MonoAOT: LLVM 23 regressions in FullAOT JIT test outcomes

[pavelsavara]

Summary

Observed on PR branch emsdk-upgrade / #129299.
runtime-llvm linux-x64 FullAOT runtime tests

• nullabletypes failures (e.g., Expected 100, Actual 666)

• Additional failures: call05_large, call05_small, and WPF_3226.

• runtime-llvm linux-x64 FullAOT:
  nullabletypes, call05_large, call05_small, WPF_3226

[pavelsavara]

Helix Failure Evidence — Build 1464283

Job: linux-x64 Release AllSubsets_Mono_LLVMFULLAOT_RuntimeTests llvmfullaot
AzDO log (Send tests to Helix): https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1464283/logs/110
Helix job: https://helix.dot.net/api/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems?api-version=2019-06-17

Total: 11 errors across 4 work items.

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Work item: jit64_5

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/jit64_5/console

Failure 1 — call05_large — System.ExecutionEngineException attempting to JIT in full-AOT mode:
16:25:54.447 Running test: JIT/jit64/localloc/call/call05_large/call05_large.dll System.ExecutionEngineException: Attempting to JIT compile method 'int LocallocTest:func0 (int,int,int,int,int,int,int,int,int*,int*)' while running in aot-only mode. See https://learn.microsoft.com/xamarin/ios/internals/limitations for more information. at LocallocTest.Main() at Program.<<Main>$>g__TestExecutor4|0_5(...) 16:25:54.450 Failed test: JIT/jit64/localloc/call/call05_large/call05_large.dll

Failure 2 — call05_small — same ExecutionEngineException:
16:25:54.451 Running test: JIT/jit64/localloc/call/call05_small/call05_small.dll System.ExecutionEngineException: Attempting to JIT compile method 'int LocallocTest:func0 (int,int,int,int,int,int,int,int,int*,int*)' while running in aot-only mode. See https://learn.microsoft.com/xamarin/ios/internals/limitations for more information. at LocallocTest.Main() at Program.<<Main>$>g__TestExecutor5|0_6(...) 16:25:54.453 Failed test: JIT/jit64/localloc/call/call05_small/call05_small.dll

Root cause: jmp IL opcode in unc0 forces a non-inlinable tail call that cannot be AOT-compiled by Mono LLVM FullAOT. The JIT is invoked at runtime, which is forbidden in --full-aot mode.

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Work item: Directed_1

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Directed_1/console

Failures 3–10: all 8 variants of �oxunboxvaluetype and castclassvaluetype nullable tests fail with wrong return code. Reproduced error pattern (shown for castclassvaluetype_r and castclassvaluetype_ro):

--- NotEmptyStructConstrainedGenQ<int>? s = Helper.Create(default(NotEmptyStructConstrainedGenQ<int>)) --- Test FAILED System.Exception: [False]!=[True]: BoxUnboxToNQGenC at Assert.AreEqual(Boolean result, Boolean expected, String comment) at NullableTest30.Run() at Test_castclassvaluetype.TestEntryPoint() Xunit.Sdk.EqualException: Assert.Equal() Failure: Values differ Expected: 100 Actual: 666 16:26:05.066 Failed test: JIT/Directed/nullabletypes/castclassvaluetype_r/castclassvaluetype_r.dll

The Expected: 100 / Actual: 666 pattern confirms TestEntryPoint catches an exception and returns error code 666 instead of the success code 100. This affects all 4 castclassvaluetype variants (_d, _do, _r, _ro) and all 3 boxunboxvaluetype variants (_do, _r, _ro).

Failing tests in this work item:

• JIT/Directed/nullabletypes/Desktop/boxunboxvaluetype_do
• JIT/Directed/nullabletypes/Desktop/boxunboxvaluetype_r
• JIT/Directed/nullabletypes/Desktop/boxunboxvaluetype_ro
• JIT/Directed/nullabletypes/castclassvaluetype_d
• JIT/Directed/nullabletypes/castclassvaluetype_do
• JIT/Directed/nullabletypes/castclassvaluetype_r
• JIT/Directed/nullabletypes/castclassvaluetype_ro

---

Work item: Regression_o_3

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Regression_o_3/console

Failure 11 — WPF_3226 — System.ExecutionEngineException trying to JIT a Marshal.StructureToPtr wrapper in full-AOT mode:
16:25:55.134 Running test: global::WPF_3226.Test_WPF_3226.TestEntryPoint() System.ExecutionEngineException: Attempting to JIT compile method '(wrapper other) void WPF_3226.MINMAXINFO:StructureToPtr (object,intptr,bool)' while running in aot-only mode. See https://learn.microsoft.com/xamarin/ios/internals/limitations for more information. at System.Runtime.InteropServices.Marshal.StructureToPtr[MINMAXINFO](MINMAXINFO structure, IntPtr ptr, Boolean fDeleteOld) at WPF_3226.Test_WPF_3226.WmGetMinMaxInfo(IntPtr lParam) at WPF_3226.Test_WPF_3226.TestEntryPoint() 16:25:55.137 Failed test: global::WPF_3226.Test_WPF_3226.TestEntryPoint()

Root cause: Marshal.StructureToPtr emits a wrapper method at runtime. Mono LLVM FullAOT cannot JIT this wrapper. This failure is a structural limitation of using generic Marshal.StructureToPtr in FullAOT mode, unrelated to the LLVM version bump.

