diff --git a/source/opt/CMakeLists.txt b/source/opt/CMakeLists.txt
index b9a586fc..aa85eb26 100644
--- a/source/opt/CMakeLists.txt
+++ b/source/opt/CMakeLists.txt
@@ -47,6 +47,7 @@ add_library(SPIRV-Tools-opt
   libspirv.cpp
   module.cpp
   set_spec_constant_default_value_pass.cpp
+  pass_manager.cpp
   strip_debug_info_pass.cpp
   types.cpp
   type_manager.cpp
diff --git a/source/opt/eliminate_dead_constant_pass.cpp b/source/opt/eliminate_dead_constant_pass.cpp
index c7a921f9..9d7a1484 100644
--- a/source/opt/eliminate_dead_constant_pass.cpp
+++ b/source/opt/eliminate_dead_constant_pass.cpp
@@ -25,7 +25,7 @@
 namespace spvtools {
 namespace opt {
 
-bool EliminateDeadConstantPass::Process(ir::Module* module) {
+Pass::Status EliminateDeadConstantPass::Process(ir::Module* module) {
   analysis::DefUseManager def_use(consumer(), module);
   std::unordered_set<ir::Instruction*> working_list;
   // Traverse all the instructions to get the initial set of dead constants as
@@ -109,7 +109,8 @@ bool EliminateDeadConstantPass::Process(ir::Module* module) {
   for (auto* da : dead_others) {
     da->ToNop();
   }
-  return !dead_consts.empty();
+  return dead_consts.empty() ? Status::SuccessWithoutChange
+                             : Status::SuccessWithChange;
 }
 
 }  // namespace opt
diff --git a/source/opt/eliminate_dead_constant_pass.h b/source/opt/eliminate_dead_constant_pass.h
index bc24ebad..80d8a9a4 100644
--- a/source/opt/eliminate_dead_constant_pass.h
+++ b/source/opt/eliminate_dead_constant_pass.h
@@ -31,7 +31,7 @@ class EliminateDeadConstantPass : public Pass {
   explicit EliminateDeadConstantPass(const MessageConsumer& c) : Pass(c) {}
 
   const char* name() const override { return "eliminate-dead-const"; }
-  bool Process(ir::Module*) override;
+  Status Process(ir::Module*) override;
 };
 
 }  // namespace opt
diff --git a/source/opt/fold_spec_constant_op_and_composite_pass.cpp b/source/opt/fold_spec_constant_op_and_composite_pass.cpp
index 6adb4976..19229925 100644
--- a/source/opt/fold_spec_constant_op_and_composite_pass.cpp
+++ b/source/opt/fold_spec_constant_op_and_composite_pass.cpp
@@ -251,7 +251,8 @@ FoldSpecConstantOpAndCompositePass::FoldSpecConstantOpAndCompositePass(
       type_mgr_(nullptr),
       id_to_const_val_() {}
 
-bool FoldSpecConstantOpAndCompositePass::ProcessImpl(ir::Module* module) {
+Pass::Status FoldSpecConstantOpAndCompositePass::ProcessImpl(
+    ir::Module* module) {
   bool modified = false;
   // Traverse through all the constant defining instructions. For Normal
   // Constants whose values are determined and do not depend on OpUndef
@@ -327,7 +328,7 @@ bool FoldSpecConstantOpAndCompositePass::ProcessImpl(ir::Module* module) {
         break;
     }
   }
-  return modified;
+  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 
 bool FoldSpecConstantOpAndCompositePass::ProcessOpSpecConstantOp(
diff --git a/source/opt/fold_spec_constant_op_and_composite_pass.h b/source/opt/fold_spec_constant_op_and_composite_pass.h
index 8b913a32..aff7af6d 100644
--- a/source/opt/fold_spec_constant_op_and_composite_pass.h
+++ b/source/opt/fold_spec_constant_op_and_composite_pass.h
@@ -53,7 +53,7 @@ class FoldSpecConstantOpAndCompositePass : public Pass {
   explicit FoldSpecConstantOpAndCompositePass(const MessageConsumer& c);
 
   const char* name() const override { return "fold-spec-const-op-composite"; }
-  bool Process(ir::Module* module) override {
+  Status Process(ir::Module* module) override {
     Initialize(module);
     return ProcessImpl(module);
   };
@@ -74,8 +74,8 @@ class FoldSpecConstantOpAndCompositePass : public Pass {
   // section of the given module, finds the Spec Constants defined with
   // OpSpecConstantOp and OpSpecConstantComposite instructions. If the result
   // value of those spec constants can be folded, fold them to their
-  // corresponding normal constants. Returns true if the module was modified.
-  bool ProcessImpl(ir::Module*);
+  // corresponding normal constants.
+  Status ProcessImpl(ir::Module*);
 
