Consolidate all range analysis related code in a separate file.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index cf16ff95ac10a9cf9effa5667c2d50d690769ca6..e9d92410e0df39ee9cf256fb19281416052a2e75 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -11,6 +11,7 @@
 #include "vm/exceptions.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
+#include "vm/flow_graph_range_analysis.h"
 #include "vm/hash_map.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
@@ -23,8 +24,6 @@
 
 namespace dart {
 
-DEFINE_FLAG(bool, array_bounds_check_elimination, true,
-    "Eliminate redundant bounds checks.");
 DEFINE_FLAG(int, getter_setter_ratio, 13,
     "Ratio of getter/setter usage used for double field unboxing heuristics");
 DEFINE_FLAG(bool, load_cse, true, "Use redundant load elimination.");
@@ -40,12 +39,9 @@ DEFINE_FLAG(bool, trace_constant_propagation, false,
 DEFINE_FLAG(bool, trace_load_optimization, false,
     "Print live sets for load optimization pass.");
 DEFINE_FLAG(bool, trace_optimization, false, "Print optimization details.");
-DEFINE_FLAG(bool, trace_range_analysis, false, "Trace range analysis progress");
 DEFINE_FLAG(bool, truncating_left_shift, true,
     "Optimize left shift to truncate if possible");
 DEFINE_FLAG(bool, use_cha, true, "Use class hierarchy analysis.");
-DEFINE_FLAG(bool, trace_integer_ir_selection, false,
-    "Print integer IR selection optimization pass.");
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, source_lines);
 DECLARE_FLAG(bool, trace_type_check_elimination);
@@ -4499,917 +4495,6 @@ bool FlowGraphOptimizer::TryInlineInstanceSetter(InstanceCallInstr* instr,
 }
 
 
-// Replaces Mint IL instructions with Uint32 IL instructions
-// when possible. Uses output of RangeAnalysis.
-class IntegerInstructionSelector : public ValueObject {
- public:
-  explicit IntegerInstructionSelector(FlowGraph* flow_graph)
-      : flow_graph_(flow_graph),
-        isolate_(NULL) {
-    ASSERT(flow_graph_ != NULL);
-    isolate_ = flow_graph_->isolate();
-    ASSERT(isolate_ != NULL);
-    selected_uint32_defs_ =
-        new(I) BitVector(flow_graph_->current_ssa_temp_index());
-  }
-
-  void Select();
-
- private:
-  bool IsPotentialUint32Definition(Definition* def);
-  void FindPotentialUint32Definitions();
-  bool IsUint32NarrowingDefinition(Definition* def);
-  void FindUint32NarrowingDefinitions();
-  bool AllUsesAreUint32Narrowing(Value* list_head);
-  bool CanBecomeUint32(Definition* def);
-  void Propagate();
-  Definition* ConstructReplacementFor(Definition* def);
-  void ReplaceInstructions();
-
-  Isolate* isolate() const { return isolate_; }
-
-  GrowableArray<Definition*> potential_uint32_defs_;
-  BitVector* selected_uint32_defs_;
-
-  FlowGraph* flow_graph_;
-  Isolate* isolate_;
-};
-
-
-void IntegerInstructionSelector::Select() {
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("---- starting integer ir selection -------\n");
-  }
-  FindPotentialUint32Definitions();
-  FindUint32NarrowingDefinitions();
-  Propagate();
-  ReplaceInstructions();
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("---- after integer ir selection -------\n");
-    FlowGraphPrinter printer(*flow_graph_);
-    printer.PrintBlocks();
-  }
-}
-
-
-bool IntegerInstructionSelector::IsPotentialUint32Definition(Definition* def) {
-  // TODO(johnmccutchan): Consider Smi operations, to avoid unnecessary tagging
-  // & untagged of intermediate results.
-  // TODO(johnmccutchan): Consider phis.
-  return def->IsBoxInteger()   ||   // BoxMint.
-         def->IsUnboxInteger() ||   // UnboxMint.
