VM: Move redundancy elimination phases into a separate file.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 14 matching lines @@
 #include "vm/stack_frame.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DEFINE_FLAG(int, getter_setter_ratio, 13,
     "Ratio of getter/setter usage used for double field unboxing heuristics");
 DEFINE_FLAG(bool, guess_icdata_cid, true,
     "Artificially create type feedback for arithmetic etc. operations"
     " by guessing the other unknown argument cid");
-DEFINE_FLAG(bool, load_cse, true, "Use redundant load elimination.");
-DEFINE_FLAG(bool, dead_store_elimination, true, "Eliminate dead stores");
 DEFINE_FLAG(int, max_polymorphic_checks, 4,
     "Maximum number of polymorphic check, otherwise it is megamorphic.");
 DEFINE_FLAG(int, max_equality_polymorphic_checks, 32,
     "Maximum number of polymorphic checks in equality operator,"
     " otherwise use megamorphic dispatch.");
 DEFINE_FLAG(bool, merge_sin_cos, false, "Merge sin/cos into sincos");
-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, truncating_left_shift, true,
     "Optimize left shift to truncate if possible");
 DEFINE_FLAG(bool, use_cha_deopt, true,
     "Use class hierarchy analysis even if it can cause deoptimization.");
 #if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_IA32)
 DEFINE_FLAG(bool, trace_smi_widening, false, "Trace Smi->Int32 widening pass.");
 #endif
 
 DECLARE_FLAG(bool, precompilation);
 DECLARE_FLAG(bool, polymorphic_with_deopt);
 DECLARE_FLAG(bool, source_lines);
 DECLARE_FLAG(bool, trace_cha);
 DECLARE_FLAG(bool, trace_field_guards);
 DECLARE_FLAG(bool, trace_type_check_elimination);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
-DECLARE_FLAG(bool, fields_may_be_reset);
 
 // Quick access to the current isolate and zone.
 #define I (isolate())
 #define Z (zone())
 
 static bool ShouldInlineSimd() {
   return FlowGraphCompiler::SupportsUnboxedSimd128();
 }
 
 
@@ skipping 563 matching lines @@
         }
       }
     }
     TryMergeTruncDivMod(&div_mod_merge);
     TryMergeMathUnary(&sin_cos_merge);
     current_iterator_ = NULL;
   }
 }
 
 
-static void EnsureSSATempIndex(FlowGraph* graph,
-                               Definition* defn,
-                               Definition* replacement) {
-  if ((replacement->ssa_temp_index() == -1) &&
-      (defn->ssa_temp_index() != -1)) {
-    graph->AllocateSSAIndexes(replacement);
-  }
-}
-
-
-static void ReplaceCurrentInstruction(ForwardInstructionIterator* iterator,
-                                      Instruction* current,
-                                      Instruction* replacement,
-                                      FlowGraph* graph) {
-  Definition* current_defn = current->AsDefinition();
-  if ((replacement != NULL) && (current_defn != NULL)) {
-    Definition* replacement_defn = replacement->AsDefinition();
-    ASSERT(replacement_defn != NULL);
-    current_defn->ReplaceUsesWith(replacement_defn);
-    EnsureSSATempIndex(graph, current_defn, replacement_defn);
-
-    if (FLAG_trace_optimization) {
-      THR_Print("Replacing v%" Pd " with v%" Pd "\n",
-                current_defn->ssa_temp_index(),
-                replacement_defn->ssa_temp_index());
-    }
-  } else if (FLAG_trace_optimization) {
-    if (current_defn == NULL) {
-      THR_Print("Removing %s\n", current->DebugName());
-    } else {
-      ASSERT(!current_defn->HasUses());
-      THR_Print("Removing v%" Pd ".\n", current_defn->ssa_temp_index());
-    }
-  }
-  iterator->RemoveCurrentFromGraph();
-}
-
-
 bool FlowGraphOptimizer::Canonicalize() {
   bool changed = false;
   for (intptr_t i = 0; i < block_order_.length(); ++i) {
     BlockEntryInstr* entry = block_order_[i];
     for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
       Instruction* current = it.Current();
       if (current->HasUnmatchedInputRepresentations()) {
         // Can't canonicalize this instruction until all conversions for its
         // inputs are inserted.
         continue;
       }
 
       Instruction* replacement = current->Canonicalize(flow_graph());
 
       if (replacement != current) {
         // For non-definitions Canonicalize should return either NULL or
         // this.
         ASSERT((replacement == NULL) || current->IsDefinition());
-        ReplaceCurrentInstruction(&it, current, replacement, flow_graph_);
+        flow_graph_->ReplaceCurrentInstruction(&it, current, replacement);
         changed = true;
       }
     }
   }
   return changed;
 }
 
 
 static bool IsUnboxedInteger(Representation rep) {
   return (rep == kUnboxedInt32) ||
@@ skipping 4354 matching lines @@
   // save enough range information in the ICData to drive this decision.
 }
 #endif
 
 void FlowGraphOptimizer::InferIntRanges() {
   RangeAnalysis range_analysis(flow_graph_);
   range_analysis.Analyze();
 }
 
 
-void TryCatchAnalyzer::Optimize(FlowGraph* flow_graph) {
-  // For every catch-block: Iterate over all call instructions inside the
-  // corresponding try-block and figure out for each environment value if it
-  // is the same constant at all calls. If yes, replace the initial definition
-  // at the catch-entry with this constant.
