softfloat/f64_roundToInt.c

   1
   2 #include <stdbool.h>
   3 #include <stdint.h>
   4 #include "platform.h"
   5 #include "internals.h"
   6 #include "specialize.h"
   7 #include "softfloat.h"
   8
   9 float64_t f64_roundToInt( float64_t a, int_fast8_t roundingMode, bool exact )
  10 {
  11     union ui64_f64 uA;
  12     uint_fast64_t uiA;
  13     int_fast16_t expA;
  14     uint_fast64_t uiZ;
  15     bool signA;
  16     uint_fast64_t lastBitMask, roundBitsMask;
  17     union ui64_f64 uZ;
  18
  19     uA.f = a;
  20     uiA = uA.ui;
  21     expA = expF64UI( uiA );
  22     if ( 0x433 <= expA ) {
  23         if ( ( expA == 0x7FF ) && fracF64UI( uiA ) ) {
  24             uiZ = softfloat_propagateNaNF64UI( uiA, 0 );
  25             goto uiZ;
  26         }
  27         return a;
  28     }
  29     if ( expA <= 0x3FE ) {
  30         if ( ! ( uiA & UINT64_C( 0x7FFFFFFFFFFFFFFF ) ) ) return a;
  31         if ( exact ) softfloat_exceptionFlags |= softfloat_flag_inexact;
  32         signA = signF64UI( uiA );
  33         switch ( roundingMode ) {
  34          case softfloat_round_nearest_even:
  35             if ( ( expA == 0x3FE ) && fracF64UI( uiA ) ) {
  36                 uiZ = packToF64UI( signA, 0x3FF, 0 );
  37                 goto uiZ;
  38             }
  39             break;
  40          case softfloat_round_min:
  41             uiZ = signA ? UINT64_C( 0xBFF0000000000000 ) : 0;
  42             goto uiZ;
  43          case softfloat_round_max:
  44             uiZ =
  45                 signA ? UINT64_C( 0x8000000000000000 )
  46                     : UINT64_C( 0x3FF0000000000000 );
  47             goto uiZ;
  48          case softfloat_round_nearest_maxMag:
  49             if ( expA == 0x3FE ) {
  50                 uiZ = packToF64UI( signA, 0x3FF, 0 );
  51                 goto uiZ;
  52             }
  53             break;
  54         }
  55         uiZ = packToF64UI( signA, 0, 0 );
  56         goto uiZ;
  57     }
  58     lastBitMask = (uint_fast64_t) 1<<( 0x433 - expA );
  59     roundBitsMask = lastBitMask - 1;
  60     uiZ = uiA;
  61     if ( roundingMode == softfloat_round_nearest_maxMag ) {
  62         uiZ += lastBitMask>>1;
  63     } else if ( roundingMode == softfloat_round_nearest_even ) {
  64         uiZ += lastBitMask>>1;
  65         if ( ! ( uiZ & roundBitsMask ) ) uiZ &= ~ lastBitMask;
  66     } else if ( roundingMode != softfloat_round_minMag ) {
  67         if ( signF64UI( uiZ ) ^ ( roundingMode == softfloat_round_max ) ) {
  68             uiZ += roundBitsMask;
  69         }
  70     }
  71     uiZ &= ~ roundBitsMask;
  72     if ( exact && ( uiZ != uiA ) ) {
  73         softfloat_exceptionFlags |= softfloat_flag_inexact;
  74     }
  75  uiZ:
  76     uZ.ui = uiZ;
  77     return uZ.f;
  78
  79 }
  80