compiler-rt/lib/fixunsdfsi.c

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

#include "int_lib.h"

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

// Assumption: double is a IEEE 64 bit floating point type 
//             su_int is a 32 bit integral type
//             value in double is representable in su_int or is negative 
//                 (no range checking performed)

// seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm

su_int
__fixunsdfsi(double a)
{
    double_bits fb;
    fb.f = a;
    int e = ((fb.u.high & 0x7FF00000) >> 20) - 1023;
    if (e < 0 || (fb.u.high & 0x80000000))
        return 0;
    return (
                0x80000000u                      |
                ((fb.u.high & 0x000FFFFF) << 11) |
                (fb.u.low >> 21)
           ) >> (31 - e);
}