File: /usr/src/linux/arch/i386/math-emu/fpu_etc.c
1 /*---------------------------------------------------------------------------+
2 | fpu_etc.c |
3 | |
4 | Implement a few FPU instructions. |
5 | |
6 | Copyright (C) 1992,1993,1994,1997 |
7 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
8 | Australia. E-mail billm@suburbia.net |
9 | |
10 | |
11 +---------------------------------------------------------------------------*/
12
13 #include "fpu_system.h"
14 #include "exception.h"
15 #include "fpu_emu.h"
16 #include "status_w.h"
17 #include "reg_constant.h"
18
19
20 static void fchs(FPU_REG *st0_ptr, u_char st0tag)
21 {
22 if ( st0tag ^ TAG_Empty )
23 {
24 signbyte(st0_ptr) ^= SIGN_NEG;
25 clear_C1();
26 }
27 else
28 FPU_stack_underflow();
29 }
30
31
32 static void fabs(FPU_REG *st0_ptr, u_char st0tag)
33 {
34 if ( st0tag ^ TAG_Empty )
35 {
36 setpositive(st0_ptr);
37 clear_C1();
38 }
39 else
40 FPU_stack_underflow();
41 }
42
43
44 static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
45 {
46 switch (st0tag)
47 {
48 case TAG_Zero:
49 setcc(SW_C3);
50 break;
51 case TAG_Valid:
52 if (getsign(st0_ptr) == SIGN_POS)
53 setcc(0);
54 else
55 setcc(SW_C0);
56 break;
57 case TAG_Special:
58 switch ( FPU_Special(st0_ptr) )
59 {
60 case TW_Denormal:
61 if (getsign(st0_ptr) == SIGN_POS)
62 setcc(0);
63 else
64 setcc(SW_C0);
65 if ( denormal_operand() < 0 )
66 {
67 #ifdef PECULIAR_486
68 /* This is weird! */
69 if (getsign(st0_ptr) == SIGN_POS)
70 setcc(SW_C3);
71 #endif /* PECULIAR_486 */
72 return;
73 }
74 break;
75 case TW_NaN:
76 setcc(SW_C0|SW_C2|SW_C3); /* Operand is not comparable */
77 EXCEPTION(EX_Invalid);
78 break;
79 case TW_Infinity:
80 if (getsign(st0_ptr) == SIGN_POS)
81 setcc(0);
82 else
83 setcc(SW_C0);
84 break;
85 default:
86 setcc(SW_C0|SW_C2|SW_C3); /* Operand is not comparable */
87 EXCEPTION(EX_INTERNAL|0x14);
88 break;
89 }
90 break;
91 case TAG_Empty:
92 setcc(SW_C0|SW_C2|SW_C3);
93 EXCEPTION(EX_StackUnder);
94 break;
95 }
96 }
97
98
99 static void fxam(FPU_REG *st0_ptr, u_char st0tag)
100 {
101 int c = 0;
102 switch (st0tag)
103 {
104 case TAG_Empty:
105 c = SW_C3|SW_C0;
106 break;
107 case TAG_Zero:
108 c = SW_C3;
109 break;
110 case TAG_Valid:
111 c = SW_C2;
112 break;
113 case TAG_Special:
114 switch ( FPU_Special(st0_ptr) )
115 {
116 case TW_Denormal:
117 c = SW_C2|SW_C3; /* Denormal */
118 break;
119 case TW_NaN:
120 /* We also use NaN for unsupported types. */
121 if ( (st0_ptr->sigh & 0x80000000) && (exponent(st0_ptr) == EXP_OVER) )
122 c = SW_C0;
123 break;
124 case TW_Infinity:
125 c = SW_C2|SW_C0;
126 break;
127 }
128 }
129 if ( getsign(st0_ptr) == SIGN_NEG )
130 c |= SW_C1;
131 setcc(c);
132 }
133
134
135 static FUNC_ST0 const fp_etc_table[] = {
136 fchs, fabs, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal,
137 ftst_, fxam, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal
138 };
139
140 void FPU_etc()
141 {
142 (fp_etc_table[FPU_rm])(&st(0), FPU_gettag0());
143 }
144