resolved conflicts for merge of 7940e44f to dalvik-dev

Change-Id: I6529b2fc27dfaedd2cb87b3697d049ccabed36ee
diff --git a/compiler/sea_ir/sea.cc b/compiler/sea_ir/sea.cc
new file mode 100644
index 0000000..c5ec2b9
--- /dev/null
+++ b/compiler/sea_ir/sea.cc
@@ -0,0 +1,701 @@
+/*
+ * Copyright (C) 2013 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 "sea.h"
+
+#include "file_output_stream.h"
+#include "instruction_tools.h"
+
+
+#define MAX_REACHING_DEF_ITERERATIONS (10)
+
+namespace sea_ir {
+
+SeaGraph SeaGraph::graph_;
+int SeaNode::current_max_node_id_ = 0;
+
+
+SeaGraph* SeaGraph::GetCurrentGraph() {
+  return &sea_ir::SeaGraph::graph_;
+}
+
+void SeaGraph::DumpSea(std::string filename) const {
+  LOG(INFO) << "Starting to write SEA string to file.";
+  std::string result;
+  result += "digraph seaOfNodes {\n";
+  for (std::vector<Region*>::const_iterator cit = regions_.begin(); cit != regions_.end(); cit++) {
+    (*cit)->ToDot(result);
+  }
+  result += "}\n";
+  art::File* file = art::OS::OpenFile(filename.c_str(), true, true);
+  art::FileOutputStream fos(file);
+  fos.WriteFully(result.c_str(), result.size());
+  LOG(INFO) << "Written SEA string to file.";
+}
+
+void SeaGraph::AddEdge(Region* src, Region* dst) const {
+  src->AddSuccessor(dst);
+  dst->AddPredecessor(src);
+}
+
+void SeaGraph::ComputeRPO(Region* current_region, int& current_rpo) {
+  current_region->SetRPO(VISITING);
+  std::vector<sea_ir::Region*>* succs = current_region->GetSuccessors();
+  for (std::vector<sea_ir::Region*>::iterator succ_it = succs->begin();
+      succ_it != succs->end(); ++succ_it) {
+    if (NOT_VISITED == (*succ_it)->GetRPO()) {
+      SeaGraph::ComputeRPO(*succ_it, current_rpo);
+    }
+  }
+  current_region->SetRPO(current_rpo--);
+}
+
+void SeaGraph::ComputeIDominators() {
+  bool changed = true;
+  while (changed) {
+    changed = false;
+    // Entry node has itself as IDOM.
+    std::vector<Region*>::iterator crt_it;
+    std::set<Region*> processedNodes;
+    // Find and mark the entry node(s).
+    for (crt_it = regions_.begin(); crt_it != regions_.end(); ++crt_it) {
+      if ((*crt_it)->GetPredecessors()->size() == 0) {
+        processedNodes.insert(*crt_it);
+        (*crt_it)->SetIDominator(*crt_it);
+      }
+    }
+    for (crt_it = regions_.begin(); crt_it != regions_.end(); ++crt_it) {
+      if ((*crt_it)->GetPredecessors()->size() == 0) {
+        continue;
+      }
+      // NewIDom = first (processed) predecessor of b.
+      Region* new_dom = NULL;
+      std::vector<Region*>* preds = (*crt_it)->GetPredecessors();
+      DCHECK(NULL != preds);
+      Region* root_pred = NULL;
+      for (std::vector<Region*>::iterator pred_it = preds->begin();
+          pred_it != preds->end(); ++pred_it) {
+        if (processedNodes.end() != processedNodes.find((*pred_it))) {
+          root_pred = *pred_it;
+          new_dom = root_pred;
+          break;
+        }
+      }
+      // For all other predecessors p of b, if idom is not set,
+      // then NewIdom = Intersect(p, NewIdom)
+      for (std::vector<Region*>::const_iterator pred_it = preds->begin();
+          pred_it != preds->end(); ++pred_it) {
+        DCHECK(NULL != *pred_it);
+        // if IDOMS[p] != UNDEFINED
+        if ((*pred_it != root_pred) && (*pred_it)->GetIDominator() != NULL) {
+          DCHECK(NULL != new_dom);
+          new_dom = SeaGraph::Intersect(*pred_it, new_dom);
+        }
+      }
+      DCHECK(NULL != *crt_it);
+      if ((*crt_it)->GetIDominator() != new_dom) {
+        (*crt_it)->SetIDominator(new_dom);
+        changed = true;
+      }
+      processedNodes.insert(*crt_it);
+    }
+  }
+
+  // For easily ordering of regions we need edges dominator->dominated.
