aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86/math-emu/reg_compare.c
blob: f37c5b5a35ad54301c36a5dd21f1fe1c394a7cf2 (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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
/*---------------------------------------------------------------------------+
 |  reg_compare.c                                                            |
 |                                                                           |
 | Compare two floating point registers                                      |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1997                                         |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   billm@suburbia.net                              |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | compare() is the core FPU_REG comparison function                         |
 +---------------------------------------------------------------------------*/

#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
#include "status_w.h"


static int compare(FPU_REG const *b, int tagb)
{
  int diff, exp0, expb;
  u_char	  	st0_tag;
  FPU_REG  	*st0_ptr;
  FPU_REG	x, y;
  u_char		st0_sign, signb = getsign(b);

  st0_ptr = &st(0);
  st0_tag = FPU_gettag0();
  st0_sign = getsign(st0_ptr);

  if ( tagb == TAG_Special )
    tagb = FPU_Special(b);
  if ( st0_tag == TAG_Special )
    st0_tag = FPU_Special(st0_ptr);

  if ( ((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
       || ((tagb != TAG_Valid) && (tagb != TW_Denormal)) )
    {
      if ( st0_tag == TAG_Zero )
	{
	  if ( tagb == TAG_Zero ) return COMP_A_eq_B;
	  if ( tagb == TAG_Valid )
	    return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
	  if ( tagb == TW_Denormal )
	    return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
	    | COMP_Denormal;
	}
      else if ( tagb == TAG_Zero )
	{
	  if ( st0_tag == TAG_Valid )
	    return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
	  if ( st0_tag == TW_Denormal )
	    return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
	    | COMP_Denormal;
	}

      if ( st0_tag == TW_Infinity )
	{
	  if ( (tagb == TAG_Valid) || (tagb == TAG_Zero) )
	    return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
	  else if ( tagb == TW_Denormal )
	    return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
	      | COMP_Denormal;
	  else if ( tagb == TW_Infinity )
	    {
	      /* The 80486 book says that infinities can be equal! */
	      return (st0_sign == signb) ? COMP_A_eq_B :
		((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
	    }
	  /* Fall through to the NaN code */
	}
      else if ( tagb == TW_Infinity )
	{
	  if ( (st0_tag == TAG_Valid) || (st0_tag == TAG_Zero) )
	    return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
	  if ( st0_tag == TW_Denormal )
	    return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
		| COMP_Denormal;
	  /* Fall through to the NaN code */
	}

      /* The only possibility now should be that one of the arguments
	 is a NaN */
      if ( (st0_tag == TW_NaN) || (tagb == TW_NaN) )
	{
	  int signalling = 0, unsupported = 0;
	  if ( st0_tag == TW_NaN )
	    {
	      signalling = (st0_ptr->sigh & 0xc0000000) == 0x80000000;
	      unsupported = !((exponent(st0_ptr) == EXP_OVER)
			      && (st0_ptr->sigh & 0x80000000));
	    }
	  if ( tagb == TW_NaN )
	    {
	      signalling |= (b->sigh & 0xc0000000) == 0x80000000;
	      unsupported |= !((exponent(b) == EXP_OVER)
			       && (b->sigh & 0x80000000));
	    }
	  if ( signalling || unsupported )
	    return COMP_No_Comp | COMP_SNaN | COMP_NaN;
	  else
	    /* Neither is a signaling NaN */
	    return COMP_No_Comp | COMP_NaN;
	}
      
      EXCEPTION(EX_Invalid);
    }
  
  if (st0_sign != signb)
    {
      return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
	| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
	    COMP_Denormal : 0);
    }

  if ( (st0_tag == TW_Denormal) || (tagb == TW_Denormal) )
    {
      FPU_to_exp16(st0_ptr, &x);
      FPU_to_exp16(b, &y);
      st0_ptr = &x;
      b = &y;
      exp0 = exponent16(st0_ptr);
      expb = exponent16(b);
    }
  else
    {
      exp0 = exponent(st0_ptr);
      expb = exponent(b);
    }

#ifdef PARANOID
  if (!(st0_ptr->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
  if (!(b->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
#endif /* PARANOID */

  diff = exp0 - expb;
  if ( diff == 0 )
    {
      diff = st0_ptr->sigh - b->sigh;  /* Works only if ms bits are
					      identical */
      if ( diff == 0 )
	{
	diff = st0_ptr->sigl > b->sigl;
	if ( diff == 0 )
	  diff = -(st0_ptr->sigl < b->sigl);
	}
    }

  if ( diff > 0 )
    {
      return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
	| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
	    COMP_Denormal : 0);
    }
  if ( diff < 0 )
    {
      return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
	| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
	    COMP_Denormal : 0);
    }

  return COMP_A_eq_B
    | ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
	COMP_Denormal : 0);

