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Annotation of kernel/machdep/i386/libc/memcpy.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* Copyright (c) 1991 NeXT Computer, Inc.  All rights reserved.
        !            26:  *
        !            27:  *      File:   libc/i386/ansi/memcpy.c
        !            28:  *      Author: Bruce Martin, NeXT Computer, Inc.
        !            29:  *
        !            30:  *      This file contains machine dependent code for block copies
        !            31:  *      on NeXT i386-based products.  Currently tuned for the i486.
        !            32:  *
        !            33:  * HISTORY
        !            34:  * 12-Aug-92  Bruce Martin ([email protected])
        !            35:  *     Created.
        !            36:  */
        !            37: 
        !            38: 
        !            39: /*
        !            40:  * 486 Factoids:
        !            41:  *  - if (move <= 16 bytes) use unrolled mem-mem mov instructions
        !            42:  *  - if (move > 16 bytes) use "rep movs" [this avoids prefetch stalls]
        !            43:  *  - Aligned read is better than aligned write. Both aligned is even better.
        !            44:  */
        !            45: 
        !            46: 
        !            47: #define MIN_TO_ALIGN   16
        !            48: 
        !            49: /*
        !            50:  * Convert a void * into a unsigned int so arithmetic can be done
        !            51:  * (Technically, the gnu C compiler is tolerant of arithmetic
        !            52:  * on void *, but ansi isn't; so we do this.)
        !            53:  */
        !            54: #define UNS(voidp)      ((unsigned int)(voidp))
        !            55: 
        !            56: /*
        !            57:  * Number of bytes addr is past an integer alignment
        !            58:  */
        !            59: #define BYTES_PAST_INT_ALIGNMENT(voidp)        (UNS(voidp) & (sizeof(int) - 1))
        !            60: 
        !            61: 
        !            62: #define CHAR(voidp, offset)    (*(char *)(UNS(voidp) + (offset)))
        !            63: 
        !            64: #if defined(NX_CURRENT_COMPILER_RELEASE) && (NX_CURRENT_COMPILER_RELEASE < 320)
        !            65: #define SIREG "e"
        !            66: #else
        !            67: #define SIREG "S"
        !            68: #endif
        !            69: 
        !            70: 
        !            71: static __inline__ void
        !            72: simple_fwd_char_copy(void *dst, const void *src, int len)
        !            73: {
        !            74:     asm("rep; movsb"
        !            75:        : /* no outputs */
        !            76:        : "&c" (len), "D" (dst), SIREG (src)
        !            77:        : "ecx", "esi", "edi");
        !            78: }
        !            79: 
        !            80: static __inline__ void
        !            81: simple_fwd_short_copy(void *dst, const void *src, int len)
        !            82: {
        !            83:     asm("rep; movsw"
        !            84:        : /* no outputs */
        !            85:        : "&c" (len>>1), "D" (dst), SIREG (src)
        !            86:        : "ecx", "esi", "edi");
        !            87: }
        !            88: 
        !            89: static __inline__ void
        !            90: simple_fwd_int_copy(void *dst, const void *src, int len)
        !            91: {
        !            92:     asm("rep; movsl"
        !            93:        : /* no outputs */
        !            94:        : "&c" (len>>2), "D" (dst), SIREG (src)
        !            95:        : "ecx", "esi", "edi");
        !            96: }
        !            97: 
        !            98: 
        !            99: void *memcpy(void *, const void *, unsigned long);
        !           100: 
        !           101: void *memcpy(void *dst, const void *src, unsigned long ulen)
        !           102: {
        !           103:     int len = ulen;
        !           104:     int need_to_move;
        !           105:     void *orig_dst = dst;
        !           106: 
        !           107:     /* Always do a forward copy */
        !           108: 
        !           109:     if (len < MIN_TO_ALIGN) {
        !           110:        simple_fwd_char_copy(dst, src, len);
        !           111:        return orig_dst;
        !           112:     }
        !           113: 
        !           114:     if (need_to_move = BYTES_PAST_INT_ALIGNMENT(src)) {
        !           115:        need_to_move = sizeof(int) - need_to_move;
        !           116:        simple_fwd_char_copy(dst, src, need_to_move);
        !           117:        len -= need_to_move;
        !           118:        UNS(dst) += need_to_move;
        !           119:        UNS(src) += need_to_move;
        !           120:     }
        !           121: 
        !           122:     simple_fwd_int_copy(dst, src, len);
        !           123: 
        !           124:     if (need_to_move = (len & 3)) {
        !           125:        UNS(src) += (len & ~3);
        !           126:        UNS(dst) += (len & ~3);
        !           127:        switch(need_to_move) {
        !           128:            case 3: CHAR(dst, 2) = CHAR(src, 2);
        !           129:            case 2: CHAR(dst, 1) = CHAR(src, 1);
        !           130:            case 1: CHAR(dst, 0) = CHAR(src, 0);
        !           131:        }
        !           132:     }
        !           133:     return orig_dst;
        !           134: }
        !           135: 
        !           136: 
        !           137: /*
        !           138:  * Exactly the same as memcpy, except for the use of a 16-bit word
        !           139:  * move in the inner loop.
        !           140:  */
        !           141: void bcopy16(const void *src, void *dst, unsigned long ulen)
        !           142: {
        !           143:     int len = ulen;
        !           144:     int need_to_move;
        !           145: 
        !           146:     /* Always do a forward copy */
        !           147: 
        !           148:     if (len < MIN_TO_ALIGN) {
        !           149:        simple_fwd_char_copy(dst, src, len);
        !           150:        return;
        !           151:     }
        !           152: 
        !           153:     if (need_to_move = BYTES_PAST_INT_ALIGNMENT(src)) {
        !           154:        need_to_move = sizeof(int) - need_to_move;
        !           155:        simple_fwd_char_copy(dst, src, need_to_move);
        !           156:        len -= need_to_move;
        !           157:        UNS(dst) += need_to_move;
        !           158:        UNS(src) += need_to_move;
        !           159:     }
        !           160: 
        !           161:     simple_fwd_short_copy(dst, src, len);
        !           162:        
        !           163:     if (need_to_move = (len & 1)) {
        !           164:        UNS(src) += (len & ~1);
        !           165:        UNS(dst) += (len & ~1);
        !           166:        if (need_to_move) {
        !           167:            CHAR(dst, 0) = CHAR(src, 0);
        !           168:        }
        !           169:     }
        !           170:     return;
        !           171: }

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