musl_1124.c

   1 #include <string.h>
   2 #include <stdint.h>
   3 #include <endian.h>
   4
   5 void *mymemcpy(void *restrict dest, const void *restrict src, size_t n)
   6 {
   7         unsigned char *d = dest;
   8         const unsigned char *s = src;
   9
  10 #ifdef __GNUC__
  11
  12 #if __BYTE_ORDER == __LITTLE_ENDIAN
  13 #define LS >>
  14 #define RS <<
  15 #else
  16 #define LS <<
  17 #define RS >>
  18 #endif
  19
  20         typedef uint32_t __attribute__((__may_alias__)) u32;
  21         uint32_t w, x;
  22
  23         for (; (uintptr_t)s % 4 && n; n--) *d++ = *s++;
  24
  25         if ((uintptr_t)d % 4 == 0) {
  26                 for (; n>=16; s+=16, d+=16, n-=16) {
  27                         *(u32 *)(d+0) = *(u32 *)(s+0);
  28                         *(u32 *)(d+4) = *(u32 *)(s+4);
  29                         *(u32 *)(d+8) = *(u32 *)(s+8);
  30                         *(u32 *)(d+12) = *(u32 *)(s+12);
  31                 }
  32                 if (n&8) {
  33                         *(u32 *)(d+0) = *(u32 *)(s+0);
  34                         *(u32 *)(d+4) = *(u32 *)(s+4);
  35                         d += 8; s += 8;
  36                 }
  37                 if (n&4) {
  38                         *(u32 *)(d+0) = *(u32 *)(s+0);
  39                         d += 4; s += 4;
  40                 }
  41                 if (n&2) {
  42                         *d++ = *s++; *d++ = *s++;
  43                 }
  44                 if (n&1) {
  45                         *d = *s;
  46                 }
  47                 return dest;
  48         }
  49
  50         if (n >= 32) switch ((uintptr_t)d % 4) {
  51         case 1:
  52                 w = *(u32 *)s;
  53                 *d++ = *s++;
  54                 *d++ = *s++;
  55                 *d++ = *s++;
  56                 n -= 3;
  57                 for (; n>=17; s+=16, d+=16, n-=16) {
  58                         x = *(u32 *)(s+1);
  59                         *(u32 *)(d+0) = (w LS 24) | (x RS 8);
  60                         w = *(u32 *)(s+5);
  61                         *(u32 *)(d+4) = (x LS 24) | (w RS 8);
  62                         x = *(u32 *)(s+9);
  63                         *(u32 *)(d+8) = (w LS 24) | (x RS 8);
  64                         w = *(u32 *)(s+13);
  65                         *(u32 *)(d+12) = (x LS 24) | (w RS 8);
  66                 }
  67                 break;
  68         case 2:
  69                 w = *(u32 *)s;
  70                 *d++ = *s++;
  71                 *d++ = *s++;
  72                 n -= 2;
  73                 for (; n>=18; s+=16, d+=16, n-=16) {
  74                         x = *(u32 *)(s+2);
  75                         *(u32 *)(d+0) = (w LS 16) | (x RS 16);
  76                         w = *(u32 *)(s+6);
  77                         *(u32 *)(d+4) = (x LS 16) | (w RS 16);
  78                         x = *(u32 *)(s+10);
  79                         *(u32 *)(d+8) = (w LS 16) | (x RS 16);
  80                         w = *(u32 *)(s+14);
  81                         *(u32 *)(d+12) = (x LS 16) | (w RS 16);
  82                 }
  83                 break;
  84         case 3:
  85                 w = *(u32 *)s;
  86                 *d++ = *s++;
  87                 n -= 1;
  88                 for (; n>=19; s+=16, d+=16, n-=16) {
  89                         x = *(u32 *)(s+3);
  90                         *(u32 *)(d+0) = (w LS 8) | (x RS 24);
  91                         w = *(u32 *)(s+7);
  92                         *(u32 *)(d+4) = (x LS 8) | (w RS 24);
  93                         x = *(u32 *)(s+11);
  94                         *(u32 *)(d+8) = (w LS 8) | (x RS 24);
  95                         w = *(u32 *)(s+15);
  96                         *(u32 *)(d+12) = (x LS 8) | (w RS 24);
  97                 }
  98                 break;
  99         }
 100         if (n&16) {
 101                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 102                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 103                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 104                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 105         }
 106         if (n&8) {
 107                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 108                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 109         }
 110         if (n&4) {
 111                 *d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
 112         }
 113         if (n&2) {
 114                 *d++ = *s++; *d++ = *s++;
 115         }
 116         if (n&1) {
 117                 *d = *s;
 118         }
 119         return dest;
 120 #endif
 121
 122         for (; n; n--) *d++ = *s++;
 123         return dest;
 124 }