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