[ci-scan] Build break: Mono MiniFullAOT amd64 assertion compiling JIT/Regression_ro_2 (exit 134)

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Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1610154
Build error leg or test failing: linux-x64 Release AllSubsets_Mono_MiniFullAot_RuntimeTests minifullaot - AOT compile CoreCLR tests (JIT/Regression_ro_2/Regression_ro_2.dll)

Pipeline: runtime-extra-platforms (definition 154), branch main. The Mono MiniFullAOT test-build leg fails while ahead-of-time compiling JIT/Regression_ro_2/Regression_ro_2.dll: the Mono AOT compiler hits an internal assertion in the amd64 backend and aborts (SIGABRT), so the AOT compile CoreCLR tests MSBuild step fails with error MSB3073 ... exited with code 134 and the whole leg is blocked before any test runs. The failure reproduces on source build 1610154 (2026-09-24) and persists into follow-up build 1611740 (2026-09-25).

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

aot-compile: compiling .../JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll
Mono Ahead of Time compiler - compiling assembly .../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 ".../Tests/Core_Root/corerun .../JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll" exited with code 134.

Error Message

{
  "ErrorMessage": [
    "mono/mini/mini-amd64.c:5347, condition `amd64_is_imm32 (ins->inst_imm)' not met",
    "JIT/Regression_ro_2/Regression_ro_2/Regression_ro_2.dll\" exited with code 134."
  ],
  "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

First build it occurred

Earliest occurrence of this Mono AOT amd64 assertion in the scanned window is build 1603402 (2026-09-19); the immediately preceding build 1601987 (2026-09-18) has the AOT compile CoreCLR tests step succeeding. The signature then recurs continuously through source build 1610154 (2026-09-24) and follow-up build 1611740 (2026-09-25).

Duplicate search

Searched open and closed Known Build Error issues, area trackers, and open/merged PRs for amd64_is_imm32, mini-amd64.c:5347, Regression_ro_2, and the MiniFullAOT leg: no existing KBE, tracker, or fix PR matches this Mono AOT amd64 immediate-encoding assertion.

---

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.

Generated by CI Outer-Loop Failure Scanner · opus48 · 997.2 AIC · ⌖ 15 AIC · ⊞ 19.2K · ◷

Report

Build	Repository	Step Name	Console log	Pull Request
1613174	dotnet/runtime	AOT compile CoreCLR tests	Log

Summary

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