+  for (std::vector<Region*>::iterator region_it = regions_.begin();
+      region_it != regions_.end(); region_it++) {
+    Region* idom = (*region_it)->GetIDominator();
+    if (idom != *region_it) {
+      idom->AddToIDominatedSet(*region_it);
+    }
+  }
+}
+
+Region* SeaGraph::Intersect(Region* i, Region* j) {
+  Region* finger1 = i;
+  Region* finger2 = j;
+  while (finger1 != finger2) {
+    while (finger1->GetRPO() > finger2->GetRPO()) {
+      DCHECK(NULL != finger1);
+      finger1 = finger1->GetIDominator(); // should have: finger1 != NULL
+      DCHECK(NULL != finger1);
+    }
+    while (finger1->GetRPO() < finger2->GetRPO()) {
+      DCHECK(NULL != finger2);
+      finger2 = finger2->GetIDominator(); // should have: finger1 != NULL
+      DCHECK(NULL != finger2);
+    }
+  }
+  return finger1; // finger1 should be equal to finger2 at this point.
+}
+
+void SeaGraph::ComputeDownExposedDefs() {
+  for (std::vector<Region*>::iterator region_it = regions_.begin();
+        region_it != regions_.end(); region_it++) {
+      (*region_it)->ComputeDownExposedDefs();
+    }
+}
+
+void SeaGraph::ComputeReachingDefs() {
+  // Iterate until the reaching definitions set doesn't change anymore.
+  // (See Cooper & Torczon, "Engineering a Compiler", second edition, page 487)
+  bool changed = true;
+  int iteration = 0;
+  while (changed && (iteration < MAX_REACHING_DEF_ITERERATIONS)) {
+    iteration++;
+    changed = false;
+    // TODO: optimize the ordering if this becomes performance bottleneck.
+    for (std::vector<Region*>::iterator regions_it = regions_.begin();
+        regions_it != regions_.end();
+        regions_it++) {
+      changed |= (*regions_it)->UpdateReachingDefs();
+    }
+  }
+  DCHECK(!changed) << "Reaching definitions computation did not reach a fixed point.";
+}
+
+
+void SeaGraph::BuildMethodSeaGraph(const art::DexFile::CodeItem* code_item,
+    const art::DexFile& dex_file) {
+  const uint16_t* code = code_item->insns_;
+  const size_t size_in_code_units = code_item->insns_size_in_code_units_;
+  // This maps target instruction pointers to their corresponding region objects.
+  std::map<const uint16_t*, Region*> target_regions;
+  size_t i = 0;
+  // Pass: Find the start instruction of basic blocks
+  //         by locating targets and flow-though instructions of branches.
+  while (i < size_in_code_units) {
+    const art::Instruction* inst = art::Instruction::At(&code[i]);
+    if (inst->IsBranch() || inst->IsUnconditional()) {
+      int32_t offset = inst->GetTargetOffset();
+      if (target_regions.end() == target_regions.find(&code[i + offset])) {
+        Region* region = GetNewRegion();
+        target_regions.insert(std::pair<const uint16_t*, Region*>(&code[i + offset], region));
+      }
+      if (inst->CanFlowThrough()
+          && (target_regions.end() == target_regions.find(&code[i + inst->SizeInCodeUnits()]))) {
+        Region* region = GetNewRegion();
+        target_regions.insert(
+            std::pair<const uint16_t*, Region*>(&code[i + inst->SizeInCodeUnits()], region));
+      }
+    }
+    i += inst->SizeInCodeUnits();
+  }
+  // Pass: Assign instructions to region nodes and
+  //         assign branches their control flow successors.
+  i = 0;
+  Region* r = GetNewRegion();
+  SignatureNode* parameter_def_node = new sea_ir::SignatureNode(code_item->registers_size_-1,
+        code_item->ins_size_);
+  r->AddChild(parameter_def_node);
+  sea_ir::InstructionNode* last_node = NULL;
+  sea_ir::InstructionNode* node = NULL;
+  while (i < size_in_code_units) {
+    const art::Instruction* inst = art::Instruction::At(&code[i]); //TODO: find workaround for this
+    last_node = node;
+    node = new sea_ir::InstructionNode(inst);
+
+    if (inst->IsBranch() || inst->IsUnconditional()) {
+      int32_t offset = inst->GetTargetOffset();
+      std::map<const uint16_t*, Region*>::iterator it = target_regions.find(&code[i + offset]);
+      DCHECK(it != target_regions.end());
+      AddEdge(r, it->second); // Add edge to branch target.
