1 /* memcopy.h -- definitions for memory copy functions. Generic C version. 2 Copyright (C) 1991, 1992, 1993, 1997 Free Software Foundation, Inc. 3 This file is part of the GNU C Library. 4 Contributed by Torbjorn Granlund (tege@sics.se). 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, see 18 <http://www.gnu.org/licenses/>. */ 19 20 /* The strategy of the memory functions is: 21 22 1. Copy bytes until the destination pointer is aligned. 23 24 2. Copy words in unrolled loops. If the source and destination 25 are not aligned in the same way, use word memory operations, 26 but shift and merge two read words before writing. 27 28 3. Copy the few remaining bytes. 29 30 This is fast on processors that have at least 10 registers for 31 allocation by GCC, and that can access memory at reg+const in one 32 instruction. 33 34 I made an "exhaustive" test of this memmove when I wrote it, 35 exhaustive in the sense that I tried all alignment and length 36 combinations, with and without overlap. */ 37 38 #include <sys/cdefs.h> 39 #include <endian.h> 40 41 /* The macros defined in this file are: 42 43 BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy) 44 45 BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy) 46 47 WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy) 48 49 WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy) 50 51 MERGE(old_word, sh_1, new_word, sh_2) 52 [I fail to understand. I feel stupid. --roland] 53 */ 54 55 /* Type to use for aligned memory operations. 56 This should normally be the biggest type supported by a single load 57 and store. */ 58 #define op_t unsigned long int 59 #define OPSIZ (sizeof(op_t)) 60 61 /* Type to use for unaligned operations. */ 62 typedef unsigned char byte; 63 64 /* Optimal type for storing bytes in registers. */ 65 #define reg_char char 66 67 #if __BYTE_ORDER == __LITTLE_ENDIAN 68 #define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2))) 69 #endif 70 #if __BYTE_ORDER == __BIG_ENDIAN 71 #define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2))) 72 #endif 73 74 /* Copy exactly NBYTES bytes from SRC_BP to DST_BP, 75 without any assumptions about alignment of the pointers. */ 76 #define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \ 77 do \ 78 { \ 79 size_t __nbytes = (nbytes); \ 80 while (__nbytes > 0) \ 81 { \ 82 byte __x = ((byte *) src_bp)[0]; \ 83 src_bp += 1; \ 84 __nbytes -= 1; \ 85 ((byte *) dst_bp)[0] = __x; \ 86 dst_bp += 1; \ 87 } \ 88 } while (0) 89 90 /* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, 91 beginning at the bytes right before the pointers and continuing towards 92 smaller addresses. Don't assume anything about alignment of the 93 pointers. */ 94 #define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \ 95 do \ 96 { \ 97 size_t __nbytes = (nbytes); \ 98 while (__nbytes > 0) \ 99 { \ 100 byte __x; \ 101 src_ep -= 1; \ 102 __x = ((byte *) src_ep)[0]; \ 103 dst_ep -= 1; \ 104 __nbytes -= 1; \ 105 ((byte *) dst_ep)[0] = __x; \ 106 } \ 107 } while (0) 108 109 /* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with 110 the assumption that DST_BP is aligned on an OPSIZ multiple. If 111 not all bytes could be easily copied, store remaining number of bytes 112 in NBYTES_LEFT, otherwise store 0. */ 113 /* extern void _wordcopy_fwd_aligned __P ((long int, long int, size_t)); */ 114 /* extern void _wordcopy_fwd_dest_aligned __P ((long int, long int, size_t)); */ 115 #define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \ 116 do \ 117 { \ 118 if (src_bp % OPSIZ == 0) \ 119 _wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ 120 else \ 121 _wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ 122 src_bp += (nbytes) & -OPSIZ; \ 123 dst_bp += (nbytes) & -OPSIZ; \ 124 (nbytes_left) = (nbytes) % OPSIZ; \ 125 } while (0) 126 127 /* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, 128 beginning at the words (of type op_t) right before the pointers and 129 continuing towards smaller addresses. May take advantage of that 130 DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be 131 easily copied, store remaining number of bytes in NBYTES_REMAINING, 132 otherwise store 0. */ 133 /* extern void _wordcopy_bwd_aligned __P ((long int, long int, size_t)); */ 134 /* extern void _wordcopy_bwd_dest_aligned __P ((long int, long int, size_t)); */ 135 #define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \ 136 do \ 137 { \ 138 if (src_ep % OPSIZ == 0) \ 139 _wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ 140 else \ 141 _wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ 142 src_ep -= (nbytes) & -OPSIZ; \ 143 dst_ep -= (nbytes) & -OPSIZ; \ 144 (nbytes_left) = (nbytes) % OPSIZ; \ 145 } while (0) 146 147 148 /* Threshold value for when to enter the unrolled loops. */ 149 #define OP_T_THRES 16 150