src/float/conv/cl_DF_to_double.cc

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