+    }
+
+    std::map<const uint16_t*, Region*>::iterator it = target_regions.find(&code[i]);
+    if (target_regions.end() != it) {
+      // Get the already created region because this is a branch target.
+      Region* nextRegion = it->second;
+      if (last_node->GetInstruction()->IsBranch()
+          && last_node->GetInstruction()->CanFlowThrough()) {
+        AddEdge(r, it->second); // Add flow-through edge.
+      }
+      r = nextRegion;
+    }
+    bool definesRegister = (0 != InstructionTools::instruction_attributes_[inst->Opcode()]
+        && (1 << kDA));
+    LOG(INFO)<< inst->GetDexPc(code) << "*** " << inst->DumpString(&dex_file)
+    << " region:" <<r->StringId() << "Definition?" << definesRegister << std::endl;
+    r->AddChild(node);
+    i += inst->SizeInCodeUnits();
+  }
+}
+
+void SeaGraph::ComputeRPO() {
+  int rpo_id = regions_.size() - 1;
+  for (std::vector<Region*>::const_iterator crt_it = regions_.begin(); crt_it != regions_.end();
+      ++crt_it) {
+    if ((*crt_it)->GetPredecessors()->size() == 0) {
+      ComputeRPO(*crt_it, rpo_id);
+    }
+  }
+}
+
+// Performs the renaming phase in traditional SSA transformations.
+// See: Cooper & Torczon, "Engineering a Compiler", second edition, page 505.)
+void SeaGraph::RenameAsSSA() {
+  utils::ScopedHashtable<int, InstructionNode*> scoped_table;
+  scoped_table.OpenScope();
+  for (std::vector<Region*>::iterator region_it = regions_.begin(); region_it != regions_.end();
+      region_it++) {
+    if ((*region_it)->GetIDominator() == *region_it) {
+      RenameAsSSA(*region_it, &scoped_table);
+    }
+  }
+
+  scoped_table.CloseScope();
+}
+
+void SeaGraph::ConvertToSSA() {
+  // Pass: find global names.
+  // The map @block maps registers to the blocks in which they are defined.
+  std::map<int, std::set<Region*> > blocks;
+  // The set @globals records registers whose use
+  // is in a different block than the corresponding definition.
+  std::set<int> globals;
+  for (std::vector<Region*>::iterator region_it = regions_.begin(); region_it != regions_.end();
+      region_it++) {
+    std::set<int> var_kill;
+    std::vector<InstructionNode*>* instructions = (*region_it)->GetInstructions();
+    for (std::vector<InstructionNode*>::iterator inst_it = instructions->begin();
+        inst_it != instructions->end(); inst_it++) {
+      std::vector<int> used_regs = (*inst_it)->GetUses();
+      for (std::size_t i = 0; i < used_regs.size(); i++) {
+        int used_reg = used_regs[i];
+        if (var_kill.find(used_reg) == var_kill.end()) {
+          globals.insert(used_reg);
+        }
+      }
+      const int reg_def = (*inst_it)->GetResultRegister();
+      if (reg_def != NO_REGISTER) {
+        var_kill.insert(reg_def);
+      }
+
+      blocks.insert(std::pair<int, std::set<Region*> >(reg_def, std::set<Region*>()));
+      std::set<Region*>* reg_def_blocks = &(blocks.find(reg_def)->second);
+      reg_def_blocks->insert(*region_it);
+    }
+  }
+
+  // Pass: Actually add phi-nodes to regions.
+  for (std::set<int>::const_iterator globals_it = globals.begin();
+      globals_it != globals.end(); globals_it++) {
+    int global = *globals_it;
+    // Copy the set, because we will modify the worklist as we go.
+    std::set<Region*> worklist((*(blocks.find(global))).second);
+    for (std::set<Region*>::const_iterator b_it = worklist.begin(); b_it != worklist.end(); b_it++) {
+      std::set<Region*>* df = (*b_it)->GetDominanceFrontier();
+      for (std::set<Region*>::const_iterator df_it = df->begin(); df_it != df->end(); df_it++) {
+        if ((*df_it)->InsertPhiFor(global)) {
+          // Check that the dominance frontier element is in the worklist already
+          // because we only want to break if the element is actually not there yet.
