Ejemplo n.º 1
0
int
sgl_frem (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
	  sgl_floating_point * dstptr, unsigned int *status)
{
	register unsigned int opnd1, opnd2, result;
	register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
	register boolean roundup = FALSE;

	opnd1 = *srcptr1;
	opnd2 = *srcptr2;
	/*
	 * check first operand for NaN's or infinity
	 */
	if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd1)) {
			if (Sgl_isnotnan(opnd2)) {
				/* invalid since first operand is infinity */
				if (Is_invalidtrap_enabled()) 
                                	return(INVALIDEXCEPTION);
                                Set_invalidflag();
                                Sgl_makequietnan(result);
				*dstptr = result;
				return(NOEXCEPTION);
			}
		}
		else {
                	/*
                 	 * is NaN; signaling or quiet?
                 	 */
                	if (Sgl_isone_signaling(opnd1)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd1);
                	}
			/* 
			 * is second operand a signaling NaN? 
			 */
			else if (Sgl_is_signalingnan(opnd2)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd2);
                		*dstptr = opnd2;
                		return(NOEXCEPTION);
			}
                	/*
                 	 * return quiet NaN
                 	 */
                	*dstptr = opnd1;
                	return(NOEXCEPTION);
		}
	} 
	/*
	 * check second operand for NaN's or infinity
	 */
	if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd2)) {
			/*
			 * return first operand
			 */
                	*dstptr = opnd1;
			return(NOEXCEPTION);
		}
                /*
                 * is NaN; signaling or quiet?
                 */
                if (Sgl_isone_signaling(opnd2)) {
                        /* trap if INVALIDTRAP enabled */
                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        /* make NaN quiet */
                        Set_invalidflag();
                        Sgl_set_quiet(opnd2);
                }
                /*
                 * return quiet NaN
                 */
                *dstptr = opnd2;
                return(NOEXCEPTION);
	}
	/*
	 * check second operand for zero
	 */
	if (Sgl_iszero_exponentmantissa(opnd2)) {
		/* invalid since second operand is zero */
		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                Set_invalidflag();
                Sgl_makequietnan(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}

	/* 
	 * get sign of result
	 */
	result = opnd1;  

	/* 
	 * check for denormalized operands
	 */
	if (opnd1_exponent == 0) {
		/* check for zero */
		if (Sgl_iszero_mantissa(opnd1)) {
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
		/* normalize, then continue */
		opnd1_exponent = 1;
		Sgl_normalize(opnd1,opnd1_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd1);
	}
	if (opnd2_exponent == 0) {
		/* normalize, then continue */
		opnd2_exponent = 1;
		Sgl_normalize(opnd2,opnd2_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd2);
	}

	/* find result exponent and divide step loop count */
	dest_exponent = opnd2_exponent - 1;
	stepcount = opnd1_exponent - opnd2_exponent;

	/*
	 * check for opnd1/opnd2 < 1
	 */
	if (stepcount < 0) {
		/*
		 * check for opnd1/opnd2 > 1/2
		 *
		 * In this case n will round to 1, so 
		 *    r = opnd1 - opnd2 
		 */
		if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
			Sgl_all(result) = ~Sgl_all(result);   /* set sign */
			/* align opnd2 with opnd1 */
			Sgl_leftshiftby1(opnd2); 
			Sgl_subtract(opnd2,opnd1,opnd2);
			/* now normalize */
                	while (Sgl_iszero_hidden(opnd2)) {
                        	Sgl_leftshiftby1(opnd2);
                        	dest_exponent--;
			}
			Sgl_set_exponentmantissa(result,opnd2);
			goto testforunderflow;
		}
		/*
		 * opnd1/opnd2 <= 1/2
		 *
		 * In this case n will round to zero, so 
		 *    r = opnd1
		 */
		Sgl_set_exponentmantissa(result,opnd1);
		dest_exponent = opnd1_exponent;
		goto testforunderflow;
	}

