rockbox/lib/rbcodec/dsp/dsp_arm.S
Michael Sevakis 230f6f4326 Lower IRAM footprint on ARM.
Move a few functions to .text that probably don't see a huge benefit
from being .icode. Will scrutinize later.

Change-Id: I7bdffc326076c5cd7e6a1c57d25d31e653920327
2012-04-29 14:10:14 -04:00

624 lines
26 KiB
ArmAsm

/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2006-2007 Thom Johansen
*
* 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"
/****************************************************************************
* void channel_mode_proc_mono(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global channel_mode_proc_mono
.type channel_mode_proc_mono, %function
channel_mode_proc_mono:
@ input: r0 = this, r1 = buf_p
ldr r1, [r1] @ r1 = buf = *buf_p;
stmfd sp!, { r4, lr } @
@
ldmia r1, { r0-r2 } @ r0 = buf->remcount, r1 = buf->p32[0],
@ r2 = buf->p32[1]
subs r0, r0, #1 @ odd: end at 0; even: end at -1
beq .mono_singlesample @ Zero? Only one sample!
@
.monoloop: @
ldmia r1, { r3, r4 } @ r3, r4 = Li0, Li1
ldmia r2, { r12, r14 } @ r12, r14 = Ri0, Ri1
mov r3, r3, asr #1 @ Mo0 = Li0 / 2 + Ri0 / 2
mov r4, r4, asr #1 @ Mo1 = Li1 / 2 + Ri1 / 2
add r12, r3, r12, asr #1 @
add r14, r4, r14, asr #1 @
subs r0, r0, #2 @
stmia r1!, { r12, r14 } @ store Mo0, Mo1
stmia r2!, { r12, r14 } @ store Mo0, Mo1
bgt .monoloop @
@
ldmpc cond=lt, regs=r4 @ if count was even, we're done
@
.mono_singlesample: @
ldr r3, [r1] @ r3 = Ls
ldr r12, [r2] @ r12 = Rs
mov r3, r3, asr #1 @ Mo = Ls / 2 + Rs / 2
add r12, r3, r12, asr #1 @
str r12, [r1] @ store Mo
str r12, [r2] @ store Mo
@
ldmpc regs=r4 @
.size channel_mode_proc_mono, .-channel_mode_proc_mono
/****************************************************************************
* void channel_mode_proc_custom(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global channel_mode_proc_custom
.type channel_mode_proc_custom, %function
channel_mode_proc_custom:
@ input: r0 = this, r1 = buf_p
ldr r2, [r0] @ r2 = &channel_mode_data = this->data
ldr r1, [r1] @ r1 = buf = *buf_p;
stmfd sp!, { r4-r10, lr }
ldmia r2, { r3, r4 } @ r3 = sw_gain, r4 = sw_cross
ldmia r1, { r0-r2 } @ r0 = buf->remcount, r1 = buf->p32[0],
@ r2 = buf->p32[1]
subs r0, r0, #1
beq .custom_single_sample @ Zero? Only one sample!
