lib/builtins/fixunsdfsi.c

   1 /* ===-- fixunsdfsi.c - Implement __fixunsdfsi -----------------------------===
   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 __fixunsdfsi for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #include "int_lib.h"
  16
  17 /* Returns: convert a to a unsigned int, rounding toward zero.
  18  *          Negative values all become zero.
  19  */
  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 su_int or is negative
  24  *                 (no range checking performed)
  25  */
  26
  27 /* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
  28
  29 ARM_EABI_FNALIAS(d2uiz, fixunsdfsi)
  30
  31 COMPILER_RT_ABI su_int
  32 __fixunsdfsi(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     return (
  40                 0x80000000u                      |
  41                 ((fb.u.s.high & 0x000FFFFF) << 11) |
  42                 (fb.u.s.low >> 21)
  43            ) >> (31 - e);
  44 }