	/*
	 * Generate result
	 *
	 * Do iterative subtract until remainder is less than operand 2.
	 */
	while (stepcount-- > 0 && Sgl_all(opnd1)) {
		if (Sgl_isnotlessthan(opnd1,opnd2))
			Sgl_subtract(opnd1,opnd2,opnd1);
		Sgl_leftshiftby1(opnd1);
	}
	/*
	 * Do last subtract, then determine which way to round if remainder 
	 * is exactly 1/2 of opnd2 
	 */
	if (Sgl_isnotlessthan(opnd1,opnd2)) {
		Sgl_subtract(opnd1,opnd2,opnd1);
		roundup = TRUE;
	}
	if (stepcount > 0 || Sgl_iszero(opnd1)) {
		/* division is exact, remainder is zero */
		Sgl_setzero_exponentmantissa(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}

	/* 
	 * Check for cases where opnd1/opnd2 < n 
	 *
	 * In this case the result's sign will be opposite that of
	 * opnd1.  The mantissa also needs some correction.
	 */
	Sgl_leftshiftby1(opnd1);
	if (Sgl_isgreaterthan(opnd1,opnd2)) {
		Sgl_invert_sign(result);
		Sgl_subtract((opnd2<<1),opnd1,opnd1);
	}
	/* check for remainder being exactly 1/2 of opnd2 */
	else if (Sgl_isequal(opnd1,opnd2) && roundup) { 
		Sgl_invert_sign(result);
	}

	/* normalize result's mantissa */
        while (Sgl_iszero_hidden(opnd1)) {
                dest_exponent--;
                Sgl_leftshiftby1(opnd1);
        }
	Sgl_set_exponentmantissa(result,opnd1);

        /* 
         * Test for underflow
         */
    testforunderflow:
	if (dest_exponent <= 0) {
                /* trap if UNDERFLOWTRAP enabled */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(result,dest_exponent,unfl);
			*dstptr = result;
			/* frem is always exact */
			return(UNDERFLOWEXCEPTION);
                }
                /*
                 * denormalize result or set to signed zero
                 */
                if (dest_exponent >= (1 - SGL_P)) {
			Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
                }
                else {
			Sgl_setzero_exponentmantissa(result);
		}
	}
	else Sgl_set_exponent(result,dest_exponent);
	*dstptr = result;
	return(NOEXCEPTION);
}
Ejemplo n.º 2
0
int
sgl_frem (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
	  sgl_floating_point * dstptr, unsigned int *status)
{
	register unsigned int opnd1, opnd2, result;
	register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
	register boolean roundup = FALSE;

	opnd1 = *srcptr1;
	opnd2 = *srcptr2;
	if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd1)) {
			if (Sgl_isnotnan(opnd2)) {
				
				if (Is_invalidtrap_enabled()) 
                                	return(INVALIDEXCEPTION);
                                Set_invalidflag();
                                Sgl_makequietnan(result);
				*dstptr = result;
				return(NOEXCEPTION);
			}
		}
		else {
                	if (Sgl_isone_signaling(opnd1)) {
                        	
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd1);
                	}
			else if (Sgl_is_signalingnan(opnd2)) {
                        	
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd2);
                		*dstptr = opnd2;
                		return(NOEXCEPTION);
			}
                	*dstptr = opnd1;
                	return(NOEXCEPTION);
		}
	} 
	if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd2)) {
                	*dstptr = opnd1;
			return(NOEXCEPTION);
		}
                if (Sgl_isone_signaling(opnd2)) {
                        
                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        
                        Set_invalidflag();
                        Sgl_set_quiet(opnd2);
                }
                *dstptr = opnd2;
                return(NOEXCEPTION);
	}
	if (Sgl_iszero_exponentmantissa(opnd2)) {
		
		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                Set_invalidflag();
                Sgl_makequietnan(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}

	result = opnd1;  

	if (opnd1_exponent == 0) {
		
		if (Sgl_iszero_mantissa(opnd1)) {
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
		
		opnd1_exponent = 1;
		Sgl_normalize(opnd1,opnd1_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd1);
	}
	if (opnd2_exponent == 0) {
		
		opnd2_exponent = 1;
		Sgl_normalize(opnd2,opnd2_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd2);
	}

	
	dest_exponent = opnd2_exponent - 1;
	stepcount = opnd1_exponent - opnd2_exponent;

	if (stepcount < 0) {
		if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
			Sgl_all(result) = ~Sgl_all(result);   
			