.custom_loop:
ldmia r1, { r5, r6 } @ r5 = Li0, r6 = Li1
ldmia r2, { r7, r8 } @ r7 = Ri0, r8 = Ri1
subs r0, r0, #2
smull r9, r10, r5, r3 @ Lc0 = Li0*gain
smull r12, r14, r7, r3 @ Rc0 = Ri0*gain
smlal r9, r10, r7, r4 @ Lc0 += Ri0*cross
smlal r12, r14, r5, r4 @ Rc0 += Li0*cross
mov r9, r9, lsr #31 @ Convert to s0.31
mov r12, r12, lsr #31
orr r5, r9, r10, asl #1
orr r7, r12, r14, asl #1
smull r9, r10, r6, r3 @ Lc1 = Li1*gain
smull r12, r14, r8, r3 @ Rc1 = Ri1*gain
smlal r9, r10, r8, r4 @ Lc1 += Ri1*cross
smlal r12, r14, r6, r4 @ Rc1 += Li1*cross
mov r9, r9, lsr #31 @ Convert to s0.31
mov r12, r12, lsr #31
orr r6, r9, r10, asl #1
orr r8, r12, r14, asl #1
stmia r1!, { r5, r6 } @ Store Lc0, Lc1
stmia r2!, { r7, r8 } @ Store Rc0, Rc1
bgt .custom_loop
ldmpc cond=lt, regs=r4-r10 @ < 0? even count
.custom_single_sample:
ldr r5, [r1] @ handle odd sample
ldr r7, [r2]
smull r9, r10, r5, r3 @ Lc0 = Li0*gain
smull r12, r14, r7, r3 @ Rc0 = Ri0*gain
smlal r9, r10, r7, r4 @ Lc0 += Ri0*cross
smlal r12, r14, r5, r4 @ Rc0 += Li0*cross
mov r9, r9, lsr #31 @ Convert to s0.31
mov r12, r12, lsr #31
orr r5, r9, r10, asl #1
orr r7, r12, r14, asl #1
str r5, [r1] @ Store Lc0
str r7, [r2] @ Store Rc0
ldmpc regs=r4-r10
.size channel_mode_proc_custom, .-channel_mode_proc_custom
/****************************************************************************
* void channel_mode_proc_karaoke(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global channel_mode_proc_karaoke
.type channel_mode_proc_karaoke, %function
channel_mode_proc_karaoke:
@ input: r0 = this, r1 = buf_p
ldr r1, [r1] @ r1 = buf = *buf_p;
stmfd sp!, { r4, lr } @
@
ldmia r1, { r0-r2 } @ r0 = buf->remcount, r1 = buf->p32[0],
@ r2 = buf->p32[1]
subs r0, r0, #1 @ odd: end at 0; even: end at -1
beq .karaoke_singlesample @ Zero? Only one sample!
@
.karaokeloop: @
ldmia r1, { r3, r4 } @ r3, r4 = Li0, Li1
ldmia r2, { r12, r14 } @ r12, r14 = Ri0, Ri1
mov r3, r3, asr #1 @ Lo0 = Li0 / 2 - Ri0 / 2
mov r4, r4, asr #1 @ Lo1 = Li1 / 2 - Ri1 / 2
sub r3, r3, r12, asr #1 @
sub r4, r4, r14, asr #1 @
rsb r12, r3, #0 @ Ro0 = -Lk0 = Rs0 / 2 - Ls0 / 2
rsb r14, r4, #0 @ Ro1 = -Lk1 = Ri1 / 2 - Li1 / 2
subs r0, r0, #2 @
stmia r1!, { r3, r4 } @ store Lo0, Lo1
stmia r2!, { r12, r14 } @ store Ro0, Ro1
bgt .karaokeloop @
@
ldmpc cond=lt, regs=r4 @ if count was even, we're done
@
.karaoke_singlesample: @
ldr r3, [r1] @ r3 = Li
ldr r12, [r2] @ r12 = Ri
mov r3, r3, asr #1 @ Lk = Li / 2 - Ri /2
sub r3, r3, r12, asr #1 @
rsb r12, r3, #0 @ Rk = -Lo = Ri / 2 - Li / 2
str r3, [r1] @ store Lo
str r12, [r2] @ store Ro
@
ldmpc regs=r4 @
.size channel_mode_proc_karaoke, .-channel_mode_proc_karaoke
/****************************************************************************
* void crossfeed_process(struct dsp_proc_entry *this,
* struct dsp_buffer **buf_p)
*/
.section .text
.global crossfeed_process
crossfeed_process:
@ input: r0 = this, r1 = buf_p
@ unfortunately, we ended up in a bit of a register squeeze here, and need
@ to keep the count on the stack :/
ldr r1, [r1] @ r1 = buf = *buf_p;
stmfd sp!, { r4-r11, lr } @ stack modified regs
