source: mainline/softfloat/generic/add.c@ ce5bcb4

/*
 * 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<add.h>
#include<comparison.h>

/** Add two Float32 numbers with same signs
 */
float32 addFloat32(float32 a, float32 b)
{
        int expdiff;
        uint32_t exp1, exp2,frac1, frac2;
        
        expdiff = a.parts.exp - b.parts.exp;
        if (expdiff < 0) {
                if (isFloat32NaN(b)) {
                        /* TODO: fix SigNaN */
                        if (isFloat32SigNaN(b)) {
                        };

                        return b;
                };
                
                if (b.parts.exp == FLOAT32_MAX_EXPONENT) { 
                        return b;
                }
                
                frac1 = b.parts.fraction;
                exp1 = b.parts.exp;
                frac2 = a.parts.fraction;
                exp2 = a.parts.exp;
                expdiff *= -1;
        } else {
                if ((isFloat32NaN(a)) || (isFloat32NaN(b))) {
                        /* TODO: fix SigNaN */
                        if (isFloat32SigNaN(a) || isFloat32SigNaN(b)) {
                        };
                        return (isFloat32NaN(a)?a:b);
                };
                
                if (a.parts.exp == FLOAT32_MAX_EXPONENT) { 
                        return a;
                }
                
                frac1 = a.parts.fraction;
                exp1 = a.parts.exp;
                frac2 = b.parts.fraction;
                exp2 = b.parts.exp;
        };
        
        if (exp1 == 0) {
                /* both are denormalized */
                frac1 += frac2;
                if (frac1 & FLOAT32_HIDDEN_BIT_MASK ) {
                        /* result is not denormalized */
                        a.parts.exp = 1;
                };
                a.parts.fraction = frac1;
                return a;
        };
        
        frac1 |= FLOAT32_HIDDEN_BIT_MASK; /* add hidden bit */

        if (exp2 == 0) {
                /* second operand is denormalized */
                --expdiff;
        } else {
                /* add hidden bit to second operand */
                frac2 |= FLOAT32_HIDDEN_BIT_MASK; 
        };
        
        /* create some space for rounding */
        frac1 <<= 6;
        frac2 <<= 6;
        
        if (expdiff < (FLOAT32_FRACTION_SIZE + 2) ) {
                frac2 >>= expdiff;
                frac1 += frac2;
        } else {
                a.parts.exp = exp1;
                a.parts.fraction = (frac1 >> 6) & (~(FLOAT32_HIDDEN_BIT_MASK));
                return a;
        }
        
        if (frac1 & (FLOAT32_HIDDEN_BIT_MASK << 7) ) {
                ++exp1;
                frac1 >>= 1;
        };
        
        /* rounding - if first bit after fraction is set then round up */
        frac1 += (0x1 << 5);
        
        if (frac1 & (FLOAT32_HIDDEN_BIT_MASK << 7)) { 
                /* rounding overflow */
                ++exp1;
                frac1 >>= 1;
        };
        
        
        if ((exp1 == FLOAT32_MAX_EXPONENT ) || (exp2 > exp1)) {
                        /* overflow - set infinity as result */
                        a.parts.exp = FLOAT32_MAX_EXPONENT;
                        a.parts.fraction = 0;
                        return a;
                        }
        
        a.parts.exp = exp1;
        
        /*Clear hidden bit and shift */
        a.parts.fraction = ((frac1 >> 6) & (~FLOAT32_HIDDEN_BIT_MASK)) ; 
        return a;
}


/** Add two Float64 numbers with same signs
 */
float64 addFloat64(float64 a, float64 b)
{
        int expdiff;
        uint32_t exp1, exp2;
        uint64_t frac1, frac2;
        
        expdiff = ((int )a.parts.exp) - b.parts.exp;
        if (expdiff < 0) {
                if (isFloat64NaN(b)) {
                        /* TODO: fix SigNaN */
                        if (isFloat64SigNaN(b)) {
                        };

                        return b;
                };
                
                /* b is infinity and a not */   
                if (b.parts.exp == FLOAT64_MAX_EXPONENT ) { 
                        return b;
                }
                
                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;
                };
                
                /* a is infinity and b not */
                if (a.parts.exp == FLOAT64_MAX_EXPONENT ) { 
                        return a;
                }
                
                frac1 = a.parts.fraction;
                exp1 = a.parts.exp;
                frac2 = b.parts.fraction;
                exp2 = b.parts.exp;
        };
        
        if (exp1 == 0) {
                /* both are denormalized */
                frac1 += frac2;
                if (frac1 & FLOAT64_HIDDEN_BIT_MASK) { 
                        /* result is not denormalized */
                        a.parts.exp = 1;
                };
                a.parts.fraction = frac1;
                return a;
        };
        
        /* add hidden bit - frac1 is sure not denormalized */
        frac1 |= FLOAT64_HIDDEN_BIT_MASK;

        /* second operand ... */
        if (exp2 == 0) {
                /* ... is denormalized */
                --expdiff;      
        } else {
                /* is not denormalized */
                frac2 |= FLOAT64_HIDDEN_BIT_MASK;
        };
        
        /* create some space for rounding */
        frac1 <<= 6;
        frac2 <<= 6;
        
        if (expdiff < (FLOAT64_FRACTION_SIZE + 2) ) {
                frac2 >>= expdiff;
                frac1 += frac2;
        } else {
                a.parts.exp = exp1;
                a.parts.fraction = (frac1 >> 6) & (~(FLOAT64_HIDDEN_BIT_MASK));
                return a;
        }
        
        if (frac1 & (FLOAT64_HIDDEN_BIT_MASK << 7) ) {
                ++exp1;
                frac1 >>= 1;
        };
        
        /* rounding - if first bit after fraction is set then round up */
        frac1 += (0x1 << 5); 
        
        if (frac1 & (FLOAT64_HIDDEN_BIT_MASK << 7)) { 
                /* rounding overflow */
                ++exp1;
                frac1 >>= 1;
        };
        
        if ((exp1 == FLOAT64_MAX_EXPONENT ) || (exp2 > exp1)) {
                        /* overflow - set infinity as result */
                        a.parts.exp = FLOAT64_MAX_EXPONENT;
                        a.parts.fraction = 0;
                        return a;
                        }
        
        a.parts.exp = exp1;
        /*Clear hidden bit and shift */
        a.parts.fraction = ( (frac1 >> 6 ) & (~FLOAT64_HIDDEN_BIT_MASK));
        
        return a;
}