			Sgl_leftshiftby1(opnd2); 
			Sgl_subtract(opnd2,opnd1,opnd2);
			
                	while (Sgl_iszero_hidden(opnd2)) {
                        	Sgl_leftshiftby1(opnd2);
                        	dest_exponent--;
			}
			Sgl_set_exponentmantissa(result,opnd2);
			goto testforunderflow;
		}
		Sgl_set_exponentmantissa(result,opnd1);
		dest_exponent = opnd1_exponent;
		goto testforunderflow;
	}

	while (stepcount-- > 0 && Sgl_all(opnd1)) {
		if (Sgl_isnotlessthan(opnd1,opnd2))
			Sgl_subtract(opnd1,opnd2,opnd1);
		Sgl_leftshiftby1(opnd1);
	}
	if (Sgl_isnotlessthan(opnd1,opnd2)) {
		Sgl_subtract(opnd1,opnd2,opnd1);
		roundup = TRUE;
	}
	if (stepcount > 0 || Sgl_iszero(opnd1)) {
		
		Sgl_setzero_exponentmantissa(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}

	Sgl_leftshiftby1(opnd1);
	if (Sgl_isgreaterthan(opnd1,opnd2)) {
		Sgl_invert_sign(result);
		Sgl_subtract((opnd2<<1),opnd1,opnd1);
	}
	
	else if (Sgl_isequal(opnd1,opnd2) && roundup) { 
		Sgl_invert_sign(result);
	}

	
        while (Sgl_iszero_hidden(opnd1)) {
                dest_exponent--;
                Sgl_leftshiftby1(opnd1);
        }
	Sgl_set_exponentmantissa(result,opnd1);

    testforunderflow:
	if (dest_exponent <= 0) {
                
                if (Is_underflowtrap_enabled()) {
                        Sgl_setwrapped_exponent(result,dest_exponent,unfl);
			*dstptr = result;
			
			return(UNDERFLOWEXCEPTION);
                }
                if (dest_exponent >= (1 - SGL_P)) {
			Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
                }
                else {
			Sgl_setzero_exponentmantissa(result);
		}
	}
	else Sgl_set_exponent(result,dest_exponent);
	*dstptr = result;
	return(NOEXCEPTION);
}
Ejemplo n.º 3
0
int
sgl_fmpy(
    sgl_floating_point *srcptr1,
    sgl_floating_point *srcptr2,
    sgl_floating_point *dstptr,
    unsigned int *status)
{
    register unsigned int opnd1, opnd2, opnd3, result;
    register int dest_exponent, count;
    register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
    boolean is_tiny;

    opnd1 = *srcptr1;
    opnd2 = *srcptr2;
    /*
     * set sign bit of result
     */
    if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result);
    else Sgl_setzero(result);
    /*
     * check first operand for NaN's or infinity
     */
    if (Sgl_isinfinity_exponent(opnd1)) {
        if (Sgl_iszero_mantissa(opnd1)) {
            if (Sgl_isnotnan(opnd2)) {
                if (Sgl_iszero_exponentmantissa(opnd2)) {
                    /*
                     * invalid since operands are infinity
                     * and zero
                     */
                    if (Is_invalidtrap_enabled())
                        return(INVALIDEXCEPTION);
                    Set_invalidflag();
                    Sgl_makequietnan(result);
                    *dstptr = result;
                    return(NOEXCEPTION);
                }
                /*
                 * return infinity
                 */
                Sgl_setinfinity_exponentmantissa(result);
                *dstptr = result;
                return(NOEXCEPTION);
            }
        }
        else {
            /*
             * is NaN; signaling or quiet?
             */
            if (Sgl_isone_signaling(opnd1)) {
                /* trap if INVALIDTRAP enabled */
                if (Is_invalidtrap_enabled())
                    return(INVALIDEXCEPTION);
                /* make NaN quiet */
                Set_invalidflag();
                Sgl_set_quiet(opnd1);
            }
            /*
             * is second operand a signaling NaN?
             */
            else if (Sgl_is_signalingnan(opnd2)) {
                /* trap if INVALIDTRAP enabled */
                if (Is_invalidtrap_enabled())
                    return(INVALIDEXCEPTION);
                /* make NaN quiet */
                Set_invalidflag();
                Sgl_set_quiet(opnd2);
                *dstptr = opnd2;
                return(NOEXCEPTION);
            }
            /*
             * return quiet NaN
             */
            *dstptr = opnd1;
            return(NOEXCEPTION);
        }
    }
    /*
     * check second operand for NaN's or infinity
     */
    if (Sgl_isinfinity_exponent(opnd2)) {
        if (Sgl_iszero_mantissa(opnd2)) {
            if (Sgl_iszero_exponentmantissa(opnd1)) {
                /* invalid since operands are zero & infinity */
                if (Is_invalidtrap_enabled())
                    return(INVALIDEXCEPTION);
                Set_invalidflag();
                Sgl_makequietnan(opnd2);
                *dstptr = opnd2;
                return(NOEXCEPTION);
            }
            /*
             * return infinity
             */
            Sgl_setinfinity_exponentmantissa(result);
            *dstptr = result;
            return(NOEXCEPTION);
        }
        /*
         * is NaN; signaling or quiet?
         */
        if (Sgl_isone_signaling(opnd2)) {
            /* trap if INVALIDTRAP enabled */
            if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);