-  const GrowableArray<CatchBlockEntryInstr*>& catch_entries =
-      flow_graph->graph_entry()->catch_entries();
-  intptr_t base = kFirstLocalSlotFromFp + flow_graph->num_non_copied_params();
-  for (intptr_t catch_idx = 0;
-       catch_idx < catch_entries.length();
-       ++catch_idx) {
-    CatchBlockEntryInstr* catch_entry = catch_entries[catch_idx];
-
-    // Initialize cdefs with the original initial definitions (ParameterInstr).
-    // The following representation is used:
-    // ParameterInstr => unknown
-    // ConstantInstr => known constant
-    // NULL => non-constant
-    GrowableArray<Definition*>* idefs = catch_entry->initial_definitions();
-    GrowableArray<Definition*> cdefs(idefs->length());
-    cdefs.AddArray(*idefs);
-
-    // exception_var and stacktrace_var are never constant.
-    intptr_t ex_idx = base - catch_entry->exception_var().index();
-    intptr_t st_idx = base - catch_entry->stacktrace_var().index();
-    cdefs[ex_idx] = cdefs[st_idx] = NULL;
-
-    for (BlockIterator block_it = flow_graph->reverse_postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-      if (block->try_index() == catch_entry->catch_try_index()) {
-        for (ForwardInstructionIterator instr_it(block);
-             !instr_it.Done();
-             instr_it.Advance()) {
-          Instruction* current = instr_it.Current();
-          if (current->MayThrow()) {
-            Environment* env = current->env()->Outermost();
-            ASSERT(env != NULL);
-            for (intptr_t env_idx = 0; env_idx < cdefs.length(); ++env_idx) {
-              if (cdefs[env_idx] != NULL &&
-                  env->ValueAt(env_idx)->BindsToConstant()) {
-                cdefs[env_idx] = env->ValueAt(env_idx)->definition();
-              }
-              if (cdefs[env_idx] != env->ValueAt(env_idx)->definition()) {
-                cdefs[env_idx] = NULL;
-              }
-            }
-          }
-        }
-      }
-    }
-    for (intptr_t j = 0; j < idefs->length(); ++j) {
-      if (cdefs[j] != NULL && cdefs[j]->IsConstant()) {
-        // TODO(fschneider): Use constants from the constant pool.
-        Definition* old = (*idefs)[j];
-        ConstantInstr* orig = cdefs[j]->AsConstant();
-        ConstantInstr* copy =
-            new(flow_graph->zone()) ConstantInstr(orig->value());
-        copy->set_ssa_temp_index(flow_graph->alloc_ssa_temp_index());
-        old->ReplaceUsesWith(copy);
-        (*idefs)[j] = copy;
-      }
-    }
-  }
-}
-
-
-LICM::LICM(FlowGraph* flow_graph) : flow_graph_(flow_graph) {
-  ASSERT(flow_graph->is_licm_allowed());
-}
-
-
-void LICM::Hoist(ForwardInstructionIterator* it,
-                 BlockEntryInstr* pre_header,
-                 Instruction* current) {
-  if (current->IsCheckClass()) {
-    current->AsCheckClass()->set_licm_hoisted(true);
-  } else if (current->IsCheckSmi()) {
-    current->AsCheckSmi()->set_licm_hoisted(true);
-  } else if (current->IsCheckEitherNonSmi()) {
-    current->AsCheckEitherNonSmi()->set_licm_hoisted(true);
-  } else if (current->IsCheckArrayBound()) {
-    current->AsCheckArrayBound()->set_licm_hoisted(true);
-  }
-  if (FLAG_trace_optimization) {
-    THR_Print("Hoisting instruction %s:%" Pd " from B%" Pd " to B%" Pd "\n",
-              current->DebugName(),
-              current->GetDeoptId(),
-              current->GetBlock()->block_id(),
-              pre_header->block_id());
-  }
-  // Move the instruction out of the loop.
-  current->RemoveEnvironment();
-  if (it != NULL) {
-    it->RemoveCurrentFromGraph();
-  } else {
-    current->RemoveFromGraph();
-  }
-  GotoInstr* last = pre_header->last_instruction()->AsGoto();
-  // Using kind kEffect will not assign a fresh ssa temporary index.
-  flow_graph()->InsertBefore(last, current, last->env(), FlowGraph::kEffect);
-  current->CopyDeoptIdFrom(*last);
-}
-
-
-void LICM::TrySpecializeSmiPhi(PhiInstr* phi,
-                               BlockEntryInstr* header,
-                               BlockEntryInstr* pre_header) {
-  if (phi->Type()->ToCid() == kSmiCid) {
-    return;
-  }
-
-  // Check if there is only a single kDynamicCid input to the phi that
-  // comes from the pre-header.
-  const intptr_t kNotFound = -1;
-  intptr_t non_smi_input = kNotFound;
-  for (intptr_t i = 0; i < phi->InputCount(); ++i) {
-    Value* input = phi->InputAt(i);
-    if (input->Type()->ToCid() != kSmiCid) {
-      if ((non_smi_input != kNotFound) ||
-          (input->Type()->ToCid() != kDynamicCid)) {
-        // There are multiple kDynamicCid inputs or there is an input that is
-        // known to be non-smi.
