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8362376: Use @Stable annotation in Java FDLIBM implementation #26341

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7fec151
JDK-8362376: Use @Stable annotation in Java FDLIBM implementation
jddarcy Jul 16, 2025
a7b86ee
Respond to review feedback and update copyright.
jddarcy Jul 17, 2025
5e1233b
Implement review feedback.
jddarcy Jul 17, 2025
f33c74f
Respond to review feedback.
jddarcy Jul 29, 2025
0746add
Cleanup and respond to review comments.
jddarcy Aug 11, 2025
f0c9b48
Small refinement and add test cases
jddarcy Aug 11, 2025
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51 changes: 30 additions & 21 deletions src/java.base/share/classes/java/lang/FdLibm.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand All @@ -25,6 +25,8 @@

package java.lang;

import jdk.internal.vm.annotation.Stable;

/**
* Port of the "Freely Distributable Math Library", version 5.3, from
* C to Java.
Expand Down Expand Up @@ -451,8 +453,10 @@ static double compute(double x) {
*/
private static final double
pio4 = 0x1.921fb54442d18p-1, // 7.85398163397448278999e-01
pio4lo= 0x1.1a62633145c07p-55, // 3.06161699786838301793e-17
T[] = {
pio4lo= 0x1.1a62633145c07p-55; // 3.06161699786838301793e-17
@Stable
private static final double[]
T = {
0x1.5555555555563p-2, // 3.33333333333334091986e-01
0x1.111111110fe7ap-3, // 1.33333333333201242699e-01
0x1.ba1ba1bb341fep-5, // 5.39682539762260521377e-02
Expand Down Expand Up @@ -546,6 +550,7 @@ static final class RemPio2 {
/*
* Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi
*/
@Stable
private static final int[] two_over_pi = {
0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,
0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,
Expand All @@ -560,6 +565,7 @@ static final class RemPio2 {
0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,
};

@Stable
private static final int[] npio2_hw = {
0x3FF921FB, 0x400921FB, 0x4012D97C, 0x401921FB, 0x401F6A7A, 0x4022D97C,
0x4025FDBB, 0x402921FB, 0x402C463A, 0x402F6A7A, 0x4031475C, 0x4032D97C,
Expand Down Expand Up @@ -807,8 +813,10 @@ static final class KernelRemPio2 {
* to produce the hexadecimal values shown.
*/

@Stable
private static final int init_jk[] = {2, 3, 4, 6}; // initial value for jk
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Suggested change
private static final int init_jk[] = {2, 3, 4, 6}; // initial value for jk
@Stable private static final int init_jk[] = {2, 3, 4, 6}; // initial value for jk

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Suggested change
private static final int init_jk[] = {2, 3, 4, 6}; // initial value for jk
@Stable
private static final int[] init_jk = {2, 3, 4, 6}; // initial value for jk

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Missed that array on my edit; will add. Thanks.


@Stable
private static final double PIo2[] = {
0x1.921fb4p0, // 1.57079625129699707031e+00
0x1.4442dp-24, // 7.54978941586159635335e-08
Expand Down Expand Up @@ -1232,20 +1240,23 @@ static double compute(double x) {
static final class Atan {
private Atan() {throw new UnsupportedOperationException();}

@Stable
private static final double atanhi[] = {
0x1.dac670561bb4fp-2, // atan(0.5)hi 4.63647609000806093515e-01
0x1.921fb54442d18p-1, // atan(1.0)hi 7.85398163397448278999e-01
0x1.f730bd281f69bp-1, // atan(1.5)hi 9.82793723247329054082e-01
0x1.921fb54442d18p0, // atan(inf)hi 1.57079632679489655800e+00
};

@Stable
private static final double atanlo[] = {
0x1.a2b7f222f65e2p-56, // atan(0.5)lo 2.26987774529616870924e-17
0x1.1a62633145c07p-55, // atan(1.0)lo 3.06161699786838301793e-17
0x1.007887af0cbbdp-56, // atan(1.5)lo 1.39033110312309984516e-17
0x1.1a62633145c07p-54, // atan(inf)lo 6.12323399573676603587e-17
};

@Stable
private static final double aT[] = {
0x1.555555555550dp-2, // 3.33333333333329318027e-01
-0x1.999999998ebc4p-3, // -1.99999999998764832476e-01
Expand Down Expand Up @@ -2245,12 +2256,8 @@ else if (j < 0xBB67A)

// Compute ss = s_h + s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5)

final double BP[] = {1.0,
1.5};
final double DP_H[] = {0.0,
0x1.2b80_34p-1}; // 5.84962487220764160156e-01
final double DP_L[] = {0.0,
0x1.cfde_b43c_fd006p-27};// 1.35003920212974897128e-08
final double DP_H = 0x1.2b80_34p-1; // 5.84962487220764160156e-01
final double DP_L = 0x1.cfde_b43c_fd006p-27; // 1.35003920212974897128e-08