   // Processes the OpSpecConstantOp instruction pointed by the given
   // instruction iterator, folds it to normal constants if possible. Returns
diff --git a/source/opt/freeze_spec_constant_value_pass.cpp b/source/opt/freeze_spec_constant_value_pass.cpp
index 6d395da3..8855c416 100644
--- a/source/opt/freeze_spec_constant_value_pass.cpp
+++ b/source/opt/freeze_spec_constant_value_pass.cpp
@@ -17,7 +17,7 @@
 namespace spvtools {
 namespace opt {
 
-bool FreezeSpecConstantValuePass::Process(ir::Module* module) {
+Pass::Status FreezeSpecConstantValuePass::Process(ir::Module* module) {
   bool modified = false;
   module->ForEachInst([&modified](ir::Instruction* inst) {
     switch (inst->opcode()) {
@@ -44,7 +44,7 @@ bool FreezeSpecConstantValuePass::Process(ir::Module* module) {
         break;
     }
   });
-  return modified;
+  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 
 }  // namespace opt
diff --git a/source/opt/freeze_spec_constant_value_pass.h b/source/opt/freeze_spec_constant_value_pass.h
index 8b214636..7dd31b42 100644
--- a/source/opt/freeze_spec_constant_value_pass.h
+++ b/source/opt/freeze_spec_constant_value_pass.h
@@ -34,7 +34,7 @@ class FreezeSpecConstantValuePass : public Pass {
   explicit FreezeSpecConstantValuePass(const MessageConsumer& c) : Pass(c) {}
 
   const char* name() const override { return "freeze-spec-const"; }
-  bool Process(ir::Module*) override;
+  Status Process(ir::Module*) override;
 };
 
 }  // namespace opt
diff --git a/source/opt/null_pass.h b/source/opt/null_pass.h
index 7e107912..5b657711 100644
--- a/source/opt/null_pass.h
+++ b/source/opt/null_pass.h
@@ -27,7 +27,7 @@ class NullPass : public Pass {
   explicit NullPass(const MessageConsumer& c) : Pass(c) {}
 
   const char* name() const override { return "null"; }
-  bool Process(ir::Module*) override { return false; }
+  Status Process(ir::Module*) override { return Status::SuccessWithoutChange; }
 };
 
 }  // namespace opt
diff --git a/source/opt/pass.h b/source/opt/pass.h
index dadb53a3..cedb7c8d 100644
--- a/source/opt/pass.h
+++ b/source/opt/pass.h
@@ -27,6 +27,16 @@ namespace opt {
 // and all analysis and transformation is done via the Process() method.
 class Pass {
  public:
+  // The status of processing a module using a pass.
+  //
+  // The numbers for the cases are assigned to make sure that Failure & anything
+  // is Failure, SuccessWithChange & any success is SuccessWithChange.
+  enum class Status {
+    Failure = 0x00,
+    SuccessWithChange = 0x10,
+    SuccessWithoutChange = 0x11,
+  };
+
   // Constructs a new pass with the given message consumer, which will be
   // invoked every time there is a message to be communicated to the outside.
   //
@@ -39,9 +49,10 @@ class Pass {
   // Returns the reference to the message consumer for this pass.
   const MessageConsumer& consumer() const { return consumer_; }
 
-  // Processes the given |module| and returns true if the given |module| is
-  // modified for optimization.
-  virtual bool Process(ir::Module* module) = 0;
+  // Processes the given |module|. Returns Status::Failure if errors occur when
+  // processing. Returns the corresponding Status::Success if processing is
+  // succesful to indicate whether changes are made to the module.
+  virtual Status Process(ir::Module* module) = 0;
 
