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Reduce register usage

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This commit is contained in:
Gwilym Kuiper 2022-05-04 16:58:46 +01:00
parent 06f701af75
commit 73b8530240
1 changed files with 13 additions and 22 deletions
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35
agb/src/sound/mixer/mixer.s
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@ -157,13 +157,15 @@ agb_arm_end agb_rs__mixer_add_stereo
cmp \reg, #127
movgt \reg, #127
and \reg, \reg, #255
.endm
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, r5, r6, r7, r8, r9, r10}
push {r4, r5, r6}
ldr r2, agb_rs__buffer_size @ loop counter
mov r4, r2
@ -182,29 +184,18 @@ agb_arm_func agb_rs__mixer_collapse
.endm
load_sample r3, r12
load_sample r5, r6
load_sample r7, r8
load_sample r9, r10
@ combine the four samples so we can store in 32-bit chunks
@ need to ensure that we don't overwrite the extra bit of the sample
and r3, r3, #255
and r12, r12, #255
and r5, r5, #255
and r6, r6, #255
and r7, r7, #255
and r8, r8, #255
and r9, r9, #255
and r10, r10, #255
@ combine all of the samples
orr r3, r3, r5, lsl #8
orr r3, r3, r7, lsl #16
orr r3, r3, r9, lsl #24
orr r12, r12, r6, lsl #8
orr r12, r12, r8, lsl #16
orr r12, r12, r10, lsl #24
load_sample r5, r6
orr r3, r3, r5, lsl #16
orr r12, r12, r6, lsl #16
load_sample r5, r6
orr r3, r3, r5, lsl #24
orr r12, r12, r6, lsl #24
str r3, [r0, r4] @ *(r0 + (r4 = SOUND_BUFFER_SIZE)) = r3
str r12, [r0], #4 @ *r0 = r12; r0 += 4
@ -212,6 +203,6 @@ agb_arm_func agb_rs__mixer_collapse
subs r2, r2, #4 @ r2 -= 4
bne 1b @ loop if not 0
pop {r4, r5, r6, r7, r8, r9, r10}
pop {r4, r5, r6}
bx lr
agb_arm_end agb_rs__mixer_collapse