+          if (worklist.find(*df_it) == worklist.end()) {
+            worklist.insert(*df_it);
+            b_it = worklist.begin();
+            break;
+          }
+        }
+      }
+    }
+  }
+  // Pass: Build edges to the definition corresponding to each use.
+  // (This corresponds to the renaming phase in traditional SSA transformations.
+  // See: Cooper & Torczon, "Engineering a Compiler", second edition, page 505.)
+  RenameAsSSA();
+}
+
+void SeaGraph::RenameAsSSA(Region* crt_region,
+    utils::ScopedHashtable<int, InstructionNode*>* scoped_table) {
+  scoped_table->OpenScope();
+  // Rename phi nodes defined in the current region.
+  std::vector<PhiInstructionNode*>* phis = crt_region->GetPhiNodes();
+  for (std::vector<PhiInstructionNode*>::iterator phi_it = phis->begin();
+      phi_it != phis->end(); phi_it++) {
+    int reg_no = (*phi_it)->GetRegisterNumber();
+    scoped_table->Add(reg_no, (*phi_it));
+  }
+  // Rename operands of instructions from the current region.
+  std::vector<InstructionNode*>* instructions = crt_region->GetInstructions();
+  for (std::vector<InstructionNode*>::const_iterator instructions_it = instructions->begin();
+      instructions_it != instructions->end(); instructions_it++) {
+    InstructionNode* current_instruction = (*instructions_it);
+    // Rename uses.
+    std::vector<int> used_regs = current_instruction->GetUses();
+    for (std::vector<int>::const_iterator reg_it = used_regs.begin();
+        reg_it != used_regs.end(); reg_it++) {
+      int current_used_reg = (*reg_it);
+      InstructionNode* definition = scoped_table->Lookup(current_used_reg);
+      current_instruction->RenameToSSA(current_used_reg, definition);
+    }
+    // Update scope table with latest definitions.
+    std::vector<int> def_regs = current_instruction->GetDefinitions();
+    for (std::vector<int>::const_iterator reg_it = def_regs.begin();
+            reg_it != def_regs.end(); reg_it++) {
+      int current_defined_reg = (*reg_it);
+      scoped_table->Add(current_defined_reg, current_instruction);
+    }
+  }
+  // Fill in uses of phi functions in CFG successor regions.
+  const std::vector<Region*>* successors = crt_region->GetSuccessors();
+  for (std::vector<Region*>::const_iterator successors_it = successors->begin();
+      successors_it != successors->end(); successors_it++) {
+    Region* successor = (*successors_it);
+    successor->SetPhiDefinitionsForUses(scoped_table, crt_region);
+  }
+
+  // Rename all successors in the dominators tree.
+  const std::set<Region*>* dominated_nodes = crt_region->GetIDominatedSet();
+  for (std::set<Region*>::const_iterator dominated_nodes_it = dominated_nodes->begin();
+      dominated_nodes_it != dominated_nodes->end(); dominated_nodes_it++) {
+    Region* dominated_node = (*dominated_nodes_it);
+    RenameAsSSA(dominated_node, scoped_table);
+  }
+  scoped_table->CloseScope();
+}
+
+void SeaGraph::CompileMethod(const art::DexFile::CodeItem* code_item,
+  uint32_t class_def_idx, uint32_t method_idx, const art::DexFile& dex_file) {
+  // Two passes: Builds the intermediate structure (non-SSA) of the sea-ir for the function.
+  BuildMethodSeaGraph(code_item, dex_file);
+  //Pass: Compute reverse post-order of regions.
+  ComputeRPO();
+  // Multiple passes: compute immediate dominators.
+  ComputeIDominators();
+  // Pass: compute downward-exposed definitions.
+  ComputeDownExposedDefs();
+  // Multiple Passes (iterative fixed-point algorithm): Compute reaching definitions
+  ComputeReachingDefs();
+  // Pass (O(nlogN)): Compute the dominance frontier for region nodes.
+  ComputeDominanceFrontier();
+  // Two Passes: Phi node insertion.
