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

   1 /* This file is distributed under the University of Illinois Open Source
   2  * License. See LICENSE.TXT for details.
   3  */
   4
   5 /* long double __floatunditf(unsigned long long x); */
   6 /* This file implements the PowerPC unsigned long long -> long double conversion */
   7
   8 #include "DD.h"
   9
  10 long double __floatunditf(uint64_t a) {
  11
  12         /* Begins with an exact copy of the code from __floatundidf */
  13
  14         static const double twop52 = 0x1.0p52;
  15         static const double twop84 = 0x1.0p84;
  16         static const double twop84_plus_twop52 = 0x1.00000001p84;
  17
  18         doublebits high = { .d = twop84 };
  19         doublebits low  = { .d = twop52 };
  20
  21         high.x |= a >> 32;                                                      /* 0x1.0p84 + high 32 bits of a */
  22         low.x |= a & UINT64_C(0x00000000ffffffff);      /* 0x1.0p52 + low 32 bits of a */
  23
  24         const double high_addend = high.d - twop84_plus_twop52;
  25
  26         /* At this point, we have two double precision numbers
  27          * high_addend and low.d, and we wish to return their sum
  28          * as a canonicalized long double:
  29          */
  30
  31         /* This implementation sets the inexact flag spuriously. */
  32         /* This could be avoided, but at some substantial cost. */
  33
  34         DD result;
  35
  36         result.s.hi = high_addend + low.d;
  37         result.s.lo = (high_addend - result.s.hi) + low.d;
  38
  39         return result.ld;
  40
  41 }