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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2006 Thom Johansen
*
* 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 .text
.global apply_crossfeed
apply_crossfeed:
lea.l (-44, %sp), %sp
movem.l %d2-%d7/%a2-%a6, (%sp) | save all regs
move.l (44+4, %sp), %a4
movem.l (%a4), %a4-%a5 | a4 = src[0], a5 = src[1]
move.l (44+8, %sp), %d7 | d7 = count
lea.l crossfeed_data, %a1
lea.l (8*4, %a1), %a0 | a0 = &delay[0][0]
move.l (%a1)+, %a6 | a6 = direct gain
movem.l (3*4, %a1), %d0-%d3 | fetch filter history samples
move.l (33*4, %a1), %d4 | fetch delay line index
movem.l (%a1), %a1-%a3 | load filter coefs
move.l %d4, %d5
lsl.l #3, %d5
add.l %d5, %a0 | point a0 to current delay position
| lea.l (%d4*4, %a0), %a0
| lea.l (%d4*4, %a0), %a0 | point a0 to current delay position
/* Register usage in loop:
* a0 = &delay[index][0], a1..a3 = b0, b1, a1 (filter coefs),
* a4 = src[0], a5 = src[1], a6 = direct gain,
* d0..d3 = history
* d4 = delay line index,
* d5,d6 = temp.
* d7 = count
*/
.cfloop:
mac.l %a2, %d0, (4, %a0), %d0, %acc0 | acc = b1*dr[n - 1] d0 = dr[n]
mac.l %a1, %d0, %acc0 | acc += b0*dr[n]
mac.l %a3, %d1, (%a4), %d5, %acc0 | acc += a1*y_l[n - 1], load left input
move.l %acc0, %d1 | get filtered delayed sample
mac.l %a6, %d5, %acc0 | acc += gain*x_l[n]
movclr.l %acc0, %d6
move.l %d6, (%a4)+ | write result
mac.l %a2, %d2, (%a0), %d2, %acc0 | acc = b1*dl[n - 1], d2 = dl[n]
move.l %d5, (%a0)+ | save left input to delay line
mac.l %a1, %d2, %acc0 | acc += b0*dl[n]
mac.l %a3, %d3, (%a5), %d5, %acc0 | acc += a1*y_r[n - 1], load right input
move.l %acc0, %d3 | get filtered delayed sample
mac.l %a6, %d5, %acc0 | acc += gain*x_r[n]
move.l %d5, (%a0)+ | save right input to delay line
movclr.l %acc0, %d6
move.l %d6, (%a5)+ | write result
addq.l #1, %d4 | index++
moveq.l #13, %d6
cmp.l %d6, %d4 | wrap index to 0 if it overflows
jlt .nowrap
moveq.l #13*8, %d4
sub.l %d4, %a0 | wrap back delay line ptr as well
clr.l %d4
.nowrap:
subq.l #1, %d7
jne .cfloop
| save data back to struct
lea.l crossfeed_data + 4*4, %a1
movem.l %d0-%d3, (%a1)
move.l %d4, (30*4, %a1)
movem.l (%sp), %d2-%d7/%a2-%a6
lea.l (44, %sp), %sp
rts
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