File: /usr/src/linux/arch/i386/math-emu/reg_constant.c
1 /*---------------------------------------------------------------------------+
2 | reg_constant.c |
3 | |
4 | All of the constant FPU_REGs |
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 "fpu_emu.h"
15 #include "status_w.h"
16 #include "reg_constant.h"
17 #include "control_w.h"
18
19
20 #define MAKE_REG(s,e,l,h) { l, h, \
21 ((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
22
23 FPU_REG const CONST_1 = MAKE_REG(POS, 0, 0x00000000, 0x80000000);
24 FPU_REG const CONST_2 = MAKE_REG(POS, 1, 0x00000000, 0x80000000);
25 FPU_REG const CONST_HALF = MAKE_REG(POS, -1, 0x00000000, 0x80000000);
26 FPU_REG const CONST_L2T = MAKE_REG(POS, 1, 0xcd1b8afe, 0xd49a784b);
27 FPU_REG const CONST_L2E = MAKE_REG(POS, 0, 0x5c17f0bc, 0xb8aa3b29);
28 FPU_REG const CONST_PI = MAKE_REG(POS, 1, 0x2168c235, 0xc90fdaa2);
29 FPU_REG const CONST_PI2 = MAKE_REG(POS, 0, 0x2168c235, 0xc90fdaa2);
30 FPU_REG const CONST_PI4 = MAKE_REG(POS, -1, 0x2168c235, 0xc90fdaa2);
31 FPU_REG const CONST_LG2 = MAKE_REG(POS, -2, 0xfbcff799, 0x9a209a84);
32 FPU_REG const CONST_LN2 = MAKE_REG(POS, -1, 0xd1cf79ac, 0xb17217f7);
33
34 /* Extra bits to take pi/2 to more than 128 bits precision. */
35 FPU_REG const CONST_PI2extra = MAKE_REG(NEG, -66,
36 0xfc8f8cbb, 0xece675d1);
37
38 /* Only the sign (and tag) is used in internal zeroes */
39 FPU_REG const CONST_Z = MAKE_REG(POS, EXP_UNDER, 0x0, 0x0);
40
41 /* Only the sign and significand (and tag) are used in internal NaNs */
42 /* The 80486 never generates one of these
43 FPU_REG const CONST_SNAN = MAKE_REG(POS, EXP_OVER, 0x00000001, 0x80000000);
44 */
45 /* This is the real indefinite QNaN */
46 FPU_REG const CONST_QNaN = MAKE_REG(NEG, EXP_OVER, 0x00000000, 0xC0000000);
47
48 /* Only the sign (and tag) is used in internal infinities */
49 FPU_REG const CONST_INF = MAKE_REG(POS, EXP_OVER, 0x00000000, 0x80000000);
50
51
52 static void fld_const(FPU_REG const *c, int adj, u_char tag)
53 {
54 FPU_REG *st_new_ptr;
55
56 if ( STACK_OVERFLOW )
57 {
58 FPU_stack_overflow();
59 return;
60 }
61 push();
62 reg_copy(c, st_new_ptr);
63 st_new_ptr->sigl += adj; /* For all our fldxxx constants, we don't need to
64 borrow or carry. */
65 FPU_settag0(tag);
66 clear_C1();
67 }
68
69 /* A fast way to find out whether x is one of RC_DOWN or RC_CHOP
70 (and not one of RC_RND or RC_UP).
71 */
72 #define DOWN_OR_CHOP(x) (x & RC_DOWN)
73
74 static void fld1(int rc)
75 {
76 fld_const(&CONST_1, 0, TAG_Valid);
77 }
78
79 static void fldl2t(int rc)
80 {
81 fld_const(&CONST_L2T, (rc == RC_UP) ? 1 : 0, TAG_Valid);
82 }
83
84 static void fldl2e(int rc)
85 {
86 fld_const(&CONST_L2E, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
87 }
88
89 static void fldpi(int rc)
90 {
91 fld_const(&CONST_PI, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
92 }
93
94 static void fldlg2(int rc)
95 {
96 fld_const(&CONST_LG2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
97 }
98
99 static void fldln2(int rc)
100 {
101 fld_const(&CONST_LN2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
102 }
103
104 static void fldz(int rc)
105 {
106 fld_const(&CONST_Z, 0, TAG_Zero);
107 }
108
109 typedef void (*FUNC_RC)(int);
110
111 static FUNC_RC constants_table[] = {
112 fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC)FPU_illegal
113 };
114
115 void fconst(void)
116 {
117 (constants_table[FPU_rm])(control_word & CW_RC);
118 }
119