8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate #17266

TobiHartmann · 2024-01-04T12:39:18Z

JDK-8287349 changed the code in LIR_Assembler::osr_entry() to use a single ldp instruction instead of two ldr instructions to load the monitor lock and object from the OSR state. This is not correct because the ldp instruction only supports a 7-bit signed immediate value. If the offset is larger, for example due to a large number of locals as in TestLargeMonitorOffset::test, we hit the Field too big for insn guarantee.

I suggest to revert JDK-8287349.

I also found two unrelated bugs when working on the reproducer: JDK-8322992 (javac) and JDK-8322996 (C2).

Thanks,
Tobias

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Issue

JDK-8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate (Bug - P3)

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Andrew Haley (@theRealAph - Reviewer)
Christian Hagedorn (@chhagedorn - Reviewer)

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… buffer is too large for immediate

bridgekeeper · 2024-01-04T12:40:02Z

👋 Welcome back thartmann! 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 · 2024-01-04T12:42:05Z

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

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mlbridge · 2024-01-04T12:44:35Z

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00: Full (de6684fd)

theRealAph · 2024-01-04T14:08:51Z

src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp

      __ str(r19, frame_map()->address_for_monitor_lock(i));
-      __ str(r20, frame_map()->address_for_monitor_object(i));
+      __ ldr(r19, Address(OSR_buf, slot_offset + 1*BytesPerWord));
+      __ str(r19, frame_map()->address_for_monitor_object(i));
    }


The macro assembler automagically fuses ldr pairs. It'd be better to fix this with:

--- a/src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp +++ b/src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp @@ -282,7 +282,8 @@ void LIR_Assembler::osr_entry() { __ bind(L); } #endif - __ ldp(r19, r20, Address(OSR_buf, slot_offset)); + __ ldr(r19, Address(OSR_buf, slot_offset)); + __ ldr(r20, Address(OSR_buf, slot_offset + BytesPerWord)); __ str(r19, frame_map()->address_for_monitor_lock(i)); __ str(r20, frame_map()->address_for_monitor_object(i)); }

Thanks for the review. I adjusted the fix accordingly.

I'm not sure why the recommended adjustment is needed. The macro assembler does fuse pairs of adjacent ldr instructions into an ldp but only when the sizes match and the offsets fit into the requisite number of bits.

So, if the two ldr instrctions ar egenerated next to each other the macroasembler should only convert to ldp where appropriate. Am I missing something here?

Doh, sorry - I misread Andrew's proposed code! Ignore the noise.

Yes, the problem @TobiHartmann is fixing is that we currently use ldp, but in very rare casesldp can't reach, so the fix we need is to change one ldp to two ldrs. In almost all cases, macroassembler will merge the ldrs.

Thanks for looking at this @adinn. Right, the macro assembler merge magic is nice, I didn't know about it.

openjdk · 2024-01-04T15:34:57Z

@TobiHartmann 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:

8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate

Reviewed-by: aph, 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 18 new commits pushed to the master branch:

f0cfd36: 8322532: JShell : Unnamed variable issue
78623c9: 8323012: C2 fails with fatal error: no reachable node should have no use
f0e2e43: 8323021: Shenandoah: Encountered reference count always attributed to first worker thread
3dc4bd8: 8322989: New test serviceability/HeapDump/FullGCHeapDumpLimitTest.java fails
1d1cd32: 8321812: Update GC tests to use execute[Limited]TestJava
868f874: 8322920: Some ProcessTools.execute* functions are declared to throw Throwable
2a9c358: 8322725: (tz) Update Timezone Data to 2023d
5235cc9: 8322583: RISC-V: Enable fast class initialization checks
3b1e56a: 8322322: Support archived full module graph when -Xbootclasspath/a is used
3fbccb0: 8322978: Remove debug agent debugMonitorTimedWait() function. It is no longer used.
... and 8 more: https://git.openjdk.org/jdk/compare/dd517c64047705d706b095d15d9fd4e0703ab39b...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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TobiHartmann · 2024-01-04T15:41:45Z

Thanks for the review, Andrew.

theRealAph · 2024-01-04T15:48:16Z

I looked through the history and I see this bug is my fault, and your fix will have to be back ported to all releases. Argh!
Thanks for fixing it.

TobiHartmann · 2024-01-04T15:53:55Z

But, as I mentioned in the description, it's a regression from JDK-8287349, right?

theRealAph · 2024-01-04T16:05:49Z

But, as I mentioned in the description, it's a regression from JDK-8287349, right?

Yeah, that's true. A "trivial performance fix," as was said at the time. Memo to myself: there are no trivial performance fixes.

TobiHartmann · 2024-01-05T07:13:27Z

Memo to myself: there are no trivial performance fixes

I'll copy that memo, it did look harmless at the time.

chhagedorn

Looks good.

TobiHartmann · 2024-01-05T13:46:48Z

Thanks, Christian!

TobiHartmann · 2024-01-05T13:47:40Z

/integrate

openjdk · 2024-01-05T13:48:36Z

Going to push as commit ade21a9.
Since your change was applied there have been 18 commits pushed to the master branch:

f0cfd36: 8322532: JShell : Unnamed variable issue
78623c9: 8323012: C2 fails with fatal error: no reachable node should have no use
f0e2e43: 8323021: Shenandoah: Encountered reference count always attributed to first worker thread
3dc4bd8: 8322989: New test serviceability/HeapDump/FullGCHeapDumpLimitTest.java fails
1d1cd32: 8321812: Update GC tests to use execute[Limited]TestJava
868f874: 8322920: Some ProcessTools.execute* functions are declared to throw Throwable
2a9c358: 8322725: (tz) Update Timezone Data to 2023d
5235cc9: 8322583: RISC-V: Enable fast class initialization checks
3b1e56a: 8322322: Support archived full module graph when -Xbootclasspath/a is used
3fbccb0: 8322978: Remove debug agent debugMonitorTimedWait() function. It is no longer used.
... and 8 more: https://git.openjdk.org/jdk/compare/dd517c64047705d706b095d15d9fd4e0703ab39b...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-01-05T13:48:42Z

@TobiHartmann Pushed as commit ade21a9.

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

TobiHartmann · 2024-01-08T09:35:00Z

/backport jdk22

openjdk · 2024-01-08T09:36:06Z

@TobiHartmann the backport was successfully created on the branch backport-TobiHartmann-ade21a96 in my personal fork of openjdk/jdk22. To create a pull request with this backport targeting openjdk/jdk22:master, just click the following link:

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Hi all,

This pull request contains a backport of commit ade21a96 from the openjdk/jdk repository.

The commit being backported was authored by Tobias Hartmann on 5 Jan 2024 and was reviewed by Andrew Haley and Christian Hagedorn.

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If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk22:

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$ git checkout backport-TobiHartmann-ade21a96
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk22.git backport-TobiHartmann-ade21a96

8310844: [AArch64] C1 compilation fails because monitor offset in OSR…

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… buffer is too large for immediate

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8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate #17266

8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate #17266

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8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate #17266

8310844: [AArch64] C1 compilation fails because monitor offset in OSR buffer is too large for immediate #17266

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