152 lines
5.1 KiB
ArmAsm
152 lines
5.1 KiB
ArmAsm
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2004 by Jens Arnold
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "config.h"
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.section .icode,"ax",@progbits
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.align 2
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.global memset
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.type memset,@function
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/* Fills a memory region with specified byte value
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* This version is optimized for speed
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*
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* arguments:
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* (4,%sp) - start address
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* (8,%sp) - data
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* (12,%sp) - length
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*
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* return value:
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* %d0 - start address (like ANSI version)
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*
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* register usage:
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* %d0 - data (spread to all 4 bytes when using long stores)
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* %d1 - temporary / data (for burst transfer)
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* %d2 - data (for burst transfer)
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* %d3 - data (for burst transfer)
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* %a0 - start address
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* %a1 - current address (runs down from end to start)
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*
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* For maximum speed this routine uses both long stores and burst mode,
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* storing whole lines with movem.l. The routine fills memory from end
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* to start in order to ease returning the start address.
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*/
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memset:
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move.l (4,%sp),%a0 /* start address */
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move.l (8,%sp),%d0 /* data */
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move.l (12,%sp),%a1 /* length */
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add.l %a0,%a1 /* %a1 = end address */
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move.l %a0,%d1
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addq.l #7,%d1
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and.l #0xFFFFFFFC,%d1 /* %d1 = first long bound + 4 */
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cmp.l %d1,%a1 /* at least one aligned longword to fill? */
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blo.b .no_longs /* no, jump directly to byte loop */
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and.l #0xFF,%d0 /* start: spread data to all 4 bytes */
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move.l %d0,%d1
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lsl.l #8,%d1
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or.l %d1,%d0 /* data now in 2 lower bytes of %d0 */
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move.l %d0,%d1
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swap %d0
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or.l %d1,%d0 /* data now in all 4 bytes of %d0 */
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move.l %a1,%d1
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and.l #0xFFFFFFFC,%d1 /* %d1 = last long bound */
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cmp.l %d1,%a1 /* any bytes to set? */
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bls.b .end_b1 /* no: skip byte loop */
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/* leading byte loop: sets 0..3 bytes */
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.loop_b1:
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move.b %d0,-(%a1) /* store byte */
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cmp.l %d1,%a1 /* runs %a1 down to last long bound */
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bhi.b .loop_b1
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.end_b1:
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moveq.l #31,%d1
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add.l %a0,%d1
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and.l #0xFFFFFFF0,%d1 /* %d1 = first line bound + 16 */
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cmp.l %d1,%a1 /* at least one full line to fill? */
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blo.b .no_lines /* no, jump to longword loop */
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mov.l %a1,%d1
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and.l #0xFFFFFFF0,%d1 /* %d1 = last line bound */
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cmp.l %d1,%a1 /* any longwords to set? */
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bls.b .end_l1 /* no: skip longword loop */
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/* leading longword loop: sets 0..3 longwords */
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.loop_l1:
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move.l %d0,-(%a1) /* store longword */
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cmp.l %d1,%a1 /* runs %a1 down to last line bound */
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bhi.b .loop_l1
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.end_l1:
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move.l %d2,-(%sp) /* free some registers */
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move.l %d3,-(%sp)
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move.l %d0,%d1 /* spread data to 4 data registers */
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move.l %d0,%d2
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move.l %d0,%d3
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lea.l (15,%a0),%a0 /* start address += 15, acct. for trl. data */
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/* main loop: set whole lines utilising burst mode */
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.loop_line:
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lea.l (-16,%a1),%a1 /* pre-decrement */
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movem.l %d0-%d3,(%a1) /* store line */
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cmp.l %a0,%a1 /* runs %a1 down to first line bound */
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bhi.b .loop_line
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lea.l (-15,%a0),%a0 /* correct start address */
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move.l (%sp)+,%d3 /* restore registers */
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move.l (%sp)+,%d2
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move.l %a0,%d1 /* %d1 = start address ... */
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addq.l #3,%d1 /* ... +3, account for possible trailing bytes */
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cmp.l %d1,%a1 /* any longwords left */
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bhi.b .loop_l2 /* yes: jump to longword loop */
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bra.b .no_longs /* no: skip loop */
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.no_lines:
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move.l %a0,%d1 /* %d1 = start address ... */
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addq.l #3,%d1 /* ... +3, account for possible trailing bytes */
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/* trailing longword loop */
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.loop_l2:
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move.l %d0,-(%a1) /* store longword */
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cmp.l %d1,%a1 /* runs %a1 down to first long bound */
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bhi.b .loop_l2
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.no_longs:
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cmp.l %a0,%a1 /* any bytes left? */
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bls.b .end_b2 /* no: skip loop */
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/* trailing byte loop */
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.loop_b2:
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move.b %d0,-(%a1) /* store byte */
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cmp.l %a0,%a1 /* runs %a1 down to start address */
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bhi.b .loop_b2
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.end_b2:
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move.l %a0,%d0 /* return start address */
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rts
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.end:
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.size memset,.end-memset
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