364 lines
11 KiB
ArmAsm
364 lines
11 KiB
ArmAsm
/* 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
|