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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 | /*#************************************************************************#*/ /*#-------------------------------------------------------------------------*/ /*# */ /*# FUNCTION NAME: memcpy() */ /*# */ /*# PARAMETERS: void* dst; Destination address. */ /*# void* src; Source address. */ /*# int len; Number of bytes to copy. */ /*# */ /*# RETURNS: dst. */ /*# */ /*# DESCRIPTION: Copies len bytes of memory from src to dst. No guarantees */ /*# about copying of overlapping memory areas. This routine is */ /*# very sensitive to compiler changes in register allocation. */ /*# Should really be rewritten to avoid this problem. */ /*# */ /*#-------------------------------------------------------------------------*/ /*# */ /*# HISTORY */ /*# */ /*# DATE NAME CHANGES */ /*# ---- ---- ------- */ /*# 941007 Kenny R Creation */ /*# 941011 Kenny R Lots of optimizations and inlining. */ /*# 941129 Ulf A Adapted for use in libc. */ /*# 950216 HP N==0 forgotten if non-aligned src/dst. */ /*# Added some optimizations. */ /*# 001025 HP Make src and dst char *. Align dst to */ /*# dword, not just word-if-both-src-and-dst- */ /*# are-misaligned. */ /*# */ /*#-------------------------------------------------------------------------*/ #include <linux/types.h> void *memcpy(void *pdst, const void *psrc, size_t pn) { /* Ok. Now we want the parameters put in special registers. Make sure the compiler is able to make something useful of this. As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop). If gcc was allright, it really would need no temporaries, and no stack space to save stuff on. */ register void *return_dst __asm__ ("r10") = pdst; register char *dst __asm__ ("r13") = pdst; register const char *src __asm__ ("r11") = psrc; register int n __asm__ ("r12") = pn; /* When src is aligned but not dst, this makes a few extra needless cycles. I believe it would take as many to check that the re-alignment was unnecessary. */ if (((unsigned long) dst & 3) != 0 /* Don't align if we wouldn't copy more than a few bytes; so we don't have to check further for overflows. */ && n >= 3) { if ((unsigned long) dst & 1) { n--; *(char*)dst = *(char*)src; src++; dst++; } if ((unsigned long) dst & 2) { n -= 2; *(short*)dst = *(short*)src; src += 2; dst += 2; } } /* Decide which copying method to use. */ if (n >= 44*2) /* Break even between movem and move16 is at 38.7*2, but modulo 44. */ { /* For large copies we use 'movem' */ /* It is not optimal to tell the compiler about clobbering any registers; that will move the saving/restoring of those registers to the function prologue/epilogue, and make non-movem sizes suboptimal. This method is not foolproof; it assumes that the "asm reg" declarations at the beginning of the function really are used here (beware: they may be moved to temporary registers). This way, we do not have to save/move the registers around into temporaries; we can safely use them straight away. If you want to check that the allocation was right; then check the equalities in the first comment. It should say "r13=r13, r11=r11, r12=r12" */ __asm__ volatile (" ;; Check that the following is true (same register names on ;; both sides of equal sign, as in r8=r8): ;; %0=r13, %1=r11, %2=r12 ;; ;; Save the registers we'll use in the movem process ;; on the stack. subq 11*4,sp movem r10,[sp] ;; Now we've got this: ;; r11 - src ;; r13 - dst ;; r12 - n ;; Update n for the first loop subq 44,r12 0: movem [r11+],r10 subq 44,r12 bge 0b movem r10,[r13+] addq 44,r12 ;; compensate for last loop underflowing n ;; Restore registers from stack movem [sp+],r10" /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n) /* Inputs */ : "0" (dst), "1" (src), "2" (n)); } /* Either we directly starts copying, using dword copying in a loop, or we copy as much as possible with 'movem' and then the last block (<44 bytes) is copied here. This will work since 'movem' will have updated src,dst,n. */ while ( n >= 16 ) { *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; n -= 16; } /* A switch() is definitely the fastest although it takes a LOT of code. * Particularly if you inline code this. */ switch (n) { case 0: break; case 1: *(char*)dst = *(char*)src; break; case 2: *(short*)dst = *(short*)src; break; case 3: *((short*)dst)++ = *((short*)src)++; *(char*)dst = *(char*)src; break; case 4: *((long*)dst)++ = *((long*)src)++; break; case 5: *((long*)dst)++ = *((long*)src)++; *(char*)dst = *(char*)src; break; case 6: *((long*)dst)++ = *((long*)src)++; *(short*)dst = *(short*)src; break; case 7: *((long*)dst)++ = *((long*)src)++; *((short*)dst)++ = *((short*)src)++; *(char*)dst = *(char*)src; break; case 8: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; break; case 9: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *(char*)dst = *(char*)src; break; case 10: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *(short*)dst = *(short*)src; break; case 11: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((short*)dst)++ = *((short*)src)++; *(char*)dst = *(char*)src; break; case 12: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; break; case 13: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *(char*)dst = *(char*)src; break; case 14: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *(short*)dst = *(short*)src; break; case 15: *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((long*)dst)++ = *((long*)src)++; *((short*)dst)++ = *((short*)src)++; *(char*)dst = *(char*)src; break; } return return_dst; /* destination pointer. */ } /* memcpy() */ |