llvm-project/compiler-rt/lib/builtins/floatunditf.c

//===-- lib/floatunditf.c - uint -> quad-precision conversion -----*- C -*-===//
//
// 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 du_int to quad-precision conversion for the
// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
// mode.
//
//===----------------------------------------------------------------------===//

#define QUAD_PRECISION
#include "fp_lib.h"

#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
COMPILER_RT_ABI fp_t __floatunditf(du_int a) {

    const int aWidth = sizeof a * CHAR_BIT;

    // Handle zero as a special case to protect clz
    if (a == 0) return fromRep(0);

    // Exponent of (fp_t)a is the width of abs(a).
    const int exponent = (aWidth - 1) - __builtin_clzll(a);
    rep_t result;

    // Shift a into the significand field and clear the implicit bit.
    const int shift = significandBits - exponent;
    result = (rep_t)a << shift ^ implicitBit;

    // Insert the exponent
    result += (rep_t)(exponent + exponentBias) << significandBits;
    return fromRep(result);
}

#endif