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Work item: Loader

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Loader/console

Failure — UnitTest_GVM_TypeLoadException — reported as failed by the Helix task but the work item log shows

Helix Failure Evidence - Build 1464283

Job: linux-x64 Release AllSubsets_Mono_LLVMFULLAOT_RuntimeTests llvmfullaot
AzDO log: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1464283/logs/110
Helix job: https://helix.dot.net/api/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems?api-version=2019-06-17

Total: 11 errors across 4 work items.

---

Work item: jit64_5

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/jit64_5/console

Failure 1 - call05_large - System.ExecutionEngineException attempting to JIT in full-AOT mode:

16:25:54.447 Running test: JIT/jit64/localloc/call/call05_large/call05_large.dll
System.ExecutionEngineException: Attempting to JIT compile method 'int LocallocTest:func0 (int,int,int,int,int,int,int,int,int*,int*)' while running in aot-only mode.
   at LocallocTest.Main()
16:25:54.450 Failed test: JIT/jit64/localloc/call/call05_large/call05_large.dll

Failure 2 - call05_small - same ExecutionEngineException:

16:25:54.451 Running test: JIT/jit64/localloc/call/call05_small/call05_small.dll
System.ExecutionEngineException: Attempting to JIT compile method 'int LocallocTest:func0 (int,int,int,int,int,int,int,int,int*,int*)' while running in aot-only mode.
   at LocallocTest.Main()
16:25:54.453 Failed test: JIT/jit64/localloc/call/call05_small/call05_small.dll

Root cause: jmp IL opcode in func0 forces a non-inlinable tail call that cannot be AOT-compiled. The JIT is invoked at runtime, which is forbidden in --full-aot mode.

---

Work item: Directed_1

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Directed_1/console

Failures 3-10: all 8 variants of boxunboxvaluetype and castclassvaluetype nullable tests. Pattern (castclassvaluetype_r shown):

--- NotEmptyStructConstrainedGenQ<int>? s = Helper.Create(default(NotEmptyStructConstrainedGenQ<int>)) ---
Test FAILED
System.Exception: [False]!=[True]: BoxUnboxToNQGenC
   at NullableTest30.Run()
   at Test_castclassvaluetype.TestEntryPoint()
Xunit.Sdk.EqualException: Assert.Equal() Failure: Values differ
Expected: 100
Actual:   666
16:26:05.066 Failed test: JIT/Directed/nullabletypes/castclassvaluetype_r/castclassvaluetype_r.dll

The Expected 100 / Actual 666 confirms TestEntryPoint catches an exception and returns error code 666. NullableTest30.BoxUnboxToNQGenC returns False when True is expected. Affects all 4 castclassvaluetype variants and all 3 boxunboxvaluetype variants.

---

Work item: Regression_o_3

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Regression_o_3/console

Failure 11 - WPF_3226 - ExecutionEngineException on Marshal.StructureToPtr wrapper:

16:25:55.134 Running test: global::WPF_3226.Test_WPF_3226.TestEntryPoint()
System.ExecutionEngineException: Attempting to JIT compile method '(wrapper other) void WPF_3226.MINMAXINFO:StructureToPtr (object,intptr,bool)' while running in aot-only mode.
   at System.Runtime.InteropServices.Marshal.StructureToPtr[MINMAXINFO](MINMAXINFO structure, IntPtr ptr, Boolean fDeleteOld)
   at WPF_3226.Test_WPF_3226.WmGetMinMaxInfo(IntPtr lParam)
   at WPF_3226.Test_WPF_3226.TestEntryPoint()
16:25:55.137 Failed test: global::WPF_3226.Test_WPF_3226.TestEntryPoint()

Root cause: Marshal.StructureToPtr emits a wrapper method at runtime. Mono LLVM FullAOT cannot JIT this wrapper. This is a structural AOT limitation unrelated to the LLVM version bump.

---

Work item: Loader

Console log: https://helix.dot.net/api/2019-06-17/jobs/f3bc3431-e44d-47b3-b4ce-492dd151bba7/workitems/Loader/console

Failure: UnitTest_GVM_TypeLoadException - reported failed by Helix task but work item log ends with 0 failures reported, exit code 0. The log is very large (~384KB) - the failure detail may be in an earlier test run stripe or in the uploaded test results XML rather than the console log.

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Summary table

Work item	Test	Root cause
jit64_5	call05_large, call05_small	jmp IL causes JIT attempt in full-AOT
Directed_1	7x nullable boxunbox/castclass	Wrong logic result - NullableTest30 BoxUnboxToNQGenC
Regression_o_3	WPF_3226	Marshal.StructureToPtr wrapper not AOT-compiled
Loader	UnitTest_GVM_TypeLoadException	Inconclusive from console log