compiler-rt/lib/builtins/fixxfdi.c

   1 //===-- fixxfdi.c - Implement __fixxfdi -----------------------------------===//
   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 __fixxfdi for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #if !_ARCH_PPC
  14
  15 #include "int_lib.h"
  16
  17 // Returns: convert a to a signed long long, rounding toward zero.
  18
  19 // Assumption: long double is an intel 80 bit floating point type padded with 6
  20 // bytes di_int is a 64 bit integral type value in long double is representable
  21 // in di_int (no range checking performed)
  22
  23 // gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee
  24 // eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm
  25 // mmmm mmmm mmmm
  26
  27 #if defined(_MSC_VER) && !defined(__clang__)
  28 // MSVC throws a warning about 'uninitialized variable use' here,
  29 // disable it for builds that warn-as-error
  30 #pragma warning(push)
  31 #pragma warning(disable : 4700)
  32 #endif
  33
  34 COMPILER_RT_ABI di_int __fixxfdi(long double a) {
  35   const di_int di_max = (di_int)((~(du_int)0) / 2);
  36   const di_int di_min = -di_max - 1;
  37   long_double_bits fb;
  38   fb.f = a;
  39   int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
  40   if (e < 0)
  41     return 0;
  42   if ((unsigned)e >= sizeof(di_int) * CHAR_BIT)
  43     return a > 0 ? di_max : di_min;
  44   di_int s = -(si_int)((fb.u.high.s.low & 0x00008000) >> 15);
  45   di_int r = fb.u.low.all;
  46   r = (du_int)r >> (63 - e);
  47   return (r ^ s) - s;
  48 }
  49
  50 #if defined(_MSC_VER) && !defined(__clang__)
  51 #pragma warning(pop)
  52 #endif
  53
  54 #endif // !_ARCH_PPC