1 /* mpfr_div_2si -- divide a floating-point number by a power of two
3 Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
4 Contributed by the Arenaire and Cacao projects, INRIA.
6 This file is part of the GNU MPFR Library.
8 The GNU MPFR Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or (at your
11 option) any later version.
13 The GNU MPFR Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16 License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
20 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23 #include "mpfr-impl.h"
26 mpfr_div_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mpfr_rnd_t rnd_mode)
30 MPFR_LOG_FUNC (("x[%#R]=%R n=%ld rnd=%d", x, x, n, rnd_mode),
31 ("y[%#R]=%R inexact=%d", y, y, inexact));
33 inexact = MPFR_UNLIKELY(y != x) ? mpfr_set (y, x, rnd_mode) : 0;
35 if (MPFR_LIKELY( MPFR_IS_PURE_FP(y) ))
37 mpfr_exp_t exp = MPFR_GET_EXP (y);
38 if (MPFR_UNLIKELY( n > 0 && (__gmpfr_emin > MPFR_EMAX_MAX - n ||
39 exp < __gmpfr_emin + n)) )
41 if (rnd_mode == MPFR_RNDN &&
42 (__gmpfr_emin > MPFR_EMAX_MAX - (n - 1) ||
43 exp < __gmpfr_emin + (n - 1) ||
44 (inexact >= 0 && mpfr_powerof2_raw (y))))
46 return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y));
49 if (MPFR_UNLIKELY(n < 0 && (__gmpfr_emax < MPFR_EMIN_MIN - n ||
50 exp > __gmpfr_emax + n)) )
51 return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y));
53 MPFR_SET_EXP (y, exp - n);