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

• Lines: 246
• Date: Thu Feb 8 16:32:44 2001
• Orig file: v2.4.1/linux/arch/cris/lib/memset.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.1/linux/arch/cris/lib/memset.c linux/arch/cris/lib/memset.c
@@ -0,0 +1,245 @@
+/*#************************************************************************#*/
+/*#-------------------------------------------------------------------------*/
+/*#                                                                         */
+/*# 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.                 */
+/*#                                                                         */
+/*#-------------------------------------------------------------------------*/
+
+/* 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,
+             unsigned int 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\tlslq 8,r13\n\tmove.b %0,r13\n\tmove.d r13,%0\n\tlslq 16,r13\n\tor.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() */