static double
MakeLowPrecisionDouble(
    int signum,			/* 1 if the number is negative, 0 otherwise */
    Tcl_WideUInt significand,	/* Significand of the number */
    int numSigDigs,		/* Number of digits in the significand */
    long exponent)		/* Power of ten */
{

    mp_int significandBig;	/* Significand expressed as a bignum. */

    /*
     * With gcc on x86, the floating point rounding mode is double-extended.
     * This causes the result of double-precision calculations to be rounded
     * twice: once to the precision of double-extended and then again to the
     * precision of double. Double-rounding introduces gratuitous errors of 1
     * ulp, so we need to change rounding mode to 53-bits. We also make
     * 'retval' volatile, so that it doesn't get promoted to a register.
     */
    volatile double retval;		/* Value of the number. */


    /*
     * Test for zero significand, which requires explicit construction
     * of -0.0. (Unary minus returns a positive zero.)
     */

    if (significand == 0) {
	return copysign(0.0, -signum);
    }

    /*
     * Set the FP control word for 53 bits, WARNING: It must be reset
     * before returning.
     */
    TCL_IEEE_DOUBLE_ROUNDING;

    if (numSigDigs <= QUICK_MAX) {
	if (exponent >= 0) {
	    if (exponent <= mmaxpow) {
		/*
		 * The significand is an exact integer, and so is
		 * 10**exponent. The product will be correct to within 1/2 ulp
		 * without special handling.

static double
MakeHighPrecisionDouble(
    int signum,			/* 1=negative, 0=nonnegative */
    mp_int *significand,	/* Exact significand of the number */
    int numSigDigs,		/* Number of significant digits */
    long exponent)		/* Power of 10 by which to multiply */
{

    int machexp = 0;		/* Machine exponent of a power of 10. */

    /*
     * With gcc on x86, the floating point rounding mode is double-extended.
     * This causes the result of double-precision calculations to be rounded
     * twice: once to the precision of double-extended and then again to the
     * precision of double. Double-rounding introduces gratuitous errors of 1
     * ulp, so we need to change rounding mode to 53-bits. We also make
     * 'retval' volatile to make sure that it doesn't get promoted to a
     * register.
     */
    volatile double retval;


    /*

     * A zero significand requires explicit construction of -0.0.
     * (Unary minus returns positive zero.)
     */

    if (mp_iszero(significand)) {
	return copysign(0.0, -signum);
    }

    /*
     * Set the 53-bit rounding mode. WARNING: It must be reset before
     * returning.
     */
    TCL_IEEE_DOUBLE_ROUNDING;

    /*
     * Make quick checks for over/underflow. Be careful to avoid
     * integer overflow when calculating with 'exponent'.
     */
    if (exponent >= 0 && exponent-1 > maxDigits-numSigDigs) {
	retval = HUGE_VAL;
	goto returnValue;
    } else if (exponent < 0 && numSigDigs+exponent < minDigits+1) {
	retval = 0.0;
	goto returnValue;
    }