softfloat/f32_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 float32_t f32_roundToInt( float32_t a, int_fast8_t roundingMode, bool exact )
  10 {
  11     union ui32_f32 uA;
  12     uint_fast32_t uiA;
  13     int_fast16_t expA;
  14     uint_fast32_t uiZ;
  15     bool signA;
  16     uint_fast32_t lastBitMask, roundBitsMask;
  17     union ui32_f32 uZ;
  18
  19     uA.f = a;
  20     uiA = uA.ui;
  21     expA = expF32UI( uiA );
  22     if ( 0x96 <= expA ) {
  23         if ( ( expA == 0xFF ) && fracF32UI( uiA ) ) {
  24             uiZ = softfloat_propagateNaNF32UI( uiA, 0 );
  25             goto uiZ;
  26         }
  27         return a;
  28     }
  29     if ( expA <= 0x7E ) {
  30         if ( ! (uint32_t) ( uiA<<1 ) ) return a;
  31         if ( exact ) softfloat_exceptionFlags |= softfloat_flag_inexact;
  32         signA = signF32UI( uiA );
  33         switch ( roundingMode ) {
  34          case softfloat_round_nearest_even:
  35             if ( ( expA == 0x7E ) && fracF32UI( uiA ) ) {
  36                 uiZ = packToF32UI( signA, 0x7F, 0 );
  37                 goto uiZ;
  38             }
  39             break;
  40          case softfloat_round_min:
  41             uiZ = signA ? 0xBF800000 : 0;
  42             goto uiZ;
  43          case softfloat_round_max:
  44             uiZ = signA ? 0x80000000 : 0x3F800000;
  45             goto uiZ;
  46          case softfloat_round_nearest_maxMag:
  47             if ( expA == 0x7E ) {
  48                 uiZ = packToF32UI( signA, 0x7F, 0 );
  49                 goto uiZ;
  50             }
  51             break;
  52         }
  53         uiZ = packToF32UI( signA, 0, 0 );
  54         goto uiZ;
  55     }
  56     lastBitMask = (uint_fast32_t) 1<<( 0x96 - expA );
  57     roundBitsMask = lastBitMask - 1;
  58     uiZ = uiA;
  59     if ( roundingMode == softfloat_round_nearest_maxMag ) {
  60         uiZ += lastBitMask>>1;
  61     } else if ( roundingMode == softfloat_round_nearest_even ) {
  62         uiZ += lastBitMask>>1;
  63         if ( ! ( uiZ & roundBitsMask ) ) uiZ &= ~ lastBitMask;
  64     } else if ( roundingMode != softfloat_round_minMag ) {
  65         if ( signF32UI( uiZ ) ^ ( roundingMode == softfloat_round_max ) ) {
  66             uiZ += roundBitsMask;
  67         }
  68     }
  69     uiZ &= ~ roundBitsMask;
  70     if ( exact && ( uiZ != uiA ) ) {
  71         softfloat_exceptionFlags |= softfloat_flag_inexact;
  72     }
  73  uiZ:
  74     uZ.ui = uiZ;
  75     return uZ.f;
  76
  77 }
  78