-        return;
-      } else {
-        non_smi_input = i;
-      }
-    }
-  }
-
-  if ((non_smi_input == kNotFound) ||
-      (phi->block()->PredecessorAt(non_smi_input) != pre_header)) {
-    return;
-  }
-
-  CheckSmiInstr* check = NULL;
-  for (Value* use = phi->input_use_list();
-       (use != NULL) && (check == NULL);
-       use = use->next_use()) {
-    check = use->instruction()->AsCheckSmi();
-  }
-
-  if (check == NULL) {
-    return;
-  }
-
-  // Host CheckSmi instruction and make this phi smi one.
-  Hoist(NULL, pre_header, check);
-
-  // Replace value we are checking with phi's input.
-  check->value()->BindTo(phi->InputAt(non_smi_input)->definition());
-
-  phi->UpdateType(CompileType::FromCid(kSmiCid));
-}
-
-
-// Load instructions handled by load elimination.
-static bool IsLoadEliminationCandidate(Instruction* instr) {
-  return instr->IsLoadField()
-      || instr->IsLoadIndexed()
-      || instr->IsLoadStaticField();
-}
-
-
-static bool IsLoopInvariantLoad(ZoneGrowableArray<BitVector*>* sets,
-                                intptr_t loop_header_index,
-                                Instruction* instr) {
-  return IsLoadEliminationCandidate(instr) &&
-      (sets != NULL) &&
-      instr->HasPlaceId() &&
-      ((*sets)[loop_header_index] != NULL) &&
-      (*sets)[loop_header_index]->Contains(instr->place_id());
-}
-
-
-void LICM::OptimisticallySpecializeSmiPhis() {
-  if (!flow_graph()->function().allows_hoisting_check_class() ||
-      FLAG_precompilation) {
-    // Do not hoist any: Either deoptimized on a hoisted check,
-    // or compiling precompiled code where we can't do optimistic
-    // hoisting of checks.
-    return;
-  }
-
-  const ZoneGrowableArray<BlockEntryInstr*>& loop_headers =
-      flow_graph()->LoopHeaders();
-
-  for (intptr_t i = 0; i < loop_headers.length(); ++i) {
-    JoinEntryInstr* header = loop_headers[i]->AsJoinEntry();
-    // Skip loop that don't have a pre-header block.
-    BlockEntryInstr* pre_header = header->ImmediateDominator();
-    if (pre_header == NULL) continue;
-
-    for (PhiIterator it(header); !it.Done(); it.Advance()) {
-      TrySpecializeSmiPhi(it.Current(), header, pre_header);
-    }
-  }
-}
-
-
-void LICM::Optimize() {
-  if (!flow_graph()->function().allows_hoisting_check_class()) {
-    // Do not hoist any.
-    return;
-  }
-
-  const ZoneGrowableArray<BlockEntryInstr*>& loop_headers =
-      flow_graph()->LoopHeaders();
-
-  ZoneGrowableArray<BitVector*>* loop_invariant_loads =
-      flow_graph()->loop_invariant_loads();
-
-  BlockEffects* block_effects = flow_graph()->block_effects();
-
-  for (intptr_t i = 0; i < loop_headers.length(); ++i) {
-    BlockEntryInstr* header = loop_headers[i];
-    // Skip loop that don't have a pre-header block.
-    BlockEntryInstr* pre_header = header->ImmediateDominator();
-    if (pre_header == NULL) continue;
-
-    for (BitVector::Iterator loop_it(header->loop_info());
-         !loop_it.Done();
-         loop_it.Advance()) {
-      BlockEntryInstr* block = flow_graph()->preorder()[loop_it.Current()];
-      for (ForwardInstructionIterator it(block);
-           !it.Done();
-           it.Advance()) {
-        Instruction* current = it.Current();
-        if ((current->AllowsCSE() &&
-             block_effects->CanBeMovedTo(current, pre_header)) ||
-            IsLoopInvariantLoad(loop_invariant_loads, i, current)) {
-          bool inputs_loop_invariant = true;
-          for (int i = 0; i < current->InputCount(); ++i) {
-            Definition* input_def = current->InputAt(i)->definition();
-            if (!input_def->GetBlock()->Dominates(pre_header)) {
-              inputs_loop_invariant = false;
-              break;
-            }
-          }
-          if (inputs_loop_invariant &&
-              !current->IsAssertAssignable() &&
-              !current->IsAssertBoolean()) {
-            // TODO(fschneider): Enable hoisting of Assert-instructions
-            // if it safe to do.
-            Hoist(&it, pre_header, current);
-          }
-        }
-      }
-    }
-  }
-}
-
-
-// Place describes an abstract location (e.g. field) that IR can load
-// from or store to.
-//
-// Places are also used to describe wild-card locations also known as aliases,
-// that essentially represent sets of places that alias each other. Places A
-// and B are said to alias each other if store into A can affect load from B.
-//
-// We distinguish the following aliases:
-//
-//   - for fields
-//     - *.f, *.@offs - field inside some object;
-//     - X.f, X.@offs - field inside an allocated object X;
-//   - for indexed accesses
-//     - *[*] - non-constant index inside some object;
-//     - *[C] - constant index inside some object;
-//     - X[*] - non-constant index inside an allocated object X;
-//     - X[C] - constant index inside an allocated object X.
