softfloat/source/f128M_to_f64.c

   1
   2 /*============================================================================
   3
   4 This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
   5 Package, Release 3e, by John R. Hauser.
   6
   7 Copyright 2011, 2012, 2013, 2014, 2015 The Regents of the University of
   8 California.  All rights reserved.
   9
  10 Redistribution and use in source and binary forms, with or without
  11 modification, are permitted provided that the following conditions are met:
  12
  13  1. Redistributions of source code must retain the above copyright notice,
  14     this list of conditions, and the following disclaimer.
  15
  16  2. Redistributions in binary form must reproduce the above copyright notice,
  17     this list of conditions, and the following disclaimer in the documentation
  18     and/or other materials provided with the distribution.
  19
  20  3. Neither the name of the University nor the names of its contributors may
  21     be used to endorse or promote products derived from this software without
  22     specific prior written permission.
  23
  24 THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
  25 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  26 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
  27 DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
  28 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  29 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  30 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  31 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  32 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  33 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  34
  35 =============================================================================*/
  36
  37 #include <stdbool.h>
  38 #include <stdint.h>
  39 #include "platform.h"
  40 #include "internals.h"
  41 #include "specialize.h"
  42 #include "softfloat.h"
  43
  44 #ifdef SOFTFLOAT_FAST_INT64
  45
  46 float64_t f128M_to_f64( const float128_t *aPtr )
  47 {
  48
  49     return f128_to_f64( *aPtr );
  50
  51 }
  52
  53 #else
  54
  55 float64_t f128M_to_f64( const float128_t *aPtr )
  56 {
  57     const uint32_t *aWPtr;
  58     uint32_t uiA96;
  59     bool sign;
  60     int32_t exp;
  61     uint64_t frac64;
  62     struct commonNaN commonNaN;
  63     uint64_t uiZ;
  64     uint32_t frac32;
  65     union ui64_f64 uZ;
  66
  67     /*------------------------------------------------------------------------
  68     *------------------------------------------------------------------------*/
  69     aWPtr = (const uint32_t *) aPtr;
  70     uiA96 = aWPtr[indexWordHi( 4 )];
  71     sign = signF128UI96( uiA96 );
  72     exp  = expF128UI96( uiA96 );
  73     frac64 = (uint64_t) fracF128UI96( uiA96 )<<32 | aWPtr[indexWord( 4, 2 )];
  74     /*------------------------------------------------------------------------
  75     *------------------------------------------------------------------------*/
  76     if ( exp == 0x7FFF ) {
  77         if ( frac64 || aWPtr[indexWord( 4, 1 )] | aWPtr[indexWord( 4, 0 )] ) {
  78             softfloat_f128MToCommonNaN( aWPtr, &commonNaN );
  79             uiZ = softfloat_commonNaNToF64UI( &commonNaN );
  80         } else {
  81             uiZ = packToF64UI( sign, 0x7FF, 0 );
  82         }
  83         goto uiZ;
  84     }
  85     /*------------------------------------------------------------------------
  86     *------------------------------------------------------------------------*/
  87     frac32 = aWPtr[indexWord( 4, 1 )];
  88     frac64 = frac64<<14 | frac32>>18;
  89     if ( (frac32 & 0x0003FFFF) || aWPtr[indexWord( 4, 0 )] ) frac64 |= 1;
  90     if ( ! (exp | frac64) ) {
  91         uiZ = packToF64UI( sign, 0, 0 );
  92         goto uiZ;
  93     }
  94     /*------------------------------------------------------------------------
  95     *------------------------------------------------------------------------*/
  96     exp -= 0x3C01;
  97     if ( sizeof (int_fast16_t) < sizeof (int32_t) ) {
  98         if ( exp < -0x1000 ) exp = -0x1000;
  99     }
 100     return
 101         softfloat_roundPackToF64(
 102             sign, exp, frac64 | UINT64_C( 0x4000000000000000 ) );
 103     /*------------------------------------------------------------------------
 104     *------------------------------------------------------------------------*/
 105  uiZ:
 106     uZ.ui = uiZ;
 107     return uZ.f;
 108
 109 }
 110
 111 #endif
 112