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crc_i386.S
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crc_i386.S
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/*
Copyright (c) 1990-2007 Info-ZIP. All rights reserved.
See the accompanying file LICENSE, version 2000-Apr-09 or later
(the contents of which are also included in zip.h) for terms of use.
If, for some reason, all these files are missing, the Info-ZIP license
also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
*/
/*
* crc_i386.S, optimized CRC calculation function for Zip and UnZip,
* created by Paul Kienitz and Christian Spieler. Last revised 07 Jan 2007.
*
* GRR 961110: incorporated Scott Field optimizations from win32/crc_i386.asm
* => overall 6% speedup in "unzip -tq" on 9MB zipfile (486-66)
*
* SPC 970402: revised for Rodney Brown's optimizations (32-bit-wide
* aligned reads for most of the data from buffer), can be
* disabled by defining the macro NO_32_BIT_LOADS
*
* SPC 971012: added Rodney Brown's additional tweaks for 32-bit-optimized
* CPUs (like the Pentium Pro, Pentium II, and probably some
* Pentium clones). This optimization is controlled by the
* preprocessor switch "__686" and is disabled by default.
* (This default is based on the assumption that most users
* do not yet work on a Pentium Pro or Pentium II machine ...)
*
* COS 050116: Enabled the 686 build by default, because there are hardly any
* pre-686 CPUs in serious use nowadays. (See SPC 970402 above.)
*
* SPC 060103: Updated code to incorporate newer optimizations found in zlib.
*
* SPC 070107: Added conditional switch to deactivate crc32() compilation.
*
* FLAT memory model assumed. Calling interface:
* - args are pushed onto the stack from right to left,
* - return value is given in the EAX register,
* - all other registers (with exception of EFLAGS) are preserved. (With
* GNU C 2.7.x, %edx and %ecx are `scratch' registers, but preserving
* them nevertheless adds only 4 single byte instructions.)
*
* This source generates the function
* ulg crc32(ulg crc, ZCONST uch *buf, extent len).
*
* Loop unrolling can be disabled by defining the macro NO_UNROLLED_LOOPS.
* This results in shorter code at the expense of reduced performance.
*/
/* This file is NOT used in conjunction with zlib, or when only creation of
* the basic CRC_32_Table (for other purpose) is requested.
*/
#if !defined(USE_ZLIB) && !defined(CRC_TABLE_ONLY)
/* Preprocess with -DNO_UNDERLINE if your C compiler does not prefix
* external symbols with an underline character '_'.
*/
#if defined(NO_UNDERLINE) || defined(__ELF__)
# define _crc32 crc32
# define _get_crc_table get_crc_table
#endif
/* Use 16-byte alignment if your assembler supports it. Warning: gas
* uses a log(x) parameter (.align 4 means 16-byte alignment). On SVR4
* the parameter is a number of bytes.
*/
#ifndef ALIGNMENT
# define ALIGNMENT .align 4,0x90
#endif
#if defined(i386) || defined(_i386) || defined(_I386) || defined(__i386)
/* This version is for 386 Unix, OS/2, MSDOS in 32 bit mode (gcc & gas).
* Warning: it uses the AT&T syntax: mov source,dest
* This file is only optional. If you want to use the C version,
* remove -DASM_CRC from CFLAGS in Makefile and set OBJA to an empty string.
*/
.file "crc_i386.S"
#if !defined(PRE_686) && !defined(__686)
/* Optimize for Pentium Pro and compatible CPUs by default. */
# define __686
#endif
#if defined(NO_STD_STACKFRAME) && defined(USE_STD_STACKFRAME)
# undef USE_STACKFRAME
#else
/* The default is to use standard stack frame entry, because it
* results in smaller code!