            /* make NaN quiet */
            Set_invalidflag();
            Sgl_set_quiet(opnd2);
        }
        /*
         * return quiet NaN
         */
        *dstptr = opnd2;
        return(NOEXCEPTION);
    }
    /*
     * Generate exponent
     */
    dest_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;

    /*
     * Generate mantissa
     */
    if (Sgl_isnotzero_exponent(opnd1)) {
        /* set hidden bit */
        Sgl_clear_signexponent_set_hidden(opnd1);
    }
    else {
        /* check for zero */
        if (Sgl_iszero_mantissa(opnd1)) {
            Sgl_setzero_exponentmantissa(result);
            *dstptr = result;
            return(NOEXCEPTION);
        }
        /* is denormalized, adjust exponent */
        Sgl_clear_signexponent(opnd1);
        Sgl_leftshiftby1(opnd1);
        Sgl_normalize(opnd1,dest_exponent);
    }
    /* opnd2 needs to have hidden bit set with msb in hidden bit */
    if (Sgl_isnotzero_exponent(opnd2)) {
        Sgl_clear_signexponent_set_hidden(opnd2);
    }
    else {
        /* check for zero */
        if (Sgl_iszero_mantissa(opnd2)) {
            Sgl_setzero_exponentmantissa(result);
            *dstptr = result;
            return(NOEXCEPTION);
        }
        /* is denormalized; want to normalize */
        Sgl_clear_signexponent(opnd2);
        Sgl_leftshiftby1(opnd2);
        Sgl_normalize(opnd2,dest_exponent);
    }

    /* Multiply two source mantissas together */

    Sgl_leftshiftby4(opnd2);     /* make room for guard bits */
    Sgl_setzero(opnd3);
    /*
     * Four bits at a time are inspected in each loop, and a
     * simple shift and add multiply algorithm is used.
     */
    for (count=1; count<SGL_P; count+=4) {
        stickybit |= Slow4(opnd3);
        Sgl_rightshiftby4(opnd3);
        if (Sbit28(opnd1)) Sall(opnd3) += (Sall(opnd2) << 3);
        if (Sbit29(opnd1)) Sall(opnd3) += (Sall(opnd2) << 2);
        if (Sbit30(opnd1)) Sall(opnd3) += (Sall(opnd2) << 1);
        if (Sbit31(opnd1)) Sall(opnd3) += Sall(opnd2);
        Sgl_rightshiftby4(opnd1);
    }
    /* make sure result is left-justified */
    if (Sgl_iszero_sign(opnd3)) {
        Sgl_leftshiftby1(opnd3);
    }
    else {
        /* result mantissa >= 2. */
        dest_exponent++;
    }
    /* check for denormalized result */
    while (Sgl_iszero_sign(opnd3)) {
        Sgl_leftshiftby1(opnd3);
        dest_exponent--;
    }
    /*
     * check for guard, sticky and inexact bits
     */
    stickybit |= Sgl_all(opnd3) << (SGL_BITLENGTH - SGL_EXP_LENGTH + 1);
    guardbit = Sbit24(opnd3);
    inexact = guardbit | stickybit;

    /* re-align mantissa */
    Sgl_rightshiftby8(opnd3);

    /*
     * round result
     */
    if (inexact && (dest_exponent>0 || Is_underflowtrap_enabled())) {
        Sgl_clear_signexponent(opnd3);
        switch (Rounding_mode()) {
        case ROUNDPLUS:
            if (Sgl_iszero_sign(result))
                Sgl_increment(opnd3);
            break;
        case ROUNDMINUS:
            if (Sgl_isone_sign(result))
                Sgl_increment(opnd3);
            break;
        case ROUNDNEAREST:
            if (guardbit) {
                if (stickybit || Sgl_isone_lowmantissa(opnd3))
                    Sgl_increment(opnd3);
            }
        }
        if (Sgl_isone_hidden(opnd3)) dest_exponent++;
    }
    Sgl_set_mantissa(result,opnd3);

