source: mainline/uspace/lib/softfloat/generic/add.c@ a69cb9a

/*
 * Copyright (c) 2005 Josef Cejka
 * Copyright (c) 2011 Petr Koupy
 * 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 Addition functions.
 */

#include <sftypes.h>
#include <add.h>
#include <comparison.h>
#include <common.h>

/**
 * Add two single-precision floats with the same signs.
 *
 * @param a First input operand.
 * @param b Second input operand.
 * @return Result of addition.
 */
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 double-precision floats with the same signs.
 *
 * @param a First input operand.
 * @param b Second input operand.
 * @return Result of addition.
 */
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;
}

/**
 * Add two quadruple-precision floats with the same signs.
 *
 * @param a First input operand.
 * @param b Second input operand.
 * @return Result of addition.
 */
float128 addFloat128(float128 a, float128 b)
{
        int expdiff;
        uint32_t exp1, exp2;
        uint64_t frac1_hi, frac1_lo, frac2_hi, frac2_lo, tmp_hi, tmp_lo;

        expdiff = ((int) a.parts.exp) - b.parts.exp;
        if (expdiff < 0) {
                if (isFloat128NaN(b)) {
                        /* TODO: fix SigNaN */
                        if (isFloat128SigNaN(b)) {
                        }

                        return b;
                }

                /* b is infinity and a not */
                if (b.parts.exp == FLOAT128_MAX_EXPONENT) {
                        return b;
                }

                frac1_hi = b.parts.frac_hi;
                frac1_lo = b.parts.frac_lo;
                exp1 = b.parts.exp;
                frac2_hi = a.parts.frac_hi;
                frac2_lo = a.parts.frac_lo;
                exp2 = a.parts.exp;
                expdiff *= -1;
        } else {
                if (isFloat128NaN(a)) {
                        /* TODO: fix SigNaN */
                        if (isFloat128SigNaN(a) || isFloat128SigNaN(b)) {
                        }
                        return a;
                }

                /* a is infinity and b not */
                if (a.parts.exp == FLOAT128_MAX_EXPONENT) {
                        return a;
                }

                frac1_hi = a.parts.frac_hi;
                frac1_lo = a.parts.frac_lo;
                exp1 = a.parts.exp;
                frac2_hi = b.parts.frac_hi;
                frac2_lo = b.parts.frac_lo;
                exp2 = b.parts.exp;
        }

        if (exp1 == 0) {
                /* both are denormalized */
                add128(frac1_hi, frac1_lo, frac2_hi, frac2_lo, &frac1_hi, &frac1_lo);

                and128(frac1_hi, frac1_lo,
                    FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO,
                    &tmp_hi, &tmp_lo);
                if (lt128(0x0ll, 0x0ll, tmp_hi, tmp_lo)) {
                        /* result is not denormalized */
                        a.parts.exp = 1;
                }

                a.parts.frac_hi = frac1_hi;
                a.parts.frac_lo = frac1_lo;
                return a;
        }

        /* add hidden bit - frac1 is sure not denormalized */
        or128(frac1_hi, frac1_lo,
            FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO,
            &frac1_hi, &frac1_lo);

        /* second operand ... */
        if (exp2 == 0) {
                /* ... is denormalized */
                --expdiff;
        } else {
                /* is not denormalized */
                or128(frac2_hi, frac2_lo,
                    FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO,
                    &frac2_hi, &frac2_lo);
        }

        /* create some space for rounding */
        lshift128(frac1_hi, frac1_lo, 6, &frac1_hi, &frac1_lo);
        lshift128(frac2_hi, frac2_lo, 6, &frac2_hi, &frac2_lo);

        if (expdiff < (FLOAT128_FRACTION_SIZE + 2)) {
                rshift128(frac2_hi, frac2_lo, expdiff, &frac2_hi, &frac2_lo);
                add128(frac1_hi, frac1_lo, frac2_hi, frac2_lo, &frac1_hi, &frac1_lo);
        } else {
                a.parts.exp = exp1;

                rshift128(frac1_hi, frac1_lo, 6, &frac1_hi, &frac1_lo);
                not128(FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO,
                    &tmp_hi, &tmp_lo);
                and128(frac1_hi, frac1_lo, tmp_hi, tmp_lo, &tmp_hi, &tmp_lo);

                a.parts.frac_hi = tmp_hi;
                a.parts.frac_lo = tmp_lo;
                return a;
        }

        lshift128(FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO, 7,
            &tmp_hi, &tmp_lo);
        and128(frac1_hi, frac1_lo, tmp_hi, tmp_lo, &tmp_hi, &tmp_lo);
        if (lt128(0x0ll, 0x0ll, tmp_hi, tmp_lo)) {
                ++exp1;
                rshift128(frac1_hi, frac1_lo, 1, &frac1_hi, &frac1_lo);
        }

        /* rounding - if first bit after fraction is set then round up */
        add128(frac1_hi, frac1_lo, 0x0ll, 0x1ll << 5, &frac1_hi, &frac1_lo);

        lshift128(FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO, 7,
           &tmp_hi, &tmp_lo);
        and128(frac1_hi, frac1_lo, tmp_hi, tmp_lo, &tmp_hi, &tmp_lo);
        if (lt128(0x0ll, 0x0ll, tmp_hi, tmp_lo)) {
                /* rounding overflow */
                ++exp1;
                rshift128(frac1_hi, frac1_lo, 1, &frac1_hi, &frac1_lo);
        }

        if ((exp1 == FLOAT128_MAX_EXPONENT ) || (exp2 > exp1)) {
                /* overflow - set infinity as result */
                a.parts.exp = FLOAT64_MAX_EXPONENT;
                a.parts.frac_hi = 0;
                a.parts.frac_lo = 0;
                return a;
        }

        a.parts.exp = exp1;
        
        /* Clear hidden bit and shift */
        rshift128(frac1_hi, frac1_lo, 6, &frac1_hi, &frac1_lo);
        not128(FLOAT128_HIDDEN_BIT_MASK_HI, FLOAT128_HIDDEN_BIT_MASK_LO,
            &tmp_hi, &tmp_lo);
        and128(frac1_hi, frac1_lo, tmp_hi, tmp_lo, &tmp_hi, &tmp_lo);

        a.parts.frac_hi = tmp_hi;
        a.parts.frac_lo = tmp_lo;

        return a;
}

/** @}
 */