8340398: [JVMCI] Unintuitive behavior of UseJVMCICompiler option

[tzezula]

Disabling the JVMCI compiler with -XX:-UseJVMCICompiler not only deactivates JVMCI-based CompileBroker compilations but also prevents the loading of the libjvmci compiler. While this works as expected for CompileBroker compilations, it poses issues for the Truffle compiler. When -XX:-UseJVMCICompiler is used, Truffle falls back to the jargraal compiler, if available. This behavior may be confusing for Truffle users.

Expected behavior:

With -XX:+UseGraalJIT, both CompileBroker compilations and Truffle compilations should utilize the libjvmci compiler, if available.
With -XX:+EnableJVMCI, CompileBroker compilations should use the C2 compiler, while only Truffle compilations should leverage the libjvmci compiler, if available.

---

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Issue

• JDK-8340398: [JVMCI] Unintuitive behavior of UseJVMCICompiler option (Bug - P4)

Reviewers

• Doug Simon (@dougxc - Reviewer)

Reviewing

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[openjdk]

@tzezula This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8340398: [JVMCI] Unintuitive behavior of UseJVMCICompiler option

Reviewed-by: dnsimon

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 78 new commits pushed to the master branch:

• 4402482: 8340585: [JVMCI] compiler/unsafe/UnsafeGetStableArrayElement.java fails with -XX:-UseCompressedClassPointers
• e60e882: 8335167: Test runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved
• 9176f68: 8340623: Remove outdated PROCESSOR_ARCHITECTURE_IA64 from Windows coding
• 88801ca: 8340590: RISC-V: C2: Small improvement to vector gather load and scatter store
• 1dd60b6: 8323688: C2: Fix UB of jlong overflow in PhaseIdealLoop::is_counted_loop()
• 4098acc: 8340146: ZGC: TestAllocateHeapAt.java should not run with UseLargePages
• 6c91a16: 8340367: Opensource few AWT image tests
• 865d99f: 8340596: Remove dead code from RequiresSetenv function in java.base/unix/native/libjli/java_md.c
• 3411f9d: 8339995: Open source several AWT focus tests - series 6
• 40cde00: 8340114: Remove outdated SelectVersion() function from the launcher and update the code comments explaining the code flow
• ... and 68 more: https://git.openjdk.org/jdk/compare/6ff287ad9aa45d8a37aafb4dd7bd9170280f5bbb...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

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[mlbridge]

Webrevs

• 02: Full - Incremental (28dbd932)
• 01: Full - Incremental (b7550463)
• 00: Full (78f57619)

[dougxc]

This check for enabling UseJVMCINativeLibrary should really be:

   if (UseJVMCICompiler) {
     if (FLAG_IS_DEFAULT(UseJVMCINativeLibrary) && !UseJVMCINativeLibrary) {
-      char path[JVM_MAXPATHLEN];
-      if (os::dll_locate_lib(path, sizeof(path), Arguments::get_dll_dir(), JVMCI_SHARED_LIBRARY_NAME)) {
+      if (JVMCI::shared_library_exists()) {
         // If a JVMCI native library is present,

but I will address that as part of JDK-8340576.

[openjdk]

⚠️ @tzezula the full name on your profile does not match the author name in this pull requests' HEAD commit. If this pull request gets integrated then the author name from this pull requests' HEAD commit will be used for the resulting commit. If you wish to push a new commit with a different author name, then please run the following commands in a local repository of your personal fork:

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[toddjonker]

If I'm reading things correctly, the doc-string for UseJVMCINativeLibrary in jvmci_globals.hpp needs updating. That currently states "Defaults to true if EnableJVMCIProduct is true and a JVMCI native library is available" but looks like it default to true if EnableJVMCI is true, regardless of the EnableJVMCIProduct setting.

[dougxc]

If I'm reading things correctly, the doc-string for UseJVMCINativeLibrary in jvmci_globals.hpp needs updating. That currently states "Defaults to true if EnableJVMCIProduct is true and a JVMCI native library is available" but looks like it default to true if EnableJVMCI is true, regardless of the EnableJVMCIProduct setting.

That is correct and I'm making that fix here. However, it wouldn't hurt to also fix it here.

[tzezula]

If I'm reading things correctly, the doc-string for UseJVMCINativeLibrary in jvmci_globals.hpp needs updating.

Fixed in 28dbd93

[tzezula]

/integrate

[openjdk]

@tzezula
Your change (at version 28dbd93) is now ready to be sponsored by a Committer.

[dougxc]

/sponsor

[openjdk]

Going to push as commit 4cd8c75.
Since your change was applied there have been 78 commits pushed to the master branch:

• 4402482: 8340585: [JVMCI] compiler/unsafe/UnsafeGetStableArrayElement.java fails with -XX:-UseCompressedClassPointers
• e60e882: 8335167: Test runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved
• 9176f68: 8340623: Remove outdated PROCESSOR_ARCHITECTURE_IA64 from Windows coding
• 88801ca: 8340590: RISC-V: C2: Small improvement to vector gather load and scatter store
• 1dd60b6: 8323688: C2: Fix UB of jlong overflow in PhaseIdealLoop::is_counted_loop()
• 4098acc: 8340146: ZGC: TestAllocateHeapAt.java should not run with UseLargePages
• 6c91a16: 8340367: Opensource few AWT image tests
• 865d99f: 8340596: Remove dead code from RequiresSetenv function in java.base/unix/native/libjli/java_md.c
• 3411f9d: 8339995: Open source several AWT focus tests - series 6
• 40cde00: 8340114: Remove outdated SelectVersion() function from the launcher and update the code comments explaining the code flow
• ... and 68 more: https://git.openjdk.org/jdk/compare/6ff287ad9aa45d8a37aafb4dd7bd9170280f5bbb...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dougxc @tzezula Pushed as commit 4cd8c75.

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