arch/x86/math-emu/reg_mul.c

   1 /*---------------------------------------------------------------------------+
   2  |  reg_mul.c                                                                |
   3  |                                                                           |
   4  | Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993,1997                                              |
   7  |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
   8  |                  E-mail   billm@suburbia.net                              |
   9  |                                                                           |
  10  | Returns the tag of the result if no exceptions or errors occurred.        |
  11  |                                                                           |
  12  +---------------------------------------------------------------------------*/
  13
  14 /*---------------------------------------------------------------------------+
  15  | The destination may be any FPU_REG, including one of the source FPU_REGs. |
  16  +---------------------------------------------------------------------------*/
  17
  18 #include "fpu_emu.h"
  19 #include "exception.h"
  20 #include "reg_constant.h"
  21 #include "fpu_system.h"
  22
  23 /*
  24   Multiply two registers to give a register result.
  25   The sources are st(deststnr) and (b,tagb,signb).
  26   The destination is st(deststnr).
  27   */
  28 /* This routine must be called with non-empty source registers */
  29 int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
  30 {
  31         FPU_REG *a = &st(deststnr);
  32         FPU_REG *dest = a;
  33         u_char taga = FPU_gettagi(deststnr);
  34         u_char saved_sign = getsign(dest);
  35         u_char sign = (getsign(a) ^ getsign(b));
  36         int tag;
  37
  38         if (!(taga | tagb)) {
  39                 /* Both regs Valid, this should be the most common case. */
  40
  41                 tag =
  42                     FPU_u_mul(a, b, dest, control_w, sign,
  43                               exponent(a) + exponent(b));
  44                 if (tag < 0) {
  45                         setsign(dest, saved_sign);
  46                         return tag;
  47                 }
  48                 FPU_settagi(deststnr, tag);
  49                 return tag;
  50         }
  51
  52         if (taga == TAG_Special)
  53                 taga = FPU_Special(a);
  54         if (tagb == TAG_Special)
  55                 tagb = FPU_Special(b);
  56
  57         if (((taga == TAG_Valid) && (tagb == TW_Denormal))
  58             || ((taga == TW_Denormal) && (tagb == TAG_Valid))
  59             || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
  60                 FPU_REG x, y;
  61                 if (denormal_operand() < 0)
  62                         return FPU_Exception;
  63
  64                 FPU_to_exp16(a, &x);
  65                 FPU_to_exp16(b, &y);
  66                 tag = FPU_u_mul(&x, &y, dest, control_w, sign,
  67                                 exponent16(&x) + exponent16(&y));
  68                 if (tag < 0) {
  69                         setsign(dest, saved_sign);
  70                         return tag;
  71                 }
  72                 FPU_settagi(deststnr, tag);
  73                 return tag;
  74         } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
  75                 if (((tagb == TW_Denormal) || (taga == TW_Denormal))
  76                     && (denormal_operand() < 0))
  77                         return FPU_Exception;
  78
  79                 /* Must have either both arguments == zero, or
  80                    one valid and the other zero.
  81                    The result is therefore zero. */
  82                 FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
  83                 /* The 80486 book says that the answer is +0, but a real
  84                    80486 behaves this way.
  85                    IEEE-754 apparently says it should be this way. */
  86                 setsign(dest, sign);
  87                 return TAG_Zero;
  88         }
  89         /* Must have infinities, NaNs, etc */
  90         else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
  91                 return real_2op_NaN(b, tagb, deststnr, &st(0));
  92         } else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
  93                    || ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
  94                 return arith_invalid(deststnr); /* Zero*Infinity is invalid */
  95         } else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
  96                    && (denormal_operand() < 0)) {
  97                 return FPU_Exception;
  98         } else if (taga == TW_Infinity) {
  99                 FPU_copy_to_regi(a, TAG_Special, deststnr);
 100                 setsign(dest, sign);
 101                 return TAG_Special;
 102         } else if (tagb == TW_Infinity) {
 103                 FPU_copy_to_regi(b, TAG_Special, deststnr);
 104                 setsign(dest, sign);
 105                 return TAG_Special;
 106         }
 107 #ifdef PARANOID
 108         else {
 109                 EXCEPTION(EX_INTERNAL | 0x102);
 110                 return FPU_Exception;
 111         }
 112 #endif /* PARANOID */
 113
 114         return 0;
 115 }