source: mainline/arch/ia32/src/fmath.c@ 3c56c94

/*
 * 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 <arch/fmath.h>
#include <print.h>

#define FMATH_MANTISA_MASK ( 0x000fffffffffffffLL )

int fmath_is_negative(double num) 
{
        fmath_ld_union_t fmath_ld_union;
        fmath_ld_union.bf = num;
        return ((fmath_ld_union.ldd[7])&0x80)==0x80; /*first bit is sign, IA32 is little endian -> 8th byte*/

} 

signed short fmath_get_binary_exponent(double num) 
{
        fmath_ld_union_t fmath_ld_union;
        fmath_ld_union.bf = num;
        return (signed short)((((fmath_ld_union.ldd[7])&0x7f)<<4) + (((fmath_ld_union.ldd[6])&0xf0)>>4)) -FMATH_EXPONENT_BIAS; /* exponent is 11 bits lenght, so sevent bits is in 8th byte and 4 bits in 7th */
}

double fmath_get_decimal_exponent(double num) 
{
        double value;
        /* log10(2)*log2(x) => log10(x) */
        __asm__ __volatile__ ( \
        "fldlg2         #load log10(2)  \n\t"   \
        "fxch %%st(1)           \n\t" \
        "fyl2x          #count st(0)*log2(st(1))->st(1); pop st(0)      \n\t" \
        : "=t" (value) : "0"(num) );
        return value;
}

__u64 fmath_get_binary_mantisa(double num) 
{
        union { __u64 _u; double _d;} un = { _d : num };
        un._u=un._u &(FMATH_MANTISA_MASK); /* mask 52 bits of mantisa*/
        return un._u;
}

double fmath_fint(double num, double *intp) 
{
        fmath_ld_union_t fmath_ld_union_num;
        fmath_ld_union_t fmath_ld_union_int;
        signed short exp;
        __u64 mask,mantisa;
        int i;
        
        exp=fmath_get_binary_exponent(num);
        
        if (exp<0) {
                *intp = 0.0;
                *intp = fmath_set_sign(0.0L,fmath_is_negative(num));
                return num;
                }
                

        if (exp>51) {
                *intp=num;
                num=0.0;
                num= fmath_set_sign(0.0L,fmath_is_negative(*intp));
                return num;
        }
        
        fmath_ld_union_num.bf = num;
        
        mask = FMATH_MANTISA_MASK>>exp;
        //mantisa = (fmath_get-binary_mantisa(num))&(~mask);
        
        for (i=0;i<7;i++) {
                /* Ugly construction for obtain sign, exponent and integer part from num */
                fmath_ld_union_int.ldd[i]=fmath_ld_union_num.ldd[i]&(((~mask)>>(i*8))&0xff);
        }
        
        fmath_ld_union_int.ldd[6]|=((fmath_ld_union_num.ldd[6])&(0xf0));
        fmath_ld_union_int.ldd[7]=fmath_ld_union_num.ldd[7];
        
        *intp=fmath_ld_union_int.bf;
        return fmath_ld_union_num.bf-fmath_ld_union_int.bf;
};
        
double fmath_set_sign(double num,__u8 sign) 
{
        fmath_ld_union_t fmath_ld_union;
        fmath_ld_union.bf = num;
        fmath_ld_union.ldd[7]=((fmath_ld_union.ldd[7])&0x7f)|(sign<<7); /* change 64th bit (IA32 is a little endian)*/
        return fmath_ld_union.bf;
}

double fmath_abs(double num) 
{
        return fmath_set_sign(num,0);
}

double fmath_dpow(double base, double exponent) 
{
        double value=1.0;
        if (base<=0.0) return base; 
        
        //2^(x*log2(10)) = 2^y = 10^x
        
        __asm__ __volatile__ (          \
                "fyl2x # ST(1):=ST(1)*log2(ST(0)), pop st(0) \n\t "             \
                "fld    %%st(0) \n\t"   \
                "frndint \n\t"          \
                "fxch %%st(1) \n\t"             \
                "fsub %%st(1),%%st(0) \n\t"     \
                "f2xm1  # ST := 2^ST -1\n\t"                    \
                "fld1 \n\t"                     \
                "faddp %%st(0),%%st(1) \n\t"    \
                "fscale #ST:=ST*2^(ST(1))\n\t"          \
                "fstp %%st(1) \n\t"             \
        "" : "=t" (value) :  "0" (base), "u" (exponent) );
        return value;
}