8308749: C2 failed: regular loops only (counted loop inside infinite loop) #14178

eme64 · 2023-05-26T13:45:23Z

I found this failure with my jasm fuzzer. Have not tried to reproduce it with plain java.

I added the code above the assert, the comments explain why:

Lines 1749 to 1763 in 1fd6699

    
           if (x->Opcode() == Op_Region) { 
        
             // x has not yet been transformed to Loop or LongCountedLoop. 
        
             // This should only happen if we are inside an infinite loop. 
        
             // It happens like this: 
        
             //   build_loop_tree -> do not attach infinite loop and nested loops 
        
             //   beautify_loops  -> does not transform the infinite and nested loops to LoopNode, because not attached yet 
        
             //   build_loop_tree -> find and attach infinite and nested loops 
        
             //   counted_loop    -> nested Regions are not yet transformed to LoopNodes, we land here 
        
             assert(x->as_Region()->is_in_infinite_subgraph(), 
        
                    "x can only be a Region and not Loop if inside infinite loop"); 
        
             // Come back later when Region is transformed to LoopNode 
        
             return false; 
        
           } 
        
           assert(x->Opcode() == Op_Loop || x->Opcode() == Op_LongCountedLoop, "regular loops only");

Here the graph just before the assert:

120 Loop -> need it to kick of beautify_loop and a second build_loop_tree
71 Region -> inifinite loop, NeverBranch is inserted on first build_loop_tree pass. Only attached to loop tree after second build_loop_tree.
x = 81 Region -> looks like a counted loop, but is only attached to the loop tree after beautify_loop in the second build_loop_tree.

Testing up to tier6 and stress testing. Passed.

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Issue

JDK-8308749: C2 failed: regular loops only (counted loop inside infinite loop) (Bug - P4)

Reviewers

Vladimir Kozlov (@vnkozlov - Reviewer)
Christian Hagedorn (@chhagedorn - Reviewer)

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$ git checkout pull/14178

Update a local copy of the PR:
$ git checkout pull/14178
$ git pull https://git.openjdk.org/jdk.git pull/14178/head

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$ git pr checkout 14178

View PR using the GUI difftool:
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https://git.openjdk.org/jdk/pull/14178.diff

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bridgekeeper · 2023-05-26T13:46:05Z

👋 Welcome back epeter! 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 · 2023-05-26T13:47:42Z

@eme64 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.

mlbridge · 2023-05-30T07:54:08Z

Webrevs

00: Full (1fd6699e)

vnkozlov · 2023-05-31T19:57:36Z

test/hotspot/jtreg/compiler/loopopts/TestCountedLoopInsideInfiniteLoop.jasm

+ * questions.
+ */
+
+super public class TestCountedLoopInsideInfiniteLoop


May be add comment why you put this into separate file and not make inner class.

@vnkozlov Is that even possible, to make jasm code inside a java file? I just repeated the pattern of other jasm tests in the same directory.

My bad. Missed that it is jasm.

vnkozlov · 2023-06-01T15:47:51Z

test/hotspot/jtreg/compiler/loopopts/TestCountedLoopInsideInfiniteLoop.jasm

+ * questions.
+ */
+
+super public class TestCountedLoopInsideInfiniteLoop


My bad. Missed that it is jasm.

openjdk · 2023-06-01T15:49:24Z

@eme64 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:

8308749: C2 failed: regular loops only (counted loop inside infinite loop)

Reviewed-by: kvn, chagedorn

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 295 new commits pushed to the master branch:

