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225 lines
7.8 KiB
225 lines
7.8 KiB
/*#************************************************************************#*/
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/*#-------------------------------------------------------------------------*/
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/*# */
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/*# FUNCTION NAME: memcpy() */
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/*# */
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/*# PARAMETERS: void* dst; Destination address. */
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/*# void* src; Source address. */
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/*# int len; Number of bytes to copy. */
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/*# */
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/*# RETURNS: dst. */
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/*# */
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/*# DESCRIPTION: Copies len bytes of memory from src to dst. No guarantees */
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/*# about copying of overlapping memory areas. This routine is */
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/*# very sensitive to compiler changes in register allocation. */
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/*# Should really be rewritten to avoid this problem. */
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/*# */
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/*#-------------------------------------------------------------------------*/
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/*# */
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/*# HISTORY */
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/*# */
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/*# DATE NAME CHANGES */
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/*# ---- ---- ------- */
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/*# 941007 Kenny R Creation */
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/*# 941011 Kenny R Lots of optimizations and inlining. */
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/*# 941129 Ulf A Adapted for use in libc. */
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/*# 950216 HP N==0 forgotten if non-aligned src/dst. */
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/*# Added some optimizations. */
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/*# 001025 HP Make src and dst char *. Align dst to */
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/*# dword, not just word-if-both-src-and-dst- */
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/*# are-misaligned. */
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/*# */
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/*#-------------------------------------------------------------------------*/
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#include <linux/types.h>
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void *memcpy(void *pdst,
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const void *psrc,
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size_t pn)
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{
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/* Ok. Now we want the parameters put in special registers.
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Make sure the compiler is able to make something useful of this.
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As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
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If gcc was alright, it really would need no temporaries, and no
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stack space to save stuff on. */
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register void *return_dst __asm__ ("r10") = pdst;
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register char *dst __asm__ ("r13") = pdst;
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register const char *src __asm__ ("r11") = psrc;
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register int n __asm__ ("r12") = pn;
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/* When src is aligned but not dst, this makes a few extra needless
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cycles. I believe it would take as many to check that the
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re-alignment was unnecessary. */
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if (((unsigned long) dst & 3) != 0
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/* Don't align if we wouldn't copy more than a few bytes; so we
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don't have to check further for overflows. */
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&& n >= 3)
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{
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if ((unsigned long) dst & 1)
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{
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n--;
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*(char*)dst = *(char*)src;
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src++;
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dst++;
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}
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if ((unsigned long) dst & 2)
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{
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n -= 2;
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*(short*)dst = *(short*)src;
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src += 2;
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dst += 2;
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}
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}
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/* Decide which copying method to use. */
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if (n >= 44*2) /* Break even between movem and
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move16 is at 38.7*2, but modulo 44. */
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{
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/* For large copies we use 'movem' */
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/* It is not optimal to tell the compiler about clobbering any
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registers; that will move the saving/restoring of those registers
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to the function prologue/epilogue, and make non-movem sizes
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suboptimal.
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This method is not foolproof; it assumes that the "asm reg"
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declarations at the beginning of the function really are used
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here (beware: they may be moved to temporary registers).
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This way, we do not have to save/move the registers around into
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temporaries; we can safely use them straight away.
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If you want to check that the allocation was right; then
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check the equalities in the first comment. It should say
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"r13=r13, r11=r11, r12=r12" */
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__asm__ volatile ("
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;; Check that the following is true (same register names on
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;; both sides of equal sign, as in r8=r8):
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;; %0=r13, %1=r11, %2=r12
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;;
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;; Save the registers we'll use in the movem process
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;; on the stack.
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subq 11*4,$sp
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movem $r10,[$sp]
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;; Now we've got this:
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;; r11 - src
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;; r13 - dst
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;; r12 - n
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;; Update n for the first loop
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subq 44,$r12
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0:
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movem [$r11+],$r10
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subq 44,$r12
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bge 0b
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movem $r10,[$r13+]
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addq 44,$r12 ;; compensate for last loop underflowing n
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;; Restore registers from stack
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movem [$sp+],$r10"
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/* Outputs */ : "=r" (dst), "=r" (src), "=r" (n)
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/* Inputs */ : "0" (dst), "1" (src), "2" (n));
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}
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/* Either we directly starts copying, using dword copying
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in a loop, or we copy as much as possible with 'movem'
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and then the last block (<44 bytes) is copied here.
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This will work since 'movem' will have updated src,dst,n. */
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while ( n >= 16 )
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{
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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n -= 16;
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}
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/* A switch() is definitely the fastest although it takes a LOT of code.
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* Particularly if you inline code this.
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*/
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switch (n)
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{
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case 0:
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break;
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case 1:
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*(char*)dst = *(char*)src;
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break;
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case 2:
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*(short*)dst = *(short*)src;
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break;
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case 3:
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*((short*)dst)++ = *((short*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 4:
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*((long*)dst)++ = *((long*)src)++;
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break;
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case 5:
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*((long*)dst)++ = *((long*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 6:
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*((long*)dst)++ = *((long*)src)++;
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*(short*)dst = *(short*)src;
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break;
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case 7:
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*((long*)dst)++ = *((long*)src)++;
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*((short*)dst)++ = *((short*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 8:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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break;
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case 9:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 10:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*(short*)dst = *(short*)src;
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break;
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case 11:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((short*)dst)++ = *((short*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 12:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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break;
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case 13:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*(char*)dst = *(char*)src;
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break;
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case 14:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*(short*)dst = *(short*)src;
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break;
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case 15:
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((long*)dst)++ = *((long*)src)++;
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*((short*)dst)++ = *((short*)src)++;
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*(char*)dst = *(char*)src;
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break;
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}
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return return_dst; /* destination pointer. */
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} /* memcpy() */
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