RFR: 8333893: Optimization for StringBuilder append boolean & null [v17]

[Chen Liang]

On Sat, 24 Aug 2024 06:27:26 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> After PR https://github.com/openjdk/jdk/pull/16245, C2 optimizes stores into primitive arrays by combining values ​​into larger stores.
>> 
>> This PR rewrites the code of appendNull and append(boolean) methods so that these two methods can be optimized by C2.
>
> Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 19 additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - replace unsafe with putChar
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - private static final field `UNSAFE`
>  - Utf16 case remove `append first utf16 char`
>  - `delete` -> `setLength`
>  - copyright 2024
>  - optimization for x64
>  - ... and 9 more: https://git.openjdk.org/jdk/compare/381c1987...61196ecd

src/java.base/share/classes/java/lang/AbstractStringBuilder.java line 640:

> 638:     private AbstractStringBuilder appendNull() {
> 639:         ensureCapacityInternal(count + 4);
> 640:         int count = this.count;

We should declare `count` before `ensureCapacitiyInternal`. Same for append boolean.

test/hotspot/jtreg/compiler/patches/java.base/java/lang/Helper.java line 136:

> 134: 
> 135:     public static int putCharsAt(byte[] value, int i, char c1, char c2, char c3, char c4) {
> 136:         return StringUTF16.putCharsAt(value, i, c1, c2, c3, c4);

Why do we remove the tests for UTF16? And should we add another set of test for LATIN1 too?

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PR Review Comment: https://git.openjdk.org/jdk/pull/19626#discussion_r1769695101
PR Review Comment: https://git.openjdk.org/jdk/pull/19626#discussion_r1769694934