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; Tremolo library
; Copyright (C) 2009 Robin Watts for Pinknoise Productions Ltd
AREA |.text|, CODE, READONLY
EXPORT render_line_arm
render_line_arm
; r0 = n
; r1 = d
; r2 = floor
; r3 = base
; <> = err
; <> = adx
; <> = ady
MOV r12,r13
STMFD r13!,{r4-r6,r11,r14}
LDMFD r12,{r11,r12,r14} ; r11 = err
; r12 = adx
; r14 = ady
rl_loop
LDR r4,[r1] ; r4 = *d
LDR r5,[r2],r3,LSL #2 ; r5 = *floor r2 = floor+base
SUBS r11,r11,r14 ; err -= ady
ADDLT r11,r11,r12 ; if (err < 0) err+=adx
SMULL r6, r5, r4, r5 ; (r6,r5) = *d * *floor
ADDLT r2, r2, #4 ; floor+=1
MOVS r6, r6, LSR #15
ADC r5, r6, r5, LSL #17 ; r5 = MULT31_SHIFT15
STR r5,[r1],#4
SUBS r0, r0, #1
BGT rl_loop
LDMFD r13!,{r4-r6,r11,PC}
END
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