0,0 → 1,139 |
/* |
* Copyright (C) 2005 Josef Cejka |
* All rights reserved. |
* |
* Redistribution and use in source and binary forms, with or without |
* modification, are permitted provided that the following conditions |
* are met: |
* |
* - Redistributions of source code must retain the above copyright |
* notice, this list of conditions and the following disclaimer. |
* - Redistributions in binary form must reproduce the above copyright |
* notice, this list of conditions and the following disclaimer in the |
* documentation and/or other materials provided with the distribution. |
* - The name of the author may not be used to endorse or promote products |
* derived from this software without specific prior written permission. |
* |
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
*/ |
|
#include "sftypes.h" |
#include "sub.h" |
|
/** Subtract two float32 numbers with same signs |
*/ |
float32 subFloat32(float32 a, float32 b) |
{ |
int expdiff; |
__u32 exp1,exp2,mant1,mant2; |
float32 result; |
|
result.f = 0; |
|
expdiff=a.parts.exp - b.parts.exp; |
if ((expdiff<0)||((expdiff==0)&&(a.parts.mantisa<b.parts.mantisa))) { |
if (isFloat32NaN(b)) { |
//TODO: fix SigNaN |
if (isFloat32SigNaN(b)) { |
}; |
return b; |
}; |
|
if (b.parts.exp==0xFF) { |
b.parts.sign=!b.parts.sign; /* num -(+-inf) = -+inf */ |
return b; |
} |
|
result.parts.sign = !a.parts.sign; |
|
mant1=b.parts.mantisa; |
exp1=b.parts.exp; |
mant2=a.parts.mantisa; |
exp2=a.parts.exp; |
expdiff*=-1; |
} else { |
if (isFloat32NaN(a)) { |
//TODO: fix SigNaN |
if ((isFloat32SigNaN(a))||(isFloat32SigNaN(b))) { |
}; |
return a; |
}; |
|
if (a.parts.exp==0xFF) { |
if (b.parts.exp==0xFF) { |
/* inf - inf => nan */ |
//TODO: fix exception |
result.binary = FLOAT32_NAN; |
return result; |
}; |
return a; |
} |
|
result.parts.sign = a.parts.sign; |
|
mant1=a.parts.mantisa; |
exp1=a.parts.exp; |
mant2=b.parts.mantisa; |
exp2=b.parts.exp; |
}; |
|
if (exp1==0) { |
//both are denormalized |
result.parts.mantisa=mant1-mant2; |
if (result.parts.mantisa>mant1) { |
//TODO: underflow exception |
return result; |
}; |
result.parts.exp=0; |
return result; |
}; |
|
// create some space for rounding |
mant1<<=6; |
mant2<<=6; |
|
mant1|=0x20000000; //add hidden bit |
|
|
if (exp2==0) { |
--expdiff; |
} else { |
mant2|=0x20000000; //hidden bit |
}; |
|
if (expdiff>24) { |
goto done; |
}; |
|
mant1 = mant1-(mant2>>expdiff); |
done: |
//TODO: find first nonzero digit and shift result and detect possibly underflow |
while ((exp1>0)&&(!(mant1&0x20000000))) { |
exp1--; |
mant1 <<= 1; |
/* TODO: fix underflow - mant1 == 0 does not necessary means underflow... */ |
}; |
|
//rounding - if first bit after mantisa is set then round up |
mant1 += 0x20; |
|
if (mant1&0x40000000) { |
++exp1; |
mant1>>=1; |
}; |
|
result.parts.mantisa = ((mant1&(~0x20000000))>>6); /*Clear hidden bit and shift */ |
result.parts.exp = exp1; |
|
return result; |
}; |
|