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/*
25  Multiply two registers to give a register result.
26  The sources are st(deststnr) and (b,tagb,signb).
27  The destination is st(deststnr).
28  */
29/* This routine must be called with non-empty source registers */
30int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
31{
32  FPU_REG *a = &st(deststnr);
33  FPU_REG *dest = a;
34  u_char taga = FPU_gettagi(deststnr);
35  u_char saved_sign = getsign(dest);
36  u_char sign = (getsign(a) ^ getsign(b));
37  int tag;
38
39
40  if ( !(taga | tagb) )
41    {
42      /* Both regs Valid, this should be the most common case. */
43
44      tag = FPU_u_mul(a, b, dest, control_w, sign, exponent(a) + exponent(b));
45      if ( tag < 0 )
46	{
47	  setsign(dest, saved_sign);
48	  return tag;
49	}
50      FPU_settagi(deststnr, tag);
51      return tag;
52    }
53
54  if ( taga == TAG_Special )
55    taga = FPU_Special(a);
56  if ( tagb == TAG_Special )
57    tagb = FPU_Special(b);
58
59  if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
60	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
61	    || ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
62    {
63      FPU_REG x, y;
64      if ( denormal_operand() < 0 )
65	return FPU_Exception;
66
67      FPU_to_exp16(a, &x);
68      FPU_to_exp16(b, &y);
69      tag = FPU_u_mul(&x, &y, dest, control_w, sign,
70		      exponent16(&x) + exponent16(&y));
71      if ( tag < 0 )
72	{
73	  setsign(dest, saved_sign);
74	  return tag;
75	}
76      FPU_settagi(deststnr, tag);
77      return tag;
78    }
79  else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) )
80    {
81      if ( ((tagb == TW_Denormal) || (taga == TW_Denormal))
82	   && (denormal_operand() < 0) )
83	return FPU_Exception;
84
85      /* Must have either both arguments == zero, or
86	 one valid and the other zero.
87	 The result is therefore zero. */
88      FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
89      /* The 80486 book says that the answer is +0, but a real
90	 80486 behaves this way.
91	 IEEE-754 apparently says it should be this way. */
92      setsign(dest, sign);
93      return TAG_Zero;
94    }
95      /* Must have infinities, NaNs, etc */
96  else if ( (taga == TW_NaN) || (tagb == TW_NaN) )
97    {
98      return real_2op_NaN(b, tagb, deststnr, &st(0));
99    }
100  else if ( ((taga == TW_Infinity) && (tagb == TAG_Zero))
101	    || ((tagb == TW_Infinity) && (taga == TAG_Zero)) )
102    {
103      return arith_invalid(deststnr);  /* Zero*Infinity is invalid */
104    }
105  else if ( ((taga == TW_Denormal) || (tagb == TW_Denormal))
106	    && (denormal_operand() < 0) )
107    {
108      return FPU_Exception;
109    }
110  else if (taga == TW_Infinity)
111    {
112      FPU_copy_to_regi(a, TAG_Special, deststnr);
113      setsign(dest, sign);
114      return TAG_Special;
115    }
116  else if (tagb == TW_Infinity)
117    {
118      FPU_copy_to_regi(b, TAG_Special, deststnr);
119      setsign(dest, sign);
120      return TAG_Special;
121    }
122
123#ifdef PARANOID
124  else
125    {
126      EXCEPTION(EX_INTERNAL|0x102);
127      return FPU_Exception;
128    }
129#endif /* PARANOID */
130
131	return 0;
132}
133