fixunsxfti.c revision b3a6901e66f55b35aa9e01bcb24134e6a65ea004 
1//===-- fixunsxfti.c - Implement __fixunsxfti -----------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements __fixunsxfti for the compiler_rt library.
11//
12//===----------------------------------------------------------------------===//
13
14#if __x86_64
15
16#include "int_lib.h"
17
18// Returns: convert a to a unsigned long long, rounding toward zero.
19//          Negative values all become zero.
20
21// Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
22//             tu_int is a 64 bit integral type
23//             value in long double is representable in tu_int or is negative
24//                 (no range checking performed)
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
29tu_int
30__fixunsxfti(long double a)
31{
32    long_double_bits fb;
33    fb.f = a;
34    int e = (fb.u.high.low & 0x00007FFF) - 16383;
35    if (e < 0 || (fb.u.high.low & 0x00008000))
36        return 0;
37    tu_int r = fb.u.low.all;
38    if (e > 63)
39        r <<= (e - 63);
40    else
41        r >>= (63 - e);
42    return r;
43}
44
45#endif
46