compiler-rt/lib/builtins/floatunsidf.c

//===-- lib/floatunsidf.c - uint -> double-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 unsigned integer to double-precision conversion for the
// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
// mode.
//
//===----------------------------------------------------------------------===//

#define DOUBLE_PRECISION
#include "fp_lib.h"

#include "int_lib.h"

COMPILER_RT_ABI fp_t __floatunsidf(su_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) - clzsi(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);
}

#if defined(__ARM_EABI__)
#if defined(COMPILER_RT_ARMHF_TARGET)
AEABI_RTABI fp_t __aeabi_ui2d(su_int a) { return __floatunsidf(a); }
#else
COMPILER_RT_ALIAS(__floatunsidf, __aeabi_ui2d)
#endif
#endif