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1.1 root 1: /*---------------------------------------------------------------------------+
2: | poly_sin.c |
3: | |
4: | Computation of an approximation of the sin function by a polynomial |
5: | |
6: | Copyright (C) 1992 W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
7: | Australia. E-mail [email protected] |
8: | |
9: | |
10: +---------------------------------------------------------------------------*/
11:
12: #include "fpu_system.h"
13: #include "exception.h"
14: #include "reg_constant.h"
15: #include "fpu_emu.h"
16:
17:
18: #define HIPOWER 5
19: static unsigned short lterms[HIPOWER][4] =
20: {
21: { 0x846a, 0x42d1, 0xb544, 0x921f},
22: { 0xe110, 0x75aa, 0xbc67, 0x1466},
23: { 0x503d, 0xa43f, 0x83c1, 0x000a},
24: { 0x8f9d, 0x7a19, 0x00f4, 0x0000},
25: { 0xda03, 0x06aa, 0x0000, 0x0000},
26: };
27:
28: static unsigned short negterms[HIPOWER][4] =
29: {
30: { 0x95ed, 0x2df2, 0xe731, 0xa55d},
31: { 0xd159, 0xe62b, 0xd2cc, 0x0132},
32: { 0x6342, 0xe9fb, 0x3c60, 0x0000},
33: { 0x6256, 0xdf5a, 0x0002, 0x0000},
34: { 0xf279, 0x000b, 0x0000, 0x0000},
35: };
36:
37:
38: /*--- poly_sine() -----------------------------------------------------------+
39: | |
40: +---------------------------------------------------------------------------*/
41: void poly_sine(FPU_REG *arg, FPU_REG *result)
42: {
43: short exponent;
44: FPU_REG Xx, Xx2, Xx4, accum, negaccum;
45:
46:
47: exponent = arg->exp - EXP_BIAS;
48:
49: if ( arg->tag == TW_Zero )
50: {
51: /* Return 0.0 */
52: reg_move(&CONST_Z, result);
53: return;
54: }
55:
56: #ifdef PARANOID
57: if ( arg->sign != 0 ) /* Can't hack a number < 0.0 */
58: {
59: EXCEPTION(EX_Invalid);
60: reg_move(&CONST_QNaN, result);
61: return;
62: }
63:
64: if ( exponent >= 0 ) /* Can't hack a number > 1.0 */
65: {
66: if ( (exponent == 0) && (arg->sigl == 0) && (arg->sigh == 0x80000000) )
67: {
68: reg_move(&CONST_1, result);
69: return;
70: }
71: EXCEPTION(EX_Invalid);
72: reg_move(&CONST_QNaN, result);
73: return;
74: }
75: #endif PARANOID
76:
77: Xx.sigl = arg->sigl;
78: Xx.sigh = arg->sigh;
79: if ( exponent < -1 )
80: {
81: /* shift the argument right by the required places */
82: if ( shrx(&(Xx.sigl), -1-exponent) >= 0x80000000U )
83: (*((long long *)(&(Xx.sigl))))++; /* round up */
84: }
85:
86: mul64((long long *)&(Xx.sigl), (long long *)&(Xx.sigl),
87: (long long *)&(Xx2.sigl));
88: mul64((long long *)&(Xx2.sigl), (long long *)&(Xx2.sigl),
89: (long long *)&(Xx4.sigl));
90:
91: /* will be a valid positive nr with expon = 0 */
92: *(short *)&(accum.sign) = 0;
93: accum.exp = 0;
94:
95: /* Do the basic fixed point polynomial evaluation */
96: polynomial(&(accum.sigl), &(Xx4.sigl), lterms, HIPOWER-1);
97:
98: /* will be a valid positive nr with expon = 0 */
99: *(short *)&(negaccum.sign) = 0;
100: negaccum.exp = 0;
101:
102: /* Do the basic fixed point polynomial evaluation */
103: polynomial(&(negaccum.sigl), &(Xx4.sigl), negterms, HIPOWER-1);
104: mul64((long long *)&(Xx2.sigl), (long long *)&(negaccum.sigl),
105: (long long *)&(negaccum.sigl));
106:
107: /* Subtract the mantissas */
108: *((long long *)(&(accum.sigl))) -= *((long long *)(&(negaccum.sigl)));
109:
110: /* Convert to 64 bit signed-compatible */
111: accum.exp = EXP_BIAS - 1 + accum.exp;
112:
113: *(short *)&(result->sign) = *(short *)&(accum.sign);
114: result->exp = accum.exp;
115: result->sigl = accum.sigl;
116: result->sigh = accum.sigh;
117:
118: normalize(result);
119:
120: reg_mul(result, arg, result);
121: reg_u_add(result, arg, result);
122:
123: /* A small overflow may be possible... but an illegal result. */
124: if ( result->exp >= EXP_BIAS )
125: {
126: if ( (result->exp > EXP_BIAS) /* Larger or equal 2.0 */
127: || (result->sigl > 1) /* Larger than 1.0+msb */
128: || (result->sigh != 0x80000000) /* Much > 1.0 */
129: )
130: {
131: #ifdef DEBUGGING
132: RE_ENTRANT_CHECK_OFF
133: printf("\nEXP=%d, MS=%08x, LS=%08x\n", result->exp,
134: result->sigh, result->sigl);
135: RE_ENTRANT_CHECK_ON
136: #endif DEBUGGING
137: EXCEPTION(EX_INTERNAL|0x103);
138: }
139:
140: #ifdef DEBUGGING
141: RE_ENTRANT_CHECK_OFF
142: printf("\n***CORRECTING ILLEGAL RESULT*** in poly_sin() computation\n");
143: printf("EXP=%d, MS=%08x, LS=%08x\n", result->exp,
144: result->sigh, result->sigl);
145: RE_ENTRANT_CHECK_ON
146: #endif DEBUGGING
147:
148: result->sigl = 0; /* Truncate the result to 1.00 */
149: }
150: }
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