diff --git a/mlir/CMakeLists.txt b/mlir/CMakeLists.txt
--- a/mlir/CMakeLists.txt
+++ b/mlir/CMakeLists.txt
@@ -141,6 +141,10 @@
 
 set(MLIR_BUILD_MLIR_C_DYLIB 0 CACHE BOOL "Builds libMLIR-C shared library.")
 
+configure_file(
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Config/mlir-config.h.cmake
+  ${MLIR_INCLUDE_DIR}/mlir/Config/mlir-config.h)
+
 #-------------------------------------------------------------------------------
 # Python Bindings Configuration
 # Requires:
diff --git a/mlir/include/mlir/Config/mlir-config.h.cmake b/mlir/include/mlir/Config/mlir-config.h.cmake
new file mode 100644
--- /dev/null
+++ b/mlir/include/mlir/Config/mlir-config.h.cmake
@@ -0,0 +1,20 @@
+//===- mlir-config.h - MLIR configuration ------------------------*- C -*-===*//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+/* This file enumerates variables from the MLIR configuration so that they
+   can be in exported headers and won't override package specific directives.
+   This is a C header that can be included in the mlir-c headers. */
+
+#ifndef MLIR_CONFIG_H
+#define MLIR_CONFIG_H
+
+/* Enable expensive checks to detect invalid pattern API usage. NDEBUG is
+   required. Running with ASAN is recommended for easier debugging. */
+#cmakedefine01 MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+
+#endif
diff --git a/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp b/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
--- a/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
+++ b/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+#include "mlir/Config/mlir-config.h"
 #include "mlir/IR/Matchers.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "mlir/Rewrite/PatternApplicator.h"
@@ -121,6 +122,18 @@
 
   /// The low-level pattern applicator.
   PatternApplicator matcher;
+
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+  /// Operation finger prints to detect invalid pattern API usage. IR is checked
+  /// against these finger prints after pattern application to detect cases
+  /// where IR was modified directly, bypassing the rewriter API.
+  DenseMap<Operation *, OperationFingerPrint> fingerprints;
+
+  /// Top-level operation of the current greedy rewrite.
+  Operation *fingerprintTopLevel = nullptr;
+
+  void invalidateFingerPrint(Operation *op);
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
 };
 } // namespace
 
@@ -225,15 +238,59 @@
         return success();
       };
 
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+      // Compute finger prints of all ops in the current rewrite scope.
+      auto clearFingerprints =
+          llvm::make_scope_exit([&]() { fingerprints.clear(); });
+      fingerprintTopLevel = config.scope ? config.scope->getParentOp() : op;
+      fingerprintTopLevel->walk(
+          [&](Operation *op) { fingerprints.try_emplace(op, op); });
+
+      // Finger print before applying a pattern.
+      OperationFingerPrint &beforeFingerPrint =
+          fingerprints.find(fingerprintTopLevel)->second;
+
+      // Apply a pattern.
+      LogicalResult matchResult =
+          matcher.matchAndRewrite(op, *this, canApply, onFailure, onSuccess);
+
+      // Finger print after applying a pattern.
+      OperationFingerPrint afterFingerPrint(fingerprintTopLevel);
+
+      if (succeeded(matchResult)) {
+        // Pattern application success => IR must have changed.
+        LLVM_DEBUG(logResultWithLine("success", "pattern matched"));
+        assert(beforeFingerPrint != afterFingerPrint &&
+              "pattern returned success but IR did not change");
+        for (const auto &it : fingerprints) {
+          // Skip top-level op, its finger print is never invalidated.
+          if (it.first == fingerprintTopLevel)
+            continue;
+          // Note: Finger print computation may crash when an op was erased
+          // without notifying the rewriter. (Run with ASAN.) It does not crash
+          // if a new op was created at the same memory location. (But then the
+          // finger print should have changed.)
+          assert(it.second == OperationFingerPrint(it.first) &&
+                 "operation finger print changed");
+        }
+      } else {
+        // Pattern application failure => IR must not have changed.
+        LLVM_DEBUG(logResultWithLine("failure", "pattern failed to match"));
+        assert(beforeFingerPrint == afterFingerPrint &&
+              "pattern returned failure but IR did change");
+      }
+#else
       LogicalResult matchResult =
           matcher.matchAndRewrite(op, *this, canApply, onFailure, onSuccess);
-      if (succeeded(matchResult))
+      if (succeeded(matchResult)) {
         LLVM_DEBUG(logResultWithLine("success", "pattern matched"));
-      else
+      } else {
         LLVM_DEBUG(logResultWithLine("failure", "pattern failed to match"));
+      }
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
 #else
       LogicalResult matchResult = matcher.matchAndRewrite(op, *this);
-#endif
+#endif // NDEBUG
 
       if (succeeded(matchResult)) {
         changed = true;
@@ -244,7 +301,18 @@
   return changed;
 }
 
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+void GreedyPatternRewriteDriver::invalidateFingerPrint(Operation *op) {
+  // Invalidate all finger prints until the top level.
+  while (op && op != fingerprintTopLevel) {
+    fingerprints.erase(op);
+    op = op->getParentOp();
+  }
+}
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+
 void GreedyPatternRewriteDriver::addToWorklist(Operation *op) {
+  assert(op && "expected valid op");
   // Gather potential ancestors while looking for a "scope" parent region.
   SmallVector<Operation *, 8> ancestors;
   Region *region = nullptr;
@@ -303,6 +371,11 @@
     logger.startLine() << "** Insert  : '" << op->getName() << "'(" << op
                        << ")\n";
   });
+
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+  invalidateFingerPrint(op->getParentOp());
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+
   if (config.listener)
     config.listener->notifyOperationInserted(op);
   if (config.strictMode == GreedyRewriteStrictness::ExistingAndNewOps)
@@ -317,6 +390,11 @@
   });
   if (config.listener)
     config.listener->notifyOperationModified(op);
+
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+  invalidateFingerPrint(op);
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+
   addToWorklist(op);
 }
 
@@ -346,6 +424,9 @@
   op->walk([this](Operation *operation) {
     removeFromWorklist(operation);
     folder.notifyRemoval(operation);
+#ifdef MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
+    invalidateFingerPrint(operation);
+#endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
   });
 
   if (config.strictMode != GreedyRewriteStrictness::AnyOp)