-         def->IsBinaryMintOp() ||
-         def->IsShiftMintOp()  ||
-         def->IsUnaryMintOp();
-}
-
-
-void IntegerInstructionSelector::FindPotentialUint32Definitions() {
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("++++ Finding potential Uint32 definitions:\n");
-  }
-
-  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
-       !block_it.Done();
-       block_it.Advance()) {
-    BlockEntryInstr* block = block_it.Current();
-
-    for (ForwardInstructionIterator instr_it(block);
-         !instr_it.Done();
-         instr_it.Advance()) {
-      Instruction* current = instr_it.Current();
-      Definition* defn = current->AsDefinition();
-      if ((defn != NULL) && (defn->ssa_temp_index() != -1)) {
-        if (IsPotentialUint32Definition(defn)) {
-          if (FLAG_trace_integer_ir_selection) {
-           OS::Print("Adding %s\n", current->ToCString());
-          }
-          potential_uint32_defs_.Add(defn);
-        }
-      }
-    }
-  }
-}
-
-
-// BinaryMintOp masks and stores into unsigned typed arrays that truncate the
-// value into a Uint32 range.
-bool IntegerInstructionSelector::IsUint32NarrowingDefinition(Definition* def) {
-  if (def->IsBinaryMintOp()) {
-    BinaryMintOpInstr* op = def->AsBinaryMintOp();
-    // Must be a mask operation.
-    if (op->op_kind() != Token::kBIT_AND) {
-      return false;
-    }
-    Range* range = op->range();
-    if ((range == NULL) ||
-        !range->IsWithin(0, static_cast<int64_t>(kMaxUint32))) {
-      return false;
-    }
-    return true;
-  }
-  // TODO(johnmccutchan): Add typed array stores.
-  return false;
-}
-
-
-void IntegerInstructionSelector::FindUint32NarrowingDefinitions() {
-  ASSERT(selected_uint32_defs_ != NULL);
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("++++ Selecting Uint32 definitions:\n");
-    OS::Print("++++ Initial set:\n");
-  }
-  for (intptr_t i = 0; i < potential_uint32_defs_.length(); i++) {
-    Definition* defn = potential_uint32_defs_[i];
-    if (IsUint32NarrowingDefinition(defn)) {
-      if (FLAG_trace_integer_ir_selection) {
-        OS::Print("Adding %s\n", defn->ToCString());
-      }
-      selected_uint32_defs_->Add(defn->ssa_temp_index());
-    }
-  }
-}
-
-
-bool IntegerInstructionSelector::AllUsesAreUint32Narrowing(Value* list_head) {
-  for (Value::Iterator it(list_head);
-       !it.Done();
-       it.Advance()) {
-    Value* use = it.Current();
-    Definition* defn = use->instruction()->AsDefinition();
-    if ((defn == NULL) ||
-        (defn->ssa_temp_index() == -1) ||
-        !selected_uint32_defs_->Contains(defn->ssa_temp_index())) {
-      return false;
-    }
-  }
-  return true;
-}
-
-
-bool IntegerInstructionSelector::CanBecomeUint32(Definition* def) {
-  ASSERT(IsPotentialUint32Definition(def));
-  if (def->IsBoxInteger()) {
-    // If a BoxInteger's input is a candidate, the box is a candidate.
-    BoxIntegerInstr* box = def->AsBoxInteger();
-    Definition* box_input = box->value()->definition();
-    return selected_uint32_defs_->Contains(box_input->ssa_temp_index());
-  }
-  // A right shift with an input outside of Uint32 range cannot be converted
-  // because we need the high bits.
-  if (def->IsShiftMintOp()) {
-    ShiftMintOpInstr* op = def->AsShiftMintOp();
-    if (op->op_kind() == Token::kSHR) {
-      Definition* shift_input = op->left()->definition();
-      ASSERT(shift_input != NULL);
-      Range* range = shift_input->range();
-      if ((range == NULL) ||
-          !range->IsWithin(0, static_cast<int64_t>(kMaxUint32))) {
-        return false;
-      }
-    }
-  }
-  if (!def->HasUses()) {
-    // No uses, skip.
-    return false;
-  }
-  return AllUsesAreUint32Narrowing(def->input_use_list()) &&
-         AllUsesAreUint32Narrowing(def->env_use_list());
-}
-
-
-void IntegerInstructionSelector::Propagate() {
-  ASSERT(selected_uint32_defs_ != NULL);
-  bool changed = true;
-  intptr_t iteration = 0;
-  while (changed) {
-    if (FLAG_trace_integer_ir_selection) {
-      OS::Print("+++ Iteration: %" Pd "\n", iteration++);
-    }
-    changed = false;
-    for (intptr_t i = 0; i < potential_uint32_defs_.length(); i++) {
-      Definition* defn = potential_uint32_defs_[i];
-      if (selected_uint32_defs_->Contains(defn->ssa_temp_index())) {
-        // Already marked as a candidate, skip.