    /*
     * Test for overflow
     */
    if (dest_exponent >= SGL_INFINITY_EXPONENT) {
        /* trap if OVERFLOWTRAP enabled */
        if (Is_overflowtrap_enabled()) {
            /*
             * Adjust bias of result
             */
            Sgl_setwrapped_exponent(result,dest_exponent,ovfl);
            *dstptr = result;
            if (inexact)
                if (Is_inexacttrap_enabled())
                    return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
                else Set_inexactflag();
            return(OVERFLOWEXCEPTION);
        }
        inexact = TRUE;
        Set_overflowflag();
        /* set result to infinity or largest number */
        Sgl_setoverflow(result);
    }
    /*
     * Test for underflow
     */
    else if (dest_exponent <= 0) {
        /* trap if UNDERFLOWTRAP enabled */
        if (Is_underflowtrap_enabled()) {
            /*
             * Adjust bias of result
             */
            Sgl_setwrapped_exponent(result,dest_exponent,unfl);
            *dstptr = result;
            if (inexact)
                if (Is_inexacttrap_enabled())
                    return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
                else Set_inexactflag();
            return(UNDERFLOWEXCEPTION);
        }

        /* Determine if should set underflow flag */
        is_tiny = TRUE;
        if (dest_exponent == 0 && inexact) {
            switch (Rounding_mode()) {
            case ROUNDPLUS:
                if (Sgl_iszero_sign(result)) {
                    Sgl_increment(opnd3);
                    if (Sgl_isone_hiddenoverflow(opnd3))
                        is_tiny = FALSE;
                    Sgl_decrement(opnd3);
                }
                break;
            case ROUNDMINUS:
                if (Sgl_isone_sign(result)) {
                    Sgl_increment(opnd3);
                    if (Sgl_isone_hiddenoverflow(opnd3))
                        is_tiny = FALSE;
                    Sgl_decrement(opnd3);
                }
                break;
            case ROUNDNEAREST:
                if (guardbit && (stickybit ||
                                 Sgl_isone_lowmantissa(opnd3))) {
                    Sgl_increment(opnd3);
                    if (Sgl_isone_hiddenoverflow(opnd3))
                        is_tiny = FALSE;
                    Sgl_decrement(opnd3);
                }
                break;
            }
        }

        /*
         * denormalize result or set to signed zero
         */
        stickybit = inexact;
        Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact);

        /* return zero or smallest number */
        if (inexact) {
            switch (Rounding_mode()) {
            case ROUNDPLUS:
                if (Sgl_iszero_sign(result)) {
                    Sgl_increment(opnd3);
                }
                break;
            case ROUNDMINUS:
                if (Sgl_isone_sign(result)) {
                    Sgl_increment(opnd3);
                }
                break;
            case ROUNDNEAREST:
                if (guardbit && (stickybit ||
                                 Sgl_isone_lowmantissa(opnd3))) {
                    Sgl_increment(opnd3);
                }
                break;
            }
            if (is_tiny) Set_underflowflag();
        }
        Sgl_set_exponentmantissa(result,opnd3);
    }
    else Sgl_set_exponent(result,dest_exponent);
    *dstptr = result;

    /* check for inexact */
    if (inexact) {
        if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
        else Set_inexactflag();
    }
    return(NOEXCEPTION);
}
Ejemplo n.º 4
0
int
sgl_fdiv (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
	  sgl_floating_point * dstptr, unsigned int *status)
{
	register unsigned int opnd1, opnd2, opnd3, result;
	register int dest_exponent, count;
	register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
	boolean is_tiny;