+  ConvertToSSA();
+}
+
+
+void SeaGraph::ComputeDominanceFrontier() {
+  for (std::vector<Region*>::iterator region_it = regions_.begin();
+      region_it != regions_.end(); region_it++) {
+    std::vector<Region*>* preds = (*region_it)->GetPredecessors();
+    if (preds->size() > 1) {
+      for (std::vector<Region*>::iterator pred_it = preds->begin();
+          pred_it != preds->end(); pred_it++) {
+        Region* runner = *pred_it;
+        while (runner != (*region_it)->GetIDominator()) {
+          runner->AddToDominanceFrontier(*region_it);
+          runner = runner->GetIDominator();
+        }
+      }
+    }
+  }
+}
+
+Region* SeaGraph::GetNewRegion() {
+  Region* new_region = new Region();
+  AddRegion(new_region);
+  return new_region;
+}
+
+void SeaGraph::AddRegion(Region* r) {
+  DCHECK(r) << "Tried to add NULL region to SEA graph.";
+  regions_.push_back(r);
+}
+
+void SeaNode::AddSuccessor(Region* successor) {
+  DCHECK(successor) << "Tried to add NULL successor to SEA node.";
+  successors_.push_back(successor);
+  return;
+}
+
+void SeaNode::AddPredecessor(Region* predecessor) {
+  DCHECK(predecessor) << "Tried to add NULL predecessor to SEA node.";
+  predecessors_.push_back(predecessor);
+}
+
+void Region::AddChild(sea_ir::InstructionNode* instruction) {
+  DCHECK(instruction) << "Tried to add NULL instruction to region node.";
+  instructions_.push_back(instruction);
+}
+
+SeaNode* Region::GetLastChild() const {
+  if (instructions_.size() > 0) {
+    return instructions_.back();
+  }
+  return NULL;
+}
+
+void Region::ToDot(std::string& result) const {
+  result += "\n// Region: \n" + StringId() + " [label=\"region " + StringId() + "(rpo=";
+  std::stringstream ss;
+  ss << rpo_;
+  result.append(ss.str());
+  if (NULL != GetIDominator()) {
+    result += " dom=" + GetIDominator()->StringId();
+  }
+  result += ")\"];\n";
+
+  // Save phi-nodes.
+  for (std::vector<PhiInstructionNode*>::const_iterator cit = phi_instructions_.begin();
+      cit != phi_instructions_.end(); cit++) {
+    (*cit)->ToDot(result);
+    result += StringId() + " -> " + (*cit)->StringId() + "; // phi-function \n";
+  }
+
+  // Save instruction nodes.
+  for (std::vector<InstructionNode*>::const_iterator cit = instructions_.begin();
+      cit != instructions_.end(); cit++) {
+    (*cit)->ToDot(result);
+    result += StringId() + " -> " + (*cit)->StringId() + "; // region -> instruction \n";
+  }
+
+  for (std::vector<Region*>::const_iterator cit = successors_.begin(); cit != successors_.end();
+      cit++) {
+    DCHECK(NULL != *cit) << "Null successor found for SeaNode" << GetLastChild()->StringId() << ".";
+    result += GetLastChild()->StringId() + " -> " + (*cit)->StringId() + ";\n\n";
+  }
+  // Save reaching definitions.
+  for (std::map<int, std::set<sea_ir::InstructionNode*>* >::const_iterator cit =
+      reaching_defs_.begin();
+      cit != reaching_defs_.end(); cit++) {
+    for (std::set<sea_ir::InstructionNode*>::const_iterator
+        reaching_set_it = (*cit).second->begin();
+        reaching_set_it != (*cit).second->end();
+        reaching_set_it++) {
+      result += (*reaching_set_it)->StringId() +
+         " -> " + StringId() +
+         " [style=dotted]; // Reaching def.\n";
+    }
+  }
+  // Save dominance frontier.
