lib/builtins/fixunsxfsi.c

/* ===-- fixunsxfsi.c - Implement __fixunsxfsi -----------------------------===
 *
 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.
 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 *
 * ===----------------------------------------------------------------------===
 *
 * This file implements __fixunsxfsi for the compiler_rt library.
 *
 * ===----------------------------------------------------------------------===
 */

#if !_ARCH_PPC

#include "int_lib.h"

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

/* Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
 *             su_int is a 32 bit integral type
 *             value in long double is representable in su_int or is negative 
 */

/* 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
 */

COMPILER_RT_ABI su_int
__fixunsxfsi(long double a)
{
    long_double_bits fb;
    fb.f = a;
    int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
    if (e < 0 || (fb.u.high.s.low & 0x00008000))
        return 0;
    if ((unsigned)e > sizeof(su_int) * CHAR_BIT)
        return ~(su_int)0;
    return fb.u.low.s.high >> (31 - e);
}

#endif /* !_ARCH_PPC */