diff --git a/mlir/include/mlir/Conversion/BufferizationToMemRef/BufferizationToMemRef.h b/mlir/include/mlir/Conversion/BufferizationToMemRef/BufferizationToMemRef.h
--- a/mlir/include/mlir/Conversion/BufferizationToMemRef/BufferizationToMemRef.h
+++ b/mlir/include/mlir/Conversion/BufferizationToMemRef/BufferizationToMemRef.h
@@ -18,7 +18,7 @@
 #define GEN_PASS_DECL_CONVERTBUFFERIZATIONTOMEMREF
 #include "mlir/Conversion/Passes.h.inc"
 
-std::unique_ptr<OperationPass<ModuleOp>> createBufferizationToMemRefPass();
+std::unique_ptr<Pass> createBufferizationToMemRefPass();
 } // namespace mlir
 
 #endif // MLIR_CONVERSION_BUFFERIZATIONTOMEMREF_BUFFERIZATIONTOMEMREF_H
diff --git a/mlir/include/mlir/Conversion/Passes.td b/mlir/include/mlir/Conversion/Passes.td
--- a/mlir/include/mlir/Conversion/Passes.td
+++ b/mlir/include/mlir/Conversion/Passes.td
@@ -187,8 +187,7 @@
 // BufferizationToMemRef
 //===----------------------------------------------------------------------===//
 
-def ConvertBufferizationToMemRef : Pass<"convert-bufferization-to-memref",
-                                        "mlir::ModuleOp"> {
+def ConvertBufferizationToMemRef : Pass<"convert-bufferization-to-memref"> {
   let summary = "Convert operations from the Bufferization dialect to the "
                 "MemRef dialect";
   let description = [{
diff --git a/mlir/lib/Conversion/BufferizationToMemRef/BufferizationToMemRef.cpp b/mlir/lib/Conversion/BufferizationToMemRef/BufferizationToMemRef.cpp
--- a/mlir/lib/Conversion/BufferizationToMemRef/BufferizationToMemRef.cpp
+++ b/mlir/lib/Conversion/BufferizationToMemRef/BufferizationToMemRef.cpp
@@ -409,6 +409,11 @@
     if (adaptor.getMemrefs().size() == 1)
       return rewriteOneMemrefMultipleRetainCase(op, adaptor, rewriter);
 
+    if (!deallocHelperFunc)
+      return op->emitError(
+          "library function required for generic lowering, but cannot be "
+          "automatically inserted when operating on functions");
+
     return rewriteGeneralCase(op, adaptor, rewriter);
   }
 
@@ -620,21 +625,29 @@
   BufferizationToMemRefPass() = default;
 
   void runOnOperation() override {
-    ModuleOp module = cast<ModuleOp>(getOperation());
-    OpBuilder builder =
-        OpBuilder::atBlockBegin(&module.getBodyRegion().front());
-    SymbolTable symbolTable(module);
+    if (!isa<ModuleOp, FunctionOpInterface>(getOperation())) {
+      emitError(getOperation()->getLoc(),
+                "root operation must be a builtin.module or a function");
+      signalPassFailure();
+      return;
+    }
 
-    // Build dealloc helper function if there are deallocs.
     func::FuncOp helperFuncOp;
-    getOperation()->walk([&](bufferization::DeallocOp deallocOp) {
-      if (deallocOp.getMemrefs().size() > 1) {
-        helperFuncOp = DeallocOpConversion::buildDeallocationHelperFunction(
-            builder, getOperation()->getLoc(), symbolTable);
-        return WalkResult::interrupt();
-      }
-      return WalkResult::advance();
-    });
+    if (auto module = dyn_cast<ModuleOp>(getOperation())) {
+      OpBuilder builder =
+          OpBuilder::atBlockBegin(&module.getBodyRegion().front());
+      SymbolTable symbolTable(module);
+
+      // Build dealloc helper function if there are deallocs.
+      getOperation()->walk([&](bufferization::DeallocOp deallocOp) {
+        if (deallocOp.getMemrefs().size() > 1) {
+          helperFuncOp = DeallocOpConversion::buildDeallocationHelperFunction(
+              builder, getOperation()->getLoc(), symbolTable);
+          return WalkResult::interrupt();
+        }
+        return WalkResult::advance();
+      });
+    }
 
     RewritePatternSet patterns(&getContext());
     patterns.add<CloneOpConversion>(patterns.getContext());
@@ -652,7 +665,6 @@
 };
 } // namespace
 
-std::unique_ptr<OperationPass<ModuleOp>>
-mlir::createBufferizationToMemRefPass() {
+std::unique_ptr<Pass> mlir::createBufferizationToMemRefPass() {
   return std::make_unique<BufferizationToMemRefPass>();
 }
diff --git a/mlir/test/Conversion/BufferizationToMemRef/bufferization-to-memref-func.mlir b/mlir/test/Conversion/BufferizationToMemRef/bufferization-to-memref-func.mlir
new file mode 100644
--- /dev/null
+++ b/mlir/test/Conversion/BufferizationToMemRef/bufferization-to-memref-func.mlir
@@ -0,0 +1,24 @@
+// RUN: mlir-opt -verify-diagnostics --pass-pipeline="builtin.module(func.func(convert-bufferization-to-memref))" -split-input-file %s | FileCheck %s
+
+// CHECK-NOT: func @deallocHelper
+// CHECK-LABEL: func @conversion_dealloc_simple
+// CHECK-SAME: [[ARG0:%.+]]: memref<2xf32>
+// CHECK-SAME: [[ARG1:%.+]]: i1
+func.func @conversion_dealloc_simple(%arg0: memref<2xf32>, %arg1: i1) {
+  bufferization.dealloc (%arg0 : memref<2xf32>) if (%arg1)
+  return
+}
+
+//      CHECk: scf.if [[ARG1]] {
+// CHECk-NEXT:   memref.dealloc [[ARG0]] : memref<2xf32>
+// CHECk-NEXT: }
+// CHECk-NEXT: return
+
+// -----
+
+func.func @conversion_dealloc_multiple_memrefs_and_retained(%arg0: memref<2xf32>, %arg1: memref<5xf32>, %arg2: memref<1xf32>, %arg3: i1, %arg4: i1, %arg5: memref<2xf32>) -> (i1, i1) {
+  // expected-error @below {{library function required for generic lowering, but cannot be automatically inserted when operating on functions}}
+  // expected-error @below {{failed to legalize operation 'bufferization.dealloc' that was explicitly marked illegal}}
+  %0:2 = bufferization.dealloc (%arg0, %arg1 : memref<2xf32>, memref<5xf32>) if (%arg3, %arg4) retain (%arg2, %arg5 : memref<1xf32>, memref<2xf32>)
+  return %0#0, %0#1 : i1, i1
+}