	opnd1 = *srcptr1;
	opnd2 = *srcptr2;
	/* 
	 * set sign bit of result 
	 */
	if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result);  
	else Sgl_setzero(result);
	/*
	 * check first operand for NaN's or infinity
	 */
	if (Sgl_isinfinity_exponent(opnd1)) {
		if (Sgl_iszero_mantissa(opnd1)) {
			if (Sgl_isnotnan(opnd2)) {
				if (Sgl_isinfinity(opnd2)) {
					/* 
					 * invalid since both operands 
					 * are infinity 
					 */
					if (Is_invalidtrap_enabled()) 
                                		return(INVALIDEXCEPTION);
                                	Set_invalidflag();
                                	Sgl_makequietnan(result);
					*dstptr = result;
					return(NOEXCEPTION);
				}
				/*
			 	 * return infinity
			 	 */
				Sgl_setinfinity_exponentmantissa(result);
				*dstptr = result;
				return(NOEXCEPTION);
			}
		}
		else {
                	/*
                 	 * is NaN; signaling or quiet?
                 	 */
                	if (Sgl_isone_signaling(opnd1)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd1);
                	}
			/* 
			 * is second operand a signaling NaN? 
			 */
			else if (Sgl_is_signalingnan(opnd2)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled())
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Sgl_set_quiet(opnd2);
                		*dstptr = opnd2;
                		return(NOEXCEPTION);
			}
                	/*
                 	 * return quiet NaN
                 	 */
                	*dstptr = opnd1;
                	return(NOEXCEPTION);
		}
	}
	/*
	 * check second operand for NaN's or infinity
	 */
	if (Sgl_isinfinity_exponent(opnd2)) {
		if (Sgl_iszero_mantissa(opnd2)) {
			/*
			 * return zero
			 */
			Sgl_setzero_exponentmantissa(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
                /*
                 * is NaN; signaling or quiet?
                 */
                if (Sgl_isone_signaling(opnd2)) {
                        /* trap if INVALIDTRAP enabled */
                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        /* make NaN quiet */
                        Set_invalidflag();
                        Sgl_set_quiet(opnd2);
                }
                /*
                 * return quiet NaN
                 */
                *dstptr = opnd2;
                return(NOEXCEPTION);
	}
	/*
	 * check for division by zero
	 */
	if (Sgl_iszero_exponentmantissa(opnd2)) {
		if (Sgl_iszero_exponentmantissa(opnd1)) {
			/* invalid since both operands are zero */
			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        Set_invalidflag();
                        Sgl_makequietnan(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
		if (Is_divisionbyzerotrap_enabled())
                        return(DIVISIONBYZEROEXCEPTION);
                Set_divisionbyzeroflag();
                Sgl_setinfinity_exponentmantissa(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}
	/*
	 * Generate exponent 
	 */
	dest_exponent = Sgl_exponent(opnd1) - Sgl_exponent(opnd2) + SGL_BIAS;

	/*
	 * Generate mantissa
	 */
	if (Sgl_isnotzero_exponent(opnd1)) {
		/* set hidden bit */
		Sgl_clear_signexponent_set_hidden(opnd1);
	}
	else {
		/* check for zero */
		if (Sgl_iszero_mantissa(opnd1)) {
			Sgl_setzero_exponentmantissa(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
                /* is denormalized; want to normalize */
                Sgl_clear_signexponent(opnd1);
                Sgl_leftshiftby1(opnd1);
		Sgl_normalize(opnd1,dest_exponent);
	}
	/* opnd2 needs to have hidden bit set with msb in hidden bit */
	if (Sgl_isnotzero_exponent(opnd2)) {
		Sgl_clear_signexponent_set_hidden(opnd2);
	}
	else {
                /* is denormalized; want to normalize */
                Sgl_clear_signexponent(opnd2);
                Sgl_leftshiftby1(opnd2);
		while(Sgl_iszero_hiddenhigh7mantissa(opnd2)) {
			Sgl_leftshiftby8(opnd2);
			dest_exponent += 8;
		}
		if(Sgl_iszero_hiddenhigh3mantissa(opnd2)) {
			Sgl_leftshiftby4(opnd2);
			dest_exponent += 4;
		}
		while(Sgl_iszero_hidden(opnd2)) {
			Sgl_leftshiftby1(opnd2);
			dest_exponent += 1;
		}
	}