*/
# ifndef USE_STD_STACKFRAME
# define USE_STD_STACKFRAME
# endif
#endif
#ifdef USE_STD_STACKFRAME
# define _STD_ENTRY pushl %ebp ; movl %esp,%ebp
# define arg1 8(%ebp)
# define arg2 12(%ebp)
# define arg3 16(%ebp)
# define _STD_LEAVE popl %ebp
#else /* !USE_STD_STACKFRAME */
# define _STD_ENTRY
# define arg1 24(%esp)
# define arg2 28(%esp)
# define arg3 32(%esp)
# define _STD_LEAVE
#endif /* ?USE_STD_STACKFRAME */
/*
* These two (three) macros make up the loop body of the CRC32 cruncher.
* registers modified:
* eax : crc value "c"
* esi : pointer to next data byte (or lword) "buf++"
* registers read:
* edi : pointer to base of crc_table array
* scratch registers:
* ebx : index into crc_table array
* (requires upper three bytes = 0 when __686 is undefined)
*/
#ifndef __686 /* optimize for 386, 486, Pentium */
#define Do_CRC /* c = (c >> 8) ^ table[c & 0xFF] */\
movb %al, %bl ;/* tmp = c & 0xFF */\
shrl $8, %eax ;/* c = (c >> 8) */\
xorl (%edi, %ebx, 4), %eax ;/* c ^= table[tmp] */
#else /* __686 : optimize for Pentium Pro and compatible CPUs */
#define Do_CRC /* c = (c >> 8) ^ table[c & 0xFF] */\
movzbl %al, %ebx ;/* tmp = c & 0xFF */\
shrl $8, %eax ;/* c = (c >> 8) */\
xorl (%edi, %ebx, 4), %eax ;/* c ^=table[tmp] */
#endif /* ?__686 */
#define Do_CRC_byte /* c = (c >> 8) ^ table[(c^*buf++)&0xFF] */\
xorb (%esi), %al ;/* c ^= *buf */\
incl %esi ;/* buf++ */\
Do_CRC
#define Do_CRC_byteof(ofs) /* c = (c >> 8) ^ table[(c^*buf++)&0xFF] */\
xorb ofs(%esi), %al ;/* c ^= *buf */\
incl %esi ;/* buf++ */\
Do_CRC
#ifndef NO_32_BIT_LOADS
# ifdef IZ_CRCOPTIM_UNFOLDTBL
/* the edx register is needed in crc calculation */
# define SavLen arg3
# define UpdCRC_lword \
movzbl %al, %ebx ; \
movl 3072(%edi,%ebx,4), %edx ; \
movzbl %ah, %ebx ; \
shrl $16, %eax ; \
xor 2048(%edi,%ebx,4), %edx ; \
movzbl %al, %ebx ; \
shrl $8,%eax ; \
xorl 1024(%edi,%ebx,4), %edx ; \
movl (%edi,%eax,4), %eax ; \
xorl %edx,%eax ;
# define UpdCRC_lword_sh(dwPtrIncr) \
movzbl %al, %ebx ; \
movl 3072(%edi,%ebx,4), %edx ; \
movzbl %ah, %ebx ; \
shrl $16, %eax ; \
xor 2048(%edi,%ebx,4), %edx ; \
movzbl %al, %ebx ; \
addl $4*(dwPtrIncr), %esi ;/* ((ulg *)buf)+=dwPtrIncr */\
shrl $8,%eax ; \
xorl 1024(%edi,%ebx,4), %edx ; \
movl (%edi,%eax,4),%eax ; \
xorl %edx,%eax ;
# else /* !IZ_CRCOPTIM_UNFOLDTBL */
/* the edx register is not needed anywhere else */
# define SavLen %edx
# define UpdCRC_lword \
Do_CRC \
Do_CRC \
Do_CRC \
Do_CRC
# define UpdCRC_lword_sh(dwPtrIncr) \
Do_CRC \
Do_CRC \
addl $4*(dwPtrIncr), %esi ;/* ((ulg *)buf)++ */\
Do_CRC \
Do_CRC
# endif /* ?IZ_CRCOPTIM_UNFOLDTBL */
#define Do_CRC_lword \