-//
-// Constant indexed places are divided into two subcategories:
-//
-//   - Access to homogeneous array-like objects: Array, ImmutableArray,
-//     OneByteString, TwoByteString. These objects can only be accessed
-//     on element by element basis with all elements having the same size.
-//     This means X[C] aliases X[K] if and only if C === K.
-//   - TypedData accesses. TypedData allow to read one of the primitive
-//     data types at the given byte offset. When TypedData is accessed through
-//     index operator on a typed array or a typed array view it is guaranteed
-//     that the byte offset is always aligned by the element size. We write
-//     these accesses as X[C|S], where C is constant byte offset and S is size
-//     of the data type. Obviously X[C|S] and X[K|U] alias if and only if either
-//     C = RoundDown(K, S) or K = RoundDown(C, U).
-//     Note that not all accesses to typed data are aligned: e.g. ByteData
-//     allows unanaligned access through it's get*/set* methods.
-//     Check in Place::SetIndex ensures that we never create a place X[C|S]
-//     such that C is not aligned by S.
-//
-// Separating allocations from other objects improves precision of the
-// load forwarding pass because of the following two properties:
-//
-//   - if X can be proven to have no aliases itself (i.e. there is no other SSA
-//     variable that points to X) then no place inside X can be aliased with any
-//     wildcard dependent place (*.f, *.@offs, *[*], *[C]);
-//   - given allocations X and Y no place inside X can be aliased with any place
-//     inside Y even if any of them or both escape.
-//
-// It important to realize that single place can belong to multiple aliases.
-// For example place X.f with aliased allocation X belongs both to X.f and *.f
-// aliases. Likewise X[C] with non-aliased allocation X belongs to X[C] and X[*]
-// aliases.
-//
-class Place : public ValueObject {
- public:
-  enum Kind {
-    kNone,
-
-    // Field location. For instance fields is represented as a pair of a Field
-    // object and an instance (SSA definition) that is being accessed.
-    // For static fields instance is NULL.
-    kField,
-
-    // VMField location. Represented as a pair of an instance (SSA definition)
-    // being accessed and offset to the field.
-    kVMField,
-
-    // Indexed location with a non-constant index.
-    kIndexed,
-
-    // Indexed location with a constant index.
-    kConstantIndexed,
-  };
-
-  // Size of the element accessed by constant index. Size is only important
-  // for TypedData because those accesses can alias even when constant indexes
-  // are not the same: X[0|4] aliases X[0|2] and X[2|2].
-  enum ElementSize {
-    // If indexed access is not a TypedData access then element size is not
-    // important because there is only a single possible access size depending
-    // on the receiver - X[C] aliases X[K] if and only if C == K.
-    // This is the size set for Array, ImmutableArray, OneByteString and
-    // TwoByteString accesses.
-    kNoSize,
-
-    // 1 byte (Int8List, Uint8List, Uint8ClampedList).
-    kInt8,
-
-    // 2 bytes (Int16List, Uint16List).
-    kInt16,
-
-    // 4 bytes (Int32List, Uint32List, Float32List).
-    kInt32,
-
-    // 8 bytes (Int64List, Uint64List, Float64List).
-    kInt64,
-
-    // 16 bytes (Int32x4List, Float32x4List, Float64x2List).
-    kInt128,
-
-    kLargestElementSize = kInt128,
-  };
-
-  Place(const Place& other)
-      : ValueObject(),
-        flags_(other.flags_),
-        instance_(other.instance_),
-        raw_selector_(other.raw_selector_),
-        id_(other.id_) {
-  }
-
-  // Construct a place from instruction if instruction accesses any place.
-  // Otherwise constructs kNone place.
-  Place(Instruction* instr, bool* is_load, bool* is_store)
-      : flags_(0),
-        instance_(NULL),
-        raw_selector_(0),
-        id_(0) {
-    switch (instr->tag()) {
-      case Instruction::kLoadField: {
-        LoadFieldInstr* load_field = instr->AsLoadField();
-        set_representation(load_field->representation());
-        instance_ = load_field->instance()->definition()->OriginalDefinition();
-        if (load_field->field() != NULL) {
-          set_kind(kField);
-          field_ = load_field->field();
-        } else {
-          set_kind(kVMField);
-          offset_in_bytes_ = load_field->offset_in_bytes();
-        }
-        *is_load = true;
-        break;
-      }
-
-      case Instruction::kStoreInstanceField: {
-        StoreInstanceFieldInstr* store =
-            instr->AsStoreInstanceField();
-        set_representation(store->RequiredInputRepresentation(
-            StoreInstanceFieldInstr::kValuePos));
-        instance_ = store->instance()->definition()->OriginalDefinition();
-        if (!store->field().IsNull()) {
-          set_kind(kField);
-          field_ = &store->field();
-        } else {
-          set_kind(kVMField);
-          offset_in_bytes_ = store->offset_in_bytes();
-        }
-        *is_store = true;
-        break;
-      }
-
-      case Instruction::kLoadStaticField:
-        set_kind(kField);
-        set_representation(instr->AsLoadStaticField()->representation());
-        field_ = &instr->AsLoadStaticField()->StaticField();
-        *is_load = true;
-        break;
-
-      case Instruction::kStoreStaticField:
-        set_kind(kField);
-        set_representation(instr->AsStoreStaticField()->
-            RequiredInputRepresentation(StoreStaticFieldInstr::kValuePos));
-        field_ = &instr->AsStoreStaticField()->field();
-        *is_store = true;
-        break;
-
-      case Instruction::kLoadIndexed: {
-        LoadIndexedInstr* load_indexed = instr->AsLoadIndexed();
-        set_representation(load_indexed->representation());
-        instance_ = load_indexed->array()->definition()->OriginalDefinition();
-        SetIndex(load_indexed->index()->definition(),
-                 load_indexed->index_scale(),
-                 load_indexed->class_id());
-        *is_load = true;
-        break;
-      }
-
-      case Instruction::kStoreIndexed: {
-        StoreIndexedInstr* store_indexed = instr->AsStoreIndexed();
-        set_representation(store_indexed->
-            RequiredInputRepresentation(StoreIndexedInstr::kValuePos));
-        instance_ = store_indexed->array()->definition()->OriginalDefinition();
-        SetIndex(store_indexed->index()->definition(),
-                 store_indexed->index_scale(),
-                 store_indexed->class_id());
-        *is_store = true;
-        break;
-      }
-
-      default:
-        break;
-    }
-  }
-
-  // Create object representing *[*] alias.
