arch/i386/math-emu/reg_compare.c

   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
  24 static int compare(FPU_REG const *b, int tagb)
  25 {
  26   int diff, exp0, expb;
  27   u_char                st0_tag;
  28   FPU_REG       *st0_ptr;
  29   FPU_REG       x, y;
  30   u_char                st0_sign, signb = getsign(b);
  31
  32   st0_ptr = &st(0);
  33   st0_tag = FPU_gettag0();
  34   st0_sign = getsign(st0_ptr);
  35
  36   if ( tagb == TAG_Special )
  37     tagb = FPU_Special(b);
  38   if ( st0_tag == TAG_Special )
  39     st0_tag = FPU_Special(st0_ptr);
  40
  41   if ( ((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
  42        || ((tagb != TAG_Valid) && (tagb != TW_Denormal)) )
  43     {
  44       if ( st0_tag == TAG_Zero )
  45         {
  46           if ( tagb == TAG_Zero ) return COMP_A_eq_B;
  47           if ( tagb == TAG_Valid )
  48             return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
  49           if ( tagb == TW_Denormal )
  50             return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
  51             | COMP_Denormal;
  52         }
  53       else if ( tagb == TAG_Zero )
  54         {
  55           if ( st0_tag == TAG_Valid )
  56             return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  57           if ( st0_tag == TW_Denormal )
  58             return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  59             | COMP_Denormal;
  60         }
  61
  62       if ( st0_tag == TW_Infinity )
  63         {
  64           if ( (tagb == TAG_Valid) || (tagb == TAG_Zero) )
  65             return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  66           else if ( tagb == TW_Denormal )
  67             return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  68               | COMP_Denormal;
  69           else if ( tagb == TW_Infinity )
  70             {
  71               /* The 80486 book says that infinities can be equal! */
  72               return (st0_sign == signb) ? COMP_A_eq_B :
  73                 ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  74             }
  75           /* Fall through to the NaN code */
  76         }
  77       else if ( tagb == TW_Infinity )
  78         {
  79           if ( (st0_tag == TAG_Valid) || (st0_tag == TAG_Zero) )
  80             return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
  81           if ( st0_tag == TW_Denormal )
  82             return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
  83                 | COMP_Denormal;
  84           /* Fall through to the NaN code */
  85         }
  86
  87       /* The only possibility now should be that one of the arguments
  88          is a NaN */
  89       if ( (st0_tag == TW_NaN) || (tagb == TW_NaN) )
  90         {
  91           int signalling = 0, unsupported = 0;
  92           if ( st0_tag == TW_NaN )
  93             {
  94               signalling = (st0_ptr->sigh & 0xc0000000) == 0x80000000;
  95               unsupported = !((exponent(st0_ptr) == EXP_OVER)
  96                               && (st0_ptr->sigh & 0x80000000));
  97             }
  98           if ( tagb == TW_NaN )
  99             {
 100               signalling |= (b->sigh & 0xc0000000) == 0x80000000;
 101               unsupported |= !((exponent(b) == EXP_OVER)
 102                                && (b->sigh & 0x80000000));
 103             }
 104           if ( signalling || unsupported )
 105             return COMP_No_Comp | COMP_SNaN | COMP_NaN;
 106           else
 107             /* Neither is a signaling NaN */
 108             return COMP_No_Comp | COMP_NaN;
 109         }
 110
 111       EXCEPTION(EX_Invalid);
 112     }
 113
 114   if (st0_sign != signb)
 115     {
 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     {
 123       FPU_to_exp16(st0_ptr, &x);
 124       FPU_to_exp16(b, &y);
 125       st0_ptr = &x;
 126       b = &y;
 127       exp0 = exponent16(st0_ptr);
 128       expb = exponent16(b);
 129     }
 130   else
 131     {
 132       exp0 = exponent(st0_ptr);
 133       expb = exponent(b);
 134     }
 135
 136 #ifdef PARANOID
 137   if (!(st0_ptr->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
 138   if (!(b->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
 139 #endif PARANOID
 140
 141   diff = exp0 - expb;
 142   if ( diff == 0 )
 143     {
 144       diff = st0_ptr->sigh - b->sigh;  /* Works only if ms bits are
 145                                               identical */
 146       if ( diff == 0 )
 147         {
 148         diff = st0_ptr->sigl > b->sigl;
 149         if ( diff == 0 )
 150           diff = -(st0_ptr->sigl < b->sigl);
 151         }
 152     }
 153
 154   if ( diff > 0 )
 155     {
 156       return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
 157         | ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
 158             COMP_Denormal : 0);
 159     }
 160   if ( diff < 0 )
 161     {
