compiler-rt/lib/builtins/floatditf.c

   1 //===-- lib/floatditf.c - integer -> quad-precision conversion ----*- C -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements di_int to quad-precision conversion for the
  10 // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
  11 // mode.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #define QUAD_PRECISION
  16 #include "fp_lib.h"
  17
  18 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
  19 COMPILER_RT_ABI fp_t __floatditf(di_int a) {
  20
  21   const int aWidth = sizeof a * CHAR_BIT;
  22
  23   // Handle zero as a special case to protect clz
  24   if (a == 0)
  25     return fromRep(0);
  26
  27   // All other cases begin by extracting the sign and absolute value of a
  28   rep_t sign = 0;
  29   du_int aAbs = (du_int)a;
  30   if (a < 0) {
  31     sign = signBit;
  32     aAbs = ~(du_int)a + 1U;
  33   }
  34
  35   // Exponent of (fp_t)a is the width of abs(a).
  36   const int exponent = (aWidth - 1) - __builtin_clzll(aAbs);
  37   rep_t result;
  38
  39   // Shift a into the significand field, rounding if it is a right-shift
  40   const int shift = significandBits - exponent;
  41   result = (rep_t)aAbs << shift ^ implicitBit;
  42
  43   // Insert the exponent
  44   result += (rep_t)(exponent + exponentBias) << significandBits;
  45   // Insert the sign bit and return
  46   return fromRep(result | sign);
  47 }
  48
  49 #endif