Windows2000/private/windbg64/lib/tenpow.c

/*
*tenpow.c - multiply a _ULDBL12 by a power of 10

*    Copyright (c) 1991-1991, Microsoft Corporation.    All rights reserved.

*Purpose:

*Revision History:
*   7-17-91    GDP    Initial version (ported from assembly)
*   05-26-92       GWK     Windbg srcs

*/


#include "mathsup.h"



extern _ULDBL12 _pow10pos[];
extern _ULDBL12 _pow10neg[];




/*
*void  __ld12mul(_ULDBL12 *px, _ULDBL12 *py) -
*   _ULDBL12 multiplication

*Purpose: multiply two _ULDBL12 numbers

*Entry: px,py: pointers to the _ULDBL12 operands

*Exit: *px contains the product

*Exceptions:

*/

void  __ld12mul(_ULDBL12 *px, _ULDBL12 *py)
{
    u_short sign = 0;
    u_short sticky_bits = 0;
    _ULDBL12 tempman; /*this is actually a 12-byte mantissa,
             not a 12-byte long double */
    int i;
    u_short expx, expy, expsum;
    int roffs,poffs,qoffs;
    int sticky;

    *UL_LO_12(&tempman) = 0;
    *UL_MED_12(&tempman) = 0;
    *UL_HI_12(&tempman) = 0;

    expx = *U_EXP_12(px);
    expy = *U_EXP_12(py);

    sign = (expx ^ expy) & (u_short)0x8000;
    expx &= 0x7fff;
    expy &= 0x7fff;
    expsum = expx+expy;
    if (expx >= LD_MAXEXP
    || expy >= LD_MAXEXP
    || expsum > LD_MAXEXP+ LD_BIASM1){
    /* overflow to infinity */
    PUT_INF_12(px,sign);
    return;
    }
    if (expsum <= LD_BIASM1-63) {
    /* underflow to zero */
    PUT_ZERO_12(px);
    return;
    }
    if (expx == 0) {
    /*
     * If this is a denormal temp real then the mantissa
     * was shifted right once to set bit 63 to zero.
     */
    expsum++; /* Correct for this */
    if (ISZERO_12(px)) {
        /* put positive sign */
        *U_EXP_12(px) = 0;
        return;
    }
    }
    if (expy == 0) {
    expsum++; /* because arg2 is denormal */
    if (ISZERO_12(py)) {
        PUT_ZERO_12(px);
        return;
    }
    }

    roffs = 0;
    for (i=0;i<5;i++) {
    int j;
    poffs = i<<1;
    qoffs = 8;
    for (j=5-i;j>0;j--) {
        u_long prod;
#ifdef MIPS
        /* a variable to hold temprary sums */
        u_long sum;
#endif
        int carry;
        u_short *p, *q;
        u_long *r;
        p = USHORT_12(px,poffs);
        q = USHORT_12(py,qoffs);
        r = ULONG_12(&tempman,roffs);
        prod = (u_long)*p * (u_long)*q;
#ifdef MIPS
        /* handle misalignment problems */
        if (i&0x1){ /* i is odd */
        carry = __addl(*MIPSALIGN(r), prod, &sum);
        *MIPSALIGN(r) =  sum;
        }
        else /* i is even */
        carry = __addl(*r, prod, r);
#else
        carry = __addl(*r,prod,r);
#endif
        if (carry) {
        /* roffs should be less than 8 in this case */
        (*USHORT_12(&tempman,roffs+4))++;
        }
        poffs+=2;
        qoffs-=2;
    }
    roffs+=2;
    }

    expsum -= LD_BIASM1;

    /* normalize */
    while ((s_short)expsum > 0 &&
       ((*UL_HI_12(&tempman) & MSB_ULONG) == 0)) {
     __shl_12(&tempman);
     expsum--;
    }

    if ((s_short)expsum <= 0) {
    expsum--;
        sticky = 0;
    while ((s_short)expsum < 0) {
        if (*U_XT_12(&tempman) & 0x1)
        sticky++;
        __shr_12(&tempman);
        expsum++;
    }
    if (sticky)
        *U_XT_12(&tempman) |= 0x1;
    }

    if (*U_XT_12(&tempman) > 0x8000 ||
     ((*UL_LO_12(&tempman) & 0x1ffff) == 0x18000)) {
    /* round up */
    if (*UL_MANLO_12(&tempman) == MAX_ULONG) {
        *UL_MANLO_12(&tempman) = 0;
        if (*UL_MANHI_12(&tempman) == MAX_ULONG) {
        *UL_MANHI_12(&tempman) = 0;
        if (*U_EXP_12(&tempman) == MAX_USHORT) {
            /* 12-byte mantissa overflow */
            *U_EXP_12(&tempman) = MSB_USHORT;
            expsum++;
        }
        else
            (*U_EXP_12(&tempman))++;
        }
        else
        (*UL_MANHI_12(&tempman))++;
    }
    else
        (*UL_MANLO_12(&tempman))++;
    }


    /* check for exponent overflow */
    if (expsum >= 0x7fff){
    PUT_INF_12(px, sign);
    return;
    }

    /* put result in px */
    *U_XT_12(px) = *USHORT_12(&tempman,2);
    *UL_MANLO_12(px) = *UL_MED_12(&tempman);
    *UL_MANHI_12(px) = *UL_HI_12(&tempman);
    *U_EXP_12(px) = expsum | sign;
}



void __multtenpow12(_ULDBL12 *pld12, int pow, unsigned mult12)
{
    _ULDBL12 *pow_10p = _pow10pos-8;
    if (pow == 0)
    return;
    if (pow < 0) {
    pow = -pow;
    pow_10p = _pow10neg-8;
    }

    if (!mult12)
    *U_XT_12(pld12) = 0;


    while (pow) {
    int last3; /* the 3 LSBits of pow */
    _ULDBL12 unround;
    _ULDBL12 *py;

    pow_10p += 7;
    last3 = pow & 0x7;
    pow >>= 3;
    if (last3 == 0)
        continue;
    py = pow_10p + last3;

#ifdef _ULDSUPPORT
    if (mult12) {
#endif
        /* do an exact 12byte multiplication */
        if (*U_XT_12(py) >= 0x8000) {
        /* copy number */
        unround = *py;
        /* unround adjacent byte */
        (*UL_MANLO_12(&unround))--;
        /* point to new operand */
        py = &unround;
        }
        __ld12mul(pld12,py);
#ifdef _ULDSUPPORT
    }
    else {
        /* do a 10byte multiplication */
        py = (_ULDBL12 *)TEN_BYTE_PART(py);
        *(long double *)TEN_BYTE_PART(pld12) *=
        *(long double *)py;
    }
#endif
    }
}