1 /*---------------------------------------------------------------------------+
2 | reg_compare.c |
3 | |
4 | Compare two floating point registers |
5 | |
6 | Copyright (C) 1992,1993,1994,1997 |
7 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
8 | E-mail billm@suburbia.net |
9 | |
10 | |
11 +---------------------------------------------------------------------------*/
12
13 /*---------------------------------------------------------------------------+
14 | compare() is the core FPU_REG comparison function |
15 +---------------------------------------------------------------------------*/
16
17 #include "fpu_system.h"
18 #include "exception.h"
19 #include "fpu_emu.h"
20 #include "control_w.h"
21 #include "status_w.h"
22
23 static int compare(FPU_REG const *b, int tagb)
24 {
25 int diff, exp0, expb;
26 u_char st0_tag;
27 FPU_REG *st0_ptr;
28 FPU_REG x, y;
29 u_char st0_sign, signb = getsign(b);
30
31 st0_ptr = &st(0);
32 st0_tag = FPU_gettag0();
33 st0_sign = getsign(st0_ptr);
34
35 if (tagb == TAG_Special)
36 tagb = FPU_Special(b);
37 if (st0_tag == TAG_Special)
38 st0_tag = FPU_Special(st0_ptr);
39
40 if (((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
41 || ((tagb != TAG_Valid) && (tagb != TW_Denormal))) {
42 if (st0_tag == TAG_Zero) {
43 if (tagb == TAG_Zero)
44 return COMP_A_eq_B;
45 if (tagb == TAG_Valid)
46 return ((signb ==
47 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
48 if (tagb == TW_Denormal)
49 return ((signb ==
50 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
51 | COMP_Denormal;
52 } else if (tagb == TAG_Zero) {
53 if (st0_tag == TAG_Valid)
54 return ((st0_sign ==
55 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
56 if (st0_tag == TW_Denormal)
57 return ((st0_sign ==
58 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
59 | COMP_Denormal;
60 }
61
62 if (st0_tag == TW_Infinity) {
63 if ((tagb == TAG_Valid) || (tagb == TAG_Zero))
64 return ((st0_sign ==
65 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
66 else if (tagb == TW_Denormal)
67 return ((st0_sign ==
68 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
69 | COMP_Denormal;
70 else if (tagb == TW_Infinity) {
71 /* The 80486 book says that infinities can be equal! */
72 return (st0_sign == signb) ? COMP_A_eq_B :
73 ((st0_sign ==
74 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
75 }
76 /* Fall through to the NaN code */
77 } else if (tagb == TW_Infinity) {
78 if ((st0_tag == TAG_Valid) || (st0_tag == TAG_Zero))
79 return ((signb ==
80 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
81 if (st0_tag == TW_Denormal)
82 return ((signb ==
83 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
84 | COMP_Denormal;
85 /* Fall through to the NaN code */
86 }
87
88 /* The only possibility now should be that one of the arguments
89 is a NaN */
90 if ((st0_tag == TW_NaN) || (tagb == TW_NaN)) {
91 int signalling = 0, unsupported = 0;
92 if (st0_tag == TW_NaN) {
93 signalling =
94 (st0_ptr->sigh & 0xc0000000) == 0x80000000;
95 unsupported = !((exponent(st0_ptr) == EXP_OVER)
96 && (st0_ptr->
97 sigh & 0x80000000));
98 }
99 if (tagb == TW_NaN) {
100 signalling |=
101 (b->sigh & 0xc0000000) == 0x80000000;
102 unsupported |= !((exponent(b) == EXP_OVER)
103 && (b->sigh & 0x80000000));
104 }
105 if (signalling || unsupported)
106 return COMP_No_Comp | COMP_SNaN | COMP_NaN;
107 else
108 /* Neither is a signaling NaN */
109 return COMP_No_Comp | COMP_NaN;
110 }
111
112 EXCEPTION(EX_Invalid);
113 }
114
115 if (st0_sign != signb) {
116 return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
117 | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
118 COMP_Denormal : 0);
119 }
120
121 if ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) {
122 FPU_to_exp16(st0_ptr, &x);
123 FPU_to_exp16(b, &y);
124 st0_ptr = &x;
125 b = &y;
126 exp0 = exponent16(st0_ptr);
127 expb = exponent16(b);
128 } else {
129 exp0 = exponent(st0_ptr);
130 expb = exponent(b);
131 }
132
133 #ifdef PARANOID
134 if (!(st0_ptr->sigh & 0x80000000))
135 EXCEPTION(EX_Invalid);
136 if (!(b->sigh & 0x80000000))
137 EXCEPTION(EX_Invalid);
138 #endif /* PARANOID */
139
140 diff = exp0 - expb;
141 if (diff == 0) {
142 diff = st0_ptr->sigh - b->sigh; /* Works only if ms bits are
143 identical */