// Poly coefs for (3/2)*(log(x)-2s-2/3*s**3
final double L1 = 0x1.3333_3333_33303p-1; // 5.99999999999994648725e-01
Expand All @@ -2259,15 +2266,17 @@ else if (j < 0xBB67A)
final double L4 = 0x1.1746_0a91_d4101p-2; // 2.72728123808534006489e-01
final double L5 = 0x1.d864_a93c_9db65p-3; // 2.30660745775561754067e-01
final double L6 = 0x1.a7e2_84a4_54eefp-3; // 2.06975017800338417784e-01
u = x_abs - BP[k]; // BP[0]=1.0, BP[1]=1.5
v = 1.0 / (x_abs + BP[k]);

double BP_k = 1.0 + 0.5*k; // BP[0]=1.0, BP[1]=1.5
u = x_abs - BP_k;
v = 1.0 / (x_abs + BP_k);
ss = u * v;
s_h = ss;
s_h = __LO(s_h, 0);
// t_h=x_abs + BP[k] High
t_h = 0.0;
t_h = __HI(t_h, ((ix >> 1) | 0x20000000) + 0x00080000 + (k << 18) );
t_l = x_abs - (t_h - BP[k]);
t_l = x_abs - (t_h - BP_k);
s_l = v * ((u - s_h * t_h) - s_h * t_l);
// Compute log(x_abs)
s2 = ss * ss;
Expand All @@ -2285,12 +2294,12 @@ else if (j < 0xBB67A)
p_h = __LO(p_h, 0);
p_l = v - (p_h - u);
z_h = CP_H * p_h; // CP_H + CP_L = 2/(3*log2)
z_l = CP_L * p_h + p_l * CP + DP_L[k];
z_l = CP_L * p_h + p_l * CP + DP_L*k;
// log2(x_abs) = (ss + ..)*2/(3*log2) = n + DP_H + z_h + z_l
t = (double)n;
t1 = (((z_h + z_l) + DP_H[k]) + t);
t1 = (((z_h + z_l) + DP_H*k) + t);
t1 = __LO(t1, 0);
t2 = z_l - (((t1 - t) - DP_H[k]) - z_h);
t2 = z_l - (((t1 - t) - DP_H*k) - z_h);
}

// Split up y into (y1 + y2) and compute (y1 + y2) * (t1 + t2)
Expand Down Expand Up @@ -2430,13 +2439,13 @@ else if (j < 0xBB67A)
static final class Exp {
private Exp() {throw new UnsupportedOperationException();}

private static final double[] half = {0.5, -0.5,};
private static final double huge = 1.0e+300;
private static final double twom1000= 0x1.0p-1000; // 9.33263618503218878990e-302 = 2^-1000
private static final double o_threshold= 0x1.62e42fefa39efp9; // 7.09782712893383973096e+02
private static final double u_threshold= -0x1.74910d52d3051p9; // -7.45133219101941108420e+02;
private static final double[] ln2HI ={ 0x1.62e42feep-1, // 6.93147180369123816490e-01
-0x1.62e42feep-1}; // -6.93147180369123816490e-01
private static final double ln2HI = 0x1.62e42feep-1; // 6.93147180369123816490e-01

@Stable
private static final double[] ln2LO ={ 0x1.a39ef35793c76p-33, // 1.90821492927058770002e-10
-0x1.a39ef35793c76p-33}; // -1.90821492927058770002e-10
private static final double invln2 = 0x1.71547652b82fep0; // 1.44269504088896338700e+00
Expand Down Expand Up @@ -2478,13 +2487,13 @@ public static double compute(double x) {
/* argument reduction */
if (hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
if(hx < 0x3FF0A2B2) { /* and |x| < 1.5 ln2 */
hi = x - ln2HI[xsb];
hi = x - ln2HI*(1 - 2*xsb); /* +/- ln2HI */
lo=ln2LO[xsb];
k = 1 - xsb - xsb;
} else {
k = (int)(invln2 * x + half[xsb]);
k = (int)(invln2 * x + 0.5 * (1 - 2*xsb) /* +/- 0.5 */ );
t = k;
hi = x - t*ln2HI[0]; /* t*ln2HI is exact here */
hi = x - t*ln2HI; /* t*ln2HI is exact here */
lo = t*ln2LO[0];
}
x = hi - lo;
Expand Down
8 changes: 6 additions & 2 deletions test/jdk/java/lang/StrictMath/ExpTests.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, 2024, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand All @@ -23,7 +23,7 @@

/*
* @test
* @bug 8139688
* @bug 8139688 8362376
* @key randomness
* @library /test/lib
* @build jdk.test.lib.RandomFactory
Expand Down Expand Up @@ -87,6 +87,10 @@ static int testExp() {
{-0x1.49f33ad2c1c58p+9, 0x1.f3ccc815431b6p-953},
{+0x1.fce66609f7428p+5, 0x1.b59724cb0bc4cp91},
{-0x1.49f33ad2c1c58p+9, 0x1.f3ccc815431b6p-953},

// Test values near 0.5*ln*(2) and 1.5*ln(2) to check refactoring
{0.34657359027997275, 1.4142135623730951},
{1.0397207708399183, 2.828427124746191},
};

for(double[] testCase: testCases)
Expand Down
19 changes: 17 additions & 2 deletions test/jdk/java/lang/StrictMath/PowTests.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand All @@ -23,7 +23,7 @@

/*
* @test
* @bug 8136874
* @bug 8136874 8362376
* @summary Tests for StrictMath.pow
*/

Expand Down Expand Up @@ -283,6 +283,21 @@ private static int testPow() {
0x1.ffffffffffd9fp1023, // 1.7976931348621944E308
},

// Check refactoring, abs(y) < 2^31, x < sqrt(3/2), x < sqrt(3)
{1.2, // x < sqrt(3/2)
5.0,
2.4883199999999994
},

{1.4142135623730951, // sqrt(3/2) < x < sqrt(3)
5.0,
5.656854249492382
},

{2.23606797749979, // x > sqrt(3)
5.0,
55.901699437494756
},
};

for (double[] testCase: testCases)
Expand Down