lib/builtins/fixunsdfti.c

   1 /* ===-- fixunsdfti.c - Implement __fixunsdfti -----------------------------===
   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 __fixunsdfti for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 #ifdef CRT_HAS_128BIT
  18
  19 /* Returns: convert a to a unsigned long long, rounding toward zero.
  20  *          Negative values all become zero.
  21  */
  22
  23 /* Assumption: double is a IEEE 64 bit floating point type
  24  *             tu_int is a 64 bit integral type
  25  *             value in double is representable in tu_int or is negative
  26  *                 (no range checking performed)
  27  */
  28
  29 /* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
  30
  31 COMPILER_RT_ABI tu_int
  32 __fixunsdfti(double a)
  33 {
  34     double_bits fb;
  35     fb.f = a;
  36     int e = ((fb.u.s.high & 0x7FF00000) >> 20) - 1023;
  37     if (e < 0 || (fb.u.s.high & 0x80000000))
  38         return 0;
  39     tu_int r = 0x0010000000000000uLL | (fb.u.all & 0x000FFFFFFFFFFFFFuLL);
  40     if (e > 52)
  41         r <<= (e - 52);
  42     else
  43         r >>= (52 - e);
  44     return r;
  45 }
  46
  47 #endif /* CRT_HAS_128BIT */