ART: Implement loop peeling/unrolling routines.

Implement loop peeling/unrolling routines using SuperblockCloner.
Fixes bug b/74198030 and provides tests for it.

Bug: b/74198030
Test: superblock_cloner_test.cc, loop_optimization_test.cc.

Change-Id: Id0d9a91575c88f8e45186441b14e903b89b007dd

1 files changed, 529 insertions, 28 deletions

diff --git a/compiler/optimizing/superblock_cloner_test.cc b/compiler/optimizing/superblock_cloner_test.cc
index f1b7bffdf5..df2e517aff 100644
--- a/compiler/optimizing/superblock_cloner_test.cc
+++ b/compiler/optimizing/superblock_cloner_test.cc
@@ -25,52 +25,65 @@ namespace art {
 
 using HBasicBlockMap = SuperblockCloner::HBasicBlockMap;
 using HInstructionMap = SuperblockCloner::HInstructionMap;
+using HBasicBlockSet = SuperblockCloner::HBasicBlockSet;
+using HEdgeSet = SuperblockCloner::HEdgeSet;
 
 // This class provides methods and helpers for testing various cloning and copying routines:
 // individual instruction cloning and cloning of the more coarse-grain structures.
 class SuperblockClonerTest : public OptimizingUnitTest {
  public:
-  SuperblockClonerTest()
-      : graph_(CreateGraph()), entry_block_(nullptr), exit_block_(nullptr), parameter_(nullptr) {}
+  SuperblockClonerTest() : graph_(CreateGraph()),
+                           entry_block_(nullptr),
+                           return_block_(nullptr),
+                           exit_block_(nullptr),
+                           parameter_(nullptr) {}
 
-  void CreateBasicLoopControlFlow(/* out */ HBasicBlock** header_p,
-                                  /* out */ HBasicBlock** body_p) {
+  void InitGraph() {
     entry_block_ = new (GetAllocator()) HBasicBlock(graph_);
     graph_->AddBlock(entry_block_);
     graph_->SetEntryBlock(entry_block_);
 
+    return_block_ = new (GetAllocator()) HBasicBlock(graph_);
+    graph_->AddBlock(return_block_);
+
+    exit_block_ = new (GetAllocator()) HBasicBlock(graph_);
+    graph_->AddBlock(exit_block_);
+    graph_->SetExitBlock(exit_block_);
+
+    entry_block_->AddSuccessor(return_block_);
+    return_block_->AddSuccessor(exit_block_);
+
+    parameter_ = new (GetAllocator()) HParameterValue(graph_->GetDexFile(),
+                                                      dex::TypeIndex(0),
+                                                      0,
+                                                      DataType::Type::kInt32);
+    entry_block_->AddInstruction(parameter_);
+    return_block_->AddInstruction(new (GetAllocator()) HReturnVoid());
+    exit_block_->AddInstruction(new (GetAllocator()) HExit());
+  }
+
+  void CreateBasicLoopControlFlow(HBasicBlock* position,
+                                  HBasicBlock* successor,
+                                  /* out */ HBasicBlock** header_p,
+                                  /* out */ HBasicBlock** body_p) {
     HBasicBlock* loop_preheader = new (GetAllocator()) HBasicBlock(graph_);
     HBasicBlock* loop_header = new (GetAllocator()) HBasicBlock(graph_);
     HBasicBlock* loop_body = new (GetAllocator()) HBasicBlock(graph_);
-    HBasicBlock* loop_exit = new (GetAllocator()) HBasicBlock(graph_);
 
     graph_->AddBlock(loop_preheader);
     graph_->AddBlock(loop_header);
     graph_->AddBlock(loop_body);
-    graph_->AddBlock(loop_exit);
 
-    exit_block_ = new (GetAllocator()) HBasicBlock(graph_);
-    graph_->AddBlock(exit_block_);
-    graph_->SetExitBlock(exit_block_);
+    position->ReplaceSuccessor(successor, loop_preheader);
 
-    entry_block_->AddSuccessor(loop_preheader);
     loop_preheader->AddSuccessor(loop_header);
     // Loop exit first to have a proper exit condition/target for HIf.
-    loop_header->AddSuccessor(loop_exit);
+    loop_header->AddSuccessor(successor);
     loop_header->AddSuccessor(loop_body);
     loop_body->AddSuccessor(loop_header);
-    loop_exit->AddSuccessor(exit_block_);
 
     *header_p = loop_header;
     *body_p = loop_body;
-
-    parameter_ = new (GetAllocator()) HParameterValue(graph_->GetDexFile(),
-                                                      dex::TypeIndex(0),
-                                                      0,
-                                                      DataType::Type::kInt32);
-    entry_block_->AddInstruction(parameter_);
-    loop_exit->AddInstruction(new (GetAllocator()) HReturnVoid());
-    exit_block_->AddInstruction(new (GetAllocator()) HExit());
   }
 
   void CreateBasicLoopDataFlow(HBasicBlock* loop_header, HBasicBlock* loop_body) {
@@ -84,11 +97,12 @@ class SuperblockClonerTest : public OptimizingUnitTest {
     // Header block.
     HPhi* phi = new (GetAllocator()) HPhi(GetAllocator(), 0, 0, DataType::Type::kInt32);
     HInstruction* suspend_check = new (GetAllocator()) HSuspendCheck();
+    HInstruction* loop_check = new (GetAllocator()) HGreaterThanOrEqual(phi, const_128);
 
     loop_header->AddPhi(phi);
     loop_header->AddInstruction(suspend_check);
-    loop_header->AddInstruction(new (GetAllocator()) HGreaterThanOrEqual(phi, const_128));
-    loop_header->AddInstruction(new (GetAllocator()) HIf(parameter_));
+    loop_header->AddInstruction(loop_check);
+    loop_header->AddInstruction(new (GetAllocator()) HIf(loop_check));
 
     // Loop body block.
     HInstruction* null_check = new (GetAllocator()) HNullCheck(parameter_, dex_pc);
@@ -97,8 +111,8 @@ class SuperblockClonerTest : public OptimizingUnitTest {
     HInstruction* array_get =
         new (GetAllocator()) HArrayGet(null_check, bounds_check, DataType::Type::kInt32, dex_pc);
     HInstruction* add =  new (GetAllocator()) HAdd(DataType::Type::kInt32, array_get, const_1);
-    HInstruction* array_set =
-        new (GetAllocator()) HArraySet(null_check, bounds_check, add, DataType::Type::kInt32, dex_pc);
+    HInstruction* array_set = new (GetAllocator()) HArraySet(
+        null_check, bounds_check, add, DataType::Type::kInt32, dex_pc);
     HInstruction* induction_inc = new (GetAllocator()) HAdd(DataType::Type::kInt32, phi, const_1);
 
     loop_body->AddInstruction(null_check);
@@ -153,6 +167,7 @@ class SuperblockClonerTest : public OptimizingUnitTest {
   HGraph* graph_;
 
   HBasicBlock* entry_block_;
+  HBasicBlock* return_block_;
   HBasicBlock* exit_block_;
 
   HInstruction* parameter_;
@@ -162,10 +177,11 @@ TEST_F(SuperblockClonerTest, IndividualInstrCloner) {
   HBasicBlock* header = nullptr;
   HBasicBlock* loop_body = nullptr;
 
-  CreateBasicLoopControlFlow(&header, &loop_body);
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
   CreateBasicLoopDataFlow(header, loop_body);
   graph_->BuildDominatorTree();
-  ASSERT_TRUE(CheckGraph());
+  EXPECT_TRUE(CheckGraph());
 
   HSuspendCheck* old_suspend_check = header->GetLoopInformation()->GetSuspendCheck();
   CloneAndReplaceInstructionVisitor visitor(graph_);
@@ -193,7 +209,8 @@ TEST_F(SuperblockClonerTest, CloneBasicBlocks) {
   HBasicBlock* loop_body = nullptr;
   ArenaAllocator* arena = graph_->GetAllocator();
 
-  CreateBasicLoopControlFlow(&header, &loop_body);
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
   CreateBasicLoopDataFlow(header, loop_body);
   graph_->BuildDominatorTree();
   ASSERT_TRUE(CheckGraph());
@@ -272,7 +289,8 @@ TEST_F(SuperblockClonerTest, AdjustControlFlowInfo) {
   HBasicBlock* loop_body = nullptr;
   ArenaAllocator* arena = graph_->GetAllocator();
 
-  CreateBasicLoopControlFlow(&header, &loop_body);
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
   CreateBasicLoopDataFlow(header, loop_body);
   graph_->BuildDominatorTree();
   ASSERT_TRUE(CheckGraph());
@@ -303,4 +321,487 @@ TEST_F(SuperblockClonerTest, AdjustControlFlowInfo) {
   EXPECT_TRUE(loop_info->IsBackEdge(*loop_body));
 }
 
+// Tests IsSubgraphConnected function for negative case.
+TEST_F(SuperblockClonerTest, IsGraphConnected) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+  ArenaAllocator* arena = graph_->GetAllocator();
+
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* unreachable_block = new (GetAllocator()) HBasicBlock(graph_);
+  graph_->AddBlock(unreachable_block);
+
+  HBasicBlockSet bb_set(
+      arena, graph_->GetBlocks().size(), false, kArenaAllocSuperblockCloner);
+  bb_set.SetBit(header->GetBlockId());
+  bb_set.SetBit(loop_body->GetBlockId());
+  bb_set.SetBit(unreachable_block->GetBlockId());
+
+  EXPECT_FALSE(IsSubgraphConnected(&bb_set, graph_));
+  EXPECT_EQ(bb_set.NumSetBits(), 1u);
+  EXPECT_TRUE(bb_set.IsBitSet(unreachable_block->GetBlockId()));
+}
+
+// Tests SuperblockCloner for loop peeling case.
+//
+// Control Flow of the example (ignoring critical edges splitting).
+//
+//       Before                    After
+//
+//         |B|                      |B|
+//          |                        |
+//          v                        v
+//         |1|                      |1|
+//          |                        |
+//          v                        v
+//         |2|<-\              (6) |2A|
+//         / \  /                   / \
+//        v   v/                   /   v
+//       |4|  |3|                 /   |3A| (7)
+//        |                      /     /
+//        v                     |     v
+//       |E|                     \   |2|<-\
+//                                \ / \   /
+//                                 v   v /
+//                                |4|  |3|
+//                                 |
+//                                 v
+//                                |E|
+TEST_F(SuperblockClonerTest, LoopPeeling) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HBasicBlockMap bb_map(
+      std::less<HBasicBlock*>(), graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+  HInstructionMap hir_map(
+      std::less<HInstruction*>(), graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+
+  HLoopInformation* loop_info = header->GetLoopInformation();
+  PeelUnrollHelper helper(loop_info, &bb_map, &hir_map);
+  EXPECT_TRUE(helper.IsLoopClonable());
+  HBasicBlock* new_header = helper.DoPeeling();
+  HLoopInformation* new_loop_info = new_header->GetLoopInformation();
+
+  EXPECT_TRUE(CheckGraph());
+
+  // Check loop body successors.
+  EXPECT_EQ(loop_body->GetSingleSuccessor(), header);
+  EXPECT_EQ(bb_map.Get(loop_body)->GetSingleSuccessor(), header);
+
+  // Check loop structure.
+  EXPECT_EQ(header, new_header);
+  EXPECT_EQ(new_loop_info->GetHeader(), header);
+  EXPECT_EQ(new_loop_info->GetBackEdges().size(), 1u);
+  EXPECT_EQ(new_loop_info->GetBackEdges()[0], loop_body);
+}
+
+// Tests SuperblockCloner for loop unrolling case.
+//
+// Control Flow of the example (ignoring critical edges splitting).
+//
+//       Before                    After
+//
+//         |B|                      |B|
+//          |                        |
+//          v                        v
+//         |1|                      |1|
+//          |                        |
+//          v                        v
+//         |2|<-\               (6) |2A|<-\
+//         / \  /                   / \    \
+//        v   v/                   /   v    \
+//       |4|  |3|                 /(7)|3A|   |
+//        |                      /     /    /
+//        v                     |     v    /
+//       |E|                     \   |2|  /
+//                                \ / \  /
+//                                 v   v/
+//                                |4| |3|
+//                                 |
+//                                 v
+//                                |E|
+TEST_F(SuperblockClonerTest, LoopUnrolling) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HBasicBlockMap bb_map(
+      std::less<HBasicBlock*>(), graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+  HInstructionMap hir_map(
+      std::less<HInstruction*>(), graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+
+  HLoopInformation* loop_info = header->GetLoopInformation();
+  PeelUnrollHelper helper(loop_info, &bb_map, &hir_map);
+  EXPECT_TRUE(helper.IsLoopClonable());
+  HBasicBlock* new_header = helper.DoUnrolling();
+
+  EXPECT_TRUE(CheckGraph());
+
+  // Check loop body successors.
+  EXPECT_EQ(loop_body->GetSingleSuccessor(), bb_map.Get(header));
+  EXPECT_EQ(bb_map.Get(loop_body)->GetSingleSuccessor(), header);
+
+  // Check loop structure.
+  EXPECT_EQ(header, new_header);
+  EXPECT_EQ(loop_info, new_header->GetLoopInformation());
+  EXPECT_EQ(loop_info->GetHeader(), new_header);
+  EXPECT_EQ(loop_info->GetBackEdges().size(), 1u);
+  EXPECT_EQ(loop_info->GetBackEdges()[0], bb_map.Get(loop_body));
+}
+
+// Checks that loop unrolling works fine for a loop with multiple back edges. Tests that after
+// the transformation the loop has a single preheader.
+TEST_F(SuperblockClonerTest, LoopPeelingMultipleBackEdges) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+
+  // Transform a basic loop to have multiple back edges.
+  HBasicBlock* latch = header->GetSuccessors()[1];
+  HBasicBlock* if_block = new (GetAllocator()) HBasicBlock(graph_);
+  HBasicBlock* temp1 = new (GetAllocator()) HBasicBlock(graph_);
+  graph_->AddBlock(if_block);
+  graph_->AddBlock(temp1);
+  header->ReplaceSuccessor(latch, if_block);
+  if_block->AddSuccessor(latch);
+  if_block->AddSuccessor(temp1);
+  temp1->AddSuccessor(header);
+
+  if_block->AddInstruction(new (GetAllocator()) HIf(parameter_));
+
+  HInstructionIterator it(header->GetPhis());
+  DCHECK(!it.Done());
+  HPhi* loop_phi = it.Current()->AsPhi();
+  HInstruction* temp_add = new (GetAllocator()) HAdd(DataType::Type::kInt32,
+                                                     loop_phi,
+                                                     graph_->GetIntConstant(2));
+  temp1->AddInstruction(temp_add);
+  temp1->AddInstruction(new (GetAllocator()) HGoto());
+  loop_phi->AddInput(temp_add);
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HLoopInformation* loop_info = header->GetLoopInformation();
+  PeelUnrollSimpleHelper helper(loop_info);
+  HBasicBlock* new_header = helper.DoPeeling();
+  EXPECT_EQ(header, new_header);
+
+  EXPECT_TRUE(CheckGraph());
+  EXPECT_EQ(header->GetPredecessors().size(), 3u);
+}
+
+static void CheckLoopStructureForLoopPeelingNested(HBasicBlock* loop1_header,
+                                                   HBasicBlock* loop2_header,
+                                                   HBasicBlock* loop3_header) {
+  EXPECT_EQ(loop1_header->GetLoopInformation()->GetHeader(), loop1_header);
+  EXPECT_EQ(loop2_header->GetLoopInformation()->GetHeader(), loop2_header);
+  EXPECT_EQ(loop3_header->GetLoopInformation()->GetHeader(), loop3_header);
+  EXPECT_EQ(loop1_header->GetLoopInformation()->GetPreHeader()->GetLoopInformation(), nullptr);
+  EXPECT_EQ(loop2_header->GetLoopInformation()->GetPreHeader()->GetLoopInformation(), nullptr);
+  EXPECT_EQ(loop3_header->GetLoopInformation()->GetPreHeader()->GetLoopInformation()->GetHeader(),
+            loop2_header);
+}
+
+TEST_F(SuperblockClonerTest, LoopPeelingNested) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+
+  // Create the following nested structure of loops
+  //   Headers:  1    2 3
+  //             [ ], [ [ ] ]
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop1_header = header;
+
+  CreateBasicLoopControlFlow(header, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop2_header = header;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop3_header = header;
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HLoopInformation* loop2_info_before = loop2_header->GetLoopInformation();
+  HLoopInformation* loop3_info_before = loop3_header->GetLoopInformation();
+
+  // Check nested loops structure.
+  CheckLoopStructureForLoopPeelingNested(loop1_header, loop2_header, loop3_header);
+  PeelUnrollSimpleHelper helper(loop1_header->GetLoopInformation());
+  helper.DoPeeling();
+  // Check that nested loops structure has not changed after the transformation.
+  CheckLoopStructureForLoopPeelingNested(loop1_header, loop2_header, loop3_header);
+
+  // Test that the loop info is preserved.
+  EXPECT_EQ(loop2_info_before, loop2_header->GetLoopInformation());
+  EXPECT_EQ(loop3_info_before, loop3_header->GetLoopInformation());
+
+  EXPECT_EQ(loop3_info_before->GetPreHeader()->GetLoopInformation(), loop2_info_before);
+  EXPECT_EQ(loop2_info_before->GetPreHeader()->GetLoopInformation(), nullptr);
+
+  EXPECT_EQ(helper.GetRegionToBeAdjusted(), nullptr);
+
+  EXPECT_TRUE(CheckGraph());
+}
+
+// Checks that the loop population is correctly propagated after an inner loop is peeled.
+TEST_F(SuperblockClonerTest, OuterLoopPopulationAfterInnerPeeled) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+
+  // Create the following nested structure of loops
+  //   Headers:  1 2 3        4
+  //             [ [ [ ] ] ], [ ]
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop1_header = header;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop2_header = header;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop3_header = header;
+
+  CreateBasicLoopControlFlow(loop1_header, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop4_header = header;
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  PeelUnrollSimpleHelper helper(loop3_header->GetLoopInformation());
+  helper.DoPeeling();
+  HLoopInformation* loop1 = loop1_header->GetLoopInformation();
+  HLoopInformation* loop2 = loop2_header->GetLoopInformation();
+  HLoopInformation* loop3 = loop3_header->GetLoopInformation();
+  HLoopInformation* loop4 = loop4_header->GetLoopInformation();
+
+  EXPECT_TRUE(loop1->Contains(*loop2_header));
+  EXPECT_TRUE(loop1->Contains(*loop3_header));
+  EXPECT_TRUE(loop1->Contains(*loop3_header->GetLoopInformation()->GetPreHeader()));
+
+  // Check that loop4 info has not been touched after local run of AnalyzeLoops.
+  EXPECT_EQ(loop4, loop4_header->GetLoopInformation());
+
+  EXPECT_TRUE(loop1->IsIn(*loop1));
+  EXPECT_TRUE(loop2->IsIn(*loop1));
+  EXPECT_TRUE(loop3->IsIn(*loop1));
+  EXPECT_TRUE(loop3->IsIn(*loop2));
+  EXPECT_TRUE(!loop4->IsIn(*loop1));
+
+  EXPECT_EQ(loop4->GetPreHeader()->GetLoopInformation(), nullptr);
+
+  EXPECT_EQ(helper.GetRegionToBeAdjusted(), loop2);
+
+  EXPECT_TRUE(CheckGraph());
+}
+
+// Checks the case when inner loop have an exit not to its immediate outer_loop but some other loop
+// in the hierarchy. Loop population information must be valid after loop peeling.
+TEST_F(SuperblockClonerTest, NestedCaseExitToOutermost) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+
+  // Create the following nested structure of loops then peel loop3.
+  //   Headers:  1 2 3
+  //             [ [ [ ] ] ]
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop1_header = header;
+  HBasicBlock* loop_body1 = loop_body;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop3_header = header;
+  HBasicBlock* loop_body3 = loop_body;
+
+  // Change the loop3 - insert an exit which leads to loop1.
+  HBasicBlock* loop3_extra_if_block = new (GetAllocator()) HBasicBlock(graph_);
+  graph_->AddBlock(loop3_extra_if_block);
+  loop3_extra_if_block->AddInstruction(new (GetAllocator()) HIf(parameter_));
+
+  loop3_header->ReplaceSuccessor(loop_body3, loop3_extra_if_block);
+  loop3_extra_if_block->AddSuccessor(loop_body1);  // Long exit.
+  loop3_extra_if_block->AddSuccessor(loop_body3);
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HBasicBlock* loop3_long_exit = loop3_extra_if_block->GetSuccessors()[0];
+  EXPECT_TRUE(loop1_header->GetLoopInformation()->Contains(*loop3_long_exit));
+
+  PeelUnrollSimpleHelper helper(loop3_header->GetLoopInformation());
+  helper.DoPeeling();
+
+  HLoopInformation* loop1 = loop1_header->GetLoopInformation();
+  // Check that after the transformation the local area for CF adjustments has been chosen
+  // correctly and loop population has been updated.
+  loop3_long_exit = loop3_extra_if_block->GetSuccessors()[0];
+  EXPECT_TRUE(loop1->Contains(*loop3_long_exit));
+
+  EXPECT_EQ(helper.GetRegionToBeAdjusted(), loop1);
+
+  EXPECT_TRUE(loop1->Contains(*loop3_header));
+  EXPECT_TRUE(loop1->Contains(*loop3_header->GetLoopInformation()->GetPreHeader()));
+
+  EXPECT_TRUE(CheckGraph());
+}
+
+TEST_F(SuperblockClonerTest, FastCaseCheck) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+  ArenaAllocator* arena = graph_->GetAllocator();
+
+  InitGraph();
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  graph_->BuildDominatorTree();
+
+  HLoopInformation* loop_info = header->GetLoopInformation();
+
+  ArenaBitVector orig_bb_set(
+      arena, graph_->GetBlocks().size(), false, kArenaAllocSuperblockCloner);
+  orig_bb_set.Union(&loop_info->GetBlocks());
+
+  HEdgeSet remap_orig_internal(graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+  HEdgeSet remap_copy_internal(graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+  HEdgeSet remap_incoming(graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
+
+  CollectRemappingInfoForPeelUnroll(true,
+                                    loop_info,
+                                    &remap_orig_internal,
+                                    &remap_copy_internal,
+                                    &remap_incoming);
+
+  // Insert some extra nodes and edges.
+  HBasicBlock* preheader = loop_info->GetPreHeader();
+  orig_bb_set.SetBit(preheader->GetBlockId());
+
+  // Adjust incoming edges.
+  remap_incoming.Clear();
+  remap_incoming.Insert(HEdge(preheader->GetSinglePredecessor(), preheader));
