src/float/conv/cl_DF_to_double.cc

   1 // cl_DF_to_double().
   2
   3 // General includes.
   4 #include "base/cl_sysdep.h"
   5
   6 // Specification.
   7 #include "cln/dfloat.h"
   8
   9
  10 // Implementation.
  11
  12 #include "float/dfloat/cl_DF.h"
  13
  14 namespace cln {
  15
  16 double double_approx (const cl_DF& obj)
  17 {
  18         union { dfloat eksplicit; double machine_double; } u;
  19         #define val u.eksplicit
  20         val = TheDfloat(obj)->dfloat_value;
  21         // Der Exponent muß um DF_exp_mid-1022 erniedrigt werden.
  22         if (DF_exp_mid>1022)
  23           #if (cl_word_size==64)
  24           { var uintL exp = (val >> DF_mant_len) & (bit(DF_exp_len)-1); // e
  25             if (exp < DF_exp_mid-1022+1)
  26               { // produziere denormalisiertes Float
  27                 val = (val & minus_bit(DF_exp_len+DF_mant_len)) // selbes Vorzeichen
  28                       | ((sint64)0 << DF_mant_len) // Exponent 0
  29                       | (((val & (bit(DF_mant_len)-1)) | bit(DF_mant_len)) // Mantisse shiften
  30                          >> (DF_exp_mid-1022+1 - exp) // shiften
  31                         );
  32               }
  33               else
  34               { val -= (sint64)(DF_exp_mid - 1022) << DF_mant_len; }
  35           }
  36           #else
  37           { var uintL exp = (val.semhi >> (DF_mant_len-32)) & (bit(DF_exp_len)-1); // e
  38             if (exp < DF_exp_mid-1022+1)
  39               { // produziere denormalisiertes Float
  40                 var uintL shiftcount = DF_exp_mid-1022+1 - exp;
  41                 val.mlo = val.mlo >> shiftcount; // Mantisse shiften
  42                 val.mlo |= val.semhi << (32-shiftcount);
  43                 val.semhi = (val.semhi & minus_bit(DF_exp_len+DF_mant_len-32)) // selbes Vorzeichen
  44                             | ((sint32)0 << (DF_mant_len-32)) // Exponent 0
  45                             | (((val.semhi & (bit(DF_mant_len-32)-1)) | bit(DF_mant_len-32)) // Mantisse shiften
  46                                >> shiftcount // shiften
  47                               );
  48               }
  49               else
  50               { val.semhi -= (sint32)(DF_exp_mid - 1022) << (DF_mant_len-32); }
  51           }
  52           #endif
  53         #undef val
  54         return u.machine_double;
  55 }
  56
  57 }  // namespace cln