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1da177e4 LT |
1 | /*---------------------------------------------------------------------------+ |
2 | | reg_divide.c | | |
3 | | | | |
4 | | Divide one FPU_REG by another and put the result in a destination FPU_REG.| | |
5 | | | | |
6 | | Copyright (C) 1996 | | |
7 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | | |
8 | | E-mail billm@jacobi.maths.monash.edu.au | | |
9 | | | | |
10 | | Return value is the tag of the answer, or-ed with FPU_Exception if | | |
11 | | one was raised, or -1 on internal error. | | |
12 | | | | |
13 | +---------------------------------------------------------------------------*/ | |
14 | ||
15 | /*---------------------------------------------------------------------------+ | |
16 | | The destination may be any FPU_REG, including one of the source FPU_REGs. | | |
17 | +---------------------------------------------------------------------------*/ | |
18 | ||
19 | #include "exception.h" | |
20 | #include "reg_constant.h" | |
21 | #include "fpu_emu.h" | |
22 | #include "fpu_system.h" | |
23 | ||
24 | /* | |
25 | Divide one register by another and put the result into a third register. | |
26 | */ | |
27 | int FPU_div(int flags, int rm, int control_w) | |
28 | { | |
3d0d14f9 IM |
29 | FPU_REG x, y; |
30 | FPU_REG const *a, *b, *st0_ptr, *st_ptr; | |
31 | FPU_REG *dest; | |
32 | u_char taga, tagb, signa, signb, sign, saved_sign; | |
33 | int tag, deststnr; | |
34 | ||
35 | if (flags & DEST_RM) | |
36 | deststnr = rm; | |
37 | else | |
38 | deststnr = 0; | |
39 | ||
40 | if (flags & REV) { | |
41 | b = &st(0); | |
42 | st0_ptr = b; | |
43 | tagb = FPU_gettag0(); | |
44 | if (flags & LOADED) { | |
45 | a = (FPU_REG *) rm; | |
46 | taga = flags & 0x0f; | |
47 | } else { | |
48 | a = &st(rm); | |
49 | st_ptr = a; | |
50 | taga = FPU_gettagi(rm); | |
51 | } | |
52 | } else { | |
53 | a = &st(0); | |
54 | st0_ptr = a; | |
55 | taga = FPU_gettag0(); | |
56 | if (flags & LOADED) { | |
57 | b = (FPU_REG *) rm; | |
58 | tagb = flags & 0x0f; | |
59 | } else { | |
60 | b = &st(rm); | |
61 | st_ptr = b; | |
62 | tagb = FPU_gettagi(rm); | |
63 | } | |
1da177e4 | 64 | } |
1da177e4 | 65 | |
3d0d14f9 IM |
66 | signa = getsign(a); |
67 | signb = getsign(b); | |
1da177e4 | 68 | |
3d0d14f9 | 69 | sign = signa ^ signb; |
1da177e4 | 70 | |
3d0d14f9 IM |
71 | dest = &st(deststnr); |
72 | saved_sign = getsign(dest); | |
1da177e4 | 73 | |
3d0d14f9 IM |
74 | if (!(taga | tagb)) { |
75 | /* Both regs Valid, this should be the most common case. */ | |
76 | reg_copy(a, &x); | |
77 | reg_copy(b, &y); | |
78 | setpositive(&x); | |
79 | setpositive(&y); | |
80 | tag = FPU_u_div(&x, &y, dest, control_w, sign); | |
1da177e4 | 81 | |
3d0d14f9 IM |
82 | if (tag < 0) |
83 | return tag; | |
1da177e4 | 84 | |
3d0d14f9 IM |
85 | FPU_settagi(deststnr, tag); |
86 | return tag; | |
87 | } | |
1da177e4 | 88 | |
3d0d14f9 IM |
89 | if (taga == TAG_Special) |
90 | taga = FPU_Special(a); | |
91 | if (tagb == TAG_Special) | |
92 | tagb = FPU_Special(b); | |
1da177e4 | 93 | |