-  static Place* CreateAnyInstanceAnyIndexAlias(Zone* zone,
-                                               intptr_t id) {
-    return Wrap(zone, Place(
-        EncodeFlags(kIndexed, kNoRepresentation, kNoSize),
-        NULL,
-        0), id);
-  }
-
-  // Return least generic alias for this place. Given that aliases are
-  // essentially sets of places we define least generic alias as a smallest
-  // alias that contains this place.
-  //
-  // We obtain such alias by a simple transformation:
-  //
-  //    - for places that depend on an instance X.f, X.@offs, X[i], X[C]
-  //      we drop X if X is not an allocation because in this case X does not
-  //      posess an identity obtaining aliases *.f, *.@offs, *[i] and *[C]
-  //      respectively;
-  //    - for non-constant indexed places X[i] we drop information about the
-  //      index obtaining alias X[*].
-  //    - we drop information about representation, but keep element size
-  //      if any.
-  //
-  Place ToAlias() const {
-    return Place(
-        RepresentationBits::update(kNoRepresentation, flags_),
-        (DependsOnInstance() && IsAllocation(instance())) ? instance() : NULL,
-        (kind() == kIndexed) ? 0 : raw_selector_);
-  }
-
-  bool DependsOnInstance() const {
-    switch (kind()) {
-      case kField:
-      case kVMField:
-      case kIndexed:
-      case kConstantIndexed:
-        return true;
-
-      case kNone:
-        return false;
-    }
-
-    UNREACHABLE();
-    return false;
-  }
-
-  // Given instance dependent alias X.f, X.@offs, X[C], X[*] return
-  // wild-card dependent alias *.f, *.@offs, *[C] or *[*] respectively.
-  Place CopyWithoutInstance() const {
-    ASSERT(DependsOnInstance());
-    return Place(flags_, NULL, raw_selector_);
-  }
-
-  // Given alias X[C] or *[C] return X[*] and *[*] respectively.
-  Place CopyWithoutIndex() const {
-    ASSERT(kind() == kConstantIndexed);
-    return Place(EncodeFlags(kIndexed, kNoRepresentation, kNoSize),
-                 instance_,
-                 0);
-  }
-
-  // Given alias X[ByteOffs|S] and a larger element size S', return
-  // alias X[RoundDown(ByteOffs, S')|S'] - this is the byte offset of a larger
-  // typed array element that contains this typed array element.
-  // In other words this method computes the only possible place with the given
-  // size that can alias this place (due to alignment restrictions).
-  // For example for X[9|kInt8] and target size kInt32 we would return
-  // X[8|kInt32].