-        continue;
-      }
-      if (defn->IsConstant()) {
-        // Skip constants.
-        continue;
-      }
-      if (CanBecomeUint32(defn)) {
-        if (FLAG_trace_integer_ir_selection) {
-          OS::Print("Adding %s\n", defn->ToCString());
-        }
-        // Found a new candidate.
-        selected_uint32_defs_->Add(defn->ssa_temp_index());
-        // Haven't reached fixed point yet.
-        changed = true;
-      }
-    }
-  }
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("Reached fixed point\n");
-  }
-}
-
-
-Definition* IntegerInstructionSelector::ConstructReplacementFor(
-    Definition* def) {
-  // Should only see mint definitions.
-  ASSERT(IsPotentialUint32Definition(def));
-  // Should not see constant instructions.
-  ASSERT(!def->IsConstant());
-  if (def->IsBinaryMintOp()) {
-    BinaryMintOpInstr* op = def->AsBinaryMintOp();
-    Token::Kind op_kind = op->op_kind();
-    Value* left = op->left()->CopyWithType();
-    Value* right = op->right()->CopyWithType();
-    intptr_t deopt_id = op->DeoptimizationTarget();
-    return new(I) BinaryUint32OpInstr(op_kind, left, right, deopt_id);
-  } else if (def->IsBoxInteger()) {
-    BoxIntegerInstr* box = def->AsBoxInteger();
-    Value* value = box->value()->CopyWithType();
-    return new(I) BoxUint32Instr(value);
-  } else if (def->IsUnboxInteger()) {
-    UnboxIntegerInstr* unbox = def->AsUnboxInteger();
-    Value* value = unbox->value()->CopyWithType();
-    intptr_t deopt_id = unbox->deopt_id();
-    return new(I) UnboxUint32Instr(value, deopt_id);
-  } else if (def->IsUnaryMintOp()) {
-    UnaryMintOpInstr* op = def->AsUnaryMintOp();
-    Token::Kind op_kind = op->op_kind();
-    Value* value = op->value()->CopyWithType();
-    intptr_t deopt_id = op->DeoptimizationTarget();
-    return new(I) UnaryUint32OpInstr(op_kind, value, deopt_id);
-  } else if (def->IsShiftMintOp()) {
-    ShiftMintOpInstr* op = def->AsShiftMintOp();
-    Token::Kind op_kind = op->op_kind();
-    Value* left = op->left()->CopyWithType();
-    Value* right = op->right()->CopyWithType();
-    intptr_t deopt_id = op->DeoptimizationTarget();
-    return new(I) ShiftUint32OpInstr(op_kind, left, right, deopt_id);
-  }
-  UNREACHABLE();
-  return NULL;
-}
-
-
-void IntegerInstructionSelector::ReplaceInstructions() {
-  if (FLAG_trace_integer_ir_selection) {
-    OS::Print("++++ Replacing instructions:\n");
-  }
-  for (intptr_t i = 0; i < potential_uint32_defs_.length(); i++) {
-    Definition* defn = potential_uint32_defs_[i];
-    if (!selected_uint32_defs_->Contains(defn->ssa_temp_index())) {
-      // Not a candidate.
-      continue;
-    }
-    Definition* replacement = ConstructReplacementFor(defn);
-    ASSERT(replacement != NULL);
-    if (FLAG_trace_integer_ir_selection) {
-      OS::Print("Replacing %s with %s\n", defn->ToCString(),
-                                          replacement->ToCString());
-    }
-    defn->ReplaceWith(replacement, NULL);
-    ASSERT(flow_graph_->VerifyUseLists());
-  }
-}
-
-void FlowGraphOptimizer::SelectIntegerInstructions() {
-  IntegerInstructionSelector iis(flow_graph_);
-  iis.Select();
-}
-
-
-// Range analysis for integer values.
-class RangeAnalysis : public ValueObject {
- public:
-  explicit RangeAnalysis(FlowGraph* flow_graph)
-      : flow_graph_(flow_graph),
-        marked_defns_(NULL) { }
-
-  // Infer ranges for all values and remove overflow checks from binary smi
-  // operations when proven redundant.
-  void Analyze();
-
- private:
-  // Collect all values that were proven to be smi in smi_values_ array and all
-  // CheckSmi instructions in smi_check_ array.
