summaryrefslogtreecommitdiffstats
path: root/arch/x86/math-emu/reg_mul.c
blob: 40f50b61bc674dc3d0028ea19c4694c48e1bc634 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
/*---------------------------------------------------------------------------+
 |  reg_mul.c                                                                |
 |                                                                           |
 | Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
 |                                                                           |
 | Copyright (C) 1992,1993,1997                                              |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   billm@suburbia.net                              |
 |                                                                           |
 | Returns the tag of the result if no exceptions or errors occurred.        |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | The destination may be any FPU_REG, including one of the source FPU_REGs. |
 +---------------------------------------------------------------------------*/

#include "fpu_emu.h"
#include "exception.h"
#include "reg_constant.h"
#include "fpu_system.h"


/*
  Multiply two registers to give a register result.
  The sources are st(deststnr) and (b,tagb,signb).
  The destination is st(deststnr).
  */
/* This routine must be called with non-empty source registers */
int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
{
  FPU_REG *a = &st(deststnr);
  FPU_REG *dest = a;
  u_char taga = FPU_gettagi(deststnr);
  u_char saved_sign = getsign(dest);
  u_char sign = (getsign(a) ^ getsign(b));
  int tag;


  if ( !(taga | tagb) )
    {
      /* Both regs Valid, this should be the most common case. */

      tag = FPU_u_mul(a, b, dest, control_w, sign, exponent(a) + exponent(b));
      if ( tag < 0 )
	{
	  setsign(dest, saved_sign);
	  return tag;
	}
      FPU_settagi(deststnr, tag);
      return tag;
    }

  if ( taga == TAG_Special )
    taga = FPU_Special(a);
  if ( tagb == TAG_Special )
    tagb = FPU_Special(b);

  if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
	    || ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
    {
      FPU_REG x, y;
      if ( denormal_operand() < 0 )
	return FPU_Exception;

      FPU_to_exp16(a, &x);
      FPU_to_exp16(b, &y);
      tag = FPU_u_mul(&x, &y, dest, control_w, sign,
		      exponent16(&x) + exponent16(&y));
      if ( tag < 0 )
	{
	  setsign(dest, saved_sign);
	  return tag;
	}
      FPU_settagi(deststnr, tag);
      return tag;
    }
  else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) )
    {
      if ( ((tagb == TW_Denormal) || (taga == TW_Denormal))
	   && (denormal_operand() < 0) )
	return FPU_Exception;

      /* Must have either both arguments == zero, or
	 one valid and the other zero.
	 The result is therefore zero. */
      FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
      /* The 80486 book says that the answer is +0, but a real
	 80486 behaves this way.
	 IEEE-754 apparently says it should be this way. */
      setsign(dest, sign);
      return TAG_Zero;
    }
      /* Must have infinities, NaNs, etc */
  else if ( (taga == TW_NaN) || (tagb == TW_NaN) )
    {
      return real_2op_NaN(b, tagb, deststnr, &st(0));
    }
  else if ( ((taga == TW_Infinity) && (tagb == TAG_Zero))
	    || ((tagb == TW_Infinity) && (taga == TAG_Zero)) )
    {
      return arith_invalid(deststnr);  /* Zero*Infinity is invalid */
    }
  else if ( ((taga == TW_Denormal) || (tagb == TW_Denormal))
	    && (denormal_operand() < 0) )
    {
      return FPU_Exception;
    }
  else if (taga == TW_Infinity)
    {
      FPU_copy_to_regi(a, TAG_Special, deststnr);
      setsign(dest, sign);
      return TAG_Special;
    }
  else if (tagb == TW_Infinity)
    {
      FPU_copy_to_regi(b, TAG_Special, deststnr);
      setsign(dest, sign);
      return TAG_Special;
    }

#ifdef PARANOID
  else
    {
      EXCEPTION(EX_INTERNAL|0x102);
      return FPU_Exception;
    }
#endif /* PARANOID */ 

	return 0;
}