Nyaaori/rockbox
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

SWCODEC, Coldfire, upsampling: Shave a couple more cycles out of the typical case and I think four bytes. Don't wanna look at this again for awhile. :)

Browse source 
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@12429 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2007-02-21 11:25:49 +00:00
parent 417bc74f83
commit 31ae2ded58
1 changed files with 8 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
apps/dsp_cf.S
View file

@ -178,22 +178,20 @@ dsp_upsample:
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]
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
swap %d5 | swap phase to high word to use
| carries to increment position
lsr.l %d1, %d6 | pos == 0?
move.l %d5, %d6 | %d6 = pos = phase >> 16
clr.w %d5 |
eor.l %d5, %d6 | pos == 0?
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 (%a3, %d6.l*4), %a3 | %a3 = s = s + pos
move.l -4(%a3), %d6 | %d6 = *(s - 1)
.word 0x51fb | tpf.l - trap next two instructions
.usstart_0:
move.l (%a3)+, %d1 | %d1 = *s++
.word 0x51fb | tpf.l - trap next two instructions
lea.l -4(%a3, %d6.l*4), %a3 | %a3 = s = &s[pos-1] (previous)
move.l (%a3)+, %d0 | %d0 = *s++
.word 0x51fa | tpf.w - trap next instruction
.usloop_1:
move.l %d6, %d0 | move previous sample to %d0
.usstart_0:
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]