-  void CollectValues();
-
-  // Iterate over smi values and constrain them at branch successors.
-  // Additionally constraint values after CheckSmi instructions.
-  void InsertConstraints();
-
-  // Iterate over uses of the given definition and discover branches that
-  // constrain it. Insert appropriate Constraint instructions at true
-  // and false successor and rename all dominated uses to refer to a
-  // Constraint instead of this definition.
-  void InsertConstraintsFor(Definition* defn);
-
-  // Create a constraint for defn, insert it after given instruction and
-  // rename all uses that are dominated by it.
-  ConstraintInstr* InsertConstraintFor(Definition* defn,
-                                       Range* constraint,
-                                       Instruction* after);
-
-  void ConstrainValueAfterBranch(Definition* defn, Value* use);
-  void ConstrainValueAfterCheckArrayBound(Definition* defn,
-                                          CheckArrayBoundInstr* check,
-                                          intptr_t use_index);
-
-  // Replace uses of the definition def that are dominated by instruction dom
-  // with uses of other definition.
-  void RenameDominatedUses(Definition* def,
-                           Instruction* dom,
-                           Definition* other);
-
-
-  // Walk the dominator tree and infer ranges for smi values.
-  void InferRanges();
-  void InferRangesRecursive(BlockEntryInstr* block);
-
-  enum Direction {
-    kUnknown,
-    kPositive,
-    kNegative,
-    kBoth
-  };
-
-  Range* InferInductionVariableRange(JoinEntryInstr* loop_header,
-                                     PhiInstr* var);
-
-  void ResetWorklist();
-  void MarkDefinition(Definition* defn);
-
-  static Direction ToDirection(Value* val);
-
-  static Direction Invert(Direction direction) {
-    return (direction == kPositive) ? kNegative : kPositive;
-  }
-
-  static void UpdateDirection(Direction* direction,
-                              Direction new_direction) {
-    if (*direction != new_direction) {
-      if (*direction != kUnknown) new_direction = kBoth;
-      *direction = new_direction;
-    }
-  }
-
-  // Remove artificial Constraint instructions and replace them with actual
-  // unconstrained definitions.
-  void RemoveConstraints();
-
-  Range* ConstraintRange(Token::Kind op, Definition* boundary);
-
-  Isolate* isolate() const { return flow_graph_->isolate(); }
-
-  FlowGraph* flow_graph_;
-
-  // Value that are known to be smi or mint.
-  GrowableArray<Definition*> values_;
-  // All CheckSmi instructions.
-  GrowableArray<CheckSmiInstr*> smi_checks_;
-
-  // All Constraints inserted during InsertConstraints phase. They are treated
-  // as smi values.
-  GrowableArray<ConstraintInstr*> constraints_;
-
-  // Bitvector for a quick filtering of known smi or mint values.
-  BitVector* definitions_;
-
-  // Worklist for induction variables analysis.
-  GrowableArray<Definition*> worklist_;
-  BitVector* marked_defns_;
-
-  DISALLOW_COPY_AND_ASSIGN(RangeAnalysis);
-};
-
-
-void RangeAnalysis::Analyze() {
-  CollectValues();
-  InsertConstraints();
-  InferRanges();
-  IntegerInstructionSelector iis(flow_graph_);
-  iis.Select();
-  RemoveConstraints();
-}
-
-
-void RangeAnalysis::CollectValues() {
-  const GrowableArray<Definition*>& initial =
-      *flow_graph_->graph_entry()->initial_definitions();
-  for (intptr_t i = 0; i < initial.length(); ++i) {
-    Definition* current = initial[i];
-    if (current->Type()->ToCid() == kSmiCid) {
-      values_.Add(current);
-    } else if (current->IsMintDefinition()) {
-      values_.Add(current);
-    }
-  }
-
-  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
-       !block_it.Done();
-       block_it.Advance()) {
-    BlockEntryInstr* block = block_it.Current();
-
-
-    if (block->IsGraphEntry() || block->IsCatchBlockEntry()) {
-      const GrowableArray<Definition*>& initial = block->IsGraphEntry()
-          ? *block->AsGraphEntry()->initial_definitions()
-          : *block->AsCatchBlockEntry()->initial_definitions();
-      for (intptr_t i = 0; i < initial.length(); ++i) {
-        Definition* current = initial[i];
-        if (current->Type()->ToCid() == kSmiCid) {
-          values_.Add(current);
-        } else if (current->IsMintDefinition()) {
-          values_.Add(current);
-        }
-      }
-    }
-
-    JoinEntryInstr* join = block->AsJoinEntry();
-    if (join != NULL) {
-      for (PhiIterator phi_it(join); !phi_it.Done(); phi_it.Advance()) {
-        PhiInstr* current = phi_it.Current();
-        if (current->Type()->ToCid() == kSmiCid) {
-          values_.Add(current);
-        }
-      }
-    }
-
-    for (ForwardInstructionIterator instr_it(block);
-         !instr_it.Done();
-         instr_it.Advance()) {
-      Instruction* current = instr_it.Current();
-      Definition* defn = current->AsDefinition();
-      if (defn != NULL) {
-        if ((defn->Type()->ToCid() == kSmiCid) &&
-            (defn->ssa_temp_index() != -1)) {
-          values_.Add(defn);
-        } else if ((defn->IsMintDefinition()) &&
-                   (defn->ssa_temp_index() != -1)) {
-          values_.Add(defn);
-        }
-      } else if (current->IsCheckSmi()) {
-        smi_checks_.Add(current->AsCheckSmi());
-      }
-    }
-  }
-}
-
-
-// Returns true if use is dominated by the given instruction.
