89:  * Retrieve the function arguments. %curmatch will hold cur_match
cannam@89:  * throughout the entire function (passed via rsi on amd64).
cannam@89:  * rdi will hold the pointer to the deflate_state (first arg on amd64)
cannam@89:  */
cannam@89: 		mov     %rsi, save_rsi
cannam@89: 		mov     %rbx, save_rbx
cannam@89: 		mov	%r12, save_r12
cannam@89: 		mov     %r13, save_r13
cannam@89: 		mov     %r14, save_r14
cannam@89: 		mov     %r15, save_r15
cannam@89: 
cannam@89: /* uInt wmask = s->w_mask;						*/
cannam@89: /* unsigned chain_length = s->max_chain_length;				*/
cannam@89: /* if (s->prev_length >= s->good_match) {				*/
cannam@89: /*     chain_length >>= 2;						*/
cannam@89: /* }									*/
cannam@89: 
cannam@89: 		movl	dsPrevLen, %eax
cannam@89: 		movl	dsGoodMatch, %ebx
cannam@89: 		cmpl	%ebx, %eax
cannam@89: 		movl	dsWMask, %eax
cannam@89: 		movl	dsMaxChainLen, %chainlenwmask
cannam@89: 		jl	LastMatchGood
cannam@89: 		shrl	$2, %chainlenwmask
cannam@89: LastMatchGood:
cannam@89: 
cannam@89: /* chainlen is decremented once beforehand so that the function can	*/
cannam@89: /* use the sign flag instead of the zero flag for the exit test.	*/
cannam@89: /* It is then shifted into the high word, to make room for the wmask	*/
cannam@89: /* value, which it will always accompany.				*/
cannam@89: 
cannam@89: 		decl	%chainlenwmask
cannam@89: 		shll	$16, %chainlenwmask
cannam@89: 		orl	%eax, %chainlenwmask
cannam@89: 
cannam@89: /* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;	*/
cannam@89: 
cannam@89: 		movl	dsNiceMatch, %eax
cannam@89: 		movl	dsLookahead, %ebx
cannam@89: 		cmpl	%eax, %ebx
cannam@89: 		jl	LookaheadLess
cannam@89: 		movl	%eax, %ebx
cannam@89: LookaheadLess:	movl	%ebx, %nicematch
cannam@89: 
cannam@89: /* register Bytef *scan = s->window + s->strstart;			*/
cannam@89: 
cannam@89: 		mov	dsWindow, %window
cannam@89: 		movl	dsStrStart, %limitd
cannam@89: 		lea	(%limit, %window), %scan
cannam@89: 
cannam@89: /* Determine how many bytes the scan ptr is off from being		*/
cannam@89: /* dword-aligned.							*/
cannam@89: 
cannam@89: 		mov	%scan, %scanalign
cannam@89: 		negl	%scanalignd
cannam@89: 		andl	$3, %scanalignd
cannam@89: 
cannam@89: /* IPos limit = s->strstart > (IPos)MAX_DIST(s) ?			*/
cannam@89: /*     s->strstart - (IPos)MAX_DIST(s) : NIL;				*/
cannam@89: 
cannam@89: 		movl	dsWSize, %eax
cannam@89: 		subl	$MIN_LOOKAHEAD, %eax
cannam@89: 		xorl	%ecx, %ecx
cannam@89: 		subl	%eax, %limitd
cannam@89: 		cmovng	%ecx, %limitd
cannam@89: 
cannam@89: /* int best_len = s->prev_length;					*/
cannam@89: 
cannam@89: 		movl	dsPrevLen, %bestlend
cannam@89: 
cannam@89: /* Store the sum of s->window + best_len in %windowbestlen locally, and in memory.	*/
cannam@89: 
cannam@89: 		lea	(%window, %bestlen), %windowbestlen
cannam@89: 		mov	%windowbestlen, _windowbestlen
cannam@89: 
cannam@89: /* register ush scan_start = *(ushf*)scan;				*/
cannam@89: /* register ush scan_end   = *(ushf*)(scan+best_len-1);			*/
cannam@89: /* Posf *prev = s->prev;						*/
cannam@89: 
cannam@89: 		movzwl	(%scan), %scanstart
cannam@89: 		movzwl	-1(%scan, %bestlen), %scanend
cannam@89: 		mov	dsPrev, %prev
cannam@89: 
cannam@89: /* Jump into the main loop.						*/
cannam@89: 
cannam@89: 		movl	%chainlenwmask, _chainlenwmask
cannam@89: 		jmp	LoopEntry
cannam@89: 
cannam@89: .balign 16
cannam@89: 
cannam@89: /* do {
cannam@89:  *     match = s->window + cur_match;
cannam@89:  *     if (*(ushf*)(match+best_len-1) != scan_end ||
cannam@89:  *         *(ushf*)match != scan_start) continue;
cannam@89:  *     [...]