-  Place ToLargerElement(ElementSize to) const {
-    ASSERT(kind() == kConstantIndexed);
-    ASSERT(element_size() != kNoSize);
-    ASSERT(element_size() < to);
-    return Place(ElementSizeBits::update(to, flags_),
-                 instance_,
-                 RoundByteOffset(to, index_constant_));
-  }
-
-
-  intptr_t id() const { return id_; }
-
-  Kind kind() const { return KindBits::decode(flags_); }
-
-  Representation representation() const {
-    return RepresentationBits::decode(flags_);
-  }
-
-  Definition* instance() const {
-    ASSERT(DependsOnInstance());
-    return instance_;
-  }
-
-  void set_instance(Definition* def) {
-    ASSERT(DependsOnInstance());
-    instance_ = def->OriginalDefinition();
-  }
-
-  const Field& field() const {
-    ASSERT(kind() == kField);
-    return *field_;
-  }
-
-  intptr_t offset_in_bytes() const {
-    ASSERT(kind() == kVMField);
-    return offset_in_bytes_;
-  }
-
-  Definition* index() const {
-    ASSERT(kind() == kIndexed);
-    return index_;
-  }
-
-  ElementSize element_size() const {
-    return ElementSizeBits::decode(flags_);
-  }
-
-  intptr_t index_constant() const {
-    ASSERT(kind() == kConstantIndexed);
-    return index_constant_;
-  }
-
-  static const char* DefinitionName(Definition* def) {
-    if (def == NULL) {
-      return "*";
-    } else {
-      return Thread::Current()->zone()->PrintToString(
-            "v%" Pd, def->ssa_temp_index());
-    }
-  }
-
-  const char* ToCString() const {
-    switch (kind()) {
-      case kNone:
-        return "<none>";
-
-      case kField: {
-        const char* field_name = String::Handle(field().name()).ToCString();
-        if (field().is_static()) {
-          return Thread::Current()->zone()->PrintToString(
-              "<%s>", field_name);
-        } else {
-          return Thread::Current()->zone()->PrintToString(
-              "<%s.%s>", DefinitionName(instance()), field_name);
-        }
-      }
-
-      case kVMField:
-        return Thread::Current()->zone()->PrintToString(
-            "<%s.@%" Pd ">",
-            DefinitionName(instance()),
-            offset_in_bytes());
-
-      case kIndexed:
-        return Thread::Current()->zone()->PrintToString(
-            "<%s[%s]>",
-            DefinitionName(instance()),
-            DefinitionName(index()));
-
-      case kConstantIndexed:
-        if (element_size() == kNoSize) {
-          return Thread::Current()->zone()->PrintToString(
-              "<%s[%" Pd "]>",
-              DefinitionName(instance()),
-              index_constant());
-        } else {
-          return Thread::Current()->zone()->PrintToString(
-              "<%s[%" Pd "|%" Pd "]>",
-              DefinitionName(instance()),
-              index_constant(),
-              ElementSizeMultiplier(element_size()));
-        }
-    }
-    UNREACHABLE();
-    return "<?>";
-  }
-
-  // Fields that are considered immutable by load optimization.
-  // Handle static finals as non-final with precompilation because
-  // they may be reset to uninitialized after compilation.
-  bool IsImmutableField() const {
-    return (kind() == kField)
-        && field().is_final()
-        && (!field().is_static() || !FLAG_fields_may_be_reset);
-  }
-
-  intptr_t Hashcode() const {
-    return (flags_ * 63 + reinterpret_cast<intptr_t>(instance_)) * 31 +
-        FieldHashcode();
-  }
-
-  bool Equals(const Place* other) const {
-    return (flags_ == other->flags_) &&
-        (instance_ == other->instance_) &&
-        SameField(other);
-  }
-
-  // Create a zone allocated copy of this place and assign given id to it.
-  static Place* Wrap(Zone* zone, const Place& place, intptr_t id);
-
-  static bool IsAllocation(Definition* defn) {
-    return (defn != NULL) &&
-        (defn->IsAllocateObject() ||
-         defn->IsCreateArray() ||
-         defn->IsAllocateUninitializedContext() ||
-         (defn->IsStaticCall() &&
-          defn->AsStaticCall()->IsRecognizedFactory()));
-  }
-
- private:
-  Place(uword flags, Definition* instance, intptr_t selector)
-      : flags_(flags),
-        instance_(instance),
-        raw_selector_(selector),
-        id_(0) {
-  }
-
-  bool SameField(const Place* other) const {
-    return (kind() == kField) ? (field().raw() == other->field().raw())
-                              : (offset_in_bytes_ == other->offset_in_bytes_);
-  }
-
-  intptr_t FieldHashcode() const {
-    return (kind() == kField) ? reinterpret_cast<intptr_t>(field().raw())
-                              : offset_in_bytes_;
-  }
-
-  void set_representation(Representation rep) {
-    flags_ = RepresentationBits::update(rep, flags_);
-  }
-
-  void set_kind(Kind kind) {
-    flags_ = KindBits::update(kind, flags_);
-  }
-
-  void set_element_size(ElementSize scale) {
-    flags_ = ElementSizeBits::update(scale, flags_);
-  }
-
-  void SetIndex(Definition* index, intptr_t scale, intptr_t class_id) {
-    ConstantInstr* index_constant = index->AsConstant();
-    if ((index_constant != NULL) && index_constant->value().IsSmi()) {
-      const intptr_t index_value = Smi::Cast(index_constant->value()).Value();
-      const ElementSize size = ElementSizeFor(class_id);
-      const bool is_typed_data = (size != kNoSize);
-
-      // If we are writing into the typed data scale the index to
-      // get byte offset. Otherwise ignore the scale.
-      if (!is_typed_data) {
-        scale = 1;
-      }
-
-      // Guard against potential multiplication overflow and negative indices.
-      if ((0 <= index_value) && (index_value < (kMaxInt32 / scale))) {
-        const intptr_t scaled_index = index_value * scale;
-
-        // Guard against unaligned byte offsets.
-        if (!is_typed_data ||
-            Utils::IsAligned(scaled_index, ElementSizeMultiplier(size))) {
-          set_kind(kConstantIndexed);
-          set_element_size(size);
-          index_constant_ = scaled_index;
-          return;
-        }
-      }
-
-      // Fallthrough: create generic _[*] place.