  private:
   const MessageConsumer& consumer_;  // Message consumer.
diff --git a/source/opt/pass_manager.cpp b/source/opt/pass_manager.cpp
new file mode 100644
index 00000000..18267db6
--- /dev/null
+++ b/source/opt/pass_manager.cpp
@@ -0,0 +1,35 @@
+// Copyright (c) 2016 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "pass_manager.h"
+
+namespace spvtools {
+namespace opt {
+
+Pass::Status PassManager::Run(ir::Module* module) {
+  auto status = Pass::Status::SuccessWithoutChange;
+  for (const auto& pass : passes_) {
+    const auto one_status = pass->Process(module);
+    if (one_status == Pass::Status::Failure) return one_status;
+    if (one_status == Pass::Status::SuccessWithChange) status = one_status;
+  }
+  // Set the Id bound in the header in case a pass forgot to do so.
+  if (status == Pass::Status::SuccessWithChange) {
+    module->SetIdBound(module->ComputeIdBound());
+  }
+  return status;
+}
+
+}  // namespace opt
+}  // namespace spvtools
diff --git a/source/opt/pass_manager.h b/source/opt/pass_manager.h
index 58c05377..61dc4b54 100644
--- a/source/opt/pass_manager.h
+++ b/source/opt/pass_manager.h
@@ -21,7 +21,7 @@
 #include "log.h"
 #include "message.h"
 #include "module.h"
-#include "passes.h"
+#include "pass.h"
 
 namespace spvtools {
 namespace opt {
@@ -35,37 +35,27 @@ class PassManager {
   explicit PassManager(MessageConsumer c) : consumer_(std::move(c)) {}
 
   // Adds an externally constructed pass.
-  void AddPass(std::unique_ptr<Pass> pass) {
-    passes_.push_back(std::move(pass));
-  }
+  void AddPass(std::unique_ptr<Pass> pass);
   // Uses the argument |args| to construct a pass instance of type |T|, and adds
   // the pass instance to this pass manger. The pass added will use this pass
   // manager's message consumer.
   template <typename T, typename... Args>
-  void AddPass(Args&&... args) {
-    passes_.emplace_back(new T(consumer_, std::forward<Args>(args)...));
-  }
+  void AddPass(Args&&... args);
 
   // Returns the number of passes added.
-  uint32_t NumPasses() const { return static_cast<uint32_t>(passes_.size()); }
+  uint32_t NumPasses() const;
   // Returns a pointer to the |index|th pass added.
-  Pass* GetPass(uint32_t index) const {
-    SPIRV_ASSERT(consumer_, index < passes_.size(), "index out of bound");
-    return passes_[index].get();
-  }
+  inline Pass* GetPass(uint32_t index) const;
 
   // Returns the message consumer.
-  const MessageConsumer& consumer() const { return consumer_; }
+  inline const MessageConsumer& consumer() const;
 
-  // Runs all passes on the given |module|.
-  void Run(ir::Module* module) {
-    bool modified = false;
-    for (const auto& pass : passes_) {
-      modified |= pass->Process(module);
-    }
-    // Set the Id bound in the header in case a pass forgot to do so.
-    if (modified) module->SetIdBound(module->ComputeIdBound());
-  }
+  // Runs all passes on the given |module|. Returns Status::Failure if errors
+  // occur when processing using one of the registered passes. All passes
+  // registered after the error-reporting pass will be skipped. Returns the
+  // corresponding Status::Success if processing is succesful to indicate
+  // whether changes are made to the module.
+  Pass::Status Run(ir::Module* module);
 
  private:
   // Consumer for messages.
@@ -74,6 +64,28 @@ class PassManager {
   std::vector<std::unique_ptr<Pass>> passes_;
 };
 
+inline void PassManager::AddPass(std::unique_ptr<Pass> pass) {
+  passes_.push_back(std::move(pass));
+}
+
+template <typename T, typename... Args>
+inline void PassManager::AddPass(Args&&... args) {
+  passes_.emplace_back(new T(consumer_, std::forward<Args>(args)...));
+}
+
+inline uint32_t PassManager::NumPasses() const {
+  return static_cast<uint32_t>(passes_.size());
+}
+
+inline Pass* PassManager::GetPass(uint32_t index) const {
+  SPIRV_ASSERT(consumer_, index < passes_.size(), "index out of bound");
+  return passes_[index].get();
+}
+
+inline const MessageConsumer& PassManager::consumer() const {
+  return consumer_;
+}
+
 }  // namespace opt
 }  // namespace spvtools
 
diff --git a/source/opt/set_spec_constant_default_value_pass.cpp b/source/opt/set_spec_constant_default_value_pass.cpp
index 68db8bfd..2e9f36fe 100644
--- a/source/opt/set_spec_constant_default_value_pass.cpp
+++ b/source/opt/set_spec_constant_default_value_pass.cpp
@@ -150,7 +150,7 @@ ir::Instruction* GetSpecIdTargetFromDecorationGroup(
 }
 };
 