+  for (std::set<Region*>::const_iterator cit = df_.begin(); cit != df_.end(); cit++) {
+    result += StringId() +
+        " -> " + (*cit)->StringId() +
+        " [color=gray]; // Dominance frontier.\n";
+  }
+  result += "// End Region.\n";
+}
+
+void Region::ComputeDownExposedDefs() {
+  for (std::vector<InstructionNode*>::const_iterator inst_it = instructions_.begin();
+      inst_it != instructions_.end(); inst_it++) {
+    int reg_no = (*inst_it)->GetResultRegister();
+    std::map<int, InstructionNode*>::iterator res = de_defs_.find(reg_no);
+    if ((reg_no != NO_REGISTER) && (res == de_defs_.end())) {
+      de_defs_.insert(std::pair<int, InstructionNode*>(reg_no, *inst_it));
+    } else {
+      res->second = *inst_it;
+    }
+  }
+  for (std::map<int, sea_ir::InstructionNode*>::const_iterator cit = de_defs_.begin();
+      cit != de_defs_.end(); cit++) {
+    (*cit).second->MarkAsDEDef();
+  }
+}
+
+const std::map<int, sea_ir::InstructionNode*>* Region::GetDownExposedDefs() const {
+  return &de_defs_;
+}
+
+std::map<int, std::set<sea_ir::InstructionNode*>* >* Region::GetReachingDefs() {
+  return &reaching_defs_;
+}
+
+bool Region::UpdateReachingDefs() {
+  std::map<int, std::set<sea_ir::InstructionNode*>* > new_reaching;
+  for (std::vector<Region*>::const_iterator pred_it = predecessors_.begin();
+      pred_it != predecessors_.end(); pred_it++) {
+    // The reaching_defs variable will contain reaching defs __for current predecessor only__
+    std::map<int, std::set<sea_ir::InstructionNode*>* > reaching_defs;
+    std::map<int, std::set<sea_ir::InstructionNode*>* >* pred_reaching = (*pred_it)->GetReachingDefs();
+    const std::map<int, InstructionNode*>* de_defs = (*pred_it)->GetDownExposedDefs();
+
+    // The definitions from the reaching set of the predecessor
+    // may be shadowed by downward exposed definitions from the predecessor,
+    // otherwise the defs from the reaching set are still good.
+    for (std::map<int, InstructionNode*>::const_iterator de_def = de_defs->begin();
+        de_def != de_defs->end(); de_def++) {
+      std::set<InstructionNode*>* solo_def;
+      solo_def = new std::set<InstructionNode*>();
+      solo_def->insert(de_def->second);
+      reaching_defs.insert(
+          std::pair<int const, std::set<InstructionNode*>*>(de_def->first, solo_def));
+    }
+    reaching_defs.insert(pred_reaching->begin(), pred_reaching->end());
+
+    // Now we combine the reaching map coming from the current predecessor (reaching_defs)
+    // with the accumulated set from all predecessors so far (from new_reaching).
+    std::map<int, std::set<sea_ir::InstructionNode*>*>::iterator reaching_it = reaching_defs.begin();
+    for (; reaching_it != reaching_defs.end(); reaching_it++) {
+      std::map<int, std::set<sea_ir::InstructionNode*>*>::iterator crt_entry =
+          new_reaching.find(reaching_it->first);
+      if (new_reaching.end() != crt_entry) {
+        crt_entry->second->insert(reaching_it->second->begin(), reaching_it->second->end());
+      } else {
+        new_reaching.insert(
+            std::pair<int, std::set<sea_ir::InstructionNode*>*>(
+                reaching_it->first,
+                reaching_it->second) );
+      }
+    }
+  }
+  bool changed = false;
+  // Because the sets are monotonically increasing,
+  // we can compare sizes instead of using set comparison.
+  // TODO: Find formal proof.
+  int old_size = 0;
+  if (-1 == reaching_defs_size_) {
+    std::map<int, std::set<sea_ir::InstructionNode*>*>::iterator reaching_it = reaching_defs_.begin();
+    for (; reaching_it != reaching_defs_.end(); reaching_it++) {
+      old_size += (*reaching_it).second->size();
+    }
+  } else {
+    old_size = reaching_defs_size_;
+  }
+  int new_size = 0;
+  std::map<int, std::set<sea_ir::InstructionNode*>*>::iterator reaching_it = new_reaching.begin();
+  for (; reaching_it != new_reaching.end(); reaching_it++) {
+    new_size += (*reaching_it).second->size();
+  }
+  if (old_size != new_size) {
+    changed = true;
+  }
+  if (changed) {
+    reaching_defs_ = new_reaching;
+    reaching_defs_size_ = new_size;
+  }
+  return changed;
+}
+
+bool Region::InsertPhiFor(int reg_no) {
