RFR: 8347009: Speed ​​up parseInt and parseLong [v5]

[Chen Liang]

On Sun, 5 Jan 2025 11:01:18 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> This is an optimization for decimal Integer.parseInt and Long.parseLong, which improves performance by about 10%. The optimization includes:
>> 1. Improve performance by parsing 2 numbers at a time, which has performance improvements for numbers with length >= 3.
>> 2. It uses charAt(0) for the first number. Assuming that the optimization can eliminate boundary checks, this will be more friendly to parsing numbers with length 1.
>> 3. It removes the reliance on the Character.digit method and eliminates the reliance on the CharacterDataLatin1#DIGITS cache array, which avoids performance degradation caused by cache misses.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   vector digit2

src/java.base/share/classes/java/lang/Integer.java line 581:

> 579:     }
> 580: 
> 581:     static boolean isDigitLatin2(int ch) {

Unused, should be removed

src/java.base/share/classes/jdk/internal/util/DecimalDigits.java line 154:

> 152:             Here we are doing a 2-Byte Vector operation on the short type.
> 153: 
> 154:             x & 0xF0 != 0xC0

Suggestion:

            x & 0xF0 != 0x30

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PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1915043154
PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1915038981