diff --git a/mlir/include/mlir/Support/MlirOptMain.h b/mlir/include/mlir/Support/MlirOptMain.h
--- a/mlir/include/mlir/Support/MlirOptMain.h
+++ b/mlir/include/mlir/Support/MlirOptMain.h
@@ -27,6 +27,9 @@
 namespace mlir {
 class DialectRegistry;
 class PassPipelineCLParser;
+class PassManager;
+
+using DefaultPassPipelineFn = llvm::function_ref<void(PassManager &pm)>;
 
 /// Perform the core processing behind `mlir-opt`:
 /// - outputStream is the stream where the resulting IR is printed.
@@ -50,7 +53,8 @@
                           DialectRegistry &registry, bool splitInputFile,
                           bool verifyDiagnostics, bool verifyPasses,
                           bool allowUnregisteredDialects,
-                          bool preloadDialectsInContext = false);
+                          bool preloadDialectsInContext = false,
+                          DefaultPassPipelineFn fn = nullptr);
 
 /// Implementation for tools like `mlir-opt`.
 /// - toolName is used for the header displayed by `--help`.
diff --git a/mlir/lib/Support/MlirOptMain.cpp b/mlir/lib/Support/MlirOptMain.cpp
--- a/mlir/lib/Support/MlirOptMain.cpp
+++ b/mlir/lib/Support/MlirOptMain.cpp
@@ -26,6 +26,7 @@
 #include "mlir/Support/FileUtilities.h"
 #include "mlir/Support/Timing.h"
 #include "mlir/Support/ToolUtilities.h"
+#include "mlir/Transforms/Passes.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/InitLLVM.h"
@@ -48,7 +49,8 @@
 static LogicalResult performActions(raw_ostream &os, bool verifyDiagnostics,
                                     bool verifyPasses, SourceMgr &sourceMgr,
                                     MLIRContext *context,
-                                    const PassPipelineCLParser &passPipeline) {
+                                    const PassPipelineCLParser &passPipeline,
+                                    DefaultPassPipelineFn fn) {
   DefaultTimingManager tm;
   applyDefaultTimingManagerCLOptions(tm);
   TimingScope timing = tm.getRootScope();
@@ -77,9 +79,14 @@
     return failure();
   };
 
-  // Build the provided pipeline.
-  if (failed(passPipeline.addToPipeline(pm, errorHandler)))
-    return failure();
+  if (passPipeline.hasAnyOccurrences()) {
+    // Build the provided pipeline.
+    if (failed(passPipeline.addToPipeline(pm, errorHandler)))
+      return failure();
+  } else if (fn) {
+    // Set default pipeline.
+    fn(pm);
+  }
 
   // Run the pipeline.
   if (failed(pm.run(*module)))
@@ -99,7 +106,8 @@
               bool verifyDiagnostics, bool verifyPasses,
               bool allowUnregisteredDialects, bool preloadDialectsInContext,
               const PassPipelineCLParser &passPipeline,
-              DialectRegistry &registry, llvm::ThreadPool &threadPool) {
+              DialectRegistry &registry, llvm::ThreadPool &threadPool,
+              DefaultPassPipelineFn fn) {
   // Tell sourceMgr about this buffer, which is what the parser will pick up.
   SourceMgr sourceMgr;
   sourceMgr.AddNewSourceBuffer(std::move(ownedBuffer), SMLoc());
@@ -122,7 +130,7 @@
   if (!verifyDiagnostics) {
     SourceMgrDiagnosticHandler sourceMgrHandler(sourceMgr, &context);
     return performActions(os, verifyDiagnostics, verifyPasses, sourceMgr,
-                          &context, passPipeline);
+                          &context, passPipeline, fn);
   }
 
   SourceMgrDiagnosticVerifierHandler sourceMgrHandler(sourceMgr, &context);
@@ -131,7 +139,7 @@
   // these actions succeed or fail, we only care what diagnostics they produce
   // and whether they match our expectations.
   (void)performActions(os, verifyDiagnostics, verifyPasses, sourceMgr, &context,
-                       passPipeline);
+                       passPipeline, fn);
 
   // Verify the diagnostic handler to make sure that each of the diagnostics
   // matched.
@@ -144,7 +152,8 @@
                                 DialectRegistry &registry, bool splitInputFile,
                                 bool verifyDiagnostics, bool verifyPasses,
                                 bool allowUnregisteredDialects,
-                                bool preloadDialectsInContext) {
+                                bool preloadDialectsInContext,
+                                DefaultPassPipelineFn fn) {
   // The split-input-file mode is a very specific mode that slices the file
   // up into small pieces and checks each independently.
   // We use an explicit threadpool to avoid creating and joining/destroying
@@ -157,14 +166,14 @@
           return processBuffer(os, std::move(chunkBuffer), verifyDiagnostics,
                                verifyPasses, allowUnregisteredDialects,
                                preloadDialectsInContext, passPipeline, registry,
-                               threadPool);
+                               threadPool, fn);
         },
         outputStream);
 
   return processBuffer(outputStream, std::move(buffer), verifyDiagnostics,
                        verifyPasses, allowUnregisteredDialects,
                        preloadDialectsInContext, passPipeline, registry,
-                       threadPool);
+                       threadPool, fn);
 }
 
 LogicalResult mlir::MlirOptMain(int argc, char **argv, llvm::StringRef toolName,
@@ -266,9 +275,11 @@
     return failure();
   }
 
-  if (failed(MlirOptMain(output->os(), std::move(file), passPipeline, registry,
-                         splitInputFile, verifyDiagnostics, verifyPasses,
-                         allowUnregisteredDialects, preloadDialectsInContext)))
+  if (failed(MlirOptMain(
+          output->os(), std::move(file), passPipeline, registry, splitInputFile,
+          verifyDiagnostics, verifyPasses, allowUnregisteredDialects,
+          preloadDialectsInContext,
+          [&](PassManager &pm) { pm.addPass(createCanonicalizerPass()); })))
     return failure();
 
   // Keep the output file if the invocation of MlirOptMain was successful.