| /*************************************************************************** |
| * __________ __ ___. |
| * 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. |
| * |
| ****************************************************************************/ |
| |
| .section .icode,"ax",@progbits |
| .align 2 |
| .global _bitswap |
| .type _bitswap,@function |
| |
| /* Flips the bits of all bytes in a memory area (required for mp3 data on |
| * the Archos). This version is optimized for speed and size. |
| * |
| * arguments: |
| * r4 - start address |
| * r5 - length |
| * |
| * return value: void |
| * |
| * register usage: |
| * r0 - temporary |
| * r1 - bit mask for rounding to long bound / low byte (after swap) |
| * r2 - high byte (after swap) / combined result |
| * r4 - data address - 4 |
| * r5 - end address - 4 |
| * r7 - flip table (addressing with signed offset) |
| * |
| * The instruction order below is devised in a way to utilize the pipelining |
| * of the SH1 to the max. |
| */ |
| |
| _bitswap: |
| mova _fliptable,r0 |
| mov r0,r7 |
| add #-4,r4 /* address is shifted by 4 */ |
| add r4,r5 /* r5 = end_address - 4 */ |
| cmp/hi r4,r5 /* at least something to do? */ |
| bf .exit /* no, get out of here! */ |
| |
| add #-3,r5 /* end offset for flipping 4 bytes per pass */ |
| mov r4,r0 |
| tst #1,r0 /* even address? */ |
| bt .start2_w /* yes, jump into main loop */ |
| |
| /* no, flip first byte */ |
| mov.b @(4,r4),r0 /* load byte, sign extension! */ |
| add #1,r4 /* early increment */ |
| mov.b @(r0,r7),r0 /* fliptable offset is signed */ |
| bra .start2_w /* jump into main loop */ |
| mov.b r0,@(3,r4) /* store byte */ |
| |
| /* main loop: flips 2 words per pass */ |
| .align 2 |
| .loop2_w: |
| mov.w @(6,r4),r0 /* load second word */ |
| add #4,r4 /* early increment */ |
| swap.b r0,r2 /* get high byte (2nd word) */ |
| exts.b r0,r0 /* prepare low byte (2nd word) */ |
| mov.b @(r0,r7),r1 /* swap low byte (2nd word) */ |
| exts.b r2,r0 /* prepare high byte (2nd word) */ |
| mov.b @(r0,r7),r2 /* swap high byte (2nd word) */ |
| extu.b r1,r0 /* zero extend low byte (2nd word) */ |
| mov.w @r4,r1 /* load first word */ |
| shll8 r2 /* shift high byte (2nd word), low byte zeroed */ |
| or r2,r0 /* put low byte (2nd word) in result */ |
| swap.b r1,r2 /* get high byte (1st word) */ |
| mov.w r0,@(2,r4) /* store result (2nd word) */ |
| exts.b r1,r0 /* prepare low byte (1st word) */ |
| mov.b @(r0,r7),r1 /* swap low byte (1st word) */ |
| exts.b r2,r0 /* prepare high byte (1st word) */ |
| mov.b @(r0,r7),r2 /* swap high byte (1st word) */ |
| extu.b r1,r0 /* zero extend low byte (1st word) */ |
| shll8 r2 /* shift high byte (1st word), low byte zeroed */ |
| or r2,r0 /* put low byte (1st word) in result */ |
| mov.w r0,@r4 /* store result (1st word) */ |
| .start2_w: |
| cmp/hi r4,r5 /* runs r4 up to last long bound */ |
| bt .loop2_w |
| |
| bra .start_b2 /* jump into trailing byte loop */ |
| add #3,r5 /* reset end offset */ |
| |
| /* trailing byte loop: flips 0..3 bytes */ |
| .loop_b2: |
| mov.b @(4,r4),r0 /* loand byte, sign extension! */ |
| add #1,r4 /* early increment */ |
| mov.b @(r0,r7),r0 /* fliptable offset is signed */ |
| mov.b r0,@(3,r4) /* store byte */ |
| .start_b2: |
| cmp/hi r4,r5 /* runs r4 up to end address */ |
| bt .loop_b2 |
| |
| .exit: |
| rts |
| nop |
| |
| .align 2 |
| .global _fliptable |
| |
| .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 |
| _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 |
| |
| |
| .end: |
| .size _bitswap,.end-_bitswap |