chromium / native_client / nacl-gcc / f80d6b9ee7f94755c697ffb7194fb01dd0c537dd / . / mpfr-2.4.1 / div_2ui.c

/* mpfr_div_2ui -- divide a floating-point number by a power of two | |

Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. | |

Contributed by the Arenaire and Cacao projects, INRIA. | |

This file is part of the GNU MPFR Library. | |

The GNU 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 GNU 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 GNU MPFR Library; see the file COPYING.LIB. If not, write to | |

the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, | |

MA 02110-1301, USA. */ | |

#include "mpfr-impl.h" | |

int | |

mpfr_div_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long n, mp_rnd_t rnd_mode) | |

{ | |

int inexact; | |

MPFR_LOG_FUNC (("x[%#R]=%R n=%lu rnd=%d", x, x, n, rnd_mode), | |

("y[%#R]=%R inexact=%d", y, y, inexact)); | |

/* Most of the times, this function is called with y==x */ | |

inexact = MPFR_UNLIKELY(y != x) ? mpfr_set (y, x, rnd_mode) : 0; | |

if (MPFR_LIKELY( MPFR_IS_PURE_FP(y)) ) | |

{ | |

/* n will have to be casted to long to make sure that the addition | |

and subtraction below (for overflow detection) are signed */ | |

while (MPFR_UNLIKELY(n > LONG_MAX)) | |

{ | |

int inex2; | |

n -= LONG_MAX; | |

inex2 = mpfr_div_2ui(y, y, LONG_MAX, rnd_mode); | |

if (inex2) | |

return inex2; /* underflow */ | |

} | |

/* MPFR_EMAX_MAX - (long) n is signed and doesn't lead to an integer | |

overflow; the first test useful so that the real test can't lead | |

to an integer overflow. */ | |

{ | |

mp_exp_t exp = MPFR_GET_EXP (y); | |

if (MPFR_UNLIKELY( __gmpfr_emin > MPFR_EMAX_MAX - (long) n || | |

exp < __gmpfr_emin + (long) n) ) | |

{ | |

if (rnd_mode == GMP_RNDN && | |

(__gmpfr_emin > MPFR_EMAX_MAX - (long) (n - 1) || | |

exp < __gmpfr_emin + (long) (n - 1) || | |

(inexact >= 0 && mpfr_powerof2_raw (y)))) | |

rnd_mode = GMP_RNDZ; | |

return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y)); | |

} | |

MPFR_SET_EXP(y, exp - (long) n); | |

} | |

} | |

return inexact; | |

} |