lib/floatdixf.c

   1 /* ===-- floatdixf.c - Implement __floatdixf -------------------------------===
   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 __floatdixf for the compiler_rt library.
  11  *
  12  * ===----------------------------------------------------------------------===
  13  */
  14
  15 #if !_ARCH_PPC
  16
  17 #include "int_lib.h"
  18
  19 /* Returns: convert a to a long double, rounding toward even. */
  20
  21 /* Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits
  22  *             di_int is a 64 bit integral type
  23  */
  24
  25 /* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
  26  * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
  27  */
  28
  29 long double
  30 __floatdixf(di_int a)
  31 {
  32     if (a == 0)
  33         return 0.0;
  34     const unsigned N = sizeof(di_int) * CHAR_BIT;
  35     const di_int s = a >> (N-1);
  36     a = (a ^ s) - s;
  37     int clz = __builtin_clzll(a);
  38     int e = (N - 1) - clz ;    /* exponent */
  39     long_double_bits fb;
  40     fb.u.high.s.low = ((su_int)s & 0x00008000) |  /* sign */
  41                       (e + 16383);                /* exponent */
  42     fb.u.low.all = a << clz;                    /* mantissa */
  43     return fb.f;
  44 }
  45
  46 #endif /* !_ARCH_PPC */