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