ldr r12, [r1] @ r12 = buf->remcount
ldr r14, [r0] @ r14 = this->data = &crossfeed_state
ldmib r1, { r2-r3 } @ r2 = buf->p32[0], r3 = buf->p32[1]
ldmia r14!, { r4-r11 } @ load direct gain and filter data
add r0, r14, #13*2*4 @ calculate end of delay
stmfd sp!, { r0, r12 } @ stack end of delay adr, count and state
ldr r0, [r0] @ fetch current delay line address
/* Register usage in loop:
* r0 = &delay[index][0], r1 = accumulator high, r2 = buf->p32[0],
* r3 = buf->p32[1], r4 = direct gain, r5-r7 = b0, b1, a1 (filter coefs),
* r8-r11 = filter history, r12 = temp, r14 = accumulator low
*/
.cfloop:
smull r14, r1, r6, r8 @ acc = b1*dr[n - 1]
smlal r14, r1, r7, r9 @ acc += a1*y_l[n - 1]
ldr r8, [r0, #4] @ r8 = dr[n]
smlal r14, r1, r5, r8 @ acc += b0*dr[n]
mov r9, r1, lsl #1 @ fix format for filter history
ldr r12, [r2] @ load left input
smlal r14, r1, r4, r12 @ acc += gain*x_l[n]
mov r1, r1, lsl #1 @ fix format
str r1, [r2], #4 @ save result
smull r14, r1, r6, r10 @ acc = b1*dl[n - 1]
smlal r14, r1, r7, r11 @ acc += a1*y_r[n - 1]
ldr r10, [r0] @ r10 = dl[n]
str r12, [r0], #4 @ save left input to delay line
smlal r14, r1, r5, r10 @ acc += b0*dl[n]
mov r11, r1, lsl #1 @ fix format for filter history
ldr r12, [r3] @ load right input
smlal r14, r1, r4, r12 @ acc += gain*x_r[n]
str r12, [r0], #4 @ save right input to delay line
mov r1, r1, lsl #1 @ fix format
ldmia sp, { r12, r14 } @ fetch delay line end addr and count from stack
str r1, [r3], #4 @ save result
cmp r0, r12 @ need to wrap to start of delay?
subhs r0, r12, #13*2*4 @ wrap back delay line ptr to start
subs r14, r14, #1 @ are we finished?
strgt r14, [sp, #4] @ nope, save count back to stack
bgt .cfloop
@ save data back to struct
str r0, [r12] @ save delay line index
sub r12, r12, #13*2*4 + 4*4 @ r12 = data->history
stmia r12, { r8-r11 } @ save filter history
add sp, sp, #8 @ remove temp variables from stack
ldmpc regs=r4-r11
.size crossfeed_process, .-crossfeed_process
/****************************************************************************
* int lin_resample_resample(struct resample_data *data,
* struct dsp_buffer *src,
* struct dsp_buffer *dst)
*/
.section .text
.global lin_resample_resample
lin_resample_resample:
@input: r0 = data, r1 = src, r2 = dst
stmfd sp!, { r4-r11, lr } @ stack modified regs
ldr r4, [r0] @ r4 = data->delta
add r10, r0, #4 @ r10 = &data->phase
ldrb r3, [r1, #17] @ r3 = num_channels,
stmfd sp!, { r1, r10 } @ stack src, &data->phase
.lrs_channel_loop:
ldr r5, [r10] @ r5 = data->phase
ldr r6, [r1] @ r6 = srcrem = src->remcount
ldr r7, [r1, r3, lsl #2] @ r7 = src->p32[ch]
ldr r8, [r2, r3, lsl #2] @ r8 = dst->p32[ch]
ldr r9, [r2, #12] @ r9 = dstrem = dst->bufcount
cmp r6, #0x8000 @ srcrem = MIN(srcrem, 0x8000)
movgt r6, #0x8000 @
mov r0, r5, lsr #16 @ pos = MIN(pos, srcrem)
cmp r0, r6 @
movgt r0, r6 @ r0 = pos = phase >> 16
cmp r0, #0 @
ldrle r11, [r10, r3, lsl #2] @ pos <= 0? r11 = last = last_sample[ch]
addgt r12, r7, r0, lsl #2 @ pos > 0? r1 = last = s[pos - 1]
ldrgt r11, [r12, #-4] @
cmp r0, r6 @
bge .lrs_channel_done @ pos >= count? channel complete
cmp r4, #0x10000 @ delta >= 1.0?
