Fixes #2358. Added to the reducer the ability to remove a function t… (…

…#2361)

* Fixes #2358.  Added to the reducer the ability to remove a function that is not directly called.  Factored out some code from the optimizer to help with this.

Android.mk

@@ -98,6 +98,7 @@ SPVTOOLS_OPT_SRC_FILES := \
 		source/opt/dominator_tree.cpp \
 		source/opt/eliminate_dead_constant_pass.cpp \
 		source/opt/eliminate_dead_functions_pass.cpp \
+		source/opt/eliminate_dead_functions_util.cpp \
 		source/opt/feature_manager.cpp \
 		source/opt/flatten_decoration_pass.cpp \
 		source/opt/fold.cpp \

BUILD.gn

@@ -496,6 +496,8 @@ static_library("spvtools_opt") {
     "source/opt/eliminate_dead_constant_pass.h",
     "source/opt/eliminate_dead_functions_pass.cpp",
     "source/opt/eliminate_dead_functions_pass.h",
+    "source/opt/eliminate_dead_functions_util.cpp",
+    "source/opt/eliminate_dead_functions_util.h",
     "source/opt/feature_manager.cpp",
     "source/opt/feature_manager.h",
     "source/opt/flatten_decoration_pass.cpp",

source/opt/CMakeLists.txt

@@ -37,6 +37,7 @@ set(SPIRV_TOOLS_OPT_SOURCES
   dominator_tree.h
   eliminate_dead_constant_pass.h
   eliminate_dead_functions_pass.h
+  eliminate_dead_functions_util.h
   feature_manager.h
   flatten_decoration_pass.h
   fold.h
@@ -131,6 +132,7 @@ set(SPIRV_TOOLS_OPT_SOURCES
   dominator_tree.cpp
   eliminate_dead_constant_pass.cpp
   eliminate_dead_functions_pass.cpp
+  eliminate_dead_functions_util.cpp
   feature_manager.cpp
   flatten_decoration_pass.cpp
   fold.cpp

source/opt/eliminate_dead_functions_pass.cpp

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "source/opt/eliminate_dead_functions_pass.h"
+#include "source/opt/eliminate_dead_functions_util.h"
 
 #include <unordered_set>
 
@@ -36,8 +37,8 @@ Pass::Status EliminateDeadFunctionsPass::Process() {
        funcIter != get_module()->end();) {
     if (live_function_set.count(&*funcIter) == 0) {
       modified = true;
-      EliminateFunction(&*funcIter);
-      funcIter = funcIter.Erase();
+      funcIter =
+          eliminatedeadfunctionsutil::EliminateFunction(context(), &funcIter);
     } else {
       ++funcIter;
     }
@@ -47,10 +48,5 @@ Pass::Status EliminateDeadFunctionsPass::Process() {
                   : Pass::Status::SuccessWithoutChange;
 }
 
-void EliminateDeadFunctionsPass::EliminateFunction(Function* func) {
-  // Remove all of the instruction in the function body
-  func->ForEachInst([this](Instruction* inst) { context()->KillInst(inst); },
-                    true);
-}
 }  // namespace opt
 }  // namespace spvtools

source/opt/eliminate_dead_functions_util.cpp

@@ -0,0 +1,32 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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 "eliminate_dead_functions_util.h"
+
+namespace spvtools {
+namespace opt {
+
+namespace eliminatedeadfunctionsutil {
+
+Module::iterator EliminateFunction(IRContext* context,
+                                   Module::iterator* func_iter) {
+  (*func_iter)
+      ->ForEachInst([context](Instruction* inst) { context->KillInst(inst); },
+                    true);
+  return func_iter->Erase();
+}
+
+}  // namespace eliminatedeadfunctionsutil
+}  // namespace opt
+}  // namespace spvtools

source/opt/eliminate_dead_functions_util.h

@@ -0,0 +1,36 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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.
+
+#ifndef SOURCE_OPT_ELIMINATE_DEAD_FUNCTIONS_UTIL_H_
+#define SOURCE_OPT_ELIMINATE_DEAD_FUNCTIONS_UTIL_H_
+
+#include "source/opt/ir_context.h"
+
+namespace spvtools {
+namespace opt {
+
+// Provides functionality for eliminating functions that are not needed, for use
+// by various analyses and passes.
+namespace eliminatedeadfunctionsutil {
+
+// Removes all of the function's instructions, removes the function from the
+// module, and returns the next iterator.
+Module::iterator EliminateFunction(IRContext* context,
+                                   Module::iterator* func_iter);
+
+}  // namespace eliminatedeadfunctionsutil
+}  // namespace opt
+}  // namespace spvtools
+
+#endif  //  SOURCE_OPT_ELIMINATE_DEAD_FUNCTIONS_UTIL_H_