-    }
-
-    set_kind(kIndexed);
-    index_ = index;
-  }
-
-  static uword EncodeFlags(Kind kind, Representation rep, ElementSize scale) {
-    ASSERT((kind == kConstantIndexed) || (scale == kNoSize));
-    return KindBits::encode(kind) |
-        RepresentationBits::encode(rep) |
-        ElementSizeBits::encode(scale);
-  }
-
-  static ElementSize ElementSizeFor(intptr_t class_id) {
-    switch (class_id) {
-      case kArrayCid:
-      case kImmutableArrayCid:
-      case kOneByteStringCid:
-      case kTwoByteStringCid:
-        // Object arrays and strings do not allow accessing them through
-        // different types. No need to attach scale.
-        return kNoSize;
-
-      case kTypedDataInt8ArrayCid:
-      case kTypedDataUint8ArrayCid:
-      case kTypedDataUint8ClampedArrayCid:
-      case kExternalTypedDataUint8ArrayCid:
-      case kExternalTypedDataUint8ClampedArrayCid:
-        return kInt8;
-
-      case kTypedDataInt16ArrayCid:
-      case kTypedDataUint16ArrayCid:
-        return kInt16;
-
-      case kTypedDataInt32ArrayCid:
-      case kTypedDataUint32ArrayCid:
-      case kTypedDataFloat32ArrayCid:
-        return kInt32;
-
-      case kTypedDataInt64ArrayCid:
-      case kTypedDataUint64ArrayCid:
-      case kTypedDataFloat64ArrayCid:
-        return kInt64;
-
-      case kTypedDataInt32x4ArrayCid:
-      case kTypedDataFloat32x4ArrayCid:
-      case kTypedDataFloat64x2ArrayCid:
-        return kInt128;
-
-      default:
-        UNREACHABLE();
-        return kNoSize;
-    }
-  }
-
-  static intptr_t ElementSizeMultiplier(ElementSize size) {
-    return 1 << (static_cast<intptr_t>(size) - static_cast<intptr_t>(kInt8));
-  }
-
-  static intptr_t RoundByteOffset(ElementSize size, intptr_t offset) {
-    return offset & ~(ElementSizeMultiplier(size) - 1);
-  }
-
-  class KindBits : public BitField<uword, Kind, 0, 3> {};
-  class RepresentationBits :
-      public BitField<uword, Representation, KindBits::kNextBit, 11> {};
-  class ElementSizeBits :
-      public BitField<uword, ElementSize, RepresentationBits::kNextBit, 3> {};
-
-  uword flags_;
-  Definition* instance_;
-  union {
-    intptr_t raw_selector_;
-    const Field* field_;
-    intptr_t offset_in_bytes_;
-    intptr_t index_constant_;
-    Definition* index_;
-  };
-
-  intptr_t id_;
-};
-
-
-class ZonePlace : public ZoneAllocated {
- public:
-  explicit ZonePlace(const Place& place) : place_(place) { }
-
-  Place* place() { return &place_; }
-
- private:
-  Place place_;
-};
-
-
-Place* Place::Wrap(Zone* zone, const Place& place, intptr_t id) {
-  Place* wrapped = (new(zone) ZonePlace(place))->place();
-  wrapped->id_ = id;
-  return wrapped;
-}
-
-
-// Correspondence between places connected through outgoing phi moves on the
-// edge that targets join.
-class PhiPlaceMoves : public ZoneAllocated {
- public:
-  // Record a move from the place with id |from| to the place with id |to| at
-  // the given block.
-  void CreateOutgoingMove(Zone* zone,
-                          BlockEntryInstr* block, intptr_t from, intptr_t to) {
-    const intptr_t block_num = block->preorder_number();
-    while (moves_.length() <= block_num) {
-      moves_.Add(NULL);
-    }
-
-    if (moves_[block_num] == NULL) {
-      moves_[block_num] = new(zone) ZoneGrowableArray<Move>(5);
-    }
-
-    moves_[block_num]->Add(Move(from, to));
-  }
-
-  class Move {
-   public:
-    Move(intptr_t from, intptr_t to) : from_(from), to_(to) { }
-
-    intptr_t from() const { return from_; }
-    intptr_t to() const { return to_; }
-
-   private:
-    intptr_t from_;
-    intptr_t to_;
-  };
-
-  typedef const ZoneGrowableArray<Move>* MovesList;
-
-  MovesList GetOutgoingMoves(BlockEntryInstr* block) const {
-    const intptr_t block_num = block->preorder_number();
-    return (block_num < moves_.length()) ?
-        moves_[block_num] : NULL;
-  }
-
- private:
-  GrowableArray<ZoneGrowableArray<Move>* > moves_;
-};
-
-
-// A map from aliases to a set of places sharing the alias. Additionally
-// carries a set of places that can be aliased by side-effects, essentially
-// those that are affected by calls.