-bool SetSpecConstantDefaultValuePass::Process(ir::Module* module) {
+Pass::Status SetSpecConstantDefaultValuePass::Process(ir::Module* module) {
   // The operand index of decoration target in an OpDecorate instruction.
   const uint32_t kTargetIdOperandIndex = 0;
   // The operand index of the decoration literal in an OpDecorate instruction.
@@ -249,7 +249,7 @@ bool SetSpecConstantDefaultValuePass::Process(ir::Module* module) {
     // No need to update the DefUse manager, as this pass does not change any
     // ids.
   }
-  return modified;
+  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 
 // Returns true if the given char is ':', '\0' or considered as blank space
diff --git a/source/opt/set_spec_constant_default_value_pass.h b/source/opt/set_spec_constant_default_value_pass.h
index 7762050f..e1c60120 100644
--- a/source/opt/set_spec_constant_default_value_pass.h
+++ b/source/opt/set_spec_constant_default_value_pass.h
@@ -42,7 +42,7 @@ class SetSpecConstantDefaultValuePass : public Pass {
       : Pass(c), spec_id_to_value_(std::move(default_values)) {}
 
   const char* name() const override { return "set-spec-const-default-value"; }
-  bool Process(ir::Module*) override;
+  Status Process(ir::Module*) override;
 
   // Parses the given null-terminated C string to get a mapping from Spec Id to
   // default value strings. Returns a unique pointer of the mapping from spec
diff --git a/source/opt/strip_debug_info_pass.cpp b/source/opt/strip_debug_info_pass.cpp
index 4a15ec11..45dd344b 100644
--- a/source/opt/strip_debug_info_pass.cpp
+++ b/source/opt/strip_debug_info_pass.cpp
@@ -17,7 +17,7 @@
 namespace spvtools {
 namespace opt {
 
-bool StripDebugInfoPass::Process(ir::Module* module) {
+Pass::Status StripDebugInfoPass::Process(ir::Module* module) {
   bool modified = !module->debugs().empty();
   module->debug_clear();
 
@@ -26,7 +26,7 @@ bool StripDebugInfoPass::Process(ir::Module* module) {
     inst->dbg_line_insts().clear();
   });
 
-  return modified;
+  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 
 }  // namespace opt
diff --git a/source/opt/strip_debug_info_pass.h b/source/opt/strip_debug_info_pass.h
index 9a8d27c2..c2bb1fd4 100644
--- a/source/opt/strip_debug_info_pass.h
+++ b/source/opt/strip_debug_info_pass.h
@@ -28,7 +28,7 @@ class StripDebugInfoPass : public Pass {
   explicit StripDebugInfoPass(const MessageConsumer& c) : Pass(c) {}
 
   const char* name() const override { return "strip-debug"; }
-  bool Process(ir::Module* module) override;
+  Status Process(ir::Module* module) override;
 };
 
 }  // namespace opt
diff --git a/source/opt/unify_const_pass.cpp b/source/opt/unify_const_pass.cpp
index 72fb3cd2..1e4da3d5 100644
--- a/source/opt/unify_const_pass.cpp
+++ b/source/opt/unify_const_pass.cpp
@@ -102,7 +102,7 @@ class ResultIdTrie {
 };
 }  // anonymous namespace
 
-bool UnifyConstantPass::Process(ir::Module* module) {
+Pass::Status UnifyConstantPass::Process(ir::Module* module) {
   bool modified = false;
   ResultIdTrie defined_constants;
   analysis::DefUseManager def_use_mgr(consumer(), module);
@@ -164,7 +164,7 @@ bool UnifyConstantPass::Process(ir::Module* module) {
         break;
     }
   }
-  return modified;
+  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 
 }  // opt
diff --git a/source/opt/unify_const_pass.h b/source/opt/unify_const_pass.h
index db17b69b..0edb10d3 100644
--- a/source/opt/unify_const_pass.h
+++ b/source/opt/unify_const_pass.h
@@ -39,7 +39,7 @@ class UnifyConstantPass : public Pass {
   explicit UnifyConstantPass(const MessageConsumer& c) : Pass(c) {}
 
   const char* name() const override { return "unify-const"; }
-  bool Process(ir::Module*) override;
+  Status Process(ir::Module*) override;
 };
 