3981297: 8309703: AIX build fails after JDK-8280982
16c3d53: 8308603: Removing do_pending_ref/enclosing_ref from MetaspaceClosure
b94b679: 8309627: Incorrect sorting of DirtyCardQueue buffers
aace3dc: 8309760: ProblemList serviceability/jvmti/vthread/FollowReferences/VThreadStackRefTest.java#default with ZGC
80edd5c: 8294985: SSLEngine throws IAE during parsing of X500Principal
bdd81b3: 8304885: Reuse stale data to improve DNS resolver resiliency
beec734: 8309692: Fix -Wconversion warnings in javaClasses
7d82479: 8309142: Refactor test/langtools/tools/javac/versions/Versions.java
f5ec93e: 8309745: Problem list open client tests failing on Ubuntu_23.04
cee5724: 8309727: Assert privileges while reading the jdk.incubator.vector.VECTOR_ACCESS_OOB_CHECK system property
... and 285 more: https://git.openjdk.org/jdk/compare/eb11508eff7b2e01b8942f4cda9fb01527a860b5...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

chhagedorn

Looks good!

eme64 · 2023-06-12T07:40:24Z

Thanks @vnkozlov @chhagedorn for the reviews!
/integrate

openjdk · 2023-06-12T07:41:02Z

Going to push as commit 6c3e621.
Since your change was applied there have been 297 commits pushed to the master branch:

f5cbe53: 8027711: Unify wildcarding syntax for CompileCommand and CompileOnly
4d66d97: 8309549: com/sun/tools/attach/warnings/DynamicLoadWarningTest.java fails on AIX
3981297: 8309703: AIX build fails after JDK-8280982
16c3d53: 8308603: Removing do_pending_ref/enclosing_ref from MetaspaceClosure
b94b679: 8309627: Incorrect sorting of DirtyCardQueue buffers
aace3dc: 8309760: ProblemList serviceability/jvmti/vthread/FollowReferences/VThreadStackRefTest.java#default with ZGC
80edd5c: 8294985: SSLEngine throws IAE during parsing of X500Principal
bdd81b3: 8304885: Reuse stale data to improve DNS resolver resiliency
beec734: 8309692: Fix -Wconversion warnings in javaClasses
7d82479: 8309142: Refactor test/langtools/tools/javac/versions/Versions.java
... and 287 more: https://git.openjdk.org/jdk/compare/eb11508eff7b2e01b8942f4cda9fb01527a860b5...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-06-12T07:41:22Z

@eme64 Pushed as commit 6c3e621.

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

8308749: failed: regular loops only (counted loop inside infinite loop

1fd6699

eme64 changed the title ~~8308749: failed: regular loops only (counted loop inside infinite loop~~ 8308749: failed: regular loops only (counted loop inside infinite loop) May 26, 2023

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label May 26, 2023

eme64 changed the title ~~8308749: failed: regular loops only (counted loop inside infinite loop)~~ 8308749: C2 failed: regular loops only (counted loop inside infinite loop) May 26, 2023

eme64 marked this pull request as ready for review May 30, 2023 07:49

openjdk bot added the rfr Pull request is ready for review label May 30, 2023

vnkozlov reviewed May 31, 2023

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vnkozlov approved these changes Jun 1, 2023

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openjdk bot added the ready Pull request is ready to be integrated label Jun 1, 2023

chhagedorn approved these changes Jun 12, 2023

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openjdk bot closed this Jun 12, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 12, 2023

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	if (x->Opcode() == Op_Region) {
	// x has not yet been transformed to Loop or LongCountedLoop.
	// This should only happen if we are inside an infinite loop.
	// It happens like this:
	// build_loop_tree -> do not attach infinite loop and nested loops
	// beautify_loops -> does not transform the infinite and nested loops to LoopNode, because not attached yet
	// build_loop_tree -> find and attach infinite and nested loops
	// counted_loop -> nested Regions are not yet transformed to LoopNodes, we land here
	assert(x->as_Region()->is_in_infinite_subgraph(),
	"x can only be a Region and not Loop if inside infinite loop");
	// Come back later when Region is transformed to LoopNode
	return false;
	}

	assert(x->Opcode() == Op_Loop \|\| x->Opcode() == Op_LongCountedLoop, "regular loops only");

8308749: C2 failed: regular loops only (counted loop inside infinite loop) #14178

8308749: C2 failed: regular loops only (counted loop inside infinite loop) #14178

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