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8369123: Still more small Float16 refactorings #27625

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761f16f
JDK-8369123: Still more small Float16 refactorings
jddarcy Oct 3, 2025
be2b4ab
Remove unneeded use of "Float16.".
jddarcy Oct 3, 2025
458bf67
Merge branch 'master' into JDK-8369123
jddarcy Oct 5, 2025
197dbfe
Respond to review feedback.
jddarcy Oct 6, 2025
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52 changes: 32 additions & 20 deletions src/jdk.incubator.vector/share/classes/jdk/incubator/vector/Float16.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@
import static jdk.incubator.vector.Float16Consts.EXP_BIT_MASK;
import static jdk.incubator.vector.Float16Consts.SIGNIF_BIT_MASK;
import static jdk.incubator.vector.Float16Consts.MAG_BIT_MASK;
import static jdk.incubator.vector.Float16Consts.EXP_BIAS;
import static jdk.incubator.vector.Float16Consts.SIGNIFICAND_WIDTH;

import static java.lang.Float.float16ToFloat;
import static java.lang.Float.floatToFloat16;
Expand Down Expand Up @@ -95,19 +97,26 @@
* <cite>IEEE Standard for Floating-Point Arithmetic</cite></a>
*/

// Currently Float16 is a value-based class and in future it is
// Currently Float16 is a value-based class and in the future it is
// expected to be aligned with Value Classes and Object as described in
// JEP-401 (https://openjdk.org/jeps/401).
@jdk.internal.ValueBased
public final class Float16
extends Number
implements Comparable<Float16> {
/** @serial */

/**
* Primitive {@code short} field to hold the bits of the {@code Float16}.
* @serial
*/
private final short value;

private static final long serialVersionUID = 16; // May not be needed when a value class?

// Functionality for future consideration:
// IEEEremainder / remainder operator remainder
// IEEEremainder and separate % operator remainder (which are
// defined to use different rounding modes, see JLS sections 15.4
// and 15.17.3).

// Do *not* define any public constructors
/**
Expand Down Expand Up @@ -147,8 +156,14 @@ private Float16(short bits) {
*/
public static final Float16 NaN = valueOf(Float.NaN);

/**
* A constant holding a zero (0.0) of type {@code Float16}.
*/
private static final Float16 ZERO = valueOf(0);

/**
* A constant holding a one (1.0) of type {@code Float16}.
*/
private static final Float16 ONE = valueOf(1);

/**
Expand Down Expand Up @@ -316,10 +331,10 @@ public static Float16 valueOf(int value) {
* @param value a {@code long} value.
*/
public static Float16 valueOf(long value) {
if (value <= -65_520L) { // -(Float16.MAX_VALUE + Float16.ulp(Float16.MAX_VALUE) / 2)
if (value <= -65_520L) { // -(MAX_VALUE + ulp(MAX_VALUE) / 2)
return NEGATIVE_INFINITY;
} else {
if (value >= 65_520L) { // Float16.MAX_VALUE + Float16.ulp(Float16.MAX_VALUE) / 2
if (value >= 65_520L) { // MAX_VALUE + ulp(MAX_VALUE) / 2
return POSITIVE_INFINITY;
}
// Remaining range of long, the integers in approx. +/-
Expand Down Expand Up @@ -427,9 +442,8 @@ public static Float16 valueOf(double d) {
// to implement a carry out from rounding the significand.
assert (0xf800 & signif_bits) == 0x0;

// Exponent bias adjust in the representation is equal to MAX_EXPONENT.
return new Float16((short)(sign_bit |
( ((exp + MAX_EXPONENT) << (PRECISION - 1)) + signif_bits ) ));
( ((exp + EXP_BIAS) << (PRECISION - 1)) + signif_bits) ));
}

/**
Expand Down Expand Up @@ -468,7 +482,7 @@ public static Float16 valueOf(String s) throws NumberFormatException {
// characters rather than codepoints.