-// Note: uses that occur at instruction itself are not dominated by it.
-static bool IsDominatedUse(Instruction* dom, Value* use) {
-  BlockEntryInstr* dom_block = dom->GetBlock();
-
-  Instruction* instr = use->instruction();
-
-  PhiInstr* phi = instr->AsPhi();
-  if (phi != NULL) {
-    return dom_block->Dominates(phi->block()->PredecessorAt(use->use_index()));
-  }
-
-  BlockEntryInstr* use_block = instr->GetBlock();
-  if (use_block == dom_block) {
-    // Fast path for the case of block entry.
-    if (dom_block == dom) return true;
-
-    for (Instruction* curr = dom->next(); curr != NULL; curr = curr->next()) {
-      if (curr == instr) return true;
-    }
-
-    return false;
-  }
-
-  return dom_block->Dominates(use_block);
-}
-
-
-void RangeAnalysis::RenameDominatedUses(Definition* def,
-                                        Instruction* dom,
-                                        Definition* other) {
-  for (Value::Iterator it(def->input_use_list());
-       !it.Done();
-       it.Advance()) {
-    Value* use = it.Current();
-
-    // Skip dead phis.
-    PhiInstr* phi = use->instruction()->AsPhi();
-    ASSERT((phi == NULL) || phi->is_alive());
-    if (IsDominatedUse(dom, use)) {
-      use->BindTo(other);
-    }
-  }
-}
-
-
-// For a comparison operation return an operation for the equivalent flipped
-// comparison: a (op) b === b (op') a.
-static Token::Kind FlipComparison(Token::Kind op) {
-  switch (op) {
-    case Token::kEQ: return Token::kEQ;
-    case Token::kNE: return Token::kNE;
-    case Token::kLT: return Token::kGT;
-    case Token::kGT: return Token::kLT;
-    case Token::kLTE: return Token::kGTE;
-    case Token::kGTE: return Token::kLTE;
-    default:
-      UNREACHABLE();
-      return Token::kILLEGAL;
-  }
-}
-
-
-// Given a boundary (right operand) and a comparison operation return
-// a symbolic range constraint for the left operand of the comparison assuming
-// that it evaluated to true.
-// For example for the comparison a < b symbol a is constrained with range
-// [Smi::kMinValue, b - 1].
-Range* RangeAnalysis::ConstraintRange(Token::Kind op, Definition* boundary) {
-  switch (op) {
-    case Token::kEQ:
-      return new(I) Range(RangeBoundary::FromDefinition(boundary),
-                          RangeBoundary::FromDefinition(boundary));
-    case Token::kNE:
-      return Range::Unknown();
-    case Token::kLT:
-      return new(I) Range(RangeBoundary::MinSmi(),
-                          RangeBoundary::FromDefinition(boundary, -1));
-    case Token::kGT:
-      return new(I) Range(RangeBoundary::FromDefinition(boundary, 1),
-                          RangeBoundary::MaxSmi());
-    case Token::kLTE:
-      return new(I) Range(RangeBoundary::MinSmi(),
-                          RangeBoundary::FromDefinition(boundary));
-    case Token::kGTE:
-      return new(I) Range(RangeBoundary::FromDefinition(boundary),
-                          RangeBoundary::MaxSmi());
-    default:
-      UNREACHABLE();
-      return Range::Unknown();
-  }
-}
-
-
-ConstraintInstr* RangeAnalysis::InsertConstraintFor(Definition* defn,
-                                                    Range* constraint_range,
-                                                    Instruction* after) {
-  // No need to constrain constants.
