RFR: 8327247: C2 uses up to 2GB of RAM to compile complex string concat in extreme cases [v3]

[Aleksey Shipilev]

On Fri, 26 Apr 2024 08:45:45 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> Splitting out the ASM-based version from #18690 to push that first under the JBS (to help backporting). Keeping #18690 open to rebase and follow-up on this as a subtask. See discussion in that #18690 for more details, discussion and motivation for this.
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Copyright and comment about ProxyClassDumper

Looks okay, thanks. Only cosmetic nits:

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 108:

> 106:     static {
> 107:         String highArity = VM.getSavedProperty("java.lang.invoke.StringConcat.highArityThreshold");
> 108:         HIGH_ARITY_THRESHOLD = Integer.parseInt(highArity != null ? highArity : "20");

Maybe write this as `= (highArity != null) ? Integer.parseInt(highArity) : 20` to help interpreter a bit.

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1105:

> 1103:             for (int c = 0; c < constants.length; c++) {
> 1104:                 if (constants[c] != null)
> 1105:                     len += constants[c].length();

Braces?

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1118:

> 1116:             );
> 1117: 
> 1118: 

Extra new-line?

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1164:

> 1162:         }
> 1163: 
> 1164: 

Extra new-line?

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18953#pullrequestreview-2024514742
PR Review Comment: https://git.openjdk.org/jdk/pull/18953#discussion_r1580723293
PR Review Comment: https://git.openjdk.org/jdk/pull/18953#discussion_r1580723981
PR Review Comment: https://git.openjdk.org/jdk/pull/18953#discussion_r1580724174
PR Review Comment: https://git.openjdk.org/jdk/pull/18953#discussion_r1580724568