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SWCODEC-Coldfire: Small upsampling tweek improves speed and size a tiny bit and prevents unneeded reloading of the previous sample. I imagine it would help most with non-iram source buffers.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@12425 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2007-02-21 07:06:58 +00:00
parent 8d7a364063
commit 7c120fb0ce
1 changed files with 21 additions and 19 deletions
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40
apps/dsp_cf.S
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@ -172,38 +172,41 @@ dsp_upsample:
.uschannel_loop:
move.l (%a0), %d5 | %d5 = phase = r->phase
move.l -4(%a1, %d2.l*4), %a3 | %a3 = s = src[ch-1]
lea.l 4(%a0, %d2.l*4), %a4 | %a4 = &r->last_sample[ch-1]
lea.l (%a3, %d3.l*4), %a5 | %a5 = src_end = &src[count]
move.l (%a4), %d0 | %d0 = last = r->last_sample[ch-1]
move.l -4(%a5), %d1 | r->last_sample[ch-1] = s[count-1]
move.l %d1, (%a4) |
move.l -4(%a2, %d2.l*4), %a4 | %a4 = d = dst[ch-1]
lea.l 4(%a0, %d2.l*4), %a5 | %a5 = &r->last_sample[ch-1]
move.l (%a5), %d0 | %d0 = last = r->last_sample[ch-1]
move.l -4(%a3, %d3.l*4), %d1 | r->last_sample[ch-1] = s[count-1]
move.l %d1, (%a5) |
moveq.l #16, %d1 | %d0 = shift
move.l %d5, %d6 | %d6 = pos = phase >> 16
lsl.l %d1, %d5 | swap phase to high word to use
| carries to increment position
lsr.l %d1, %d6 | pos == 0?
bne.b .usstart_1 | no? transistion from down
move.l (%a3), %d1 | %d1 = s[0]
sub.l %d0, %d1 | diff = s[pos] - last
bra.b .usloop_0 | jump to typical start point
.usstart_1:
beq.b .usstart_0 | no? transistion from down
cmp.l %d3, %d6 | past end of samples?
bge.b .usloop_skip | yes? skip loop
lea.l 4(%a3, %d6.l*4), %a3 | %a3 = s + pos + 1
movem.l -8(%a3), %d0-%d1 | %d0 = *(s - 2), %d1 = *(s - 1)
.word 0x51fa | tpf.w - trap next instruction
.usstart_0:
move.l (%a3)+, %d1 | %d1 = *s++
.word 0x51fb | tpf.l - trap next two instructions
.usloop_1:
lea.l -4(%a3, %d6.l*4), %a5 | load s[pos-1] and s[pos]
movem.l (%a5), %d0-%d1 |
move.l %d6, %d0 | move previous sample to %d0
move.l (%a3)+, %d1 | fetch next sample
move.l %d1, %d6 | save sample value
sub.l %d0, %d1 | %d1 = diff = s[pos] - s[pos-1]
.usloop_0:
move.l %d0, %acc0 | %acc0 = previous sample
lsr.l #1, %d5 | make phase into frac
mac.l %d1, %d5, %acc0 | %acc0 += diff * frac
move.l %acc0, %d7 |
mac.l %d1, %d5, %acc0 | %acc0 = diff * frac
movclr.l %acc0, %d7 | %d7 = product
lsl.l #1, %d5 | restore frac to phase
move.l %d7, (%a4)+ | *d++ = %d0
add.l %d0, %d7 | %d7 = last + product
move.l %d7, (%a4)+ | *d++ = %d7
add.l %d4, %d5 | phase += delta
bcc.b .usloop_0 | load next values?
addq.l #1, %d6 | increment position
cmp.l %d3, %d6 | pos < count?
cmp.l %a5, %a3 | src < src_end?
blt.b .usloop_1 | yes? continue resampling
.usloop_skip:
subq.l #1, %d2 | ch > 0?
@ -212,9 +215,8 @@ dsp_upsample:
move.l %d5, (%a0) | ...and save in r->phase
move.l %a4, %d0 | return d - d[0]
sub.l (%a2), %d0 |
asr.l #2, %d0 | convert bytes->samples
movem.l (%sp), %d2-%d7/%a2-%a5 | restore non-clobberables
move.l %acc1, %acc0 | clear %acc0
asr.l #2, %d0 | convert bytes->samples
lea.l 40(%sp), %sp | cleanup stack
rts | buh-bye
.usend: