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Annotation of kernel/machdep/i386/libc/memmove.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/memmove.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:  * 9-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: 
        !            48: #define MIN_TO_ALIGN   16
        !            49: 
        !            50: /*
        !            51:  * Convert a void * into a unsigned int so arithmetic can be done
        !            52:  * (Technically, the gnu C compiler is tolerant of arithmetic
        !            53:  * on void *, but ansi isn't; so we do this.)
        !            54:  */
        !            55: #define UNS(voidp)      ((unsigned int)(voidp))
        !            56: 
        !            57: /*
        !            58:  * Number of bytes addr is past an integer alignment
        !            59:  */
        !            60: #define BYTES_PAST_INT_ALIGNMENT(voidp)        (UNS(voidp) & (sizeof(int) - 1))
        !            61: 
        !            62: #if defined(NX_CURRENT_COMPILER_RELEASE) && (NX_CURRENT_COMPILER_RELEASE < 320)
        !            63: #define SIREG "e"
        !            64: #else
        !            65: #define SIREG "S"
        !            66: #endif
        !            67: 
        !            68: 
        !            69: static inline void
        !            70: simple_fwd_char_copy(void *dst, const void *src, int len)
        !            71: {
        !            72:     asm("rep; movsb"
        !            73:        : /* no outputs */
        !            74:        : "&c" (len), "D" (dst), SIREG (src)
        !            75:        : "ecx", "esi", "edi");
        !            76: }
        !            77: 
        !            78: static inline void
        !            79: simple_bkwd_char_copy(void *dst, const void *src, int len)
        !            80: {
        !            81:     /* NOTE: assumes DF flag is set */
        !            82:     UNS(src)--;
        !            83:     UNS(dst)--;
        !            84:     asm("rep; movsb"
        !            85:        : /* no outputs */
        !            86:        : "&c" (len), "D" (dst), SIREG (src)
        !            87:        : "ecx", "esi", "edi");
        !            88: }
        !            89: 
        !            90: 
        !            91: static inline void
        !            92: simple_fwd_int_copy(void *dst, const void *src, int len)
        !            93: {
        !            94:     asm("rep; movsl"
        !            95:        : /* no outputs */
        !            96:        : "&c" (len>>2), "D" (dst), SIREG (src)
        !            97:        : "ecx", "esi", "edi");
        !            98: }
        !            99: 
        !           100: static inline void
        !           101: simple_bkwd_int_copy(void *dst, const void *src, int len)
        !           102: {
        !           103:     /* NOTE: assumes DF flag is set */
        !           104:     UNS(dst) -= sizeof(int);
        !           105:     UNS(src) -= sizeof(int);
        !           106:     asm("rep; movsl"
        !           107:        : /* no outputs */
        !           108:        : "&c" (len>>2), "D" (dst), SIREG (src)
        !           109:        : "ecx", "esi", "edi");
        !           110: }
        !           111: 
        !           112: 
        !           113: void *memmove(void *, const void *, unsigned long);
        !           114: 
        !           115: void bcopy(const void *src, void *dst, unsigned long ulen)
        !           116: {
        !           117:     (void) memmove(dst, src, ulen);
        !           118: }
        !           119: 
        !           120: void ovbcopy(const void *src, void *dst, unsigned long ulen)
        !           121: {
        !           122:     (void) memmove(dst, src, ulen);
        !           123: }
        !           124: 
        !           125: 
        !           126: void *memmove(void *dst, const void *src, unsigned long ulen)
        !           127: {
        !           128:     int len = ulen;
        !           129:     int need_to_move;
        !           130:     void *orig_dst = dst;
        !           131: 
        !           132:     if ((dst <= src) || (src + ulen <= dst)) {
        !           133:        /* Forward copy */
        !           134: 
        !           135:        if (len < MIN_TO_ALIGN) {
        !           136:            simple_fwd_char_copy(dst, src, len);
        !           137:            return orig_dst;
        !           138:        }
        !           139: 
        !           140:        if (need_to_move = BYTES_PAST_INT_ALIGNMENT(src)) {
        !           141:            need_to_move = sizeof(int) - need_to_move;
        !           142:            simple_fwd_char_copy(dst, src, need_to_move);
        !           143:            len -= need_to_move;
        !           144:            UNS(dst) += need_to_move;
        !           145:            UNS(src) += need_to_move;
        !           146:        }
        !           147: 
        !           148:        simple_fwd_int_copy(dst, src, len);
        !           149:        
        !           150:        if (need_to_move = (len & 3)) {
        !           151:            UNS(src) += (len & ~3);
        !           152:            UNS(dst) += (len & ~3);
        !           153:            simple_fwd_char_copy(dst, src, need_to_move);
        !           154:        }
        !           155:     } else {
        !           156:        /* Backward copy */
        !           157: 
        !           158:        UNS(src) += len;
        !           159:        UNS(dst) += len;
        !           160: 
        !           161:        /* Set decrement bit */
        !           162:        asm("std");
        !           163: 
        !           164:        if (len <= MIN_TO_ALIGN) {
        !           165:            simple_bkwd_char_copy(dst, src, len);
        !           166:            /* Clear decrement bit */
        !           167:            asm("cld");
        !           168:            return orig_dst;
        !           169:        }
        !           170: 
        !           171:        if (need_to_move = BYTES_PAST_INT_ALIGNMENT(src)) {
        !           172:            simple_bkwd_char_copy(dst, src, need_to_move);
        !           173:            len -= need_to_move;
        !           174:            UNS(dst) -= need_to_move;
        !           175:            UNS(src) -= need_to_move;
        !           176:        }
        !           177: 
        !           178:        simple_bkwd_int_copy(dst, src, len);
        !           179: 
        !           180:        if (need_to_move = (len & 3)) {
        !           181:            UNS(src) -= (len & ~3);
        !           182:            UNS(dst) -= (len & ~3);
        !           183:            simple_bkwd_char_copy(dst, src, need_to_move);
        !           184:        }
        !           185: 
        !           186:        /* Clear decrement bit */
        !           187:        asm("cld");
        !           188:     }
        !           189:     return orig_dst;
        !           190: }

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