-  if (defn->IsConstant()) return NULL;
-
-  ConstraintInstr* constraint = new(I) ConstraintInstr(
-      new(I) Value(defn), constraint_range);
-  flow_graph_->InsertAfter(after, constraint, NULL, FlowGraph::kValue);
-  RenameDominatedUses(defn, constraint, constraint);
-  constraints_.Add(constraint);
-  return constraint;
-}
-
-
-void RangeAnalysis::ConstrainValueAfterBranch(Definition* defn, Value* use) {
-  BranchInstr* branch = use->instruction()->AsBranch();
-  RelationalOpInstr* rel_op = branch->comparison()->AsRelationalOp();
-  if ((rel_op != NULL) && (rel_op->operation_cid() == kSmiCid)) {
-    // Found comparison of two smis. Constrain defn at true and false
-    // successors using the other operand as a boundary.
-    Definition* boundary;
-    Token::Kind op_kind;
-    if (use->use_index() == 0) {  // Left operand.
-      boundary = rel_op->InputAt(1)->definition();
-      op_kind = rel_op->kind();
-    } else {
-      ASSERT(use->use_index() == 1);  // Right operand.
-      boundary = rel_op->InputAt(0)->definition();
-      // InsertConstraintFor assumes that defn is left operand of a
-      // comparison if it is right operand flip the comparison.
-      op_kind = FlipComparison(rel_op->kind());
-    }
-
-    // Constrain definition at the true successor.
-    ConstraintInstr* true_constraint =
-        InsertConstraintFor(defn,
-                            ConstraintRange(op_kind, boundary),
-                            branch->true_successor());
-    // Mark true_constraint an artificial use of boundary. This ensures
-    // that constraint's range is recalculated if boundary's range changes.
-    if (true_constraint != NULL) {
-      true_constraint->AddDependency(boundary);
-      true_constraint->set_target(branch->true_successor());
-    }
-
-    // Constrain definition with a negated condition at the false successor.
-    ConstraintInstr* false_constraint =
-        InsertConstraintFor(
-            defn,
-            ConstraintRange(Token::NegateComparison(op_kind), boundary),
-            branch->false_successor());
-    // Mark false_constraint an artificial use of boundary. This ensures
-    // that constraint's range is recalculated if boundary's range changes.
-    if (false_constraint != NULL) {
-      false_constraint->AddDependency(boundary);
-      false_constraint->set_target(branch->false_successor());
-    }
-  }
-}
-
-
-void RangeAnalysis::InsertConstraintsFor(Definition* defn) {
-  for (Value* use = defn->input_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    if (use->instruction()->IsBranch()) {
-      ConstrainValueAfterBranch(defn, use);
-    } else if (use->instruction()->IsCheckArrayBound()) {
-      ConstrainValueAfterCheckArrayBound(
-          defn,
-          use->instruction()->AsCheckArrayBound(),
-          use->use_index());
-    }
-  }
-}
-
-
-void RangeAnalysis::ConstrainValueAfterCheckArrayBound(
-    Definition* defn, CheckArrayBoundInstr* check, intptr_t use_index) {
-  Range* constraint_range = NULL;
-  if (use_index == CheckArrayBoundInstr::kIndexPos) {
-    Definition* length = check->length()->definition();
-    constraint_range = new(I) Range(
-        RangeBoundary::FromConstant(0),
-        RangeBoundary::FromDefinition(length, -1));
-  } else {
-    ASSERT(use_index == CheckArrayBoundInstr::kLengthPos);
-    Definition* index = check->index()->definition();
-    constraint_range = new(I) Range(
-        RangeBoundary::FromDefinition(index, 1),
-        RangeBoundary::MaxSmi());
-  }
-  InsertConstraintFor(defn, constraint_range, check);
-}
-
-
-void RangeAnalysis::InsertConstraints() {
-  for (intptr_t i = 0; i < smi_checks_.length(); i++) {
-    CheckSmiInstr* check = smi_checks_[i];
-    ConstraintInstr* constraint =
-        InsertConstraintFor(check->value()->definition(),
-                            Range::UnknownSmi(),
-                            check);
-    if (constraint == NULL) {
-      // No constraint was needed.
