sysdeps/powerpc/powerpc32/power4/memcopy.h

   1 /* memcopy.h -- definitions for memory copy functions.  Generic C version.
   2    Copyright (C) 1991-2015 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 <sysdeps/generic/memcopy.h>
  39
  40 /* The macros defined in this file are:
  41
  42    BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
  43
  44    BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
  45
  46    WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
  47
  48    WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
  49
  50    MERGE(old_word, sh_1, new_word, sh_2)
  51      [I fail to understand.  I feel stupid.  --roland]
  52 */
  53
  54
  55 /* Threshold value for when to enter the unrolled loops.  */
  56 #undef  OP_T_THRES
  57 #define OP_T_THRES 16
  58
  59 /* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
  60    without any assumptions about alignment of the pointers.  */
  61 #undef BYTE_COPY_FWD
  62 #define BYTE_COPY_FWD(dst_bp, src_bp, nbytes)                                 \
  63   do                                                                          \
  64     {                                                                         \
  65       size_t __nbytes = (nbytes);                                             \
  66       if (__nbytes & 1)                                                       \
  67         {                                                                     \
  68           ((byte *) dst_bp)[0] =  ((byte *) src_bp)[0];                       \
  69           src_bp += 1;                                                        \
  70           dst_bp += 1;                                                        \
  71           __nbytes -= 1;                                                      \
  72         }                                                                     \
  73       while (__nbytes > 0)                                                    \
  74         {                                                                     \
  75           byte __x = ((byte *) src_bp)[0];                                    \
  76           byte __y = ((byte *) src_bp)[1];                                    \
  77           src_bp += 2;                                                        \
  78           __nbytes -= 2;                                                      \
  79           ((byte *) dst_bp)[0] = __x;                                         \
  80           ((byte *) dst_bp)[1] = __y;                                         \
  81           dst_bp += 2;                                                        \
  82         }                                                                     \
  83     } while (0)
  84
  85 /* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
  86    beginning at the bytes right before the pointers and continuing towards
  87    smaller addresses.  Don't assume anything about alignment of the
  88    pointers.  */
  89 #undef BYTE_COPY_BWD
  90 #define BYTE_COPY_BWD(dst_ep, src_ep, nbytes)                                 \
  91   do                                                                          \
  92     {                                                                         \
  93       size_t __nbytes = (nbytes);                                             \
  94       if (__nbytes & 1)                                                       \
  95         {                                                                     \
  96           src_ep -= 1;                                                        \
  97           dst_ep -= 1;                                                        \
  98           ((byte *) dst_ep)[0] =  ((byte *) src_ep)[0];                       \
  99           __nbytes -= 1;                                                      \
 100         }                                                                     \
 101       while (__nbytes > 0)                                                    \
 102         {                                                                     \
 103           byte __x, __y;                                                      \
 104           src_ep -= 2;                                                        \
 105           __y = ((byte *) src_ep)[1];                                         \
 106           __x = ((byte *) src_ep)[0];                                         \
 107           dst_ep -= 2;                                                        \
 108           __nbytes -= 2;                                                      \
 109           ((byte *) dst_ep)[1] = __y;                                         \
 110           ((byte *) dst_ep)[0] = __x;                                         \
 111         }                                                                     \
 112     } while (0)
 113
 114 /* The powerpc memcpy implementation is safe to use for memmove.  */
 115 #undef MEMCPY_OK_FOR_FWD_MEMMOVE
 116 #define MEMCPY_OK_FOR_FWD_MEMMOVE 1