lib/fixdfti.c

   1 /* ===-- fixdfti.c - Implement __fixdfti -----------------------------------===
   2  *
   3  *                     The LLVM Compiler Infrastructure
   4  *
   5  * This file is dual licensed under the MIT and the University of Illinois Open
   6  * Source Licenses. See LICENSE.TXT for details.
   7  *
   8  * ===----------------------------------------------------------------------===
   9  *
  10  * This file implements __fixdfti for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 #if __x86_64
  18
  19 /* Returns: convert a to a signed long long, rounding toward zero. */
  20
  21 /* Assumption: double is a IEEE 64 bit floating point type
  22  *             su_int is a 32 bit integral type
  23  *             value in double is representable in ti_int (no range checking performed)
  24  */
  25
  26 /* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
  27
  28 ti_int
  29 __fixdfti(double a)
  30 {
  31     double_bits fb;
  32     fb.f = a;
  33     int e = ((fb.u.s.high & 0x7FF00000) >> 20) - 1023;
  34     if (e < 0)
  35         return 0;
  36     ti_int s = (si_int)(fb.u.s.high & 0x80000000) >> 31;
  37     ti_int r = 0x0010000000000000uLL | (0x000FFFFFFFFFFFFFuLL & fb.u.all);
  38     if (e > 52)
  39         r <<= (e - 52);
  40     else
  41         r >>= (52 - e);
  42     return (r ^ s) - s;
  43 }
  44
  45 #endif