cannam@89:  * } while ((cur_match = prev[cur_match & wmask]) > limit
cannam@89:  *          && --chain_length != 0);
cannam@89:  *
cannam@89:  * Here is the inner loop of the function. The function will spend the
cannam@89:  * majority of its time in this loop, and majority of that time will
cannam@89:  * be spent in the first ten instructions.
cannam@89:  */
cannam@89: LookupLoop:
cannam@89: 		andl	%chainlenwmask, %curmatchd
cannam@89: 		movzwl	(%prev, %curmatch, 2), %curmatchd
cannam@89: 		cmpl	%limitd, %curmatchd
cannam@89: 		jbe	LeaveNow
cannam@89: 		subl	$0x00010000, %chainlenwmask
cannam@89: 		js	LeaveNow
cannam@89: LoopEntry:	cmpw	-1(%windowbestlen, %curmatch), %scanendw
cannam@89: 		jne	LookupLoop
cannam@89: 		cmpw	%scanstartw, (%window, %curmatch)
cannam@89: 		jne	LookupLoop
cannam@89: 
cannam@89: /* Store the current value of chainlen.					*/
cannam@89: 		movl	%chainlenwmask, _chainlenwmask
cannam@89: 
cannam@89: /* %scan is the string under scrutiny, and %prev to the string we	*/
cannam@89: /* are hoping to match it up with. In actuality, %esi and %edi are	*/
cannam@89: /* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is	*/
cannam@89: /* initialized to -(MAX_MATCH_8 - scanalign).				*/
cannam@89: 
cannam@89: 		mov	$(-MAX_MATCH_8), %rdx
cannam@89: 		lea	(%curmatch, %window), %windowbestlen
cannam@89: 		lea	MAX_MATCH_8(%windowbestlen, %scanalign), %windowbestlen
cannam@89: 		lea	MAX_MATCH_8(%scan, %scanalign), %prev
cannam@89: 
cannam@89: /* the prefetching below makes very little difference... */
cannam@89: 		prefetcht1	(%windowbestlen, %rdx)
cannam@89: 		prefetcht1	(%prev, %rdx)
cannam@89: 
cannam@89: /*
cannam@89:  * Test the strings for equality, 8 bytes at a time. At the end,
cannam@89:  * adjust %rdx so that it is offset to the exact byte that mismatched.
cannam@89:  *
cannam@89:  * It should be confessed that this loop usually does not represent
cannam@89:  * much of the total running time. Replacing it with a more
cannam@89:  * straightforward "rep cmpsb" would not drastically degrade
cannam@89:  * performance -- unrolling it, for example, makes no difference.
