compiler-rt/lib/builtins/ppc/floatditf.c

   1 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   2 // See https://llvm.org/LICENSE.txt for license information.
   3 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   4
   5 // long double __floatditf(long long x);
   6 // This file implements the PowerPC long long -> long double conversion
   7
   8 #include "DD.h"
   9
  10 long double __floatditf(int64_t a) {
  11
  12   static const double twop32 = 0x1.0p32;
  13   static const double twop52 = 0x1.0p52;
  14
  15   doublebits low = {.d = twop52};
  16   low.x |= a & UINT64_C(0x00000000ffffffff); // 0x1.0p52 + low 32 bits of a.
  17
  18   const double high_addend = (double)((int32_t)(a >> 32)) * twop32 - twop52;
  19
  20   // At this point, we have two double precision numbers
  21   // high_addend and low.d, and we wish to return their sum
  22   // as a canonicalized long double:
  23
  24   // This implementation sets the inexact flag spuriously.
  25   // This could be avoided, but at some substantial cost.
  26
  27   DD result;
  28
  29   result.s.hi = high_addend + low.d;
  30   result.s.lo = (high_addend - result.s.hi) + low.d;
  31
  32   return result.ld;
  33 }