239a91c28c
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@4337 a1c6a512-1295-4272-9138-f99709370657
131 lines
4.9 KiB
ArmAsm
131 lines
4.9 KiB
ArmAsm
/***************************************************************************
|
|
* __________ __ ___.
|
|
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
|
|
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
|
|
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
|
|
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
|
|
* \/ \/ \/ \/ \/
|
|
* $Id$
|
|
*
|
|
* Copyright (C) 2002 by Magnus Holmgren
|
|
*
|
|
* 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.
|
|
*
|
|
****************************************************************************/
|
|
|
|
.section .icode,"ax",@progbits
|
|
.align 2
|
|
.global _bitswap
|
|
.type _bitswap,@function
|
|
|
|
/* Registers used:
|
|
*
|
|
* r0 Temporary (required by some instructions)
|
|
* r1 Low byte
|
|
* r2 High byte / final result
|
|
* r4 &Data
|
|
* r5 Length
|
|
* r7 Flip table
|
|
*/
|
|
|
|
/* The instruction order below is a bit strange, because:
|
|
* 1) Keeping load/stores on longword boundaries means the instruction fetch
|
|
* won't compete with the memory access (because instructions are fetched
|
|
* in pairs).
|
|
* 2) Using the result of a fetch in the next instruction causes a stall
|
|
* (except in certain circumstances).
|
|
* See the SH-1 programming manual for details.
|
|
*/
|
|
|
|
_bitswap:
|
|
mov.l .fliptable,r7
|
|
add #-2,r4 /* ptr is used shifted by 2 */
|
|
add r4,r5 /* r5 = end_address - 2 */
|
|
add #-1,r5 /* r5 = &last_byte - 2 */
|
|
mov r4,r0
|
|
tst #1,r0 /* even address? */
|
|
bt .init /* yes */
|
|
|
|
add #1,r4 /* r4 now even */
|
|
mov.b @(1,r4),r0 /* no, swap first byte */
|
|
extu.b r0,r0
|
|
mov.b @(r0,r7),r0
|
|
mov.b r0,@(1,r4)
|
|
|
|
.init:
|
|
cmp/hi r4,r5 /* at least 2 bytes to swap? */
|
|
bf .last /* no, skip main loop */
|
|
|
|
.loop:
|
|
mov.w @(2,r4),r0 /* data to flip */
|
|
add #2,r4 /* early increment */
|
|
swap.b r0,r2 /* get high byte */
|
|
extu.b r0,r0 /* prepare low byte */
|
|
mov.b @(r0,r7),r1 /* swap low byte */
|
|
extu.b r2,r0 /* prepare high byte */
|
|
mov.b @(r0,r7),r2 /* swap high byte */
|
|
extu.b r1,r1 /* zero extend low byte */
|
|
shll8 r2 /* shift high byte, low byte zeroed */
|
|
or r1,r2 /* put low byte in result */
|
|
mov.w r2,@r4 /* store result, ptr already incr'd */
|
|
cmp/hi r4,r5 /* while &last_byte > data */
|
|
bt .loop
|
|
|
|
.last:
|
|
cmp/eq r4,r5 /* if behind (&last_byte - 2), exit */
|
|
bf .exit
|
|
|
|
mov.b @(2,r4),r0 /* swap last byte */
|
|
extu.b r0,r0
|
|
mov.b @(r0,r7),r0
|
|
mov.b r0,@(2,r4)
|
|
|
|
.exit:
|
|
rts
|
|
nop
|
|
|
|
.align 2
|
|
|
|
.fliptable:
|
|
.long _fliptable
|
|
|
|
_fliptable:
|
|
.byte 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0
|
|
.byte 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0
|
|
.byte 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8
|
|
.byte 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8
|
|
.byte 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4
|
|
.byte 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4
|
|
.byte 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec
|
|
.byte 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc
|
|
.byte 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2
|
|
.byte 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2
|
|
.byte 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea
|
|
.byte 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa
|
|
.byte 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6
|
|
.byte 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6
|
|
.byte 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee
|
|
.byte 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe
|
|
.byte 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1
|
|
.byte 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1
|
|
.byte 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9
|
|
.byte 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9
|
|
.byte 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5
|
|
.byte 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5
|
|
.byte 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed
|
|
.byte 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd
|
|
.byte 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3
|
|
.byte 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3
|
|
.byte 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb
|
|
.byte 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb
|
|
.byte 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7
|
|
.byte 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7
|
|
.byte 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef
|
|
.byte 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff
|
|
|
|
.end:
|
|
.size _bitswap,.end-_bitswap
|