-      continue;
-    }
-    // Mark the constraint's value's reaching type as smi.
-    CompileType* smi_compile_type =
-        ZoneCompileType::Wrap(CompileType::FromCid(kSmiCid));
-    constraint->value()->SetReachingType(smi_compile_type);
-  }
-
-  for (intptr_t i = 0; i < values_.length(); i++) {
-    InsertConstraintsFor(values_[i]);
-  }
-
-  for (intptr_t i = 0; i < constraints_.length(); i++) {
-    InsertConstraintsFor(constraints_[i]);
-  }
-}
-
-
-void RangeAnalysis::ResetWorklist() {
-  if (marked_defns_ == NULL) {
-    marked_defns_ = new(I) BitVector(flow_graph_->current_ssa_temp_index());
-  } else {
-    marked_defns_->Clear();
-  }
-  worklist_.Clear();
-}
-
-
-void RangeAnalysis::MarkDefinition(Definition* defn) {
-  // Unwrap constrained value.
-  while (defn->IsConstraint()) {
-    defn = defn->AsConstraint()->value()->definition();
-  }
-
-  if (!marked_defns_->Contains(defn->ssa_temp_index())) {
-    worklist_.Add(defn);
-    marked_defns_->Add(defn->ssa_temp_index());
-  }
-}
-
-
-RangeAnalysis::Direction RangeAnalysis::ToDirection(Value* val) {
-  if (val->BindsToConstant()) {
-    return (Smi::Cast(val->BoundConstant()).Value() >= 0) ? kPositive
-                                                          : kNegative;
-  } else if (val->definition()->range() != NULL) {
-    Range* range = val->definition()->range();
-    if (Range::ConstantMin(range).ConstantValue() >= 0) {
-      return kPositive;
-    } else if (Range::ConstantMax(range).ConstantValue() <= 0) {
-      return kNegative;
-    }
-  }
-  return kUnknown;
-}
-
-
-Range* RangeAnalysis::InferInductionVariableRange(JoinEntryInstr* loop_header,
-                                                  PhiInstr* var) {
-  BitVector* loop_info = loop_header->loop_info();
-
-  Definition* initial_value = NULL;
-  Direction direction = kUnknown;
-
-  ResetWorklist();
-  MarkDefinition(var);
-  while (!worklist_.is_empty()) {
-    Definition* defn = worklist_.RemoveLast();
-
-    if (defn->IsPhi()) {
-      PhiInstr* phi = defn->AsPhi();
-      for (intptr_t i = 0; i < phi->InputCount(); i++) {
-        Definition* defn = phi->InputAt(i)->definition();
-
-        if (!loop_info->Contains(defn->GetBlock()->preorder_number())) {
-          // The value is coming from outside of the loop.
-          if (initial_value == NULL) {
-            initial_value = defn;
-            continue;
-          } else if (initial_value == defn) {
-            continue;
-          } else {
-            return NULL;
-          }
-        }
-
-        MarkDefinition(defn);
-      }
-    } else if (defn->IsBinarySmiOp()) {
-      BinarySmiOpInstr* binary_op = defn->AsBinarySmiOp();
-
-      switch (binary_op->op_kind()) {
-        case Token::kADD: {
-          const Direction growth_right =
-              ToDirection(binary_op->right());
-          if (growth_right != kUnknown) {
-            UpdateDirection(&direction, growth_right);
-            MarkDefinition(binary_op->left()->definition());
-            break;
-          }
-
-          const Direction growth_left =
-              ToDirection(binary_op->left());
-          if (growth_left != kUnknown) {
-            UpdateDirection(&direction, growth_left);
-            MarkDefinition(binary_op->right()->definition());
-            break;
-          }
-
-          return NULL;
-        }
-
-        case Token::kSUB: {
-          const Direction growth_right =
-              ToDirection(binary_op->right());
-          if (growth_right != kUnknown) {
-            UpdateDirection(&direction, Invert(growth_right));
-            MarkDefinition(binary_op->left()->definition());
-            break;
-          }
-          return NULL;
-        }
-
-        default:
-          return NULL;
-      }
-    } else {
-      return NULL;
-    }
-  }
-
-
-  // We transitively discovered all dependencies of the given phi
-  // and confirmed that it depends on a single value coming from outside of
-  // the loop and some linear combinations of itself.
