arch/i386/math-emu/fpu_etc.c

   1 /*---------------------------------------------------------------------------+
   2  |  fpu_etc.c                                                                |
   3  |                                                                           |
   4  | Implement a few FPU instructions.                                         |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993,1994,1997                                         |
   7  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   8  |                       Australia.  E-mail   billm@suburbia.net             |
   9  |                                                                           |
  10  |                                                                           |
  11  +---------------------------------------------------------------------------*/
  12
  13 #include "fpu_system.h"
  14 #include "exception.h"
  15 #include "fpu_emu.h"
  16 #include "status_w.h"
  17 #include "reg_constant.h"
  18
  19
  20 static void fchs(FPU_REG *st0_ptr, u_char st0tag)
  21 {
  22   if ( st0tag ^ TAG_Empty )
  23     {
  24       signbyte(st0_ptr) ^= SIGN_NEG;
  25       clear_C1();
  26     }
  27   else
  28     FPU_stack_underflow();
  29 }
  30
  31
  32 static void fabs(FPU_REG *st0_ptr, u_char st0tag)
  33 {
  34   if ( st0tag ^ TAG_Empty )
  35     {
  36       setpositive(st0_ptr);
  37       clear_C1();
  38     }
  39   else
  40     FPU_stack_underflow();
  41 }
  42
  43
  44 static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
  45 {
  46   switch (st0tag)
  47     {
  48     case TAG_Zero:
  49       setcc(SW_C3);
  50       break;
  51     case TAG_Valid:
  52       if (getsign(st0_ptr) == SIGN_POS)
  53         setcc(0);
  54       else
  55         setcc(SW_C0);
  56       break;
  57     case TAG_Special:
  58       switch ( FPU_Special(st0_ptr) )
  59         {
  60         case TW_Denormal:
  61           if (getsign(st0_ptr) == SIGN_POS)
  62             setcc(0);
  63           else
  64             setcc(SW_C0);
  65           if ( denormal_operand() < 0 )
  66             {
  67 #ifdef PECULIAR_486
  68               /* This is weird! */
  69               if (getsign(st0_ptr) == SIGN_POS)
  70                 setcc(SW_C3);
  71 #endif /* PECULIAR_486 */
  72               return;
  73             }
  74           break;
  75         case TW_NaN:
  76           setcc(SW_C0|SW_C2|SW_C3);   /* Operand is not comparable */
  77           EXCEPTION(EX_Invalid);
  78           break;
  79         case TW_Infinity:
  80           if (getsign(st0_ptr) == SIGN_POS)
  81             setcc(0);
  82           else
  83             setcc(SW_C0);
  84           break;
  85         default:
  86           setcc(SW_C0|SW_C2|SW_C3);   /* Operand is not comparable */
  87           EXCEPTION(EX_INTERNAL|0x14);
  88           break;
  89         }
  90       break;
  91     case TAG_Empty:
  92       setcc(SW_C0|SW_C2|SW_C3);
  93       EXCEPTION(EX_StackUnder);
  94       break;
  95     }
  96 }
  97
  98
  99 static void fxam(FPU_REG *st0_ptr, u_char st0tag)
 100 {
 101   int c = 0;
 102   switch (st0tag)
 103     {
 104     case TAG_Empty:
 105       c = SW_C3|SW_C0;
 106       break;
 107     case TAG_Zero:
 108       c = SW_C3;
 109       break;
 110     case TAG_Valid:
 111       c = SW_C2;
 112       break;
 113     case TAG_Special:
 114       switch ( FPU_Special(st0_ptr) )
 115         {
 116         case TW_Denormal:
 117           c = SW_C2|SW_C3;  /* Denormal */
 118           break;
 119         case TW_NaN:
 120           /* We also use NaN for unsupported types. */
 121           if ( (st0_ptr->sigh & 0x80000000) && (exponent(st0_ptr) == EXP_OVER) )
 122             c = SW_C0;
 123           break;
 124         case TW_Infinity:
 125           c = SW_C2|SW_C0;
 126           break;
 127         }
 128     }
 129   if ( getsign(st0_ptr) == SIGN_NEG )
 130     c |= SW_C1;
 131   setcc(c);
 132 }
 133
 134
 135 static FUNC_ST0 const fp_etc_table[] = {
 136   fchs, fabs, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal,
 137   ftst_, fxam, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal
 138 };
 139
 140 void FPU_etc(void)
 141 {
 142   (fp_etc_table[FPU_rm])(&st(0), FPU_gettag0());
 143 }