xorl (%esi), %eax ;/* c ^= *(ulg *)buf */\
UpdCRC_lword_sh(1) /* ... ((ulg *)buf)++ */
#define Do_CRC_4lword \
xorl (%esi), %eax ;/* c ^= *(ulg *)buf */\
UpdCRC_lword \
xorl 4(%esi), %eax ;/* c ^= *((ulg *)buf+1) */\
UpdCRC_lword \
xorl 8(%esi), %eax ;/* c ^= *((ulg *)buf+2) */\
UpdCRC_lword \
xorl 12(%esi), %eax ;/* c ^= *((ulg *)buf]+3 */\
UpdCRC_lword_sh(4) /* ... ((ulg *)buf)+=4 */
#endif /* !NO_32_BIT_LOADS */
.text
.globl _crc32
_crc32: /* ulg crc32(ulg crc, uch *buf, extent len) */
_STD_ENTRY
pushl %edi
pushl %esi
pushl %ebx
pushl %edx
pushl %ecx
movl arg2, %esi /* 2nd arg: uch *buf */
subl %eax, %eax /* > if (!buf) */
testl %esi, %esi /* > return 0; */
jz .L_fine /* > else { */
call _get_crc_table
movl %eax, %edi
movl arg1, %eax /* 1st arg: ulg crc */
#ifndef __686
subl %ebx, %ebx /* ebx=0; bl usable as dword */
#endif
movl arg3, %ecx /* 3rd arg: extent len */
notl %eax /* > c = ~crc; */
testl %ecx, %ecx
#ifndef NO_UNROLLED_LOOPS
jz .L_bail
# ifndef NO_32_BIT_LOADS
/* Assert now have positive length */
.L_align_loop:
testl $3, %esi /* Align buf on lword boundary */
jz .L_aligned_now
Do_CRC_byte
decl %ecx
jnz .L_align_loop
.L_aligned_now:
# endif /* !NO_32_BIT_LOADS */
movl %ecx, SavLen /* save current value of len */
shrl $4, %ecx /* ecx = len / 16 */
jz .L_No_Sixteens
/* align loop head at start of 486 internal cache line !! */
ALIGNMENT
.L_Next_Sixteen:
# ifndef NO_32_BIT_LOADS
Do_CRC_4lword
# else /* NO_32_BIT_LOADS */
Do_CRC_byteof(0)
Do_CRC_byteof(1)
Do_CRC_byteof(2)
Do_CRC_byteof(3)
Do_CRC_byteof(4)
Do_CRC_byteof(5)
Do_CRC_byteof(6)
Do_CRC_byteof(7)
Do_CRC_byteof(8)
Do_CRC_byteof(9)
Do_CRC_byteof(10)
Do_CRC_byteof(11)
Do_CRC_byteof(12)
Do_CRC_byteof(13)
Do_CRC_byteof(14)
Do_CRC_byteof(15)
addl $16,%esi ;/* buf += 16 */
# endif /* ?NO_32_BIT_LOADS */
decl %ecx
jnz .L_Next_Sixteen
.L_No_Sixteens:
movl SavLen, %ecx
andl $15, %ecx /* ecx = len % 16 */
# ifndef NO_32_BIT_LOADS
shrl $2,%ecx /* ecx = len / 4 */
jz .L_No_Fours
.L_Next_Four:
Do_CRC_lword
decl %ecx
jnz .L_Next_Four
.L_No_Fours:
movl SavLen,%ecx
andl $3,%ecx /* ecx = len % 4 */
# endif /* !NO_32_BIT_LOADS */
#endif /* !NO_UNROLLED_LOOPS */
jz .L_bail /* > if (len) */
/* align loop head at start of 486 internal cache line !! */
ALIGNMENT
.L_loupe: /* > do { */
Do_CRC_byte /* c = CRC32(c,*buf++,crctab);*/
decl %ecx /* > } while (--len); */
jnz .L_loupe
.L_bail: /* > } */
notl %eax /* > return ~c; */
.L_fine:
popl %ecx
popl %edx
popl %ebx
popl %esi
popl %edi
_STD_LEAVE
ret
#else
error: this asm version is for 386 only
#endif /* i386 || _i386 || _I386 || __i386 */
#endif /* !USE_ZLIB && !CRC_TABLE_ONLY */