 }  // namespace opt
diff --git a/test/opt/pass_fixture.h b/test/opt/pass_fixture.h
index 9cc831cf..9ce5fc99 100644
--- a/test/opt/pass_fixture.h
+++ b/test/opt/pass_fixture.h
@@ -48,17 +48,17 @@ class PassTest : public TestT {
   // Runs the given |pass| on the binary assembled from the |assembly|, and
   // disassebles the optimized binary. Returns a tuple of disassembly string
   // and the boolean value returned from pass Process() function.
-  std::tuple<std::string, bool> OptimizeAndDisassemble(
+  std::tuple<std::string, opt::Pass::Status> OptimizeAndDisassemble(
       opt::Pass* pass, const std::string& original, bool skip_nop) {
     std::unique_ptr<ir::Module> module =
         BuildModule(SPV_ENV_UNIVERSAL_1_1, consumer_, original);
     EXPECT_NE(nullptr, module) << "Assembling failed for shader:\n"
                                << original << std::endl;
     if (!module) {
-      return std::make_tuple(std::string(), false);
+      return std::make_tuple(std::string(), opt::Pass::Status::Failure);
     }
 
-    const bool modified = pass->Process(module.get());
+    const auto status = pass->Process(module.get());
 
     std::vector<uint32_t> binary;
     module->ToBinary(&binary, skip_nop);
@@ -66,14 +66,14 @@ class PassTest : public TestT {
     EXPECT_TRUE(tools_.Disassemble(binary, &optimized))
         << "Disassembling failed for shader:\n"
         << original << std::endl;
-    return std::make_tuple(optimized, modified);
+    return std::make_tuple(optimized, status);
   }
 
   // Runs a single pass of class |PassT| on the binary assembled from the
   // |assembly|, disassembles the optimized binary. Returns a tuple of
   // disassembly string and the boolean value from the pass Process() function.
   template <typename PassT, typename... Args>
-  std::tuple<std::string, bool> SinglePassRunAndDisassemble(
+  std::tuple<std::string, opt::Pass::Status> SinglePassRunAndDisassemble(
       const std::string& assembly, bool skip_nop, Args&&... args) {
     auto pass = MakeUnique<PassT>(consumer_, std::forward<Args>(args)...);
     return OptimizeAndDisassemble(pass.get(), assembly, skip_nop);
@@ -88,11 +88,13 @@ class PassTest : public TestT {
                              const std::string& expected, bool skip_nop,
                              Args&&... args) {
     std::string optimized;
-    bool modified = false;
-    std::tie(optimized, modified) = SinglePassRunAndDisassemble<PassT>(
+    auto status = opt::Pass::Status::SuccessWithoutChange;
+    std::tie(optimized, status) = SinglePassRunAndDisassemble<PassT>(
         original, skip_nop, std::forward<Args>(args)...);
     // Check whether the pass returns the correct modification indication.
-    EXPECT_EQ(original != expected, modified);
+    EXPECT_NE(opt::Pass::Status::Failure, status);
+    EXPECT_EQ(original == expected,
+              status == opt::Pass::Status::SuccessWithoutChange);
     EXPECT_EQ(expected, optimized);
   }
 
diff --git a/test/opt/test_fold_spec_const_op_composite.cpp b/test/opt/test_fold_spec_const_op_composite.cpp
index 051c9131..b84bf268 100644
--- a/test/opt/test_fold_spec_const_op_composite.cpp
+++ b/test/opt/test_fold_spec_const_op_composite.cpp
@@ -206,15 +206,16 @@ TEST_P(FoldSpecConstantOpAndCompositePassTest, ParamTestCase) {
 
   // Run the optimization and get the result code in disassembly.
   std::string optimized;
-  bool modified = false;
-  std::tie(optimized, modified) =
+  auto status = opt::Pass::Status::SuccessWithoutChange;
+  std::tie(optimized, status) =
       SinglePassRunAndDisassemble<opt::FoldSpecConstantOpAndCompositePass>(
           original, /* skip_nop = */ true);
 