+
+  HBasicBlockMap bb_map(std::less<HBasicBlock*>(), arena->Adapter(kArenaAllocSuperblockCloner));
+  HInstructionMap hir_map(std::less<HInstruction*>(), arena->Adapter(kArenaAllocSuperblockCloner));
+
+  SuperblockCloner cloner(graph_,
+                          &orig_bb_set,
+                          &bb_map,
+                          &hir_map);
+  cloner.SetSuccessorRemappingInfo(&remap_orig_internal, &remap_copy_internal, &remap_incoming);
+
+  EXPECT_FALSE(cloner.IsFastCase());
+}
+
+// Helper for FindCommonLoop which also check that FindCommonLoop is symmetric.
+static HLoopInformation* FindCommonLoopCheck(HLoopInformation* loop1, HLoopInformation* loop2) {
+  HLoopInformation* common_loop12 = FindCommonLoop(loop1, loop2);
+  HLoopInformation* common_loop21 = FindCommonLoop(loop2, loop1);
+  EXPECT_EQ(common_loop21, common_loop12);
+  return common_loop12;
+}
+
+// Tests FindCommonLoop function on a loop nest.
+TEST_F(SuperblockClonerTest, FindCommonLoop) {
+  HBasicBlock* header = nullptr;
+  HBasicBlock* loop_body = nullptr;
+
+  InitGraph();
+
+  // Create the following nested structure of loops
+  //   Headers:  1 2 3      4      5
+  //             [ [ [ ] ], [ ] ], [ ]
+  CreateBasicLoopControlFlow(entry_block_, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop1_header = header;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop2_header = header;
+
+  CreateBasicLoopControlFlow(header, header->GetSuccessors()[1], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop3_header = header;
+
+  CreateBasicLoopControlFlow(loop2_header, loop2_header->GetSuccessors()[0], &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop4_header = header;
+
+  CreateBasicLoopControlFlow(loop1_header, return_block_, &header, &loop_body);
+  CreateBasicLoopDataFlow(header, loop_body);
+  HBasicBlock* loop5_header = header;
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  HLoopInformation* loop1 = loop1_header->GetLoopInformation();
+  HLoopInformation* loop2 = loop2_header->GetLoopInformation();
+  HLoopInformation* loop3 = loop3_header->GetLoopInformation();
+  HLoopInformation* loop4 = loop4_header->GetLoopInformation();
+  HLoopInformation* loop5 = loop5_header->GetLoopInformation();
+
+  EXPECT_TRUE(loop1->IsIn(*loop1));
+  EXPECT_TRUE(loop2->IsIn(*loop1));
+  EXPECT_TRUE(loop3->IsIn(*loop1));
+  EXPECT_TRUE(loop3->IsIn(*loop2));
+  EXPECT_TRUE(loop4->IsIn(*loop1));
+
+  EXPECT_FALSE(loop5->IsIn(*loop1));
+  EXPECT_FALSE(loop4->IsIn(*loop2));
+  EXPECT_FALSE(loop4->IsIn(*loop3));
+
+  EXPECT_EQ(loop1->GetPreHeader()->GetLoopInformation(), nullptr);
+  EXPECT_EQ(loop4->GetPreHeader()->GetLoopInformation(), loop1);
+
+  EXPECT_EQ(FindCommonLoopCheck(nullptr, nullptr), nullptr);
+  EXPECT_EQ(FindCommonLoopCheck(loop2, nullptr), nullptr);
+
+  EXPECT_EQ(FindCommonLoopCheck(loop1, loop1), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop1, loop2), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop1, loop3), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop1, loop4), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop1, loop5), nullptr);
+
+  EXPECT_EQ(FindCommonLoopCheck(loop2, loop3), loop2);
+  EXPECT_EQ(FindCommonLoopCheck(loop2, loop4), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop2, loop5), nullptr);
+
+  EXPECT_EQ(FindCommonLoopCheck(loop3, loop4), loop1);
+  EXPECT_EQ(FindCommonLoopCheck(loop3, loop5), nullptr);
+
+  EXPECT_EQ(FindCommonLoopCheck(loop4, loop5), nullptr);
+
+  EXPECT_EQ(FindCommonLoopCheck(loop5, loop5), loop5);
+}
+
 }  // namespace art