[Mlir-commits] [mlir] [MLIR] Print more user-friendly error message when generating local reproducer and threading is enabled (PR #144905)

[Artemiy Bulavin]

https://github.com/abulavin created https://github.com/llvm/llvm-project/pull/144905

Currently if you run `mlir-opt` with `--mlir-pass-pipeline-local-reproducer` `--mlir-pass-pipeline-crash-reproducer` and don't provide `--mlir-disable-threading` you will get an LLVM error printed that suggests this is a bug and needs to be reported to LLVM. For example:

```
LLVM ERROR: Local crash reproduction can't be setup on a pass-manager without disabling multi-threading first.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
```


However, according to the local reproducer generation [documentation](https://mlir.llvm.org/docs/PassManagement/#local-reproducer-generation), disabling threading is required in order to generate a local reproducer. The current error message suggests this is a bug despite the MLIR documentation stating that this is a necessary constraint. Not disabling threading in this scenario is a user error so I have changed the error to be a pass manager `emitError` to reflect this.

An error is still printed but not in the same way that asks the user to file a bug report. I think this should help prevent any future confusion, such as what may have arised here https://github.com/llvm/llvm-project/issues/128344

Unit test added.

>From b5826708debcb41787d565bc608cb18eb0823919 Mon Sep 17 00:00:00 2001
From: Artemiy Bulavin <artemiyb at graphcore.ai>
Date: Thu, 19 Jun 2025 13:37:21 +0000
Subject: [PATCH] Print more user-friendly error message when generating local
 reproducer and threading is enabled

fixup: remove module in test
---
 mlir/lib/Pass/PassManagerOptions.cpp                    | 8 ++++++++
 mlir/test/mlir-opt/local-reproducer-with-threading.mlir | 5 +++++
 2 files changed, 13 insertions(+)
 create mode 100644 mlir/test/mlir-opt/local-reproducer-with-threading.mlir

diff --git a/mlir/lib/Pass/PassManagerOptions.cpp b/mlir/lib/Pass/PassManagerOptions.cpp
index dd119a75f4069..305bf72bb4799 100644
--- a/mlir/lib/Pass/PassManagerOptions.cpp
+++ b/mlir/lib/Pass/PassManagerOptions.cpp
@@ -146,6 +146,14 @@ LogicalResult mlir::applyPassManagerCLOptions(PassManager &pm) {
   if (!options.isConstructed())
     return failure();
 
+  if (options->reproducerFile.getNumOccurrences() && options->localReproducer &&
+      pm.getContext()->isMultithreadingEnabled()) {
+    emitError(UnknownLoc::get(pm.getContext()))
+        << "Local crash reproduction may not be used without disabling "
+           "mutli-threading first.";
+    return failure();
+  }
+
   // Generate a reproducer on crash/failure.
   if (options->reproducerFile.getNumOccurrences())
     pm.enableCrashReproducerGeneration(options->reproducerFile,
diff --git a/mlir/test/mlir-opt/local-reproducer-with-threading.mlir b/mlir/test/mlir-opt/local-reproducer-with-threading.mlir
new file mode 100644
index 0000000000000..10ebaed1c63da
--- /dev/null
+++ b/mlir/test/mlir-opt/local-reproducer-with-threading.mlir
@@ -0,0 +1,5 @@
+// Test that attempting to create a local crash reproducer without disabling threading
+// prints an error from the pass manager (as opposed to crashing with a stack trace).
+
+// RUN: mlir-opt --mlir-pass-pipeline-local-reproducer --mlir-pass-pipeline-crash-reproducer=%t 2>&1 %s | FileCheck %s
+// CHECK: error: Local crash reproduction may not be used without disabling mutli-threading first.