   // Check the optimized code, but ignore the OpName instructions.
+  EXPECT_NE(opt::Pass::Status::Failure, status);
   EXPECT_EQ(
-      StripOpNameInstructions(expected) != StripOpNameInstructions(original),
-      modified);
+      StripOpNameInstructions(expected) == StripOpNameInstructions(original),
+      status == opt::Pass::Status::SuccessWithoutChange);
   EXPECT_EQ(StripOpNameInstructions(expected),
             StripOpNameInstructions(optimized));
 }
diff --git a/test/opt/test_line_debug_info.cpp b/test/opt/test_line_debug_info.cpp
index 3e86ed0c..a4af4974 100644
--- a/test/opt/test_line_debug_info.cpp
+++ b/test/opt/test_line_debug_info.cpp
@@ -25,10 +25,15 @@ class NopifyPass : public opt::Pass {
   explicit NopifyPass(const MessageConsumer& c) : opt::Pass(c) {}
 
   const char* name() const override { return "NopifyPass"; }
-  bool Process(ir::Module* module) override {
-    module->ForEachInst([](ir::Instruction* inst) { inst->ToNop(); },
-                        /* run_on_debug_line_insts = */ false);
-    return true;
+  Status Process(ir::Module* module) override {
+    bool modified = false;
+    module->ForEachInst(
+        [&modified](ir::Instruction* inst) {
+          inst->ToNop();
+          modified = true;
+        },
+        /* run_on_debug_line_insts = */ false);
+    return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
   }
 };
 
diff --git a/test/opt/test_pass_manager.cpp b/test/opt/test_pass_manager.cpp
index b365ad25..71ca3aca 100644
--- a/test/opt/test_pass_manager.cpp
+++ b/test/opt/test_pass_manager.cpp
@@ -78,10 +78,9 @@ class AppendOpNopPass : public opt::Pass {
   explicit AppendOpNopPass(const MessageConsumer& c) : opt::Pass(c) {}
 
   const char* name() const override { return "AppendOpNop"; }
-  bool Process(ir::Module* module) override {
-    auto inst = MakeUnique<ir::Instruction>();
-    module->AddDebugInst(std::move(inst));
-    return true;
+  Status Process(ir::Module* module) override {
+    module->AddDebugInst(MakeUnique<ir::Instruction>());
+    return Status::SuccessWithChange;
   }
 };
 
@@ -93,12 +92,11 @@ class AppendMultipleOpNopPass : public opt::Pass {
       : opt::Pass(c), num_nop_(num_nop) {}
 
   const char* name() const override { return "AppendOpNop"; }
-  bool Process(ir::Module* module) override {
+  Status Process(ir::Module* module) override {
     for (uint32_t i = 0; i < num_nop_; i++) {
-      auto inst = MakeUnique<ir::Instruction>();
-      module->AddDebugInst(std::move(inst));
+      module->AddDebugInst(MakeUnique<ir::Instruction>());
     }
-    return true;
+    return Status::SuccessWithChange;
   }
 
  private:
@@ -111,10 +109,10 @@ class DuplicateInstPass : public opt::Pass {
   explicit DuplicateInstPass(const MessageConsumer& c) : opt::Pass(c) {}
 
   const char* name() const override { return "DuplicateInst"; }
-  bool Process(ir::Module* module) override {
+  Status Process(ir::Module* module) override {
     auto inst = MakeUnique<ir::Instruction>(*(--module->debug_end()));
     module->AddDebugInst(std::move(inst));
-    return true;
+    return Status::SuccessWithChange;
   }
 };
 
@@ -149,11 +147,11 @@ class AppendTypeVoidInstPass : public opt::Pass {
       : opt::Pass(c), result_id_(result_id) {}
 
   const char* name() const override { return "AppendTypeVoidInstPass"; }
-  bool Process(ir::Module* module) override {
+  Status Process(ir::Module* module) override {
     auto inst = MakeUnique<ir::Instruction>(SpvOpTypeVoid, 0, result_id_,
                                             std::vector<ir::Operand>{});
     module->AddType(std::move(inst));
-    return true;
+    return Status::SuccessWithChange;
   }
 
  private:
diff --git a/test/opt/test_unify_const.cpp b/test/opt/test_unify_const.cpp
index 3a323721..58132017 100644
--- a/test/opt/test_unify_const.cpp
+++ b/test/opt/test_unify_const.cpp
@@ -114,8 +114,8 @@ class UnifyConstantTest : public PassTest<T> {
 
