Port fdlibm hypot to Java

FULL PRODUCT VERSION :
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
Math.hypot is excessively slow. Running it in a simple timing loop gives a run time of about 800 nanoseconds on an i7 2.67 GHz. The pure Java method provided below runs in 40 nanoseconds.


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
/**
* <b>hypot</b>
* @param x
* @param y
* @return sqrt(x*x +y*y) without intermediate overflow or underflow.
* @Note Math.hypot is unnecessarily slow. This returns the identical result to
* Math.hypot with reasonable run times (~40 nsec vs. 800 nsec).
* <p>The logic for computing z is copied from "Freely Distributable Math Library"
* fdlibm's e_hypot.c. This minimizes rounding error to provide 1 ulb accuracy.
*/
public static double hypot(double x, double y) {

if (Double.isInfinite(x) || Double.isInfinite(y)) return Double.POSITIVE_INFINITY;
if (Double.isNaN(x) || Double.isNaN(y)) return Double.NaN;

x = Math.abs(x);
y = Math.abs(y);

if (x < y) {
double d = x;
x = y;
y = d;
}

int xi = Math.getExponent(x);
int yi = Math.getExponent(y);

if (xi > yi + 27) return x;

int bias = 0;
if (xi > 510 || xi < -511) {
bias = xi;
x = Math.scalb(x, -bias);
y = Math.scalb(y, -bias);
}

// translated from "Freely Distributable Math Library" e_hypot.c to minimize rounding errors
double z = 0;
if (x > 2*y) {
double x1 = Double.longBitsToDouble(Double.doubleToLongBits(x) & 0xffffffff00000000L);
double x2 = x - x1;
z = Math.sqrt(x1*x1 + (y*y + x2*(x+x1)));
} else {
double t = 2 * x;
double t1 = Double.longBitsToDouble(Double.doubleToLongBits(t) & 0xffffffff00000000L);
double t2 = t - t1;
double y1 = Double.longBitsToDouble(Double.doubleToLongBits(y) & 0xffffffff00000000L);
double y2 = y - y1;
double x_y = x - y;
z = Math.sqrt(t1*y1 + (x_y*x_y + (t1*y2 + t2*y))); // Note: 2*x*y <= x*x + y*y
}

if (bias == 0) {
return z;
} else {
return Math.scalb(z, bias);
}
}