summaryrefslogtreecommitdiff
path: root/engine/multiply_divide.asm
blob: ec16c42bba7a23c884a359fe5034b38b24b190cc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
_Multiply: ; 37d41 (d:7d41)
	ld a, $8
	ld b, a
	xor a
	ld [H_PRODUCT], a
	ld [H_MULTIPLYBUFFER], a
	ld [H_MULTIPLYBUFFER+1], a
	ld [H_MULTIPLYBUFFER+2], a
	ld [H_MULTIPLYBUFFER+3], a
.loop
	ld a, [H_MULTIPLIER]
	srl a
	ld [H_MULTIPLIER], a ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	jr nc, .smallMultiplier
	ld a, [H_MULTIPLYBUFFER+3]
	ld c, a
	ld a, [H_MULTIPLICAND+2]
	add c
	ld [H_MULTIPLYBUFFER+3], a
	ld a, [H_MULTIPLYBUFFER+2]
	ld c, a
	ld a, [H_MULTIPLICAND+1]
	adc c
	ld [H_MULTIPLYBUFFER+2], a
	ld a, [H_MULTIPLYBUFFER+1]
	ld c, a
	ld a, [H_MULTIPLICAND] ; (aliases: H_MULTIPLICAND)
	adc c
	ld [H_MULTIPLYBUFFER+1], a
	ld a, [H_MULTIPLYBUFFER]
	ld c, a
	ld a, [H_PRODUCT] ; (aliases: H_PRODUCT, H_PASTLEADINGZEROES, H_QUOTIENT)
	adc c
	ld [H_MULTIPLYBUFFER], a
.smallMultiplier
	dec b
	jr z, .done
	ld a, [H_MULTIPLICAND+2]
	sla a
	ld [H_MULTIPLICAND+2], a
	ld a, [H_MULTIPLICAND+1]
	rl a
	ld [H_MULTIPLICAND+1], a
	ld a, [H_MULTIPLICAND]
	rl a
	ld [H_MULTIPLICAND], a
	ld a, [H_PRODUCT]
	rl a
	ld [H_PRODUCT], a
	jr .loop
.done
	ld a, [H_MULTIPLYBUFFER+3]
	ld [H_PRODUCT+3], a
	ld a, [H_MULTIPLYBUFFER+2]
	ld [H_PRODUCT+2], a
	ld a, [H_MULTIPLYBUFFER+1]
	ld [H_PRODUCT+1], a
	ld a, [H_MULTIPLYBUFFER]
	ld [H_PRODUCT], a
	ret

_Divide: ; 37da5 (d:7da5)
	xor a
	ld [H_DIVIDEBUFFER], a
	ld [H_DIVIDEBUFFER+1], a
	ld [H_DIVIDEBUFFER+2], a
	ld [H_DIVIDEBUFFER+3], a
	ld [H_DIVIDEBUFFER+4], a
	ld a, $9
	ld e, a
.asm_37db3
	ld a, [H_DIVIDEBUFFER]
	ld c, a
	ld a, [H_DIVIDEND+1] ; (aliases: H_MULTIPLICAND)
	sub c
	ld d, a
	ld a, [H_DIVISOR] ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	ld c, a
	ld a, [H_DIVIDEND] ; (aliases: H_PRODUCT, H_PASTLEADINGZEROES, H_QUOTIENT)
	sbc c
	jr c, .asm_37dce
	ld [H_DIVIDEND], a ; (aliases: H_PRODUCT, H_PASTLEADINGZEROES, H_QUOTIENT)
	ld a, d
	ld [H_DIVIDEND+1], a ; (aliases: H_MULTIPLICAND)
	ld a, [H_DIVIDEBUFFER+4]
	inc a
	ld [H_DIVIDEBUFFER+4], a
	jr .asm_37db3
.asm_37dce
	ld a, b
	cp $1
	jr z, .asm_37e18
	ld a, [H_DIVIDEBUFFER+4]
	sla a
	ld [H_DIVIDEBUFFER+4], a
	ld a, [H_DIVIDEBUFFER+3]
	rl a
	ld [H_DIVIDEBUFFER+3], a
	ld a, [H_DIVIDEBUFFER+2]
	rl a
	ld [H_DIVIDEBUFFER+2], a
	ld a, [H_DIVIDEBUFFER+1]
	rl a
	ld [H_DIVIDEBUFFER+1], a
	dec e
	jr nz, .asm_37e04
	ld a, $8
	ld e, a
	ld a, [H_DIVIDEBUFFER]
	ld [H_DIVISOR], a ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	xor a
	ld [H_DIVIDEBUFFER], a
	ld a, [H_DIVIDEND+1] ; (aliases: H_MULTIPLICAND)
	ld [H_DIVIDEND], a ; (aliases: H_PRODUCT, H_PASTLEADINGZEROES, H_QUOTIENT)
	ld a, [H_DIVIDEND+2]
	ld [H_DIVIDEND+1], a ; (aliases: H_MULTIPLICAND)
	ld a, [H_DIVIDEND+3]
	ld [H_DIVIDEND+2], a
.asm_37e04
	ld a, e
	cp $1
	jr nz, .asm_37e0a
	dec b
.asm_37e0a
	ld a, [H_DIVISOR] ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	srl a
	ld [H_DIVISOR], a ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	ld a, [H_DIVIDEBUFFER]
	rr a
	ld [H_DIVIDEBUFFER], a
	jr .asm_37db3
.asm_37e18
	ld a, [H_DIVIDEND+1] ; (aliases: H_MULTIPLICAND)
	ld [H_REMAINDER], a ; (aliases: H_DIVISOR, H_MULTIPLIER, H_POWEROFTEN)
	ld a, [H_DIVIDEBUFFER+4]
	ld [H_QUOTIENT+3], a
	ld a, [H_DIVIDEBUFFER+3]
	ld [H_QUOTIENT+2], a
	ld a, [H_DIVIDEBUFFER+2]
	ld [H_QUOTIENT+1], a ; (aliases: H_MULTIPLICAND)
	ld a, [H_DIVIDEBUFFER+1]
	ld [H_DIVIDEND], a ; (aliases: H_PRODUCT, H_PASTLEADINGZEROES, H_QUOTIENT)
	ret