-  // Compute the range based on initial value and the direction of the growth.
-  switch (direction) {
-    case kPositive:
-      return new(I) Range(RangeBoundary::FromDefinition(initial_value),
-                          RangeBoundary::MaxSmi());
-
-    case kNegative:
-      return new(I) Range(RangeBoundary::MinSmi(),
-                          RangeBoundary::FromDefinition(initial_value));
-
-    case kUnknown:
-    case kBoth:
-      return Range::UnknownSmi();
-  }
-
-  UNREACHABLE();
-  return NULL;
-}
-
-
-void RangeAnalysis::InferRangesRecursive(BlockEntryInstr* block) {
-  JoinEntryInstr* join = block->AsJoinEntry();
-  if (join != NULL) {
-    const bool is_loop_header = (join->loop_info() != NULL);
-    for (PhiIterator it(join); !it.Done(); it.Advance()) {
-      PhiInstr* phi = it.Current();
-      if (definitions_->Contains(phi->ssa_temp_index())) {
-        if (is_loop_header) {
-          // Try recognizing simple induction variables.
-          Range* range = InferInductionVariableRange(join, phi);
-          if (range != NULL) {
-            phi->range_ = range;
-            continue;
-          }
-        }
-
-        phi->InferRange();
-      }
-    }
-  }
-
-  for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
-    Instruction* current = it.Current();
-
-    Definition* defn = current->AsDefinition();
-    if ((defn != NULL) &&
-        (defn->ssa_temp_index() != -1) &&
-        definitions_->Contains(defn->ssa_temp_index())) {
-      defn->InferRange();
-    } else if (FLAG_array_bounds_check_elimination &&
-               current->IsCheckArrayBound()) {
-      CheckArrayBoundInstr* check = current->AsCheckArrayBound();
-      RangeBoundary array_length =
-          RangeBoundary::FromDefinition(check->length()->definition());
-      if (check->IsRedundant(array_length)) {
-        it.RemoveCurrentFromGraph();
-      }
-    }
-  }
-
-  for (intptr_t i = 0; i < block->dominated_blocks().length(); ++i) {
-    InferRangesRecursive(block->dominated_blocks()[i]);
-  }
-}
-
-
-void RangeAnalysis::InferRanges() {
-  if (FLAG_trace_range_analysis) {
-    OS::Print("---- before range analysis -------\n");
-    FlowGraphPrinter printer(*flow_graph_);
-    printer.PrintBlocks();
-  }
-  // Initialize bitvector for quick filtering of int values.
-  definitions_ =
-      new(I) BitVector(flow_graph_->current_ssa_temp_index());
-  for (intptr_t i = 0; i < values_.length(); i++) {
-    definitions_->Add(values_[i]->ssa_temp_index());
-  }
-  for (intptr_t i = 0; i < constraints_.length(); i++) {
-    definitions_->Add(constraints_[i]->ssa_temp_index());
-  }
-
-  // Infer initial values of ranges.
-  const GrowableArray<Definition*>& initial =
-      *flow_graph_->graph_entry()->initial_definitions();
-  for (intptr_t i = 0; i < initial.length(); ++i) {
-    Definition* definition = initial[i];
-    if (definitions_->Contains(definition->ssa_temp_index())) {
-      definition->InferRange();
-    }
-  }
-  InferRangesRecursive(flow_graph_->graph_entry());
-
-  if (FLAG_trace_range_analysis) {
-    OS::Print("---- after range analysis -------\n");
-    FlowGraphPrinter printer(*flow_graph_);
-    printer.PrintBlocks();
-  }
-}
-
-
-void RangeAnalysis::RemoveConstraints() {
-  for (intptr_t i = 0; i < constraints_.length(); i++) {
-    Definition* def = constraints_[i]->value()->definition();
-    // Some constraints might be constraining constraints. Unwind the chain of
-    // constraints until we reach the actual definition.
-    while (def->IsConstraint()) {
-      def = def->AsConstraint()->value()->definition();
-    }
-    constraints_[i]->ReplaceUsesWith(def);
-    constraints_[i]->RemoveFromGraph();
-  }
-}
-
-
 void FlowGraphOptimizer::InferIntRanges() {
   RangeAnalysis range_analysis(flow_graph_);
   range_analysis.Analyze();