cannam@89:  */
cannam@89: 
cannam@89: #undef USE_SSE	/* works, but is 6-7% slower, than non-SSE... */
cannam@89: 
cannam@89: LoopCmps:
cannam@89: #ifdef USE_SSE
cannam@89: 		/* Preload the SSE registers */
cannam@89: 		movdqu	  (%windowbestlen, %rdx), %xmm1
cannam@89: 		movdqu	  (%prev, %rdx), %xmm2
cannam@89: 		pcmpeqb	%xmm2, %xmm1
cannam@89: 		movdqu	16(%windowbestlen, %rdx), %xmm3
cannam@89: 		movdqu	16(%prev, %rdx), %xmm4
cannam@89: 		pcmpeqb	%xmm4, %xmm3
cannam@89: 		movdqu	32(%windowbestlen, %rdx), %xmm5
cannam@89: 		movdqu	32(%prev, %rdx), %xmm6
cannam@89: 		pcmpeqb	%xmm6, %xmm5
cannam@89: 		movdqu	48(%windowbestlen, %rdx), %xmm7
cannam@89: 		movdqu	48(%prev, %rdx), %xmm8
cannam@89: 		pcmpeqb	%xmm8, %xmm7
cannam@89: 
cannam@89: 		/* Check the comparisions' results */
cannam@89: 		pmovmskb %xmm1, %rax
cannam@89: 		notw	%ax
cannam@89: 		bsfw	%ax, %ax
cannam@89: 		jnz	LeaveLoopCmps
cannam@89: 		
cannam@89: 		/* this is the only iteration of the loop with a possibility of having
cannam@89: 		   incremented rdx by 0x108 (each loop iteration add 16*4 = 0x40 
cannam@89: 		   and (0x40*4)+8=0x108 */
cannam@89: 		add	$8, %rdx
cannam@89: 		jz LenMaximum
cannam@89: 		add	$8, %rdx
cannam@89: 
cannam@89: 		
cannam@89: 		pmovmskb %xmm3, %rax
cannam@89: 		notw	%ax
cannam@89: 		bsfw	%ax, %ax
cannam@89: 		jnz	LeaveLoopCmps
cannam@89: 		
cannam@89: 		
cannam@89: 		add	$16, %rdx
cannam@89: 
cannam@89: 
cannam@89: 		pmovmskb %xmm5, %rax
cannam@89: 		notw	%ax
cannam@89: 		bsfw	%ax, %ax
cannam@89: 		jnz	LeaveLoopCmps
cannam@89: 		
cannam@89: 		add	$16, %rdx
cannam@89: 
cannam@89: 
cannam@89: 		pmovmskb %xmm7, %rax
cannam@89: 		notw	%ax
cannam@89: 		bsfw	%ax, %ax
cannam@89: 		jnz	LeaveLoopCmps
cannam@89: 		
cannam@89: 		add	$16, %rdx
cannam@89: 		
cannam@89: 		jmp	LoopCmps
cannam@89: LeaveLoopCmps:	add	%rax, %rdx
cannam@89: #else
cannam@89: 		mov	(%windowbestlen, %rdx), %rax
cannam@89: 		xor	(%prev, %rdx), %rax
cannam@89: 		jnz	LeaveLoopCmps
cannam@89: 		
cannam@89: 		mov	8(%windowbestlen, %rdx), %rax
cannam@89: 		xor	8(%prev, %rdx), %rax
cannam@89: 		jnz	LeaveLoopCmps8
cannam@89: 
cannam@89: 		mov	16(%windowbestlen, %rdx), %rax
cannam@89: 		xor	16(%prev, %rdx), %rax
cannam@89: 		jnz	LeaveLoopCmps16
cannam@89: 				
cannam@89: 		add	$24, %rdx
cannam@89: 		jnz	LoopCmps
cannam@89: 		jmp	LenMaximum
cannam@89: #	if 0
cannam@89: /*
cannam@89:  * This three-liner is tantalizingly simple, but bsf is a slow instruction,
cannam@89:  * and the complicated alternative down below is quite a bit faster. Sad...
