1 files changed, 109 insertions, 0 deletions
diff --git a/firmware/asm/sh/memset.S b/firmware/asm/sh/memset.S
new file mode 100644
index 0000000000..8cae1ea112
--- /dev/null
+++ b/firmware/asm/sh/memset.S
@@ -0,0 +1,109 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2004 by Jens Arnold
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * 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