src/compiler-rt/lib/builtins/floatunditf.c

   1 //===-- lib/floatunditf.c - uint -> quad-precision conversion -----*- C -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is dual licensed under the MIT and the University of Illinois Open
   6 // Source Licenses. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements du_int to quad-precision conversion for the
  11 // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
  12 // mode.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #define QUAD_PRECISION
  17 #include "fp_lib.h"
  18
  19 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
  20 COMPILER_RT_ABI fp_t __floatunditf(du_int a) {
  21
  22     const int aWidth = sizeof a * CHAR_BIT;
  23
  24     // Handle zero as a special case to protect clz
  25     if (a == 0) return fromRep(0);
  26
  27     // Exponent of (fp_t)a is the width of abs(a).
  28     const int exponent = (aWidth - 1) - __builtin_clzll(a);
  29     rep_t result;
  30
  31     // Shift a into the significand field and clear the implicit bit.
  32     const int shift = significandBits - exponent;
  33     result = (rep_t)a << shift ^ implicitBit;
  34
  35     // Insert the exponent
  36     result += (rep_t)(exponent + exponentBias) << significandBits;
  37     return fromRep(result);
  38 }
  39
  40 #endif