}


/* This function requires that st(0) is not empty */
int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
{
  int f = 0, c;

  c = compare(loaded_data, loaded_tag);

  if (c & COMP_NaN)
    {
      EXCEPTION(EX_Invalid);
      f = SW_C3 | SW_C2 | SW_C0;
    }
  else
    switch (c & 7)
      {
      case COMP_A_lt_B:
	f = SW_C0;
	break;
      case COMP_A_eq_B:
	f = SW_C3;
	break;
      case COMP_A_gt_B:
	f = 0;
	break;
      case COMP_No_Comp:
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#ifdef PARANOID
      default:
	EXCEPTION(EX_INTERNAL|0x121);
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#endif /* PARANOID */
      }
  setcc(f);
  if (c & COMP_Denormal)
    {
      return denormal_operand() < 0;
    }
  return 0;
}


static int compare_st_st(int nr)
{
  int f = 0, c;
  FPU_REG *st_ptr;

  if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
    {
      setcc(SW_C3 | SW_C2 | SW_C0);
      /* Stack fault */
      EXCEPTION(EX_StackUnder);
      return !(control_word & CW_Invalid);
    }

  st_ptr = &st(nr);
  c = compare(st_ptr, FPU_gettagi(nr));
  if (c & COMP_NaN)
    {
      setcc(SW_C3 | SW_C2 | SW_C0);
      EXCEPTION(EX_Invalid);
      return !(control_word & CW_Invalid);
    }
  else
    switch (c & 7)
      {
      case COMP_A_lt_B:
	f = SW_C0;
	break;
      case COMP_A_eq_B:
	f = SW_C3;
	break;
      case COMP_A_gt_B:
	f = 0;
	break;
      case COMP_No_Comp:
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#ifdef PARANOID
      default:
	EXCEPTION(EX_INTERNAL|0x122);
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#endif /* PARANOID */
      }
  setcc(f);
  if (c & COMP_Denormal)
    {
      return denormal_operand() < 0;
    }
  return 0;
}


static int compare_u_st_st(int nr)
{
  int f = 0, c;
  FPU_REG *st_ptr;

  if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
    {
      setcc(SW_C3 | SW_C2 | SW_C0);
      /* Stack fault */
      EXCEPTION(EX_StackUnder);
      return !(control_word & CW_Invalid);
    }

  st_ptr = &st(nr);
  c = compare(st_ptr, FPU_gettagi(nr));
  if (c & COMP_NaN)
    {
      setcc(SW_C3 | SW_C2 | SW_C0);
      if (c & COMP_SNaN)       /* This is the only difference between
				  un-ordered and ordinary comparisons */
	{
	  EXCEPTION(EX_Invalid);
	  return !(control_word & CW_Invalid);
	}
      return 0;
    }
  else
    switch (c & 7)
      {
      case COMP_A_lt_B:
	f = SW_C0;
	break;
      case COMP_A_eq_B:
	f = SW_C3;
	break;
      case COMP_A_gt_B:
	f = 0;
	break;
      case COMP_No_Comp:
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#ifdef PARANOID
      default:
	EXCEPTION(EX_INTERNAL|0x123);
	f = SW_C3 | SW_C2 | SW_C0;
	break;
#endif /* PARANOID */ 
      }
  setcc(f);
  if (c & COMP_Denormal)
    {
      return denormal_operand() < 0;
    }
  return 0;
}

/*---------------------------------------------------------------------------*/

void fcom_st(void)
{
  /* fcom st(i) */
  compare_st_st(FPU_rm);
}


void fcompst(void)
{
  /* fcomp st(i) */
  if ( !compare_st_st(FPU_rm) )
    FPU_pop();
}


void fcompp(void)
{
  /* fcompp */
  if (FPU_rm != 1)
    {
      FPU_illegal();
      return;
    }
  if ( !compare_st_st(1) )
      poppop();
}


void fucom_(void)
{
  /* fucom st(i) */
  compare_u_st_st(FPU_rm);

}


void fucomp(void)
{
  /* fucomp st(i) */
  if ( !compare_u_st_st(FPU_rm) )
    FPU_pop();
}


void fucompp(void)
{
  /* fucompp */
  if (FPU_rm == 1)
    {
      if ( !compare_u_st_st(1) )
	poppop();
    }
  else
    FPU_illegal();
}