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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 | /*#************************************************************************#*/ /*#-------------------------------------------------------------------------*/ /*# */ /*# FUNCTION NAME: memset() */ /*# */ /*# PARAMETERS: void* dst; Destination address. */ /*# int c; Value of byte to write. */ /*# int len; Number of bytes to write. */ /*# */ /*# RETURNS: dst. */ /*# */ /*# DESCRIPTION: Sets the memory dst of length len bytes to c, as standard. */ /*# Framework taken from memcpy. This routine is */ /*# very sensitive to compiler changes in register allocation. */ /*# Should really be rewritten to avoid this problem. */ /*# */ /*#-------------------------------------------------------------------------*/ /*# */ /*# HISTORY */ /*# */ /*# DATE NAME CHANGES */ /*# ---- ---- ------- */ /*# 990713 HP Tired of watching this function (or */ /*# really, the nonoptimized generic */ /*# implementation) take up 90% of simulator */ /*# output. Measurements needed. */ /*# */ /*#-------------------------------------------------------------------------*/ #include <linux/types.h> /* No, there's no macro saying 12*4, since it is "hard" to get it into the asm in a good way. Thus better to expose the problem everywhere. */ /* Assuming 1 cycle per dword written or read (ok, not really true), and one per instruction, then 43+3*(n/48-1) <= 24+24*(n/48-1) so n >= 45.7; n >= 0.9; we win on the first full 48-byte block to set. */ #define ZERO_BLOCK_SIZE (1*12*4) void *memset(void *pdst, int c, size_t plen) { /* Ok. Now we want the parameters put in special registers. Make sure the compiler is able to make something useful of this. */ register char *return_dst __asm__ ("r10") = pdst; register int n __asm__ ("r12") = plen; register int lc __asm__ ("r11") = c; /* Most apps use memset sanely. Only those memsetting about 3..4 bytes or less get penalized compared to the generic implementation - and that's not really sane use. */ /* Ugh. This is fragile at best. Check with newer GCC releases, if they compile cascaded "x |= x << 8" sanely! */ __asm__("movu.b %0,r13\n\t" "lslq 8,r13\n\t" "move.b %0,r13\n\t" "move.d r13,%0\n\t" "lslq 16,r13\n\t" "or.d r13,%0" : "=r" (lc) : "0" (lc) : "r13"); { register char *dst __asm__ ("r13") = pdst; /* This is NONPORTABLE, but since this whole routine is */ /* grossly nonportable that doesn't matter. */ if (((unsigned long) pdst & 3) != 0 /* Oops! n=0 must be a legal call, regardless of alignment. */ && n >= 3) { if ((unsigned long)dst & 1) { *dst = (char) lc; n--; dst++; } if ((unsigned long)dst & 2) { *(short *)dst = lc; n -= 2; dst += 2; } } /* Now the fun part. For the threshold value of this, check the equation above. */ /* Decide which copying method to use. */ if (n >= ZERO_BLOCK_SIZE) { /* 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, r12=r12, r11=r11" */ __asm__ volatile (" ;; Check that the following is true (same register names on ;; both sides of equal sign, as in r8=r8): ;; %0=r13, %1=r12, %4=r11 ;; ;; Save the registers we'll clobber in the movem process ;; on the stack. Don't mention them to gcc, it will only be ;; upset. subq 11*4,sp movem r10,[sp] move.d r11,r0 move.d r11,r1 move.d r11,r2 move.d r11,r3 move.d r11,r4 move.d r11,r5 move.d r11,r6 move.d r11,r7 move.d r11,r8 move.d r11,r9 move.d r11,r10 ;; Now we've got this: ;; r13 - dst ;; r12 - n ;; Update n for the first loop subq 12*4,r12 0: subq 12*4,r12 bge 0b movem r11,[r13+] addq 12*4,r12 ;; compensate for last loop underflowing n ;; Restore registers from stack movem [sp+],r10" /* Outputs */ : "=r" (dst), "=r" (n) /* Inputs */ : "0" (dst), "1" (n), "r" (lc)); } /* 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)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; 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) lc; break; case 2: *(short*)dst = (short) lc; break; case 3: *((short*)dst)++ = (short) lc; *(char*)dst = (char) lc; break; case 4: *((long*)dst)++ = lc; break; case 5: *((long*)dst)++ = lc; *(char*)dst = (char) lc; break; case 6: *((long*)dst)++ = lc; *(short*)dst = (short) lc; break; case 7: *((long*)dst)++ = lc; *((short*)dst)++ = (short) lc; *(char*)dst = (char) lc; break; case 8: *((long*)dst)++ = lc; *((long*)dst)++ = lc; break; case 9: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *(char*)dst = (char) lc; break; case 10: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *(short*)dst = (short) lc; break; case 11: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((short*)dst)++ = (short) lc; *(char*)dst = (char) lc; break; case 12: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; break; case 13: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; *(char*)dst = (char) lc; break; case 14: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; *(short*)dst = (short) lc; break; case 15: *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((long*)dst)++ = lc; *((short*)dst)++ = (short) lc; *(char*)dst = (char) lc; break; } } return return_dst; /* destination pointer. */ } /* memset() */ |