     // optimized code
     std::string optimized_before_strip;
-    bool modified = false;
-    std::tie(optimized_before_strip, modified) =
+    auto status = opt::Pass::Status::SuccessWithoutChange;
+    std::tie(optimized_before_strip, status) =
         this->template SinglePassRunAndDisassemble<opt::UnifyConstantPass>(
             test_builder.GetCode(),
             /* skip_nop = */ true);
@@ -124,8 +124,10 @@ class UnifyConstantTest : public PassTest<T> {
     std::tie(optimized_without_opnames, optimized_opnames) =
         StripOpNameInstructionsToSet(optimized_before_strip);
 
-    // Flag "modified" should be returned correctly.
-    EXPECT_EQ(expected_without_opnames != original_without_opnames, modified);
+    // Flag "status" should be returned correctly.
+    EXPECT_NE(opt::Pass::Status::Failure, status);
+    EXPECT_EQ(expected_without_opnames == original_without_opnames,
+              status == opt::Pass::Status::SuccessWithoutChange);
     // Code except OpName instructions should be exactly the same.
     EXPECT_EQ(expected_without_opnames, optimized_without_opnames);
     // OpName instructions can be in different order, but the content must be
@@ -208,11 +210,11 @@ TEST_F(UnifyFrontEndConstantSingleTest, SkipWhenResultIdHasDecorations) {
       });
 
   expected_builder
-    .AppendAnnotations({
+      .AppendAnnotations({
           "OpDecorate %f_1 RelaxedPrecision",
           "OpDecorate %f_2_dup RelaxedPrecision",
-        })
-  .AppendTypesConstantsGlobals({
+      })
+      .AppendTypesConstantsGlobals({
           // clang-format off
           "%float = OpTypeFloat 32",
           "%_pf_float = OpTypePointer Function %float",
@@ -223,7 +225,7 @@ TEST_F(UnifyFrontEndConstantSingleTest, SkipWhenResultIdHasDecorations) {
           "%f_3 = OpConstant %float 3",
           // clang-format on
       })
-  .AppendInMain({
+      .AppendInMain({
           // clang-format off
           "%f_var = OpVariable %_pf_float Function",
           "OpStore %f_var %f_1_dup",
@@ -231,8 +233,8 @@ TEST_F(UnifyFrontEndConstantSingleTest, SkipWhenResultIdHasDecorations) {
           "OpStore %f_var %f_3",
           // clang-format on
       })
-  .AppendNames({
-      "OpName %f_3 \"f_3_dup\"",
+      .AppendNames({
+          "OpName %f_3 \"f_3_dup\"",
       });
 
   Check(expected_builder, test_builder);
@@ -300,8 +302,7 @@ TEST_F(UnifyFrontEndConstantSingleTest, UnifyWithDecorationOnTypes) {
           "OpStore %flat_d_var %flat_d_1",
       })
       .AppendNames({
-          "OpName %flat_1 \"flat_1_dup\"",
-          "OpName %flat_d_1 \"flat_d_1_dup\"",
+          "OpName %flat_1 \"flat_1_dup\"", "OpName %flat_d_1 \"flat_d_1_dup\"",
       });
 
   Check(expected_builder, test_builder);
@@ -348,7 +349,7 @@ TEST_P(UnifyFrontEndConstantParamTest, TestCase) {
 
 INSTANTIATE_TEST_CASE_P(Case, UnifyFrontEndConstantParamTest,
                         ::testing::ValuesIn(std::vector<UnifyConstantTestCase>({
-        // clang-format off
+                            // clang-format off
         // basic tests for scalar constants
         {
           // preserved constants
@@ -974,7 +975,7 @@ INSTANTIATE_TEST_CASE_P(Case, UnifyFrontEndConstantParamTest,
             "OpName %signed_22 \"signed_22_dup\"",
           },
         },
-        // clang-format on
-    })));
+                            // clang-format on
+                        })));
 
 }  // anonymous namespace
diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index d15b27c4..5f51669b 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -20,6 +20,7 @@
 #include "source/opt/build_module.h"
 #include "source/opt/ir_loader.h"
 #include "source/opt/pass_manager.h"
+#include "source/opt/passes.h"
 #include "tools/io.h"
 
 using namespace spvtools;