compiler-rt/lib/builtins/fixunsxfti.c

   1 //===-- fixunsxfti.c - Implement __fixunsxfti -----------------------------===//
   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 __fixunsxfti for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 #ifdef CRT_HAS_128BIT
  16
  17 // Returns: convert a to a unsigned long long, rounding toward zero.
  18 //          Negative values all become zero.
  19
  20 // Assumption: long double is an intel 80 bit floating point type padded with 6
  21 // bytes tu_int is a 128 bit integral type value in long double is representable
  22 // in tu_int or is negative
  23
  24 // gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee
  25 // eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm
  26 // mmmm mmmm mmmm
  27
  28 COMPILER_RT_ABI tu_int __fixunsxfti(long double a) {
  29   long_double_bits fb;
  30   fb.f = a;
  31   int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
  32   if (e < 0 || (fb.u.high.s.low & 0x00008000))
  33     return 0;
  34   if ((unsigned)e > sizeof(tu_int) * CHAR_BIT)
  35     return ~(tu_int)0;
  36   tu_int r = fb.u.low.all;
  37   if (e > 63)
  38     r <<= (e - 63);
  39   else
  40     r >>= (63 - e);
  41   return r;
  42 }
  43
  44 #endif // CRT_HAS_128BIT