lib/fixunsxfti.c

//===-- fixunsxfti.c - Implement __fixunsxfti -----------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements __fixunsxfti for the compiler_rt library.
//
//===----------------------------------------------------------------------===//

#if __x86_64

#include "int_lib.h"

// Returns: convert a to a unsigned long long, rounding toward zero.
//          Negative values all become zero.

// Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
//             tu_int is a 64 bit integral type
//             value in long double is representable in tu_int or is negative 
//                 (no range checking performed)

// gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
// 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm

tu_int
__fixunsxfti(long double a)
{
    long_double_bits fb;
    fb.f = a;
    int e = (fb.u.high.low & 0x00007FFF) - 16383;
    if (e < 0 || (fb.u.high.low & 0x00008000))
        return 0;
    tu_int r = fb.u.low.all;
    if (e > 63)
        r <<= (e - 63);
    else
        r >>= (63 - e);
    return r;
}

#endif