ldrhs r12, [r7, r0, lsl #2] @ yes? r12 = s[pos]
bhs .lrs_dsstart @ yes? is downsampling
/** Upsampling **/
mov r5, r5, lsl #16 @ Move phase into high halfword
add r7, r7, r0, lsl #2 @ r7 = &s[pos]
sub r0, r6, r0 @ r0 = dte = srcrem - pos
.lrs_usloop_1:
ldr r12, [r7], #4 @ r12 = s[pos]
sub r14, r12, r11 @ r14 = diff = s[pos] - s[pos - 1]
.lrs_usloop_0:
mov r1, r5, lsr #16 @ r1 = frac = phase >> 16
@ keep frac in Rs to take advantage of multiplier early termination
smull r1, r10, r14, r1 @ r1, r10 = diff * frac (lo, hi)
add r1, r11, r1, lsr #16 @ r1 = out = last + frac*diff
add r1, r1, r10, lsl #16 @
str r1, [r8], #4 @ *d++ = out
subs r9, r9, #1 @ destination full?
bls .lrs_usfull @ yes? channel is done
adds r5, r5, r4, lsl #16 @ phase += delta << 16
bcc .lrs_usloop_0 @ if carry is set, pos is incremented
subs r0, r0, #1 @ if srcrem > 0, do another sample
mov r11, r12 @ r11 = last = s[pos-1] (pos changed)
bgt .lrs_usloop_1
b .lrs_usdone
.lrs_usfull:
adds r5, r5, r4, lsl #16 @ do missed phase increment
subcs r0, r0, #1 @ do missed srcrem decrement
movcs r11, r12 @ r11 = s[pos-1] (pos changed)
.lrs_usdone:
sub r0, r6, r0 @ r0 = pos = srcrem - dte
orr r5, r5, r0 @ reconstruct swapped phase
mov r5, r5, ror #16 @ swap pos and frac for phase
b .lrs_channel_done @
/** Downsampling **/
.lrs_dsloop:
add r10, r7, r0, lsl #2 @ r10 = &s[pos]
ldmda r10, { r11, r12 } @ r11 = last, r12 = s[pos]
.lrs_dsstart:
sub r14, r12, r11 @ r14 = diff = s[pos] - s[pos - 1]
@ keep frac in Rs to take advantage of multiplier early termination
bic r1, r5, r0, lsl #16 @ frac = phase & 0xffff
smull r1, r10, r14, r1 @ r1, r10 = diff * frac (lo, hi)
add r5, r5, r4 @ phase += delta
subs r9, r9, #1 @ destination full? ...
mov r0, r5, lsr #16 @ pos = phase >> 16
add r1, r11, r1, lsr #16 @ r1 = out = last + frac*diff
add r1, r1, r10, lsl #16 @
str r1, [r8], #4 @ *d++ = out
cmpgt r6, r0 @ ... || pos >= srcrem? ...
bgt .lrs_dsloop @ ... no, do more samples
cmp r0, r6 @ pos = MIN(pos, srcrem)
movgt r0, r6 @
sub r1, r0, #1 @ pos must always be > 0 since step >= 1.0
ldr r11, [r7, r1, lsl #2] @ r11 = s[pos - 1]
.lrs_channel_done:
ldmia sp, { r1, r10 } @ recover src, &data->phase
str r11, [r10, r3, lsl #2] @ last_sample[ch] = last
subs r3, r3, #1 @
bgt .lrs_channel_loop @
ldr r6, [r2, #12] @ r6 = dst->bufcount
sub r5, r5, r0, lsl #16 @ r5 = phase - (pos << 16)
str r5, [r10] @ data->phase = r5
sub r6, r6, r9 @ r6 = dst->bufcount - dstrem = dstcount
str r6, [r2] @ dst->remcount = dstcount
add sp, sp, #8 @ adjust stack for temp variables
ldmpc regs=r4-r11 @ ... and we're out
.size lin_resample_resample, .-lin_resample_resample
/****************************************************************************
* void pga_process(struct dsp_proc_entry *this, struct dsp_buffer **buf_p)
*/
.section .text
.global pga_process
.type pga_process, %function
pga_process:
@ input: r0 = this, r1 = buf_p
ldr r0, [r0] @ r0 = data = this->data (&pga_data)
ldr r1, [r1] @ r1 = buf = *buf_p;
stmfd sp!, { r4-r8, lr }
ldr r4, [r0] @ r4 = data->gain
ldr r0, [r1], #4 @ r0 = buf->remcount, r1 = buf->p32
ldrb r3, [r1, #13] @ r3 = buf->format.num_channels
.pga_channelloop:
ldr r2, [r1], #4 @ r2 = buf->p32[ch] and inc index of p32
subs r12, r0, #1 @ r12 = count - 1
beq .pga_singlesample @ Zero? Only one sample!
.pga_loop:
ldmia r2, { r5, r6 } @ load r5, r6 from r2 (*p32[ch])
smull r7, r8, r5, r4 @ r7 = FRACMUL_SHL(r5, r4, 8)
smull r14, r5, r6, r4 @ r14 = FRACMUL_SHL(r6, r4, 8)
subs r12, r12, #2
mov r7, r7, lsr #23
mov r14, r14, lsr #23
orr r7, r7, r8, asl #9
orr r14, r14, r5, asl #9
stmia r2!, { r7, r14 } @ save r7, r14 to *p32[ch] and increment
bgt .pga_loop @ end of pga loop
blt .pga_evencount @ < 0? even count
.pga_singlesample:
ldr r5, [r2] @ handle odd sample
smull r7, r8, r5, r4 @ r7 = FRACMUL_SHL(r5, r4, 8)
mov r7, r7, lsr #23
orr r7, r7, r8, asl #9
str r7, [r2]
.pga_evencount:
subs r3, r3, #1
bgt .pga_channelloop @ end of channel loop
ldmpc regs=r4-r8
.size pga_process, .-pga_process
/****************************************************************************
* void filter_process(struct dsp_filter *f, int32_t *buf[], int count,
* unsigned int channels)
*
* define HIGH_PRECISION as '1' to make filtering calculate lower bits after
* shifting. without this, "shift" - 1 of the lower bits will be lost here.
*/
#define HIGH_PRECISION 0
#if CONFIG_CPU == PP5002
.section .icode
#else
.text
#endif
.global filter_process
filter_process:
@input: r0 = f, r1 = buf, r2 = count, r3 = channels
stmfd sp!, { r4-r11, lr } @ save all clobbered regs
ldmia r0!, { r4-r8 } @ load coefs, r0 = f->history
sub r3, r3, #1 @ r3 = ch = channels - 1
stmfd sp!, { r0-r3 } @ save adjusted params
ldrb r14, [r0, #32] @ r14 = shift
@ Channels are processed high to low while history is saved low to high
@ It's really noone's business how we do this
.fp_channelloop:
ldmia r0, { r9-r12 } @ load history, r0 = history[channels-ch-1]
ldr r3, [r1, r3, lsl #2] @ r3 = buf[ch]
@ r9-r12 = history, r4-r8 = coefs, r0..r1 = accumulator,
@ r2 = number of samples, r3 = buf[ch], r14 = shift amount
.fp_loop:
@ Direct form 1 filtering code.
