diff --git a/mlir/lib/Transforms/Canonicalizer.cpp b/mlir/lib/Transforms/Canonicalizer.cpp
--- a/mlir/lib/Transforms/Canonicalizer.cpp
+++ b/mlir/lib/Transforms/Canonicalizer.cpp
@@ -21,22 +21,17 @@
 namespace {
 /// Canonicalize operations in nested regions.
 struct Canonicalizer : public CanonicalizerBase<Canonicalizer> {
+  Canonicalizer() = default;
   Canonicalizer(const GreedyRewriteConfig &config,
                 ArrayRef<std::string> disabledPatterns,
-                ArrayRef<std::string> enabledPatterns)
-      : config(config) {
+                ArrayRef<std::string> enabledPatterns) {
+    this->topDownProcessingEnabled = config.useTopDownTraversal;
+    this->enableRegionSimplification = config.enableRegionSimplification;
+    this->maxIterations = config.maxIterations;
     this->disabledPatterns = disabledPatterns;
     this->enabledPatterns = enabledPatterns;
   }
 
-  Canonicalizer() {
-    // Default constructed Canonicalizer takes its settings from command line
-    // options.
-    config.useTopDownTraversal = topDownProcessingEnabled;
-    config.enableRegionSimplification = enableRegionSimplification;
-    config.maxIterations = maxIterations;
-  }
-
   /// Initialize the canonicalizer by building the set of patterns used during
   /// execution.
   LogicalResult initialize(MLIRContext *context) override {
@@ -51,11 +46,16 @@
     return success();
   }
   void runOnOperation() override {
+    GreedyRewriteConfig config;
+    config.useTopDownTraversal = topDownProcessingEnabled;
+    config.enableRegionSimplification = enableRegionSimplification;
+    config.maxIterations = maxIterations;
+    llvm::dbgs() << "canonicalizer config.useTopDownTraveral = "
+                 << config.useTopDownTraversal << "\n";
     (void)applyPatternsAndFoldGreedily(getOperation()->getRegions(), patterns,
                                        config);
   }
 
-  GreedyRewriteConfig config;
   FrozenRewritePatternSet patterns;
 };
 } // namespace