	/* Divide the source mantissas */

	/*
	 * A non_restoring divide algorithm is used.
	 */
	Sgl_subtract(opnd1,opnd2,opnd1);
	Sgl_setzero(opnd3);
	for (count=1;count<=SGL_P && Sgl_all(opnd1);count++) {
		Sgl_leftshiftby1(opnd1);
		Sgl_leftshiftby1(opnd3);
		if (Sgl_iszero_sign(opnd1)) {
			Sgl_setone_lowmantissa(opnd3);
			Sgl_subtract(opnd1,opnd2,opnd1);
		}
		else Sgl_addition(opnd1,opnd2,opnd1);
	}
	if (count <= SGL_P) {
		Sgl_leftshiftby1(opnd3);
		Sgl_setone_lowmantissa(opnd3);
		Sgl_leftshift(opnd3,SGL_P-count);
		if (Sgl_iszero_hidden(opnd3)) {
			Sgl_leftshiftby1(opnd3);
			dest_exponent--;
		}
	}
	else {
		if (Sgl_iszero_hidden(opnd3)) {
			/* need to get one more bit of result */
			Sgl_leftshiftby1(opnd1);
			Sgl_leftshiftby1(opnd3);
			if (Sgl_iszero_sign(opnd1)) {
				Sgl_setone_lowmantissa(opnd3);
				Sgl_subtract(opnd1,opnd2,opnd1);
			}
			else Sgl_addition(opnd1,opnd2,opnd1);
			dest_exponent--;
		}
		if (Sgl_iszero_sign(opnd1)) guardbit = TRUE;
		stickybit = Sgl_all(opnd1);
	}
	inexact = guardbit | stickybit;

	/* 
	 * round result 
	 */
	if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) {
		Sgl_clear_signexponent(opnd3);
		switch (Rounding_mode()) {
			case ROUNDPLUS: 
				if (Sgl_iszero_sign(result)) 
					Sgl_increment_mantissa(opnd3);
				break;
			case ROUNDMINUS: 
				if (Sgl_isone_sign(result)) 
					Sgl_increment_mantissa(opnd3);
				break;
			case ROUNDNEAREST:
				if (guardbit) {
			   	if (stickybit || Sgl_isone_lowmantissa(opnd3))
			      	    Sgl_increment_mantissa(opnd3);
				}
		}
		if (Sgl_isone_hidden(opnd3)) dest_exponent++;
	}
	Sgl_set_mantissa(result,opnd3);

        /* 
         * Test for overflow
         */
	if (dest_exponent >= SGL_INFINITY_EXPONENT) {
                /* trap if OVERFLOWTRAP enabled */
                if (Is_overflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(result,dest_exponent,ovfl);
                        *dstptr = result;
                        if (inexact) 
                            if (Is_inexacttrap_enabled())
                                return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return(OVERFLOWEXCEPTION);
                }
		Set_overflowflag();
                /* set result to infinity or largest number */
		Sgl_setoverflow(result);
		inexact = TRUE;
	}
        /* 
         * Test for underflow
         */
	else if (dest_exponent <= 0) {
                /* trap if UNDERFLOWTRAP enabled */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(result,dest_exponent,unfl);
                        *dstptr = result;
                        if (inexact) 
                            if (Is_inexacttrap_enabled())
                                return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return(UNDERFLOWEXCEPTION);
                }

		/* Determine if should set underflow flag */
		is_tiny = TRUE;
		if (dest_exponent == 0 && inexact) {
			switch (Rounding_mode()) {
			case ROUNDPLUS: 
				if (Sgl_iszero_sign(result)) {
					Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
                			    is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			case ROUNDMINUS: 
				if (Sgl_isone_sign(result)) {
					Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
                			    is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit || 
				    Sgl_isone_lowmantissa(opnd3))) {
				      	Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
                			    is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			}
		}

                /*
                 * denormalize result or set to signed zero
                 */
		stickybit = inexact;
		Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact);

		/* return rounded number */ 
		if (inexact) {
			switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Sgl_iszero_sign(result)) {
					Sgl_increment(opnd3);
				}
				break;
			case ROUNDMINUS: 
				if (Sgl_isone_sign(result))  {
					Sgl_increment(opnd3);
				}
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit || 
				    Sgl_isone_lowmantissa(opnd3))) {
			      		Sgl_increment(opnd3);
				}
				break;
			}
                	if (is_tiny) Set_underflowflag();
                }
		Sgl_set_exponentmantissa(result,opnd3);
	}
	else Sgl_set_exponent(result,dest_exponent);
	*dstptr = result;
	/* check for inexact */
	if (inexact) {
		if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
		else  Set_inexactflag();
	}
	return(NOEXCEPTION);
}