patch-2.4.2 linux/arch/cris/lib/string.c

• Lines: 224
• Date: Thu Feb 8 16:32:44 2001
• Orig file: v2.4.1/linux/arch/cris/lib/string.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.1/linux/arch/cris/lib/string.c linux/arch/cris/lib/string.c
@@ -0,0 +1,223 @@
+/*#************************************************************************#*/
+/*#-------------------------------------------------------------------------*/
+/*#                                                                         */
+/*# 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.				    */
+/*#                                                                         */
+/*#-------------------------------------------------------------------------*/
+
+void *memcpy(void *pdst,
+             const void *psrc,
+             unsigned int 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() */