2 files changed, 397 insertions, 0 deletions

diff --git a/contrib/asm586/README.586 b/contrib/asm586/README.586
new file mode 100644
index 0000000..6bb78f3
--- /dev/null
+++ b/contrib/asm586/README.586
@@ -0,0 +1,43 @@
+This is a patched version of zlib modified to use
+Pentium-optimized assembly code in the deflation algorithm. The files
+changed/added by this patch are:
+
+README.586
+match.S
+
+The effectiveness of these modifications is a bit marginal, as the the
+program's bottleneck seems to be mostly L1-cache contention, for which
+there is no real way to work around without rewriting the basic
+algorithm. The speedup on average is around 5-10% (which is generally
+less than the amount of variance between subsequent executions).
+However, when used at level 9 compression, the cache contention can
+drop enough for the assembly version to achieve 10-20% speedup (and
+sometimes more, depending on the amount of overall redundancy in the
+files). Even here, though, cache contention can still be the limiting
+factor, depending on the nature of the program using the zlib library.
+This may also mean that better improvements will be seen on a Pentium
+with MMX, which suffers much less from L1-cache contention, but I have
+not yet verified this.
+
+Note that this code has been tailored for the Pentium in particular,
+and will not perform well on the Pentium Pro (due to the use of a
+partial register in the inner loop).
+
+If you are using an assembler other than GNU as, you will have to
+translate match.S to use your assembler's syntax. (Have fun.)
+
+Brian Raiter
+breadbox@muppetlabs.com
+April, 1998
+
+
+Added for zlib 1.1.3:
+
+The patches come from
+http://www.muppetlabs.com/~breadbox/software/assembly.html
+
+To compile zlib with this asm file, copy match.S to the zlib directory
+then do:
+
+CFLAGS="-O3 -DASMV" ./configure
+make OBJA=match.o
diff --git a/contrib/asm586/match.S b/contrib/asm586/match.S
new file mode 100644
index 0000000..8f16140
--- /dev/null
+++ b/contrib/asm586/match.S
@@ -0,0 +1,354 @@
+/* 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.)
+ */
+#define dsWSize                 36
+#define dsWMask                 44
+#define dsWindow                48
+#define dsPrev                  56
+#define dsMatchLen              88
+#define dsPrevMatch             92
+#define dsStrStart              100
+#define dsMatchStart            104
+#define dsLookahead             108
+#define dsPrevLen               112
+#define dsMaxChainLen           116
+#define dsGoodMatch             132
+#define dsNiceMatch             136
+
+
+.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