3d0d14f9 | 94 | if (((taga == TAG_Valid) && (tagb == TW_Denormal)) |
1da177e4 | 95 | || ((taga == TW_Denormal) && (tagb == TAG_Valid)) |
3d0d14f9 IM |
96 | || ((taga == TW_Denormal) && (tagb == TW_Denormal))) { |
97 | if (denormal_operand() < 0) | |
98 | return FPU_Exception; | |
99 | ||
100 | FPU_to_exp16(a, &x); | |
101 | FPU_to_exp16(b, &y); | |
102 | tag = FPU_u_div(&x, &y, dest, control_w, sign); | |
103 | if (tag < 0) | |
104 | return tag; | |
105 | ||
106 | FPU_settagi(deststnr, tag); | |
107 | return tag; | |
108 | } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { | |
109 | if (tagb != TAG_Zero) { | |
110 | /* Want to find Zero/Valid */ | |
111 | if (tagb == TW_Denormal) { | |
112 | if (denormal_operand() < 0) | |
113 | return FPU_Exception; | |
114 | } | |
115 | ||
116 | /* The result is zero. */ | |
117 | FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); | |
118 | setsign(dest, sign); | |
119 | return TAG_Zero; | |
120 | } | |
121 | /* We have an exception condition, either 0/0 or Valid/Zero. */ | |
122 | if (taga == TAG_Zero) { | |
123 | /* 0/0 */ | |
124 | return arith_invalid(deststnr); | |
125 | } | |
126 | /* Valid/Zero */ | |
127 | return FPU_divide_by_zero(deststnr, sign); | |
1da177e4 | 128 | } |
3d0d14f9 IM |
129 | /* Must have infinities, NaNs, etc */ |
130 | else if ((taga == TW_NaN) || (tagb == TW_NaN)) { | |
131 | if (flags & LOADED) | |
132 | return real_2op_NaN((FPU_REG *) rm, flags & 0x0f, 0, | |
133 | st0_ptr); | |
134 | ||
135 | if (flags & DEST_RM) { | |
136 | int tag; | |
137 | tag = FPU_gettag0(); | |
138 | if (tag == TAG_Special) | |
139 | tag = FPU_Special(st0_ptr); | |
140 | return real_2op_NaN(st0_ptr, tag, rm, | |
141 | (flags & REV) ? st0_ptr : &st(rm)); | |
142 | } else { | |
143 | int tag; | |
144 | tag = FPU_gettagi(rm); | |
145 | if (tag == TAG_Special) | |
146 | tag = FPU_Special(&st(rm)); | |
147 | return real_2op_NaN(&st(rm), tag, 0, | |
148 | (flags & REV) ? st0_ptr : &st(rm)); | |
149 | } | |
150 | } else if (taga == TW_Infinity) { | |
151 | if (tagb == TW_Infinity) { | |
152 | /* infinity/infinity */ | |
153 | return arith_invalid(deststnr); | |
154 | } else { | |
155 | /* tagb must be Valid or Zero */ | |
156 | if ((tagb == TW_Denormal) && (denormal_operand() < 0)) | |
157 | return FPU_Exception; | |
158 | ||
159 | /* Infinity divided by Zero or Valid does | |
160 | not raise and exception, but returns Infinity */ | |
161 | FPU_copy_to_regi(a, TAG_Special, deststnr); | |
162 | setsign(dest, sign); | |
163 | return taga; | |
164 | } | |
165 | } else if (tagb == TW_Infinity) { | |
166 | if ((taga == TW_Denormal) && (denormal_operand() < 0)) | |
167 | return FPU_Exception; | |
168 | ||
169 | /* The result is zero. */ | |
170 | FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); | |
171 | setsign(dest, sign); | |
172 | return TAG_Zero; | |
1da177e4 | 173 | } |
1da177e4 | 174 | #ifdef PARANOID |
3d0d14f9 IM |
175 | else { |
176 | EXCEPTION(EX_INTERNAL | 0x102); | |
177 | return FPU_Exception; | |
178 | } | |
179 | #endif /* PARANOID */ | |
1da177e4 LT |
180 | |
181 | return 0; | |
182 | } |