@ y[n] = b0*x[i] + b1*x[i - 1] + b2*x[i - 2] + a1*y[i - 1] + a2*y[i - 2],
@ where y[] is output and x[] is input. This is performed out of order to
@ reuse registers, we're pretty short on regs.
smull r0, r1, r5, r9 @ acc = b1*x[i - 1]
smlal r0, r1, r6, r10 @ acc += b2*x[i - 2]
mov r10, r9 @ fix input history
ldr r9, [r3] @ load input and fix history
smlal r0, r1, r7, r11 @ acc += a1*y[i - 1]
smlal r0, r1, r8, r12 @ acc += a2*y[i - 2]
smlal r0, r1, r4, r9 @ acc += b0*x[i] /* avoid stall on arm9 */
mov r12, r11 @ fix output history
mov r11, r1, asl r14 @ get upper part of result and shift left
#if HIGH_PRECISION
rsb r1, r14, #32 @ get shift amount for lower part
orr r11, r11, r0, lsr r1 @ then mix in correctly shifted lower part
#endif
str r11, [r3], #4 @ save result
subs r2, r2, #1 @ are we done with this channel?
bgt .fp_loop @
ldr r3, [sp, #12] @ r3 = ch
ldr r0, [sp] @ r0 = history[channels-ch-1]
subs r3, r3, #1 @ all channels processed?
stmia r0!, { r9-r12 } @ save back history, history++
ldmhsib sp, { r1-r2 } @ r1 = buf, r2 = count
strhs r3, [sp, #12] @ store ch
strhs r0, [sp] @ store history[channels-ch-1]
bhs .fp_channelloop
add sp, sp, #16 @ compensate for temp storage
ldmpc regs=r4-r11
.size filter_process, .-filter_process
#if ARM_ARCH < 6
/****************************************************************************
* void sample_output_mono(struct sample_io_data *this,
* struct dsp_buffer *src,
* struct dsp_buffer *dst)
*/
.section .icode
.global sample_output_mono
.type sample_output_mono, %function
sample_output_mono:
@ input: r0 = this, r1 = src, r2 = dst
stmfd sp!, { r4-r6, lr }
ldr r0, [r0] @ r0 = this->outcount
ldr r3, [r2, #4] @ r2 = dst->p16out
ldr r2, [r1, #4] @ r1 = src->p32[0]
ldrb r1, [r1, #19] @ r2 = src->format.output_scale
mov r4, #1
mov r4, r4, lsl r1 @ r4 = 1 << (scale-1)
mov r4, r4, lsr #1
mvn r14, #0x8000 @ r14 = 0xffff7fff, needed for
@ clipping and masking
subs r0, r0, #1 @
beq .som_singlesample @ Zero? Only one sample!
