RFR: 8357822: C2: Multiple string optimization tests are no longer testing string concatenation optimizations

[Roberto Castañeda Lozano]

On Tue, 3 Jun 2025 07:17:47 GMT, Daniel Skantz <dskantz at openjdk.org> wrote:

> This PR updates a few tests to reintroduce testing of string concatenation optimizations since a few bugs have recently been identified in this area.
> 
> Selection criteria: performed a text search on the test suite and identified tests for string concatenations or string optimizations that are not currently compiled with `-XDstringConcat=inline` and are not using StringBuilders explicitly.
> 
> Testing: T1-4.
> 
> Extra testing: ran the tests manually with `-XX:+PrintOptimizeStringConcat` and verified that the tests are exercising string optimizations after the fix.

test/hotspot/jtreg/compiler/intrinsics/string/TestStringIntrinsics.java line 1:

> 1: /*

Do we need to add a second run at all to this test case? As far as I can see, all `concat*` test cases use explicit string builders and already exercise C2's string concatenation optimizations.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25610#discussion_r2126842291