+  if (!ContainsPhiFor(reg_no)) {
+    phi_set_.insert(reg_no);
+    PhiInstructionNode* new_phi = new PhiInstructionNode(reg_no);
+    phi_instructions_.push_back(new_phi);
+    return true;
+  }
+  return false;
+}
+
+void Region::SetPhiDefinitionsForUses(
+    const utils::ScopedHashtable<int, InstructionNode*>* scoped_table, Region* predecessor) {
+  int predecessor_id = -1;
+  for (unsigned int crt_pred_id = 0; crt_pred_id < predecessors_.size(); crt_pred_id++) {
+    if (predecessors_.at(crt_pred_id) == predecessor) {
+      predecessor_id = crt_pred_id;
+    }
+  }
+  DCHECK_NE(-1, predecessor_id);
+  for (std::vector<PhiInstructionNode*>::iterator phi_it = phi_instructions_.begin();
+      phi_it != phi_instructions_.end(); phi_it++) {
+    PhiInstructionNode* phi = (*phi_it);
+    int reg_no = phi->GetRegisterNumber();
+    InstructionNode* definition = scoped_table->Lookup(reg_no);
+    phi->RenameToSSA(reg_no, definition, predecessor_id);
+  }
+}
+
+void InstructionNode::ToDot(std::string& result) const {
+  result += "// Instruction: \n" + StringId() +
+      " [label=\"" + instruction_->DumpString(NULL) + "\"";
+  if (de_def_) {
+    result += "style=bold";
+  }
+  result += "];\n";
+  // SSA definitions:
+  for (std::map<int, InstructionNode* >::const_iterator def_it = definition_edges_.begin();
+      def_it != definition_edges_.end(); def_it++) {
+    if (NULL != def_it->second) {
+      result += def_it->second->StringId() + " -> " + StringId() +"[color=red,label=\"";
+      std::stringstream ss;
+      ss << def_it->first;
+      result.append(ss.str());
+      result += "\"] ; // ssa edge\n";
+    }
+  }
+}
+
+void InstructionNode::MarkAsDEDef() {
+  de_def_ = true;
+}
+
+int InstructionNode::GetResultRegister() const {
+  if (instruction_->HasVRegA()) {
+    return instruction_->VRegA();
+  }
+  return NO_REGISTER;
+}
+
+std::vector<int> InstructionNode::GetDefinitions() const {
+  // TODO: Extend this to handle instructions defining more than one register (if any)
+  // The return value should be changed to pointer to field then; for now it is an object
+  // so that we avoid possible memory leaks from allocating objects dynamically.
+  std::vector<int> definitions;
+  int result = GetResultRegister();
+  if (NO_REGISTER != result) {
+    definitions.push_back(result);
+  }
+  return definitions;
+}
+
+std::vector<int> InstructionNode::GetUses() {
+  std::vector<int> uses; // Using vector<> instead of set<> because order matters.
+
+  if (!InstructionTools::IsDefinition(instruction_) && (instruction_->HasVRegA())) {
+    int vA = instruction_->VRegA();
+    uses.push_back(vA);
+  }
+  if (instruction_->HasVRegB()) {
+    int vB = instruction_->VRegB();
+    uses.push_back(vB);
+  }
+  if (instruction_->HasVRegC()) {
+    int vC = instruction_->VRegC();
+    uses.push_back(vC);
+  }
+  // TODO: Add support for function argument registers.
+  return uses;
+}
+
+void PhiInstructionNode::ToDot(std::string& result) const {
+  result += "// PhiInstruction: \n" + StringId() +
+      " [label=\"" + "PHI(";
+  std::stringstream phi_reg_stream;
+  phi_reg_stream << register_no_;
+  result.append(phi_reg_stream.str());
+  result += ")\"";
+  result += "];\n";
+
+  for (std::vector<std::map<int, InstructionNode*>*>::const_iterator pred_it = definition_edges_.begin();
+      pred_it != definition_edges_.end(); pred_it++) {
+    std::map<int, InstructionNode*>* defs_from_pred = *pred_it;
+    for (std::map<int, InstructionNode* >::const_iterator def_it = defs_from_pred->begin();
+        def_it != defs_from_pred->end(); def_it++) {
+      if (NULL != def_it->second) {
+        result += def_it->second->StringId() + " -> " + StringId() +"[color=red,label=\"vR = ";
+        std::stringstream ss;
+        ss << def_it->first;
+        result.append(ss.str());
+        result += "\"] ; // phi-ssa edge\n";
+      } else {
+        result += StringId() + " -> " + StringId() +"[color=blue,label=\"vR = ";
+        std::stringstream ss;
+        ss << def_it->first;
+        result.append(ss.str());
+        result += "\"] ; // empty phi-ssa edge\n";
+      }
+    }
+  }
+}
+} // end namespace sea_ir