RFR: 8294982: Implementation of Classfile API [v43]

[Paul Sandoz]

On Tue, 7 Mar 2023 14:35:22 GMT, Adam Sotona <asotona at openjdk.org> wrote:

>> src/java.base/share/classes/jdk/internal/classfile/impl/EntryMap.java line 176:
>> 
>>> 174:     }
>>> 175: 
>>> 176:     public static long nextPowerOfTwo( long x ) {
>> 
>> If you like you can change the implementation to be:
>> 
>> x = -1 >>> Long.numberOfLeadingZeros(x - 1);
>> return x + 1;
>> 
>> See `ConcurrentHashMap`.
>
> `Long:numberOfLeadingZeros` implementation uses more method calls, conditional statements and binary operations. I would prefer to stick with the current implementation for its speed and simplicity.

`numberOfLeadingZeros` is an intrinsic, so it will compile down to a machine instruction. Up to you.

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PR: https://git.openjdk.org/jdk/pull/10982