LXR linux/arch/x86/math-emu/reg

   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 */
  29int 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}
 116