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+/***************************************************************************
+ * __________ __ ___.
+ * Open \______ \ ____ ____ | | _\_ |__ _______ ___
+ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
+ * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
+ * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
+ * \/ \/ \/ \/ \/
+ * $Id$
+ *
+ * Copyright (C) 2004 by Jens Arnold
+ *
+ * All files in this archive are subject to the GNU General Public License.
+ * See the file COPYING in the source tree root for full license agreement.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "config.h"
+
+ .section .icode,"ax",@progbits
+
+ .align 2
+ .global _memset
+ .type _memset,@function
+
+/* Fills a memory region with specified byte value
+ * This version is optimized for speed
+ *
+ * arguments:
+ * r4 - start address
+ * r5 - data
+ * r6 - length
+ *
+ * return value:
+ * r0 - start address (like ANSI version)
+ *
+ * register usage:
+ * r0 - temporary
+ * r1 - start address +11 for main loop
+ * r4 - start address
+ * r5 - data (spread to all 4 bytes when using long stores)
+ * r6 - current address (runs down from end to start)
+ *
+ * The instruction order below is devised in a way to utilize the pipelining
+ * of the SH1 to the max. The routine fills memory from end to start in
+ * order to utilize the auto-decrementing store instructions.
+ */
+
+_memset:
+ neg r4,r0
+ and #3,r0 /* r0 = (4 - align_offset) % 4 */
+ add #4,r0
+ cmp/hs r0,r6 /* at least one aligned longword to fill? */
+ add r4,r6 /* r6 = end_address */
+ bf .no_longs /* no, jump directly to byte loop */
+
+ extu.b r5,r5 /* start: spread data to all 4 bytes */
+ swap.b r5,r0
+ or r0,r5 /* data now in 2 lower bytes of r5 */
+ swap.w r5,r0
+ or r0,r5 /* data now in all 4 bytes of r5 */
+
+ mov r6,r0
+ tst #3,r0 /* r0 already long aligned? */
+ bt .end_b1 /* yes: skip loop */
+
+ /* leading byte loop: sets 0..3 bytes */
+.loop_b1:
+ mov.b r5,@-r0 /* store byte */
+ tst #3,r0 /* r0 long aligned? */
+ bf .loop_b1 /* runs r0 down until long aligned */
+
+ mov r0,r6 /* r6 = last long bound */
+ nop /* keep alignment */
+
+.end_b1:
+ mov r4,r1 /* r1 = start_address... */
+ add #11,r1 /* ... + 11, combined for rounding and offset */
+ xor r1,r0
+ tst #4,r0 /* bit 2 tells whether an even or odd number of */
+ bf .loop_odd /* longwords to set */
+
+ /* main loop: set 2 longs per pass */
+.loop_2l:
+ mov.l r5,@-r6 /* store first long */
+.loop_odd:
+ cmp/hi r1,r6 /* runs r6 down to first long bound */
+ mov.l r5,@-r6 /* store second long */
+ bt .loop_2l
+
+.no_longs:
+ cmp/hi r4,r6 /* any bytes left? */
+ bf .end_b2 /* no: skip loop */
+
+ /* trailing byte loop */
+.loop_b2:
+ mov.b r5,@-r6 /* store byte */
+ cmp/hi r4,r6 /* runs r6 down to the start address */
+ bt .loop_b2
+
+.end_b2:
+ rts
+ mov r4,r0 /* return start address */
+
+.end:
+ .size _memset,.end-_memset