if (trialResult == 0.0 // handles signed zeros
|| Math.abs(trialResult) > (65504.0 + 32.0) || // Float.MAX_VALUE + ulp(MAX_VALUE),
|| Math.abs(trialResult) > (65504.0 + 32.0) || // MAX_VALUE + ulp(MAX_VALUE),
// handles infinities too
Double.isNaN(trialResult) ||
noDoubleRoundingToFloat16(trialResult)) {
Expand Down Expand Up @@ -899,7 +913,7 @@ public int hashCode() {
*/
public static int hashCode(Float16 value) {
// Use bit-pattern of canonical NaN for hashing.
Float16 f16 = isNaN(value) ? Float16.NaN : value;
Float16 f16 = isNaN(value) ? NaN : value;
return (int)float16ToRawShortBits(f16);
}

Expand Down Expand Up @@ -946,7 +960,7 @@ public static short float16ToRawShortBits(Float16 f16) {
*/
public static short float16ToShortBits(Float16 f16) {
if (isNaN(f16)) {
return Float16.NaN.value;
return NaN.value;
}
return f16.value;
}
Expand Down Expand Up @@ -1531,8 +1545,8 @@ public static int getExponent(Float16 f16) {
*/
/*package*/ static int getExponent0(short bits) {
// package private to be usable in java.lang.Float.
int bin16ExpBits = 0x0000_7c00 & bits; // Five exponent bits.
return (bin16ExpBits >> (PRECISION - 1)) - 15;
int bin16ExpBits = EXP_BIT_MASK & bits; // Five exponent bits.
return (bin16ExpBits >> (PRECISION - 1)) - EXP_BIAS;
}

/**
Expand Down Expand Up @@ -1563,10 +1577,10 @@ public static Float16 ulp(Float16 f16) {
int exp = getExponent(f16);

return switch(exp) {
case MAX_EXPONENT + 1 -> abs(f16); // NaN or infinity
case MIN_EXPONENT - 1 -> Float16.MIN_VALUE; // zero or subnormal
case MAX_EXPONENT + 1 -> abs(f16); // NaN or infinity
case MIN_EXPONENT - 1 -> MIN_VALUE; // zero or subnormal
default -> {
assert exp <= MAX_EXPONENT && exp >= MIN_EXPONENT;
assert exp <= MAX_EXPONENT && exp >= MIN_EXPONENT: "Out of range exponent";
// ulp(x) is usually 2^(SIGNIFICAND_WIDTH-1)*(2^ilogb(x))
// Let float -> float16 conversion handle encoding issues.
yield scalb(ONE, exp - (PRECISION - 1));
Expand Down Expand Up @@ -1687,8 +1701,7 @@ public static Float16 scalb(Float16 v, int scaleFactor) {
// nonzero value by it would be guaranteed to over or
// underflow; due to rounding, scaling down takes an
// additional power of two which is reflected here
final int MAX_SCALE = Float16.MAX_EXPONENT + -Float16.MIN_EXPONENT +
Float16Consts.SIGNIFICAND_WIDTH + 1;
final int MAX_SCALE = MAX_EXPONENT + -MIN_EXPONENT + SIGNIFICAND_WIDTH + 1;

// Make sure scaling factor is in a reasonable range
scaleFactor = Math.clamp(scaleFactor, -MAX_SCALE, MAX_SCALE);
Expand Down Expand Up @@ -1725,9 +1738,8 @@ public static Float16 scalb(Float16 v, int scaleFactor) {
* @see Math#copySign(double, double)
*/
public static Float16 copySign(Float16 magnitude, Float16 sign) {
return shortBitsToFloat16((short) ((float16ToRawShortBits(sign) & SIGN_BIT_MASK) |
(float16ToRawShortBits(magnitude) &
(EXP_BIT_MASK | SIGNIF_BIT_MASK) )));
return shortBitsToFloat16((short)((float16ToRawShortBits(sign) & SIGN_BIT_MASK) |
(float16ToRawShortBits(magnitude) & MAG_BIT_MASK)));
}

/**
Expand Down