/* mpfr_set_ld -- convert a machine long double to a multiple precision floating-point number Copyright 2002, 2003, 2004, 2005 Free Software Foundation, Inc. This file is part of the MPFR Library. The MPFR Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The MPFR Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the MPFR Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include #include "mpfr-impl.h" /* Various i386 systems have been seen with float.h LDBL constants equal to the DBL ones, whereas they ought to be bigger, reflecting the 10-byte IEEE extended format on that processor. gcc 3.2.1 on FreeBSD and Solaris has been seen with the problem, and gcc 2.95.4 on FreeBSD 4.7. */ #if HAVE_LDOUBLE_IEEE_EXT_LITTLE static const struct { char bytes[10]; long double dummy; /* for memory alignment */ } ldbl_max_struct = { { '\377','\377','\377','\377', '\377','\377','\377','\377', '\376','\177' }, 0.0 }; #define MPFR_LDBL_MAX (* (const long double *) ldbl_max_struct.bytes) #else #define MPFR_LDBL_MAX LDBL_MAX #endif int mpfr_set_ld (mpfr_ptr r, long double d, mp_rnd_t rnd_mode) { mpfr_t t, u; int inexact, shift_exp = 0; long double x; LONGDOUBLE_NAN_ACTION (d, goto nan); if (d > MPFR_LDBL_MAX) { mpfr_set_inf (r, 1); return 0; } if (d < -MPFR_LDBL_MAX) { mpfr_set_inf (r, -1); return 0; } if (d == 0.0) return mpfr_set_d (r, (double) d, rnd_mode); mpfr_init2 (t, MPFR_LDBL_MANT_DIG); mpfr_init2 (u, IEEE_DBL_MANT_DIG); mpfr_save_emin_emax (); convert: x = d; mpfr_set_ui (t, 0, GMP_RNDN); while (x != (long double) 0.0) { if ((x > (long double) DBL_MAX) || ((-x) > (long double) DBL_MAX)) { long double div9, div10, div11, div12, div13; #define TWO_64 18446744073709551616.0 /* 2^64 */ #define TWO_128 (TWO_64 * TWO_64) #define TWO_256 (TWO_128 * TWO_128) div9 = (long double) (double) (TWO_256 * TWO_256); /* 2^(2^9) */ div10 = div9 * div9; div11 = div10 * div10; /* 2^(2^11) */ div12 = div11 * div11; /* 2^(2^12) */ div13 = div12 * div12; /* 2^(2^13) */ if (ABS(x) >= div13) { x /= div13; /* exact */ shift_exp += 8192; } if (ABS(x) >= div12) { x /= div12; /* exact */ shift_exp += 4096; } if (ABS(x) >= div11) { x /= div11; /* exact */ shift_exp += 2048; } if (ABS(x) >= div10) { x /= div10; /* exact */ shift_exp += 1024; } /* warning: we may have DBL_MAX=2^1024*(1-2^(-53)) < x < 2^1024, therefore we have one extra exponent reduction step */ if (ABS(x) >= div9) { x /= div9; /* exact */ shift_exp += 512; } } else { long double div9, div10, div11; div9 = (long double) (double) 7.4583407312002067432909653e-155; /* div9 = 2^(-2^9) */ div10 = div9 * div9; /* 2^(-2^10) */ div11 = div10 * div10; /* 2^(-2^11) if extended precision */ /* since -DBL_MAX <= x <= DBL_MAX, the cast to double should not overflow here */ inexact = mpfr_set_d (u, (double) x, GMP_RNDZ); MPFR_ASSERTD(inexact == 0); if (x != (long double) 0.0 && ABS(x) < div10 && div11 != (long double) 0.0 && div11 / div10 == div10) /* possible underflow */ { long double div12, div13; /* After the divisions, any bit of x must be >= div10, hence the possible division by div9. */ div12 = div11 * div11; /* 2^(-2^12) */ div13 = div12 * div12; /* 2^(-2^13) */ if (ABS(x) <= div13) { x /= div13; /* exact */ shift_exp -= 8192; } if (ABS(x) <= div12) { x /= div12; /* exact */ shift_exp -= 4096; } if (ABS(x) <= div11) { x /= div11; /* exact */ shift_exp -= 2048; } if (ABS(x) <= div10) { x /= div10; /* exact */ shift_exp -= 1024; } if (ABS(x) <= div9) { x /= div9; /* exact */ shift_exp -= 512; } } else { if (mpfr_add (t, t, u, GMP_RNDZ) != 0) { if (!mpfr_number_p (t)) break; /* Inexact. This cannot happen unless the C implementation "lies" on the precision or when long doubles are implemented with FP expansions like under Mac OS X. */ if (MPFR_PREC (t) != MPFR_PREC (r) + 1) { /* We assume that MPFR_PREC (r) < MPFR_PREC_MAX. The precision MPFR_PREC (r) + 1 allows us to deduce the rounding bit and the sticky bit. */ mpfr_set_prec (t, MPFR_PREC (r) + 1); goto convert; } else { mp_limb_t *tp; int rb_mask; /* Since mpfr_add was inexact, the sticky bit is 1. */ tp = MPFR_MANT (t); rb_mask = MPFR_LIMB_ONE << (BITS_PER_MP_LIMB - 1 - (MPFR_PREC (r) & (BITS_PER_MP_LIMB - 1))); if (rnd_mode == GMP_RNDN) rnd_mode = (*tp & rb_mask) ^ MPFR_IS_NEG (t) ? GMP_RNDU : GMP_RNDD; *tp |= rb_mask; break; } } x -= (long double) mpfr_get_d1 (u); /* exact */ } } } inexact = mpfr_mul_2si (r, t, shift_exp, rnd_mode); mpfr_clear (t); mpfr_clear (u); mpfr_restore_emin_emax (); return mpfr_check_range (r, inexact, rnd_mode); nan: MPFR_SET_NAN(r); MPFR_RET_NAN; }