source/reduce/CMakeLists.txt

@@ -25,6 +25,8 @@ set(SPIRV_TOOLS_REDUCE_SOURCES
         reduction_pass.h
         reduction_util.h
         remove_instruction_reduction_opportunity.h
+        remove_function_reduction_opportunity.h
+        remove_function_reduction_opportunity_finder.h
         remove_opname_instruction_reduction_opportunity_finder.h
         remove_unreferenced_instruction_reduction_opportunity_finder.h
         structured_loop_to_selection_reduction_opportunity.h
@@ -41,6 +43,8 @@ set(SPIRV_TOOLS_REDUCE_SOURCES
         reduction_opportunity.cpp
         reduction_pass.cpp
         reduction_util.cpp
+        remove_function_reduction_opportunity.cpp
+        remove_function_reduction_opportunity_finder.cpp
         remove_instruction_reduction_opportunity.cpp
         remove_unreferenced_instruction_reduction_opportunity_finder.cpp
         remove_opname_instruction_reduction_opportunity_finder.cpp

source/reduce/remove_function_reduction_opportunity.cpp

@@ -0,0 +1,40 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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 "remove_function_reduction_opportunity.h"
+#include "source/opt/eliminate_dead_functions_util.h"
+
+namespace spvtools {
+namespace reduce {
+
+bool RemoveFunctionReductionOpportunity::PreconditionHolds() {
+  // Removing one function cannot influence whether another function can be
+  // removed.
+  return true;
+}
+
+void RemoveFunctionReductionOpportunity::Apply() {
+  for (opt::Module::iterator function_it = context_->module()->begin();
+       function_it != context_->module()->end(); ++function_it) {
+    if (&*function_it == function_) {
+      opt::eliminatedeadfunctionsutil::EliminateFunction(context_,
+                                                         &function_it);
+      return;
+    }
+  }
+  assert(0 && "Function to be removed was not found.");
+}
+
+}  // namespace reduce
+}  // namespace spvtools

source/reduce/remove_function_reduction_opportunity.h

@@ -0,0 +1,49 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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.
+
+#ifndef SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_H_
+#define SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_H_
+
+#include "reduction_opportunity.h"
+#include "source/opt/function.h"
+
+namespace spvtools {
+namespace reduce {
+
+// An opportunity to remove an unreferenced function.
+class RemoveFunctionReductionOpportunity : public ReductionOpportunity {
+ public:
+  // Creates an opportunity to remove |function| from the module represented by
+  // |context|.
+  RemoveFunctionReductionOpportunity(opt::IRContext* context,
+                                     opt::Function* function)
+      : context_(context), function_(function) {}
+
+  bool PreconditionHolds() override;
+
+ protected:
+  void Apply() override;
+
+ private:
+  // The IR context for the module under analysis.
+  opt::IRContext* context_;
+
+  // The function that can be removed.
+  opt::Function* function_;
+};
+
+}  // namespace reduce
+}  // namespace spvtools
+
+#endif  //   SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_H_

source/reduce/remove_function_reduction_opportunity_finder.cpp

@@ -0,0 +1,42 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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 "remove_function_reduction_opportunity_finder.h"
+#include "remove_function_reduction_opportunity.h"
+
+namespace spvtools {
+namespace reduce {
+
+std::vector<std::unique_ptr<ReductionOpportunity>>
+RemoveFunctionReductionOpportunityFinder::GetAvailableOpportunities(
+    opt::IRContext* context) const {
+  std::vector<std::unique_ptr<ReductionOpportunity>> result;
+  // Consider each function.
+  for (auto& function : *context->module()) {
+    if (context->get_def_use_mgr()->NumUses(function.result_id()) > 0) {
+      // If the function is referenced, ignore it.
+      continue;
+    }
+    result.push_back(
+        MakeUnique<RemoveFunctionReductionOpportunity>(context, &function));
+  }
+  return result;
+}
+
+std::string RemoveFunctionReductionOpportunityFinder::GetName() const {
+  return "RemoveFunctionReductionOpportunityFinder";
+}
+
+}  // namespace reduce
+}  // namespace spvtools

source/reduce/remove_function_reduction_opportunity_finder.h

@@ -0,0 +1,42 @@
+// Copyright (c) 2019 Google LLC
+//
+// 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.
+
+#ifndef SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_FINDER_H_
+#define SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_FINDER_H_
+
+#include "source/reduce/reduction_opportunity_finder.h"
+
+namespace spvtools {
+namespace reduce {
+
+// A finder of opportunities to remove unreferenced functions.
+class RemoveFunctionReductionOpportunityFinder
+    : public ReductionOpportunityFinder {
+ public:
+  RemoveFunctionReductionOpportunityFinder() = default;
+
+  ~RemoveFunctionReductionOpportunityFinder() override = default;
+
+  std::string GetName() const final;
+
+  std::vector<std::unique_ptr<ReductionOpportunity>> GetAvailableOpportunities(
+      opt::IRContext* context) const final;
+
+ private:
+};
+
+}  // namespace reduce
+}  // namespace spvtools
+
+#endif  //   SOURCE_REDUCE_REMOVE_FUNCTION_REDUCTION_OPPORTUNITY_FINDER_H_

test/reduce/CMakeLists.txt

@@ -20,6 +20,7 @@ add_spvtools_unittest(TARGET reduce
         reduce_test_util.cpp
         reduce_test_util.h
         reducer_test.cpp
+        remove_function_test.cpp
         remove_opname_instruction_test.cpp
         remove_unreferenced_instruction_test.cpp
         structured_loop_to_selection_test.cpp