src/libcompiler_builtins/compiler-rt/lib/builtins/fixxfti.c

   1 /* ===-- fixxfti.c - Implement __fixxfti -----------------------------------===
   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 __fixxfti 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 signed long long, rounding toward zero. */
  20
  21 /* Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
  22  *             ti_int is a 128 bit integral type
  23  *             value in long double is representable in ti_int
  24  */
  25
  26 /* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
  27  * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
  28  */
  29
  30 COMPILER_RT_ABI ti_int
  31 __fixxfti(long double a)
  32 {
  33     const ti_int ti_max = (ti_int)((~(tu_int)0) / 2);
  34     const ti_int ti_min = -ti_max - 1;
  35     long_double_bits fb;
  36     fb.f = a;
  37     int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
  38     if (e < 0)
  39         return 0;
  40     ti_int s = -(si_int)((fb.u.high.s.low & 0x00008000) >> 15);
  41     ti_int r = fb.u.low.all;
  42     if ((unsigned)e >= sizeof(ti_int) * CHAR_BIT)
  43         return a > 0 ? ti_max : ti_min;
  44     if (e > 63)
  45         r <<= (e - 63);
  46     else
  47         r >>= (63 - e);
  48     return (r ^ s) - s;
  49 }
  50
  51 #endif /* CRT_HAS_128BIT */