 162       return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
 163         | ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
 164             COMP_Denormal : 0);
 165     }
 166
 167   return COMP_A_eq_B
 168     | ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
 169         COMP_Denormal : 0);
 170
 171 }
 172
 173
 174 /* This function requires that st(0) is not empty */
 175 int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
 176 {
 177   int f, c;
 178
 179   c = compare(loaded_data, loaded_tag);
 180
 181   if (c & COMP_NaN)
 182     {
 183       EXCEPTION(EX_Invalid);
 184       f = SW_C3 | SW_C2 | SW_C0;
 185     }
 186   else
 187     switch (c & 7)
 188       {
 189       case COMP_A_lt_B:
 190         f = SW_C0;
 191         break;
 192       case COMP_A_eq_B:
 193         f = SW_C3;
 194         break;
 195       case COMP_A_gt_B:
 196         f = 0;
 197         break;
 198       case COMP_No_Comp:
 199         f = SW_C3 | SW_C2 | SW_C0;
 200         break;
 201 #ifdef PARANOID
 202       default:
 203         EXCEPTION(EX_INTERNAL|0x121);
 204         f = SW_C3 | SW_C2 | SW_C0;
 205         break;
 206 #endif PARANOID
 207       }
 208   setcc(f);
 209   if (c & COMP_Denormal)
 210     {
 211       return denormal_operand() < 0;
 212     }
 213   return 0;
 214 }
 215
 216
 217 static int compare_st_st(int nr)
 218 {
 219   int f, c;
 220   FPU_REG *st_ptr;
 221
 222   if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
 223     {
 224       setcc(SW_C3 | SW_C2 | SW_C0);
 225       /* Stack fault */
 226       EXCEPTION(EX_StackUnder);
 227       return !(control_word & CW_Invalid);
 228     }
 229
 230   st_ptr = &st(nr);
 231   c = compare(st_ptr, FPU_gettagi(nr));
 232   if (c & COMP_NaN)
 233     {
 234       setcc(SW_C3 | SW_C2 | SW_C0);
 235       EXCEPTION(EX_Invalid);
 236       return !(control_word & CW_Invalid);
 237     }
 238   else
 239     switch (c & 7)
 240       {
 241       case COMP_A_lt_B:
 242         f = SW_C0;
 243         break;
 244       case COMP_A_eq_B:
 245         f = SW_C3;
 246         break;
 247       case COMP_A_gt_B:
 248         f = 0;
 249         break;
 250       case COMP_No_Comp:
 251         f = SW_C3 | SW_C2 | SW_C0;
 252         break;
 253 #ifdef PARANOID
 254       default:
 255         EXCEPTION(EX_INTERNAL|0x122);
 256         f = SW_C3 | SW_C2 | SW_C0;
 257         break;
 258 #endif PARANOID
 259       }
 260   setcc(f);
 261   if (c & COMP_Denormal)
 262     {
 263       return denormal_operand() < 0;
 264     }
 265   return 0;
 266 }
 267
 268
 269 static int compare_u_st_st(int nr)
 270 {
 271   int f, c;
 272   FPU_REG *st_ptr;
 273
 274   if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
 275     {
 276       setcc(SW_C3 | SW_C2 | SW_C0);
 277       /* Stack fault */
 278       EXCEPTION(EX_StackUnder);
 279       return !(control_word & CW_Invalid);
 280     }
 281
 282   st_ptr = &st(nr);
 283   c = compare(st_ptr, FPU_gettagi(nr));
 284   if (c & COMP_NaN)
 285     {
 286       setcc(SW_C3 | SW_C2 | SW_C0);
 287       if (c & COMP_SNaN)       /* This is the only difference between
 288                                   un-ordered and ordinary comparisons */
 289         {
 290           EXCEPTION(EX_Invalid);
 291           return !(control_word & CW_Invalid);
 292         }
 293       return 0;
 294     }
 295   else
 296     switch (c & 7)
 297       {
 298       case COMP_A_lt_B:
 299         f = SW_C0;
 300         break;
 301       case COMP_A_eq_B:
 302         f = SW_C3;
 303         break;
 304       case COMP_A_gt_B:
 305         f = 0;
 306         break;
 307       case COMP_No_Comp:
 308         f = SW_C3 | SW_C2 | SW_C0;
 309         break;
 310 #ifdef PARANOID
 311       default:
 312         EXCEPTION(EX_INTERNAL|0x123);
 313         f = SW_C3 | SW_C2 | SW_C0;
 314         break;
 315 #endif PARANOID
 316       }
 317   setcc(f);
 318   if (c & COMP_Denormal)
 319     {
 320       return denormal_operand() < 0;
 321     }
 322   return 0;
 323 }
 324
 325 /*---------------------------------------------------------------------------*/
 326
 327 void fcom_st()
 328 {
 329   /* fcom st(i) */
 330   compare_st_st(FPU_rm);
 331 }
 332
 333
 334 void fcompst()
 335 {
 336   /* fcomp st(i) */
 337   if ( !compare_st_st(FPU_rm) )
 338     FPU_pop();
 339 }
 340
 341
 342 void fcompp()
 343 {
 344   /* fcompp */
 345   if (FPU_rm != 1)
 346     {
 347       FPU_illegal();
 348       return;
 349     }
 350   if ( !compare_st_st(1) )
 351       poppop();
 352 }
 353
 354
 355 void fucom_()
 356 {
 357   /* fucom st(i) */
 358   compare_u_st_st(FPU_rm);
 359
 360 }
 361
 362
 363 void fucomp()
 364 {
 365   /* fucomp st(i) */
 366   if ( !compare_u_st_st(FPU_rm) )
 367     FPU_pop();
 368 }
 369
 370
 371 void fucompp()
 372 {
 373   /* fucompp */
 374   if (FPU_rm == 1)
 375     {
 376       if ( !compare_u_st_st(1) )
 377         poppop();
 378     }
 379   else
 380     FPU_illegal();
 381 }