softfloat/s_roundPackToF64.c

   1
   2 #include <stdbool.h>
   3 #include <stdint.h>
   4 #include "platform.h"
   5 #include "primitives.h"
   6 #include "internals.h"
   7 #include "softfloat.h"
   8
   9 float64_t
  10  softfloat_roundPackToF64( bool sign, int_fast16_t exp, uint_fast64_t sig )
  11 {
  12     int roundingMode;
  13     bool roundNearestEven;
  14     int roundIncrement, roundBits;
  15     bool isTiny;
  16     uint_fast64_t uiZ;
  17     union ui64_f64 uZ;
  18
  19     roundingMode = softfloat_roundingMode;
  20     roundNearestEven = ( roundingMode == softfloat_round_nearest_even );
  21     roundIncrement = 0x200;
  22     if (
  23            ! roundNearestEven
  24         && ( roundingMode != softfloat_round_nearest_maxMag )
  25     ) {
  26         roundIncrement =
  27                ( roundingMode == softfloat_round_minMag )
  28             || ( roundingMode
  29                      == ( sign ? softfloat_round_max : softfloat_round_min ) )
  30                 ? 0
  31                 : 0x3FF;
  32     }
  33     roundBits = sig & 0x3FF;
  34     if ( 0x7FD <= (uint16_t) exp ) {
  35         if ( exp < 0 ) {
  36             isTiny =
  37                    ( softfloat_detectTininess
  38                          == softfloat_tininess_beforeRounding )
  39                 || ( exp < -1 )
  40                 || ( sig + roundIncrement < UINT64_C( 0x8000000000000000 ) );
  41             sig = softfloat_shift64RightJam( sig, - exp );
  42             exp = 0;
  43             roundBits = sig & 0x3FF;
  44             if ( isTiny && roundBits ) {
  45                 softfloat_raiseFlags( softfloat_flag_underflow );
  46             }
  47         } else if (
  48             ( 0x7FD < exp )
  49                 || ( UINT64_C( 0x8000000000000000 ) <= sig + roundIncrement )
  50         ) {
  51             softfloat_raiseFlags(
  52                 softfloat_flag_overflow | softfloat_flag_inexact );
  53             uiZ = packToF64UI( sign, 0x7FF, 0 ) - ! roundIncrement;
  54             goto uiZ;
  55         }
  56     }
  57     if ( roundBits ) softfloat_exceptionFlags |= softfloat_flag_inexact;
  58     sig = ( sig + roundIncrement )>>10;
  59     sig &= ~ ( ! ( roundBits ^ 0x200 ) & roundNearestEven );
  60     uiZ = packToF64UI( sign, sig ? exp : 0, sig );
  61  uiZ:
  62     uZ.ui = uiZ;
  63     return uZ.f;
  64
  65 }
  66