[ci-scan] Build break: Mono AOT compiler SIGABRT (mini-amd64.c amd64_is_imm32) on JIT/Regression_ro_2

[github-actions]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1613653
Build error leg or test failing: linux-x64 Release AllSubsets_Mono_MiniFullAot_RuntimeTests minifullaot - AOT compile CoreCLR tests (JIT/Regression_ro_2)

KBE authoring guidance (ci-failure-scan)

• Error Details is for readers. Paste the full exception, stack trace, or build error excerpt so the failure is understandable without opening the raw log.
• Build Analysis parses only the single JSON block under Error Message.
• ErrorMessage is a case-sensitive ordinal String.Contains substring copied verbatim from the failing log.
• Set BuildRetry to true only for a clear infrastructure retry case. ExcludeConsoleLog disables Helix console-log scanning.

Error Details

The Mono AOT compiler (minifullaot leg) crashes with a SIGABRT while AOT-compiling JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll, failing the AOT compile CoreCLR tests step of the linux-x64 Release AllSubsets_Mono_MiniFullAot_RuntimeTests minifullaot leg. The build break reproduces in every sampled build across the scanned window.

Mono Ahead of Time compiler - compiling assembly /__w/1/s/artifacts/tests/coreclr/linux.x64.Release/JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll
* Assertion at /__w/1/s/src/mono/mono/mini/mini-amd64.c:5347, condition `amd64_is_imm32 (ins->inst_imm)' not met

=================================================================
	Native Crash Reporting
=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

/__w/1/s/src/mono/msbuild/aot-compile.proj(19,9): error MSB3073: The command "/__w/1/s/artifacts/tests/coreclr/linux.x64.Release/Tests/Core_Root/corerun /__w/1/s/artifacts/tests/coreclr/linux.x64.Release/JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll" exited with code 134.

Error Message

{
  "ErrorMessage": [
    "compiling assembly /__w/1/s/artifacts/tests/coreclr/linux.x64.Release/JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll",
    "Assertion at /__w/1/s/src/mono/mono/mini/mini-amd64.c:5347, condition `amd64_is_imm32 (ins->inst_imm)' not met"
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Agentic workflow metadata (ci-failure-scan)

Workflow artifact: ci-failure-scan
Artifact kind: kbe-verification
Verified match count: 1 hits in failure.log

---

Filed by ci-failure-scan (detection only). ci-failure-fix walks open [ci-scan] KBEs and either opens a small fix PR or comments here to loop in owners — it never disables the test.

Note

This issue was generated by the ci-failure-scan Copilot workflow.

Generated by CI Outer-Loop Failure Scanner · opus48 · 993 AIC · ⌖ 10.8 AIC · ⊞ 19.2K · ◷

Report

Build	Repository	Step Name	Console log	Pull Request
1619076	dotnet/runtime	AOT compile CoreCLR tests	Log
1617850	dotnet/runtime	AOT compile CoreCLR tests	Log	#134549
1617342	dotnet/runtime	AOT compile CoreCLR tests	Log
1615702	dotnet/runtime	AOT compile CoreCLR tests	Log
1615485	dotnet/runtime	AOT compile CoreCLR tests	Log	#134819

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
2	5	5

[github-actions]

Workflow artifact: ci-fix
Artifact kind: handoff
Linked KBE: #134832

Note

AI/Copilot-generated triage note.

This Known Build Error has no producible automated code change (reason: JIT/GC codegen — must not be auto-fixed), so I could not open even a best-effort PR. Looping in owners so it can be fixed forward rather than muted.

Root cause (best analysis)

The Linux x64 MiniFullAOT compiler aborts while compiling JIT/Regression_ro_2/Regression_ro_2.dll: mini-amd64.c:5347 asserts because amd64_is_imm32 (ins->inst_imm) is false. The KBE reports this in two builds during the preceding 24 hours, including the AOT compile CoreCLR tests leg. This is a Mono AMD64 AOT code-generation assertion, not a test expectation or harness failure.

Evidence

• Failing build: 1613653
• First build it occurred: 1613653 — scanner did not provide an earlier first-occurrence build in the KBE body
• Possible related PR: none identified with sufficient confidence

Suggested reviewers / area contacts

• Area owners (area-VM-meta-mono): @steveisok, @vitek-karas

A fix likely needs a Mono AOT AMD64 codegen investigation to identify the instruction/immediate emitted while compiling Regression_ro_2; no test was disabled or changed.

Structured data:

{
  "artifact_kind": "handoff",
  "linked_kbe": 134832,
  "workflow_artifact": "ci-fix"
}

Generated by CI Outer-Loop Failure Fixer · gpt56 · 47.5 AIC · ⌖ 12.6 AIC · ⊞ 26.9K · ◷