0,0 → 1,265 |
/* |
* 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. |
*/ |
|
/** @addtogroup softfloat |
* @{ |
*/ |
/** @file |
*/ |
|
#include<sftypes.h> |
#include<sub.h> |
#include<comparison.h> |
|
/** Subtract two float32 numbers with same signs |
*/ |
float32 subFloat32(float32 a, float32 b) |
{ |
int expdiff; |
uint32_t exp1, exp2, frac1, frac2; |
float32 result; |
|
result.f = 0; |
|
expdiff = a.parts.exp - b.parts.exp; |
if ((expdiff < 0 ) || ((expdiff == 0) && (a.parts.fraction < b.parts.fraction))) { |
if (isFloat32NaN(b)) { |
/* TODO: fix SigNaN */ |
if (isFloat32SigNaN(b)) { |
}; |
return b; |
}; |
|
if (b.parts.exp == FLOAT32_MAX_EXPONENT) { |
b.parts.sign = !b.parts.sign; /* num -(+-inf) = -+inf */ |
return b; |
} |
|
result.parts.sign = !a.parts.sign; |
|
frac1 = b.parts.fraction; |
exp1 = b.parts.exp; |
frac2 = a.parts.fraction; |
exp2 = a.parts.exp; |
expdiff *= -1; |
} else { |
if (isFloat32NaN(a)) { |
/* TODO: fix SigNaN */ |
if (isFloat32SigNaN(a) || isFloat32SigNaN(b)) { |
}; |
return a; |
}; |
|
if (a.parts.exp == FLOAT32_MAX_EXPONENT) { |
if (b.parts.exp == FLOAT32_MAX_EXPONENT) { |
/* inf - inf => nan */ |
/* TODO: fix exception */ |
result.binary = FLOAT32_NAN; |
return result; |
}; |
return a; |
} |
|
result.parts.sign = a.parts.sign; |
|
frac1 = a.parts.fraction; |
exp1 = a.parts.exp; |
frac2 = b.parts.fraction; |
exp2 = b.parts.exp; |
}; |
|
if (exp1 == 0) { |
/* both are denormalized */ |
result.parts.fraction = frac1-frac2; |
if (result.parts.fraction > frac1) { |
/* TODO: underflow exception */ |
return result; |
}; |
result.parts.exp = 0; |
return result; |
}; |
|
/* add hidden bit */ |
frac1 |= FLOAT32_HIDDEN_BIT_MASK; |
|
if (exp2 == 0) { |
/* denormalized */ |
--expdiff; |
} else { |
/* normalized */ |
frac2 |= FLOAT32_HIDDEN_BIT_MASK; |
}; |
|
/* create some space for rounding */ |
frac1 <<= 6; |
frac2 <<= 6; |
|
if (expdiff > FLOAT32_FRACTION_SIZE + 1) { |
goto done; |
}; |
|
frac1 = frac1 - (frac2 >> expdiff); |
done: |
/* TODO: find first nonzero digit and shift result and detect possibly underflow */ |
while ((exp1 > 0) && (!(frac1 & (FLOAT32_HIDDEN_BIT_MASK << 6 )))) { |
--exp1; |
frac1 <<= 1; |
/* TODO: fix underflow - frac1 == 0 does not necessary means underflow... */ |
}; |
|
/* rounding - if first bit after fraction is set then round up */ |
frac1 += 0x20; |
|
if (frac1 & (FLOAT32_HIDDEN_BIT_MASK << 7)) { |
++exp1; |
frac1 >>= 1; |
}; |
|
/*Clear hidden bit and shift */ |
result.parts.fraction = ((frac1 >> 6) & (~FLOAT32_HIDDEN_BIT_MASK)); |
result.parts.exp = exp1; |
|
return result; |
} |
|
/** Subtract two float64 numbers with same signs |
*/ |
float64 subFloat64(float64 a, float64 b) |
{ |
int expdiff; |
uint32_t exp1, exp2; |
uint64_t frac1, frac2; |
float64 result; |
|
result.d = 0; |
|
expdiff = a.parts.exp - b.parts.exp; |
if ((expdiff < 0 ) || ((expdiff == 0) && (a.parts.fraction < b.parts.fraction))) { |
if (isFloat64NaN(b)) { |
/* TODO: fix SigNaN */ |
if (isFloat64SigNaN(b)) { |
}; |
return b; |
}; |
|
if (b.parts.exp == FLOAT64_MAX_EXPONENT) { |
b.parts.sign = !b.parts.sign; /* num -(+-inf) = -+inf */ |
return b; |
} |
|
result.parts.sign = !a.parts.sign; |
|
frac1 = b.parts.fraction; |
exp1 = b.parts.exp; |
frac2 = a.parts.fraction; |
exp2 = a.parts.exp; |
expdiff *= -1; |
} else { |
if (isFloat64NaN(a)) { |
/* TODO: fix SigNaN */ |
if (isFloat64SigNaN(a) || isFloat64SigNaN(b)) { |
}; |
return a; |
}; |
|
if (a.parts.exp == FLOAT64_MAX_EXPONENT) { |
if (b.parts.exp == FLOAT64_MAX_EXPONENT) { |
/* inf - inf => nan */ |
/* TODO: fix exception */ |
result.binary = FLOAT64_NAN; |
return result; |
}; |
return a; |
} |
|
result.parts.sign = a.parts.sign; |
|
frac1 = a.parts.fraction; |
exp1 = a.parts.exp; |
frac2 = b.parts.fraction; |
exp2 = b.parts.exp; |
}; |
|
if (exp1 == 0) { |
/* both are denormalized */ |
result.parts.fraction = frac1 - frac2; |
if (result.parts.fraction > frac1) { |
/* TODO: underflow exception */ |
return result; |
}; |
result.parts.exp = 0; |
return result; |
}; |
|
/* add hidden bit */ |
frac1 |= FLOAT64_HIDDEN_BIT_MASK; |
|
if (exp2 == 0) { |
/* denormalized */ |
--expdiff; |
} else { |
/* normalized */ |
frac2 |= FLOAT64_HIDDEN_BIT_MASK; |
}; |
|
/* create some space for rounding */ |
frac1 <<= 6; |
frac2 <<= 6; |
|
if (expdiff > FLOAT64_FRACTION_SIZE + 1) { |
goto done; |
}; |
|
frac1 = frac1 - (frac2 >> expdiff); |
done: |
/* TODO: find first nonzero digit and shift result and detect possibly underflow */ |
while ((exp1 > 0) && (!(frac1 & (FLOAT64_HIDDEN_BIT_MASK << 6 )))) { |
--exp1; |
frac1 <<= 1; |
/* TODO: fix underflow - frac1 == 0 does not necessary means underflow... */ |
}; |
|
/* rounding - if first bit after fraction is set then round up */ |
frac1 += 0x20; |
|
if (frac1 & (FLOAT64_HIDDEN_BIT_MASK << 7)) { |
++exp1; |
frac1 >>= 1; |
}; |
|
/*Clear hidden bit and shift */ |
result.parts.fraction = ((frac1 >> 6) & (~FLOAT64_HIDDEN_BIT_MASK)); |
result.parts.exp = exp1; |
|
return result; |
} |
|
|
/** @} |
*/ |
|