8358781: C2 fails with assert "bad profile data type" when TypeProfileCasts is disabled #26640

sarannat · 2025-08-05T10:40:19Z

Issue
An error, assert(data->is_ReceiverTypeData()) failed: bad profile data type, is encountered during C2 compilation due to bad profile data. This occurs when the code is compiled with TypeProfileCasts option disabled.

Analysis
The assertion failure occurs in record_profiled_receiver_for_speculation that analyzes the profiling information in the method data to determine whether a null value has been observed in the instanceof operation. This information is encoded in the BitData during profiling. When the method identifies that a null has been seen, it proceeds to inspect the associated ReceiverTypeData to see if the type check is always performed against null. However, in this scenario, the incoming profiling data is of type BitData rather than ReceiverTypeData, leading to the assertion failure.

The profiling information for null seen for operations aastore, instanceof, and checkcast is recorded by the method profile_null_seen (insrc/hotspot/cpu/x86/templateTable_x86.cpp). On investigating this method, it can be observed that the method data pointer is not updated for VirtualCallData (which is a subclass of ReceiverTypeData) when the TypeProfileCasts option is disabled.

Solution
My proposal is to inspect the ReceiverTypeData in function record_profiled_receiver_for_speculation only if TypeProfileCasts is enabled (this is based on the fact that the relevant method data pointer is not updated when TypeProfileCasts is disabled).

Question to reviewers
Do you think this is a reasonable fix ?

Testing
GitHub Actions
tier1 to tier3 on windows-x64, linux-x64, linux-aarch64, macosx-x64, and macosx-aarch64.

Progress

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Commit message must refer to an issue

Issue

JDK-8358781: C2 fails with assert "bad profile data type" when TypeProfileCasts is disabled (Bug - P4)

Reviewers

Manuel Hässig (@mhaessig - Committer)
Damon Fenacci (@dafedafe - Committer) Review applies to 0089ba25
Vladimir Kozlov (@vnkozlov - Reviewer)

Reviewing

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$ git pull https://git.openjdk.org/jdk.git pull/26640/head

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$ git pr checkout 26640

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bridgekeeper · 2025-08-05T10:40:48Z

👋 Welcome back snatarajan! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-08-05T10:41:24Z

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8358781: C2 fails with assert "bad profile data type" when TypeProfileCasts is disabled

Reviewed-by: mhaessig, kvn, dfenacci

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 125 new commits pushed to the master branch:

ca753eb: 8365165: Zap C-heap memory at delete/free
190e113: 8364263: HttpClient: Improve encapsulation of ProxyServer
166ea12: 8365543: UnixNativeDispatcher.init should lookup open64at and stat64at on AIX
... and 122 more: https://git.openjdk.org/jdk/compare/ba0ae4cb28aa520d5244077349e35ef1bb475b61...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 · 2025-08-05T10:42:19Z

@sarannat The following label will be automatically applied to this pull request:

hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

…8781

mlbridge · 2025-08-06T21:45:42Z

Webrevs

mhaessig

Thank you for working on this, @sarannat! The fix seems reasonable to me since GraphKit::maybe_cast_profiled_receiver has a similar exception.

However, you are missing a regression test or a noreg-* label in JBS. However, in this case, I think a small regression test is warranted.

dafedafe

Thanks for fixing this @sarannat. Apart from the missing regression test already mentioned by @mhaessig the fix looks good to me.
Just a quick question: did you try to run some testing with -XX:-TypeProfileCasts?

sarannat · 2025-08-12T09:01:43Z

@mhaessig and @dafedafe : Thank you for the review. I have now added a test case.
@dafedafe : I have tested -XX:-TypeProfileCasts with few examples.I want to highlight the example of the test in /test/hotspot/jtreg/compiler/tiered/TypeProfileCasts.java. When I ran this with -XX:-TypeProfileCasts option and TieredCompilation disabled, it did crash with the same error.

mhaessig

Thank you for adding the test. Apart from my question, this looks good to me.

mhaessig · 2025-08-12T09:33:21Z

test/hotspot/jtreg/compiler/arguments/TestProfileCasts.java

+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 100_000; i++) {


Do you really need 100'000 iterations to get it to compile or can you reduce it a bit?

I have reduced this to 100 after I checked that the (new) test fails without the current fix.

Excellent, thank you!

You can also use -XX:CompileThresholdScaling=f (specify f as 0.1, for example) flag to trigger compilation early to make sure 100 is enough.

Thank you for the suggestion. The test works without this addition. However, I have added
-XX:CompileThresholdScaling=0.01 to be on safe side.

vnkozlov

Looks good.

sarannat · 2025-08-18T08:11:37Z

Thank you for the review. Please sponsor

sarannat · 2025-08-18T08:12:03Z

/integrate

mhaessig · 2025-08-18T08:13:12Z

/sponsor

openjdk · 2025-08-18T08:15:24Z

@sarannat
Your change (at version 00d2e4e) is now ready to be sponsored by a Committer.

openjdk · 2025-08-18T08:16:33Z

Going to push as commit 2b756ab.
Since your change was applied there have been 125 commits pushed to the master branch:

ca753eb: 8365165: Zap C-heap memory at delete/free
190e113: 8364263: HttpClient: Improve encapsulation of ProxyServer
166ea12: 8365543: UnixNativeDispatcher.init should lookup open64at and stat64at on AIX
... and 122 more: https://git.openjdk.org/jdk/compare/ba0ae4cb28aa520d5244077349e35ef1bb475b61...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-08-18T08:16:41Z

@mhaessig @sarannat Pushed as commit 2b756ab.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Initial Fix

b2ab979

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Aug 5, 2025

Merge branch 'master' of https://github.com/sarannat/jdk into JDK-835…

0089ba2

…8781

sarannat marked this pull request as ready for review August 6, 2025 21:38

openjdk bot added the rfr Pull request is ready for review label Aug 6, 2025

mhaessig suggested changes Aug 7, 2025

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dafedafe approved these changes Aug 8, 2025

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adding test

767f4e8

mhaessig approved these changes Aug 12, 2025

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addressing review: reducing number of iteration

31c645d

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sarannat added 2 commits August 13, 2025 11:59

add CompileThresholdScaling

dad5a19

formating code

00d2e4e

vnkozlov approved these changes Aug 14, 2025

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8358781: C2 fails with assert "bad profile data type" when TypeProfileCasts is disabled #26640

8358781: C2 fails with assert "bad profile data type" when TypeProfileCasts is disabled #26640

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