1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /*---------------------------------------------------------------------------+ |
3 | | reg_divide.c | |
4 | | | |
5 | | Divide one FPU_REG by another and put the result in a destination FPU_REG.| |
6 | | | |
7 | | Copyright (C) 1996 | |
8 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | |
9 | | E-mail billm@jacobi.maths.monash.edu.au | |
10 | | | |
11 | | Return value is the tag of the answer, or-ed with FPU_Exception if | |
12 | | one was raised, or -1 on internal error. | |
13 | | | |
14 | +---------------------------------------------------------------------------*/ |
15 | |
16 | /*---------------------------------------------------------------------------+ |
17 | | The destination may be any FPU_REG, including one of the source FPU_REGs. | |
18 | +---------------------------------------------------------------------------*/ |
19 | |
20 | #include "exception.h" |
21 | #include "reg_constant.h" |
22 | #include "fpu_emu.h" |
23 | #include "fpu_system.h" |
24 | |
25 | /* |
26 | Divide one register by another and put the result into a third register. |
27 | */ |
28 | int FPU_div(int flags, int rm, int control_w) |
29 | { |
30 | FPU_REG x, y; |
31 | FPU_REG const *a, *b, *st0_ptr, *st_ptr; |
32 | FPU_REG *dest; |
33 | u_char taga, tagb, signa, signb, sign, saved_sign; |
34 | int tag, deststnr; |
35 | |
36 | if (flags & DEST_RM) |
37 | deststnr = rm; |
38 | else |
39 | deststnr = 0; |
40 | |
41 | if (flags & REV) { |
42 | b = &st(0); |
43 | st0_ptr = b; |
44 | tagb = FPU_gettag0(); |
45 | if (flags & LOADED) { |
46 | a = (FPU_REG *) rm; |
47 | taga = flags & 0x0f; |
48 | } else { |
49 | a = &st(rm); |
50 | st_ptr = a; |
51 | taga = FPU_gettagi(stnr: rm); |
52 | } |
53 | } else { |
54 | a = &st(0); |
55 | st0_ptr = a; |
56 | taga = FPU_gettag0(); |
57 | if (flags & LOADED) { |
58 | b = (FPU_REG *) rm; |
59 | tagb = flags & 0x0f; |
60 | } else { |
61 | b = &st(rm); |
62 | st_ptr = b; |
63 | tagb = FPU_gettagi(stnr: rm); |
64 | } |
65 | } |
66 | |
67 | signa = getsign(a); |
68 | signb = getsign(b); |
69 | |
70 | sign = signa ^ signb; |
71 | |
72 | dest = &st(deststnr); |
73 | saved_sign = getsign(dest); |
74 | |
75 | if (!(taga | tagb)) { |
76 | /* Both regs Valid, this should be the most common case. */ |
77 | reg_copy(x: a, y: &x); |
78 | reg_copy(x: b, y: &y); |
79 | setpositive(&x); |
80 | setpositive(&y); |
81 | tag = FPU_u_div(arg1: &x, arg2: &y, answ: dest, control_w, sign); |
82 | |
83 | if (tag < 0) |
84 | return tag; |
85 | |
86 | FPU_settagi(stnr: deststnr, tag); |
87 | return tag; |
88 | } |
89 | |
90 | if (taga == TAG_Special) |
91 | taga = FPU_Special(ptr: a); |
92 | if (tagb == TAG_Special) |
93 | tagb = FPU_Special(ptr: b); |
94 | |
95 | if (((taga == TAG_Valid) && (tagb == TW_Denormal)) |
96 | || ((taga == TW_Denormal) && (tagb == TAG_Valid)) |
97 | || ((taga == TW_Denormal) && (tagb == TW_Denormal))) { |
98 | if (denormal_operand() < 0) |
99 | return FPU_Exception; |
100 | |
101 | FPU_to_exp16(a, x: &x); |
102 | FPU_to_exp16(a: b, x: &y); |
103 | tag = FPU_u_div(arg1: &x, arg2: &y, answ: dest, control_w, sign); |
104 | if (tag < 0) |
105 | return tag; |
106 | |
107 | FPU_settagi(stnr: deststnr, tag); |
108 | return tag; |
109 | } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { |
110 | if (tagb != TAG_Zero) { |
111 | /* Want to find Zero/Valid */ |
112 | if (tagb == TW_Denormal) { |
113 | if (denormal_operand() < 0) |
114 | return FPU_Exception; |
115 | } |
116 | |
117 | /* The result is zero. */ |
118 | FPU_copy_to_regi(r: &CONST_Z, TAG_Zero, stnr: deststnr); |
119 | setsign(dest, sign); |
120 | return TAG_Zero; |
121 | } |
122 | /* We have an exception condition, either 0/0 or Valid/Zero. */ |
123 | if (taga == TAG_Zero) { |
124 | /* 0/0 */ |
125 | return arith_invalid(deststnr); |
126 | } |
127 | /* Valid/Zero */ |
128 | return FPU_divide_by_zero(deststnr, sign); |
129 | } |
130 | /* Must have infinities, NaNs, etc */ |
131 | else if ((taga == TW_NaN) || (tagb == TW_NaN)) { |
132 | if (flags & LOADED) |
133 | return real_2op_NaN(b: (FPU_REG *) rm, tagb: flags & 0x0f, deststnr: 0, |
134 | defaultNaN: st0_ptr); |
135 | |
136 | if (flags & DEST_RM) { |
137 | int tag; |
138 | tag = FPU_gettag0(); |
139 | if (tag == TAG_Special) |
140 | tag = FPU_Special(ptr: st0_ptr); |
141 | return real_2op_NaN(b: st0_ptr, tagb: tag, deststnr: rm, |
142 | defaultNaN: (flags & REV) ? st0_ptr : &st(rm)); |
143 | } else { |
144 | int tag; |
145 | tag = FPU_gettagi(stnr: rm); |
146 | if (tag == TAG_Special) |
147 | tag = FPU_Special(ptr: &st(rm)); |
148 | return real_2op_NaN(b: &st(rm), tagb: tag, deststnr: 0, |
149 | defaultNaN: (flags & REV) ? st0_ptr : &st(rm)); |
150 | } |
151 | } else if (taga == TW_Infinity) { |
152 | if (tagb == TW_Infinity) { |
153 | /* infinity/infinity */ |
154 | return arith_invalid(deststnr); |
155 | } else { |
156 | /* tagb must be Valid or Zero */ |
157 | if ((tagb == TW_Denormal) && (denormal_operand() < 0)) |
158 | return FPU_Exception; |
159 | |
160 | /* Infinity divided by Zero or Valid does |
161 | not raise and exception, but returns Infinity */ |
162 | FPU_copy_to_regi(r: a, TAG_Special, stnr: deststnr); |
163 | setsign(dest, sign); |
164 | return taga; |
165 | } |
166 | } else if (tagb == TW_Infinity) { |
167 | if ((taga == TW_Denormal) && (denormal_operand() < 0)) |
168 | return FPU_Exception; |
169 | |
170 | /* The result is zero. */ |
171 | FPU_copy_to_regi(r: &CONST_Z, TAG_Zero, stnr: deststnr); |
172 | setsign(dest, sign); |
173 | return TAG_Zero; |
174 | } |
175 | #ifdef PARANOID |
176 | else { |
177 | EXCEPTION(EX_INTERNAL | 0x102); |
178 | return FPU_Exception; |
179 | } |
180 | #endif /* PARANOID */ |
181 | |
182 | return 0; |
183 | } |
184 | |