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8302028: Port fdlibm atan2 to Java

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Reviewed-by: bpb
This commit is contained in:
Joe Darcy 2023-02-22 22:49:59 +00:00
parent 07e976ac26
commit fcaf871408
6 changed files with 615 additions and 28 deletions
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110
src/java.base/share/classes/java/lang/FdLibm.java
View file

@ -394,6 +394,116 @@ class FdLibm {
}
}
/**
* Returns the angle theta from the conversion of rectangular
* coordinates (x, y) to polar coordinates (r, theta).
*
* Method :
* 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
* 2. Reduce x to positive by (if x and y are unexceptional):
* ARG (x+iy) = arctan(y/x) ... if x > 0,
* ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
*
* Special cases:
*
* ATAN2((anything), NaN ) is NaN;
* ATAN2(NAN , (anything) ) is NaN;
* ATAN2(+-0, +(anything but NaN)) is +-0 ;
* ATAN2(+-0, -(anything but NaN)) is +-pi ;
* ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
* ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
* ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
* ATAN2(+-INF,+INF ) is +-pi/4 ;
* ATAN2(+-INF,-INF ) is +-3pi/4;
* ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
*
* Constants:
* The hexadecimal values are the intended ones for the following
* constants. The decimal values may be used, provided that the
* compiler will convert from decimal to binary accurately enough
* to produce the hexadecimal values shown.
*/
static class Atan2 {
private Atan2() {throw new UnsupportedOperationException();}
private static final double
tiny = 1.0e-300,
pi_o_4 = 0x1.921fb54442d18p-1, // 7.8539816339744827900E-01
pi_o_2 = 0x1.921fb54442d18p0, // 1.5707963267948965580E+00
pi_lo = 0x1.1a62633145c07p-53; // 1.2246467991473531772E-16
static double compute(double y, double x) {
double z;
int k, m, hx, hy, ix, iy;
/*unsigned*/ int lx, ly;
hx = __HI(x);
ix = hx & 0x7fff_ffff;
lx = __LO(x);
hy = __HI(y);
iy = hy&0x7fff_ffff;
ly = __LO(y);
if (Double.isNaN(x) || Double.isNaN(y))
return x + y;
if (((hx - 0x3ff0_0000) | lx) == 0) // x = 1.0
return StrictMath.atan(y);
m = ((hy >> 31) & 1)|((hx >> 30) & 2); // 2*sign(x) + sign(y)
// when y = 0
if ((iy | ly) == 0) {
switch(m) {
case 0:
case 1: return y; // atan(+/-0, +anything) = +/-0
case 2: return Math.PI + tiny; // atan(+0, -anything) = pi
case 3: return -Math.PI - tiny; // atan(-0, -anything) = -pi
}
}
// when x = 0
if ((ix | lx) == 0) {
return (hy < 0)? -pi_o_2 - tiny : pi_o_2 + tiny;
}
// when x is INF
if (ix == 0x7ff0_0000) {
if (iy == 0x7ff0_0000) {
switch(m) {
case 0: return pi_o_4 + tiny; // atan(+INF, +INF)
case 1: return -pi_o_4 - tiny; // atan(-INF, +INF)
case 2: return 3.0*pi_o_4 + tiny; // atan(+INF, -INF)
case 3: return -3.0*pi_o_4 - tiny; // atan(-INF, -INF)
}
} else {
switch(m) {
case 0: return 0.0; // atan(+..., +INF)
case 1: return -0.0; // atan(-..., +INF)
case 2: return Math.PI + tiny; // atan(+..., -INF)
case 3: return -Math.PI - tiny; // atan(-..., -INF)
}
}
}
// when y is INF
if (iy == 0x7ff0_0000) {
return (hy < 0)? -pi_o_2 - tiny : pi_o_2 + tiny;
}
// compute y/x
k = (iy - ix) >> 20;
if (k > 60) { // |y/x| > 2**60
z = pi_o_2+0.5*pi_lo;
} else if (hx < 0 && k < -60) { // |y|/x < -2**60
z = 0.0;
} else { // safe to do y/x
z = StrictMath.atan(Math.abs(y/x));
}
switch (m) {
case 0: return z; // atan(+, +)
case 1: return -z; // atan(-, +)
case 2: return Math.PI - (z - pi_lo); // atan(+, -)
default: return (z - pi_lo) - Math.PI; // atan(-, -), case 3
}
}
}
/**
* cbrt(x)
* Return cube root of x

4
src/java.base/share/classes/java/lang/StrictMath.java
View file

@ -547,7 +547,9 @@ public final class StrictMath {
* in polar coordinates that corresponds to the point
* (<i>x</i>,&nbsp;<i>y</i>) in Cartesian coordinates.
*/
public static native double atan2(double y, double x);
public static double atan2(double y, double x) {
return FdLibm.Atan2.compute(y, x);
}
/**
* Returns the value of the first argument raised to the power of the