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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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 "control_flow_simplifier.h"
#include "base/arena_allocator.h"
#include "base/macros.h"
#include "builder.h"
#include "nodes.h"
#include "optimizing_unit_test.h"
#include "side_effects_analysis.h"
namespace art HIDDEN {
class ControlFlowSimplifierTest : public OptimizingUnitTest {
protected:
HPhi* ConstructBasicGraphForSelect(HBasicBlock* return_block, HInstruction* instr) {
HParameterValue* bool_param = MakeParam(DataType::Type::kBool);
HIntConstant* const1 = graph_->GetIntConstant(1);
auto [if_block, then_block, else_block] = CreateDiamondPattern(return_block, bool_param);
AddOrInsertInstruction(then_block, instr);
HPhi* phi = MakePhi(return_block, {instr, const1});
return phi;
}
bool CheckGraphAndTryControlFlowSimplifier() {
graph_->BuildDominatorTree();
EXPECT_TRUE(CheckGraph());
SideEffectsAnalysis side_effects(graph_);
side_effects.Run();
return HControlFlowSimplifier(graph_, /*handles*/ nullptr, /*stats*/ nullptr).Run();
}
};
// HDivZeroCheck might throw and should not be hoisted from the conditional to an unconditional.
TEST_F(ControlFlowSimplifierTest, testZeroCheckPreventsSelect) {
HBasicBlock* return_block = InitEntryMainExitGraphWithReturnVoid();
HParameterValue* param = MakeParam(DataType::Type::kInt32);
HDivZeroCheck* instr = new (GetAllocator()) HDivZeroCheck(param, 0);
HPhi* phi = ConstructBasicGraphForSelect(return_block, instr);
ManuallyBuildEnvFor(instr, {param, graph_->GetIntConstant(1)});
EXPECT_FALSE(CheckGraphAndTryControlFlowSimplifier());
EXPECT_INS_RETAINED(phi);
}
// Test that ControlFlowSimplifier succeeds with HAdd.
TEST_F(ControlFlowSimplifierTest, testSelectWithAdd) {
HBasicBlock* return_block = InitEntryMainExitGraphWithReturnVoid();
HParameterValue* param = MakeParam(DataType::Type::kInt32);
HAdd* instr = new (GetAllocator()) HAdd(DataType::Type::kInt32, param, param, /*dex_pc=*/ 0);
HPhi* phi = ConstructBasicGraphForSelect(return_block, instr);
EXPECT_TRUE(CheckGraphAndTryControlFlowSimplifier());
EXPECT_INS_REMOVED(phi);
}
// Test that ControlFlowSimplifier succeeds if there is an additional `HPhi` with identical inputs.
TEST_F(ControlFlowSimplifierTest, testSelectWithAddAndExtraPhi) {
// Create a graph with three blocks merging to the `return_block`.
HBasicBlock* return_block = InitEntryMainExitGraphWithReturnVoid();
HParameterValue* bool_param1 = MakeParam(DataType::Type::kBool);
HParameterValue* bool_param2 = MakeParam(DataType::Type::kBool);
HParameterValue* param = MakeParam(DataType::Type::kInt32);
HInstruction* const0 = graph_->GetIntConstant(0);
auto [if_block1, left, mid] = CreateDiamondPattern(return_block, bool_param1);
HBasicBlock* if_block2 = AddNewBlock();
if_block1->ReplaceSuccessor(mid, if_block2);
HBasicBlock* right = AddNewBlock();
if_block2->AddSuccessor(mid);
if_block2->AddSuccessor(right);
HIf* if2 = MakeIf(if_block2, bool_param2);
right->AddSuccessor(return_block);
MakeGoto(right);
ASSERT_TRUE(PredecessorsEqual(return_block, {left, mid, right}));
HAdd* add = MakeBinOp<HAdd>(right, DataType::Type::kInt32, param, param);
HPhi* phi1 = MakePhi(return_block, {param, param, add});
HPhi* phi2 = MakePhi(return_block, {param, const0, const0});
// Prevent second `HSelect` match. Do not rely on the "instructions per branch" limit.
MakeInvokeStatic(left, DataType::Type::kVoid, {}, {});
EXPECT_TRUE(CheckGraphAndTryControlFlowSimplifier());
ASSERT_BLOCK_RETAINED(left);
ASSERT_BLOCK_REMOVED(mid);
ASSERT_BLOCK_REMOVED(right);
HInstruction* select = if2->GetPrevious(); // `HSelect` is inserted before `HIf`.
ASSERT_TRUE(select->IsSelect());
ASSERT_INS_RETAINED(phi1);
ASSERT_TRUE(InputsEqual(phi1, {param, select}));
ASSERT_INS_RETAINED(phi2);
ASSERT_TRUE(InputsEqual(phi2, {param, const0}));
}
// Test `HSelect` optimization in an irreducible loop.
TEST_F(ControlFlowSimplifierTest, testSelectInIrreducibleLoop) {
HBasicBlock* return_block = InitEntryMainExitGraphWithReturnVoid();
auto [split, left_header, right_header, body] = CreateIrreducibleLoop(return_block);
HParameterValue* split_param = MakeParam(DataType::Type::kBool);
HParameterValue* bool_param = MakeParam(DataType::Type::kBool);
HParameterValue* n_param = MakeParam(DataType::Type::kInt32);
MakeIf(split, split_param);
HInstruction* const0 = graph_->GetIntConstant(0);
HInstruction* const1 = graph_->GetIntConstant(1);
auto [left_phi, right_phi, add] =
MakeLinearIrreducibleLoopVar(left_header, right_header, body, const1, const0, const1);
HCondition* condition = MakeCondition(left_header, kCondGE, left_phi, n_param);
MakeIf(left_header, condition);
auto [if_block, then_block, else_block] = CreateDiamondPattern(body, bool_param);
HPhi* phi = MakePhi(body, {const1, const0});
EXPECT_TRUE(CheckGraphAndTryControlFlowSimplifier());
HLoopInformation* loop_info = left_header->GetLoopInformation();
ASSERT_TRUE(loop_info != nullptr);
ASSERT_TRUE(loop_info->IsIrreducible());
EXPECT_INS_REMOVED(phi);
ASSERT_TRUE(if_block->GetFirstInstruction()->IsSelect());
ASSERT_EQ(if_block, add->GetBlock()); // Moved when merging blocks.
for (HBasicBlock* removed_block : {then_block, else_block, body}) {
ASSERT_BLOCK_REMOVED(removed_block);
uint32_t removed_block_id = removed_block->GetBlockId();
ASSERT_FALSE(loop_info->GetBlocks().IsBitSet(removed_block_id)) << removed_block_id;
}
}
} // namespace art
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