1 /* mpfr_set_float128 -- convert a machine __float128 number to 2 a multiple precision floating-point number 3 4 Copyright 2012-2018 Free Software Foundation, Inc. 5 Contributed by the AriC and Caramba projects, INRIA. 6 7 This file is part of the GNU MPFR Library. 8 9 The GNU MPFR Library is free software; you can redistribute it and/or modify 10 it under the terms of the GNU Lesser General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or (at your 12 option) any later version. 13 14 The GNU MPFR Library is distributed in the hope that it will be useful, but 15 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 16 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 17 License for more details. 18 19 You should have received a copy of the GNU Lesser General Public License 20 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 21 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 22 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 23 24 #include <float.h> /* for DBL_MAX */ 25 26 #define MPFR_NEED_LONGLONG_H 27 #include "mpfr-impl.h" 28 29 #ifdef MPFR_WANT_FLOAT128 30 31 /* The q suffix is a GNU C extension, but so is __float128. */ 32 #define MPFR_FLOAT128_MAX 0x1.ffffffffffffffffffffffffffffp+16383q 33 34 int 35 mpfr_set_float128 (mpfr_ptr r, __float128 d, mpfr_rnd_t rnd_mode) 36 { 37 mpfr_t t; 38 mp_limb_t *tp; 39 int inexact, shift_exp, neg, e, i; 40 __float128 p[14], q[14]; 41 MPFR_SAVE_EXPO_DECL (expo); 42 43 /* Check for NaN */ 44 if (MPFR_UNLIKELY (DOUBLE_ISNAN (d))) 45 { 46 MPFR_SET_NAN(r); 47 MPFR_RET_NAN; 48 } 49 50 /* Check for INF */ 51 if (MPFR_UNLIKELY (d > MPFR_FLOAT128_MAX)) 52 { 53 MPFR_SET_INF (r); 54 MPFR_SET_POS (r); 55 return 0; 56 } 57 else if (MPFR_UNLIKELY (d < -MPFR_FLOAT128_MAX)) 58 { 59 MPFR_SET_INF (r); 60 MPFR_SET_NEG (r); 61 return 0; 62 } 63 /* Check for ZERO */ 64 else if (MPFR_UNLIKELY (d == (__float128) 0.0)) 65 return mpfr_set_d (r, (double) d, rnd_mode); 66 67 shift_exp = 0; /* invariant: remainder to deal with is d*2^shift_exp */ 68 neg = d < 0; 69 if (d < 0) 70 d = -d; 71 72 /* Scaling, avoiding (slow) divisions. Should the tables be cached? */ 73 if (d >= 1.0) 74 { 75 p[0] = 2.0; 76 q[0] = 0.5; 77 e = 1; 78 /* p[i] = 2^(2^i), q[i] = 1/p[i] */ 79 for (i = 0; i < 13 && d >= p[i]; i++) 80 { 81 p[i+1] = p[i] * p[i]; 82 q[i+1] = q[i] * q[i]; 83 e <<= 1; 84 } 85 for (; i >= 0; e >>= 1, i--) 86 if (d >= p[i]) 87 { 88 d *= q[i]; 89 shift_exp += e; 90 } 91 d *= 0.5; 92 shift_exp++; 93 } 94 else if (d < 0.5) 95 { 96 p[0] = 2.0; 97 q[0] = 0.5; 98 e = 1; 99 /* p[i] = 2^(2^i), q[i] = 1/p[i] */ 100 for (i = 0; i < 13 && d < q[i]; i++) 101 { 102 p[i+1] = p[i] * p[i]; 103 q[i+1] = q[i] * q[i]; 104 e <<= 1; 105 } 106 /* The while() may be needed for i = 13 due to subnormals. 107 This can probably be improved without yielding an underflow. */ 108 for (; i >= 0; e >>= 1, i--) 109 while (d < q[i]) 110 { 111 d *= p[i]; 112 shift_exp -= e; 113 } 114 } 115 116 MPFR_ASSERTD (d >= 0.5 && d < 1.0); 117 118 mpfr_init2 (t, IEEE_FLOAT128_MANT_DIG); 119 tp = MPFR_MANT (t); 120 121 MPFR_SAVE_EXPO_MARK (expo); 122 MPFR_SET_EXP (t, shift_exp); 123 MPFR_SET_SIGN (t, neg ? MPFR_SIGN_NEG : MPFR_SIGN_POS); 124 125 for (i = MPFR_LAST_LIMB (t); i >= 0; i--) 126 { 127 d *= 2 * (__float128) MPFR_LIMB_HIGHBIT; 128 tp[i] = (mp_limb_t) d; 129 d -= tp[i]; 130 } 131 132 inexact = mpfr_set (r, t, rnd_mode); 133 mpfr_clear (t); 134 135 MPFR_SAVE_EXPO_FREE (expo); 136 return mpfr_check_range (r, inexact, rnd_mode); 137 } 138 139 #endif /* MPFR_WANT_FLOAT128 */ 140