RFR: 8347009: Speed ​​up parseInt and parseLong [v13]

[Raffaello Giulietti]

On Sat, 1 Feb 2025 10:07:25 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 with a new target base due to a merge or a rebase. The pull request now contains 29 commits:
> 
>  - Merge remote-tracking branch 'upstream/master' into optim_parse_int_long_202501
>    
>    # Conflicts:
>    #	src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
>  - multiply 10
>  - copyright
>  - error message
>  - Merge remote-tracking branch 'upstream/master' into optim_parse_int_long_202501
>    
>    # Conflicts:
>    #	src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
>  - use &
>  - from @rgiulietti
>  - remove unused
>  - Update src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
>    
>    Co-authored-by: Chen Liang <liach at openjdk.org>
>  - vector digit2
>  - ... and 19 more: https://git.openjdk.org/jdk/compare/651ac3cc...1fb40bb9

src/java.base/share/classes/java/lang/Integer.java line 525:

> 523:             return parseInt0(s, radix);
> 524:         }
> 525:         int fc = value[0];

Suggestion:

        /* Accumulating negatively avoids surprises near MAX_VALUE */
        int fc = value[0];

src/java.base/share/classes/java/lang/Long.java line 561:

> 559:             return parseLong0(s, radix);
> 560:         }
> 561:         int fc = value[0];

Suggestion:

        /* Accumulating negatively avoids surprises near MAX_VALUE */
        int fc = value[0];

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1940916020
PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1940916196