cannam@89:  */
cannam@89: 
cannam@89: LeaveLoopCmps:	bsf	%rax, %rax /* find the first non-zero bit */
cannam@89: 		shrl	$3, %eax /* divide by 8 to get the byte */
cannam@89: 		add	%rax, %rdx
cannam@89: #	else
cannam@89: LeaveLoopCmps16:
cannam@89: 		add	$8, %rdx
cannam@89: LeaveLoopCmps8:
cannam@89: 		add	$8, %rdx
cannam@89: LeaveLoopCmps:	testl   $0xFFFFFFFF, %eax /* Check the first 4 bytes */
cannam@89: 		jnz     Check16
cannam@89: 		add     $4, %rdx
cannam@89: 		shr     $32, %rax
cannam@89: Check16:        testw   $0xFFFF, %ax
cannam@89: 		jnz     LenLower
cannam@89: 		add	$2, %rdx
cannam@89: 		shrl	$16, %eax
cannam@89: LenLower:	subb	$1, %al
cannam@89: 		adc	$0, %rdx
cannam@89: #	endif
cannam@89: #endif
cannam@89: 
cannam@89: /* Calculate the length of the match. If it is longer than MAX_MATCH,	*/
cannam@89: /* then automatically accept it as the best possible match and leave.	*/
cannam@89: 
cannam@89: 		lea	(%prev, %rdx), %rax
cannam@89: 		sub	%scan, %rax
cannam@89: 		cmpl	$MAX_MATCH, %eax
cannam@89: 		jge	LenMaximum
cannam@89: 
cannam@89: /* If the length of the match is not longer than the best match we	*/
cannam@89: /* have so far, then forget it and return to the lookup loop.		*/
cannam@89: 
cannam@89: 		cmpl	%bestlend, %eax
cannam@89: 		jg	LongerMatch
cannam@89: 		mov	_windowbestlen, %windowbestlen
cannam@89: 		mov	dsPrev, %prev
cannam@89: 		movl	_chainlenwmask, %edx
cannam@89: 		jmp	LookupLoop
cannam@89: 
cannam@89: /*         s->match_start = cur_match;					*/
cannam@89: /*         best_len = len;						*/
cannam@89: /*         if (len >= nice_match) break;				*/
cannam@89: /*         scan_end = *(ushf*)(scan+best_len-1);			*/
cannam@89: 
cannam@89: LongerMatch:
cannam@89: 		movl	%eax, %bestlend
cannam@89: 		movl	%curmatchd, dsMatchStart
cannam@89: 		cmpl	%nicematch, %eax
cannam@89: 		jge	LeaveNow
cannam@89: 
cannam@89: 		lea	(%window, %bestlen), %windowbestlen
cannam@89: 		mov	%windowbestlen, _windowbestlen
cannam@89: 
cannam@89: 		movzwl	-1(%scan, %rax), %scanend
cannam@89: 		mov	dsPrev, %prev
cannam@89: 		movl	_chainlenwmask, %chainlenwmask
cannam@89: 		jmp	LookupLoop
cannam@89: 
cannam@89: /* Accept the current string, with the maximum possible length.		*/
cannam@89: 
cannam@89: LenMaximum:
cannam@89: 		movl	$MAX_MATCH, %bestlend
cannam@89: 		movl	%curmatchd, dsMatchStart
cannam@89: 
cannam@89: /* if ((uInt)best_len <= s->lookahead) return (uInt)best_len;		*/
cannam@89: /* return s->lookahead;							*/
cannam@89: 
cannam@89: LeaveNow:
cannam@89: 		movl	dsLookahead, %eax
cannam@89: 		cmpl	%eax, %bestlend
cannam@89: 		cmovngl	%bestlend, %eax
cannam@89: LookaheadRet:
cannam@89: 
cannam@89: /* Restore the registers and return from whence we came.			*/
cannam@89: 
cannam@89: 	mov	save_rsi, %rsi
cannam@89: 	mov	save_rbx, %rbx
cannam@89: 	mov	save_r12, %r12
cannam@89: 	mov	save_r13, %r13
cannam@89: 	mov	save_r14, %r14
cannam@89: 	mov	save_r15, %r15
cannam@89: 
cannam@89: 	ret
cannam@89: 
cannam@89: match_init:	ret