144 if (diff == 0) {
145 diff = st0_ptr->sigl > b->sigl;
146 if (diff == 0)
147 diff = -(st0_ptr->sigl < b->sigl);
148 }
149 }
150
151 if (diff > 0) {
152 return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
153 | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
154 COMP_Denormal : 0);
155 }
156 if (diff < 0) {
157 return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
158 | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
159 COMP_Denormal : 0);
160 }
161
162 return COMP_A_eq_B
163 | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
164 COMP_Denormal : 0);
165
166 }
167
168 /* This function requires that st(0) is not empty */
169 int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
170 {
171 int f = 0, c;
172
173 c = compare(loaded_data, loaded_tag);
174
175 if (c & COMP_NaN) {
176 EXCEPTION(EX_Invalid);
177 f = SW_C3 | SW_C2 | SW_C0;
178 } else
179 switch (c & 7) {
180 case COMP_A_lt_B:
181 f = SW_C0;
182 break;
183 case COMP_A_eq_B:
184 f = SW_C3;
185 break;
186 case COMP_A_gt_B:
187 f = 0;
188 break;
189 case COMP_No_Comp:
190 f = SW_C3 | SW_C2 | SW_C0;
191 break;
192 #ifdef PARANOID
193 default:
194 EXCEPTION(EX_INTERNAL | 0x121);
195 f = SW_C3 | SW_C2 | SW_C0;
196 break;
197 #endif /* PARANOID */
198 }
199 setcc(f);
200 if (c & COMP_Denormal) {
201 return denormal_operand() < 0;
202 }
203 return 0;
204 }
205
206 static int compare_st_st(int nr)
207 {
208 int f = 0, c;
209 FPU_REG *st_ptr;
210
211 if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
212 setcc(SW_C3 | SW_C2 | SW_C0);
213 /* Stack fault */
214 EXCEPTION(EX_StackUnder);
215 return !(control_word & CW_Invalid);
216 }
217
218 st_ptr = &st(nr);
219 c = compare(st_ptr, FPU_gettagi(nr));
220 if (c & COMP_NaN) {
221 setcc(SW_C3 | SW_C2 | SW_C0);
222 EXCEPTION(EX_Invalid);
223 return !(control_word & CW_Invalid);
224 } else
225 switch (c & 7) {
226 case COMP_A_lt_B:
227 f = SW_C0;
228 break;
229 case COMP_A_eq_B:
230 f = SW_C3;
231 break;
232 case COMP_A_gt_B:
233 f = 0;
234 break;
235 case COMP_No_Comp:
236 f = SW_C3 | SW_C2 | SW_C0;
237 break;
238 #ifdef PARANOID
239 default:
240 EXCEPTION(EX_INTERNAL | 0x122);
241 f = SW_C3 | SW_C2 | SW_C0;
242 break;
243 #endif /* PARANOID */
244 }
245 setcc(f);
246 if (c & COMP_Denormal) {
247 return denormal_operand() < 0;
248 }
249 return 0;
250 }
251
252 static int compare_u_st_st(int nr)
253 {
254 int f = 0, c;
255 FPU_REG *st_ptr;
256
257 if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
258 setcc(SW_C3 | SW_C2 | SW_C0);
259 /* Stack fault */
260 EXCEPTION(EX_StackUnder);
261 return !(control_word & CW_Invalid);
262 }
263
264 st_ptr = &st(nr);
265 c = compare(st_ptr, FPU_gettagi(nr));
266 if (c & COMP_NaN) {
267 setcc(SW_C3 | SW_C2 | SW_C0);
268 if (c & COMP_SNaN) { /* This is the only difference between
269 un-ordered and ordinary comparisons */
270 EXCEPTION(EX_Invalid);
271 return !(control_word & CW_Invalid);
272 }
273 return 0;
274 } else
275 switch (c & 7) {
276 case COMP_A_lt_B:
277 f = SW_C0;
278 break;
279 case COMP_A_eq_B:
280 f = SW_C3;
281 break;
282 case COMP_A_gt_B:
283 f = 0;
284 break;
285 case COMP_No_Comp:
286 f = SW_C3 | SW_C2 | SW_C0;
287 break;
288 #ifdef PARANOID
289 default:
290 EXCEPTION(EX_INTERNAL | 0x123);
291 f = SW_C3 | SW_C2 | SW_C0;
292 break;
293 #endif /* PARANOID */
294 }
295 setcc(f);
296 if (c & COMP_Denormal) {
297 return denormal_operand() < 0;
298 }
299 return 0;
300 }
301
302 /*---------------------------------------------------------------------------*/
303
304 void fcom_st(void)
305 {
306 /* fcom st(i) */
307 compare_st_st(FPU_rm);
308 }
309
310 void fcompst(void)
311 {
312 /* fcomp st(i) */
313 if (!compare_st_st(FPU_rm))
314 FPU_pop();
315 }
316
317 void fcompp(void)
318 {
319 /* fcompp */
320 if (FPU_rm != 1) {
321 FPU_illegal();
322 return;
323 }
324 if (!compare_st_st(1))
325 poppop();
326 }
327
328 void fucom_(void)
329 {
330 /* fucom st(i) */
331 compare_u_st_st(FPU_rm);
332
333 }
334
335 void fucomp(void)
336 {
337 /* fucomp st(i) */
338 if (!compare_u_st_st(FPU_rm))
339 FPU_pop();
340 }
341
342 void fucompp(void)
343 {
344 /* fucompp */
345 if (FPU_rm == 1) {
346 if (!compare_u_st_st(1))
347 poppop();
348 } else
349 FPU_illegal();
350 }
351
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