JDK-8357822 : C2: Multiple string optimization tests are no longer testing string concatenation optimizations
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 9,11,17,21,25,26
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2025-05-27
  • Updated: 2025-09-15
  • Resolved: 2025-06-09
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JDK 21 JDK 25 JDK 26
21.0.10-oracleFixed 25.0.2Fixed 26 b02Fixed
Related Reports
Relates :  
JDK-8357105 - C2: compilation fails with "assert(false) failed: empty program detected during loop optimization"
Description
Test7179138_2.java and other tests are no longer testing string concatenation optimizations since string concatenation no longer uses StringBuilders by default.

Test7179138_1.java has found three bugs, so these tests might be good to run with a configuration that uses StringBuilders for string concatenation. We could add a run with -XDstringConcat=inline to Test7179138_2.java and other affected tests.
Comments
[jdk21u-fix-request] Approval Request from Rui Li A clean backport for https://bugs.openjdk.org/browse/JDK-8357822. Backport this for the parity with 21.0.10-oracle.
12-09-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk21u-dev/pull/2205 Date: 2025-09-12 20:03:31 +0000
12-09-2025
[jdk25u-fix-request] Approval Request from Francesco Andreuzzi Applies cleanly. Adds tests for string concatenation optimization in C2. The tests are nice to have around since they've already spotted bugs in the past.
06-08-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk25u/pull/73 Date: 2025-08-06 16:21:38 +0000
06-08-2025
Changeset: 6c616c71 Branch: master Author: Daniel Skantz <dskantz@openjdk.org> Date: 2025-06-09 06:11:05 +0000 URL: https://git.openjdk.org/jdk/commit/6c616c71ec9a8ee6e0203921deef20d09db39698
09-06-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk/pull/25610 Date: 2025-06-03 07:17:47 +0000
03-06-2025
I found a few more tests.
02-06-2025
An ambitious solution or follow-up RFE is adding IR checks to stringopts tests.
27-05-2025
ILW = Test does not work anymore (but passes), single test, no workaround but you run -XDstringConcat=inline = MLM = P4
27-05-2025
https://github.com/openjdk/jdk/compare/master...danielogh:jdk:stringopts_4?expand=1
27-05-2025