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  */
27int 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}
208