lib/fixunsxfti.c

   1 /* ===-- fixunsxfti.c - Implement __fixunsxfti -----------------------------===
   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 __fixunsxfti for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #if __x86_64
  16
  17 #include "int_lib.h"
  18
  19 /* Returns: convert a to a unsigned long long, rounding toward zero.
  20  *          Negative values all become zero.
  21  */
  22
  23 /* Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
  24  *             tu_int is a 64 bit integral type
  25  *             value in long double is representable in tu_int or is negative
  26  *                 (no range checking performed)
  27  */
  28
  29 /* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
  30  * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
  31  */
  32
  33 tu_int
  34 __fixunsxfti(long double a)
  35 {
  36     long_double_bits fb;
  37     fb.f = a;
  38     int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
  39     if (e < 0 || (fb.u.high.s.low & 0x00008000))
  40         return 0;
  41     tu_int r = fb.u.low.all;
  42     if (e > 63)
  43         r <<= (e - 63);
  44     else
  45         r >>= (63 - e);
  46     return r;
  47 }
  48
  49 #endif