floatundixf.c revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0 
1/* ===-- floatundixf.c - Implement __floatundixf ---------------------------===
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 __floatundixf 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 *             du_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 */
28COMPILER_RT_ABI long double
29__floatundixf(du_int a)
30{
31    if (a == 0)
32        return 0.0;
33    const unsigned N = sizeof(du_int) * CHAR_BIT;
34    int clz = __builtin_clzll(a);
35    int e = (N - 1) - clz ;    /* exponent */
36    long_double_bits fb;
37    fb.u.high.s.low = (e + 16383);              /* exponent */
38    fb.u.low.all = a << clz;                   /* mantissa */
39    return fb.f;
40}
41
42#endif /* _ARCH_PPC */
43