RFR: JDK-8289551: Conversions between bit representations of half precision values and floats

[Raffaello Giulietti]

On Fri, 8 Jul 2022 06:11:22 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> Initial implementation.

test/jdk/java/lang/Float/SixteenBitFormats.java line 239:

> 237:         public static boolean isNaN(short binary16) {
> 238:             return ((binary16 & 0x7c00) == 0x7c00) // Max exponent and...
> 239:                 && ((binary16 & 0x03ff) != 0 );    // significand nonzero.

return (binary16 & 0x7fff) > 0x7c00;

is more concise

test/jdk/java/lang/Float/SixteenBitFormats.java line 244:

> 242:         public static short negate(short binary16) {
> 243:             return (short)(((binary16 & 0x8000) ^ 0x8000) | // Isolate and flip sign bit
> 244:                            (binary16 & 0x7fff));

return (short)(binary16 ^ 0x8000);

is shorter

test/jdk/java/lang/Float/SixteenBitFormats.java line 263:

> 261:         }
> 262:     }
> 263: }

The last invocation to `Integer.compare()` is not correct.
For example, if `bin16_1 = -1 `and `bin16_2 = 1`, the invocation returns 1, which is incorrect.

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PR: https://git.openjdk.org/jdk/pull/9422