.somloop:
ldmia r2!, { r5, r6 }
add r5, r5, r4 @ r6 = (r6 + 1<<(scale-1)) >> scale
mov r5, r5, asr r1
mov r12, r5, asr #15
teq r12, r12, asr #31
eorne r5, r14, r5, asr #31 @ Clip (-32768...+32767)
add r6, r6, r4
mov r6, r6, asr r1 @ r7 = (r7 + 1<<(scale-1)) >> scale
mov r12, r6, asr #15
teq r12, r12, asr #31
eorne r6, r14, r6, asr #31 @ Clip (-32768...+32767)
and r5, r5, r14, lsr #16
and r6, r6, r14, lsr #16
orr r5, r5, r5, lsl #16 @ pack first 2 halfwords into 1 word
orr r6, r6, r6, lsl #16 @ pack last 2 halfwords into 1 word
stmia r3!, { r5, r6 }
subs r0, r0, #2
bgt .somloop
ldmpc cond=lt, regs=r4-r6 @ even 'count'? return
.som_singlesample:
ldr r5, [r2] @ do odd sample
add r5, r5, r4
mov r5, r5, asr r1
mov r12, r5, asr #15
teq r12, r12, asr #31
eorne r5, r14, r5, asr #31
and r5, r5, r14, lsr #16 @ pack 2 halfwords into 1 word
orr r5, r5, r5, lsl #16
str r5, [r3]
ldmpc regs=r4-r6
.size sample_output_mono, .-sample_output_mono
/****************************************************************************
* void sample_output_stereo(struct sample_io_data *this,
* struct dsp_buffer *src,
* struct dsp_buffer *dst)
*/
.section .icode
.global sample_output_stereo
.type sample_output_stereo, %function
sample_output_stereo:
@ input: r0 = this, r1 = src, r2 = dst
stmfd sp!, { r4-r9, lr }
ldr r0, [r0] @ r0 = this->outcount
ldr r3, [r2, #4] @ r3 = dsp->p16out
ldmib r1, { r2, r5 } @ r2 = src->p32[0], r5 = src->p32[1]
ldrb r1, [r1, #19] @ r1 = src->format.output_scale
mov r4, #1
mov r4, r4, lsl r1 @ r4 = 1 << (scale-1)
mov r4, r4, lsr #1 @
mvn r14, #0x8000 @ r14 = 0xffff7fff, needed for
@ clipping and masking
subs r0, r0, #1 @
beq .sos_singlesample @ Zero? Only one sample!
.sosloop:
ldmia r2!, { r6, r7 } @ 2 left
ldmia r5!, { r8, r9 } @ 2 right
add r6, r6, r4 @ r6 = (r6 + 1<<(scale-1)) >> scale
mov r6, r6, asr r1
mov r12, r6, asr #15
teq r12, r12, asr #31
eorne r6, r14, r6, asr #31 @ Clip (-32768...+32767)
add r7, r7, r4
mov r7, r7, asr r1 @ r7 = (r7 + 1<<(scale-1)) >> scale
mov r12, r7, asr #15
teq r12, r12, asr #31
eorne r7, r14, r7, asr #31 @ Clip (-32768...+32767)
add r8, r8, r4 @ r8 = (r8 + 1<<(scale-1)) >> scale
mov r8, r8, asr r1
mov r12, r8, asr #15
teq r12, r12, asr #31
eorne r8, r14, r8, asr #31 @ Clip (-32768...+32767)
add r9, r9, r4 @ r9 = (r9 + 1<<(scale-1)) >> scale
mov r9, r9, asr r1
mov r12, r9, asr #15
teq r12, r12, asr #31
eorne r9, r14, r9, asr #31 @ Clip (-32768...+32767)
and r6, r6, r14, lsr #16 @ pack first 2 halfwords into 1 word
orr r8, r6, r8, asl #16
and r7, r7, r14, lsr #16 @ pack last 2 halfwords into 1 word
orr r9, r7, r9, asl #16
stmia r3!, { r8, r9 }
subs r0, r0, #2
bgt .sosloop
ldmpc cond=lt, regs=r4-r9 @ even 'count'? return
.sos_singlesample:
ldr r6, [r2] @ left odd sample
ldr r8, [r5] @ right odd sample
add r6, r6, r4 @ r6 = (r7 + 1<<(scale-1)) >> scale
mov r6, r6, asr r1
mov r12, r6, asr #15
teq r12, r12, asr #31
eorne r6, r14, r6, asr #31 @ Clip (-32768...+32767)
add r8, r8, r4 @ r8 = (r8 + 1<<(scale-1)) >> scale
mov r8, r8, asr r1
mov r12, r8, asr #15
teq r12, r12, asr #31
eorne r8, r14, r8, asr #31 @ Clip (-32768...+32767)
and r6, r6, r14, lsr #16 @ pack 2 halfwords into 1 word
orr r8, r6, r8, asl #16
str r8, [r3]
ldmpc regs=r4-r9
.size sample_output_stereo, .-sample_output_stereo
#endif /* ARM_ARCH < 6 */