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Calculate 2 samples per loop

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This commit is contained in:
Gwilym Kuiper 2022-04-26 21:08:22 +01:00
parent 260f664c36
commit 245cafa599
1 changed files with 11 additions and 5 deletions
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16
agb/src/sound/mixer/mixer.s
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@ -163,7 +163,7 @@ agb_arm_func agb_rs__mixer_collapse
@ Arguments:
@ r0 = target buffer (i8)
@ r1 = input buffer (i16) of fixnums with 4 bits of precision (read in sets of i16 in an i32)
push {r4}
push {r4, r5, r6}
ldr r2, agb_rs__buffer_size @ loop counter
mov r4, r2
@ -182,13 +182,19 @@ agb_arm_func agb_rs__mixer_collapse
.endm
load_sample r3, r12
load_sample r5, r6
strb r3, [r0, r4] @ *(r0 + (r4 = SOUND_BUFFER_SIZE)) = r3
strb r12, [r0], #1 @ *r0 = r12; r0++
and r3, r3, #255 @ combine the two samples so we can store in 16-bit chunks
and r12, r12, #255
orr r3, r3, r5, lsl #8
orr r12, r12, r6, lsl #8
subs r2, r2, #1 @ r2 -= 1
strh r3, [r0, r4] @ *(r0 + (r4 = SOUND_BUFFER_SIZE)) = r3
strh r12, [r0], #2 @ *r0 = r12; r0 += 2
subs r2, r2, #2 @ r2 -= 2
bne 1b @ loop if not 0
pop {r4}
pop {r4, r5, r6}
bx lr
agb_arm_end agb_rs__mixer_collapse