arch/i386/math-emu/reg_divide.c

   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 {
  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     {
  42       b = &st(0);
  43       st0_ptr = b;
  44       tagb = FPU_gettag0();
  45       if ( flags & LOADED )
  46         {
  47           a = (FPU_REG *)rm;
  48           taga = flags & 0x0f;
  49         }
  50       else
  51         {
  52           a = &st(rm);
  53           st_ptr = a;
  54           taga = FPU_gettagi(rm);
  55         }
  56     }
  57   else
  58     {
  59       a = &st(0);
  60       st0_ptr = a;
  61       taga = FPU_gettag0();
  62       if ( flags & LOADED )
  63         {
  64           b = (FPU_REG *)rm;
  65           tagb = flags & 0x0f;
  66         }
  67       else
  68         {
  69           b = &st(rm);
  70           st_ptr = b;
  71           tagb = FPU_gettagi(rm);
  72         }
  73     }
  74
  75   signa = getsign(a);
  76   signb = getsign(b);
  77
  78   sign = signa ^ signb;
  79
  80   dest = &st(deststnr);
  81   saved_sign = getsign(dest);
  82
  83   if ( !(taga | tagb) )
  84     {
  85       /* Both regs Valid, this should be the most common case. */
  86       reg_copy(a, &x);
  87       reg_copy(b, &y);
  88       setpositive(&x);
  89       setpositive(&y);
  90       tag = FPU_u_div(&x, &y, dest, control_w, sign);
  91
  92       if ( tag < 0 )
  93         return tag;
  94
  95       FPU_settagi(deststnr, tag);
  96       return tag;
  97     }
  98
  99   if ( taga == TAG_Special )
 100     taga = FPU_Special(a);
 101   if ( tagb == TAG_Special )
 102     tagb = FPU_Special(b);
 103
 104   if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
 105             || ((taga == TW_Denormal) && (tagb == TAG_Valid))
 106             || ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
 107     {
 108       if ( denormal_operand() < 0 )
 109         return FPU_Exception;
 110
 111       FPU_to_exp16(a, &x);
 112       FPU_to_exp16(b, &y);
 113       tag = FPU_u_div(&x, &y, dest, control_w, sign);
 114       if ( tag < 0 )
 115         return tag;
 116
 117       FPU_settagi(deststnr, tag);
 118       return tag;
 119     }
 120   else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) )
 121     {
 122       if ( tagb != TAG_Zero )
 123         {
 124           /* Want to find Zero/Valid */
 125           if ( tagb == TW_Denormal )
 126             {
 127               if ( denormal_operand() < 0 )
 128                 return FPU_Exception;
 129             }
 130
 131           /* The result is zero. */
 132           FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
 133           setsign(dest, sign);
 134           return TAG_Zero;
 135         }
 136       /* We have an exception condition, either 0/0 or Valid/Zero. */
 137       if ( taga == TAG_Zero )
 138         {
 139           /* 0/0 */
 140           return arith_invalid(deststnr);
 141         }
 142       /* Valid/Zero */
 143       return FPU_divide_by_zero(deststnr, sign);
 144     }
 145   /* Must have infinities, NaNs, etc */
 146   else if ( (taga == TW_NaN) || (tagb == TW_NaN) )
 147     {
 148       if ( flags & LOADED )
 149         return real_2op_NaN((FPU_REG *)rm, flags & 0x0f, 0, st0_ptr);
 150
 151       if ( flags & DEST_RM )
 152         {
 153           int tag;
 154           tag = FPU_gettag0();
 155           if ( tag == TAG_Special )
 156             tag = FPU_Special(st0_ptr);
 157           return real_2op_NaN(st0_ptr, tag, rm, (flags & REV) ? st0_ptr : &st(rm));
 158         }
 159       else
 160         {
 161           int tag;
 162           tag = FPU_gettagi(rm);
 163           if ( tag == TAG_Special )
 164             tag = FPU_Special(&st(rm));
 165           return real_2op_NaN(&st(rm), tag, 0, (flags & REV) ? st0_ptr : &st(rm));
 166         }
 167     }
 168   else if (taga == TW_Infinity)
 169     {
 170       if (tagb == TW_Infinity)
 171         {
 172           /* infinity/infinity */
 173           return arith_invalid(deststnr);
 174         }
 175       else
 176         {
 177           /* tagb must be Valid or Zero */
 178           if ( (tagb == TW_Denormal) && (denormal_operand() < 0) )
 179             return FPU_Exception;
 180
 181           /* Infinity divided by Zero or Valid does
 182              not raise and exception, but returns Infinity */
 183           FPU_copy_to_regi(a, TAG_Special, deststnr);
 184           setsign(dest, sign);
 185           return taga;
 186         }
 187     }
 188   else if (tagb == TW_Infinity)
 189     {
 190       if ( (taga == TW_Denormal) && (denormal_operand() < 0) )
 191         return FPU_Exception;
 192
 193       /* The result is zero. */
 194       FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
 195       setsign(dest, sign);
 196       return TAG_Zero;
 197     }
 198 #ifdef PARANOID
 199   else
 200     {
 201       EXCEPTION(EX_INTERNAL|0x102);
 202       return FPU_Exception;
 203     }
 204 #endif /* PARANOID */
 205
 206         return 0;
 207 }