-class AliasedSet : public ZoneAllocated {
- public:
-  AliasedSet(Zone* zone,
-             DirectChainedHashMap<PointerKeyValueTrait<Place> >* places_map,
-             ZoneGrowableArray<Place*>* places,
-             PhiPlaceMoves* phi_moves)
-      : zone_(zone),
-        places_map_(places_map),
-        places_(*places),
-        phi_moves_(phi_moves),
-        aliases_(5),
-        aliases_map_(),
-        typed_data_access_sizes_(),
-        representatives_(),
-        killed_(),
-        aliased_by_effects_(new(zone) BitVector(zone, places->length())) {
-    InsertAlias(Place::CreateAnyInstanceAnyIndexAlias(zone_,
-        kAnyInstanceAnyIndexAlias));
-    for (intptr_t i = 0; i < places_.length(); i++) {
-      AddRepresentative(places_[i]);
-    }
-    ComputeKillSets();
-  }
-
-  intptr_t LookupAliasId(const Place& alias) {
-    const Place* result = aliases_map_.Lookup(&alias);
-    return (result != NULL) ? result->id() : static_cast<intptr_t>(kNoAlias);
-  }
-
-  BitVector* GetKilledSet(intptr_t alias) {
-    return (alias < killed_.length()) ? killed_[alias] : NULL;
-  }
-
-  intptr_t max_place_id() const { return places().length(); }
-  bool IsEmpty() const { return max_place_id() == 0; }
-
-  BitVector* aliased_by_effects() const { return aliased_by_effects_; }
-
-  const ZoneGrowableArray<Place*>& places() const {
-    return places_;
-  }
-
-  Place* LookupCanonical(Place* place) const {
-    return places_map_->Lookup(place);
-  }
-
-  void PrintSet(BitVector* set) {
-    bool comma = false;
-    for (BitVector::Iterator it(set);
-         !it.Done();
-         it.Advance()) {
-      if (comma) {
-        THR_Print(", ");
-      }
-      THR_Print("%s", places_[it.Current()]->ToCString());
-      comma = true;
-    }
-  }
-
-  const PhiPlaceMoves* phi_moves() const { return phi_moves_; }
-
-  void RollbackAliasedIdentites() {
-    for (intptr_t i = 0; i < identity_rollback_.length(); ++i) {
-      identity_rollback_[i]->SetIdentity(AliasIdentity::Unknown());
-    }
-  }
-
-  // Returns false if the result of an allocation instruction can't be aliased
-  // by another SSA variable and true otherwise.
-  bool CanBeAliased(Definition* alloc) {
-    if (!Place::IsAllocation(alloc)) {
-      return true;
-    }
-
-    if (alloc->Identity().IsUnknown()) {
-      ComputeAliasing(alloc);
-    }
-
-    return !alloc->Identity().IsNotAliased();
-  }
-
-  enum {
-    kNoAlias = 0
-  };
-
- private:
-  enum {
-    // Artificial alias that is used to collect all representatives of the
-    // *[C], X[C] aliases for arbitrary C.
-    kAnyConstantIndexedAlias = 1,
-
-    // Artificial alias that is used to collect all representatives of
-    // *[C] alias for arbitrary C.
-    kUnknownInstanceConstantIndexedAlias = 2,
-
-    // Artificial alias that is used to collect all representatives of
-    // X[*] alias for all X.
-    kAnyAllocationIndexedAlias = 3,
-
-    // *[*] alias.
-    kAnyInstanceAnyIndexAlias = 4
-  };
-
-  // Compute least generic alias for the place and assign alias id to it.
-  void AddRepresentative(Place* place) {
-    if (!place->IsImmutableField()) {
-      const Place* alias = CanonicalizeAlias(place->ToAlias());
-      EnsureSet(&representatives_, alias->id())->Add(place->id());
-
-      // Update cumulative representative sets that are used during
-      // killed sets computation.
-      if (alias->kind() == Place::kConstantIndexed) {
-        if (CanBeAliased(alias->instance())) {
-          EnsureSet(&representatives_, kAnyConstantIndexedAlias)->
-              Add(place->id());
-        }
-
-        if (alias->instance() == NULL) {
-          EnsureSet(&representatives_, kUnknownInstanceConstantIndexedAlias)->
-              Add(place->id());
-        }
-
-        // Collect all element sizes used to access TypedData arrays in
-        // the function. This is used to skip sizes without representatives
-        // when computing kill sets.
-        if (alias->element_size() != Place::kNoSize) {
-          typed_data_access_sizes_.Add(alias->element_size());
-        }
-      } else if ((alias->kind() == Place::kIndexed) &&
-                 CanBeAliased(place->instance())) {
-        EnsureSet(&representatives_, kAnyAllocationIndexedAlias)->
-            Add(place->id());
-      }
-
-      if (!IsIndependentFromEffects(place)) {
-        aliased_by_effects_->Add(place->id());
-      }
-    }
-  }
-
-  void ComputeKillSets() {
-    for (intptr_t i = 0; i < aliases_.length(); ++i) {
-      const Place* alias = aliases_[i];
-      // Add all representatives to the kill set.
-      AddAllRepresentatives(alias->id(), alias->id());
-      ComputeKillSet(alias);
-    }
-
-    if (FLAG_trace_load_optimization) {
-      THR_Print("Aliases KILL sets:\n");
-      for (intptr_t i = 0; i < aliases_.length(); ++i) {
-        const Place* alias = aliases_[i];
-        BitVector* kill = GetKilledSet(alias->id());
-
-        THR_Print("%s: ", alias->ToCString());
-        if (kill != NULL) {
-          PrintSet(kill);
-        }
-        THR_Print("\n");
-      }
-    }
-  }
-
-  void InsertAlias(const Place* alias) {
-    aliases_map_.Insert(alias);
-    aliases_.Add(alias);
-  }
-
-  const Place* CanonicalizeAlias(const Place& alias) {
-    const Place* canonical = aliases_map_.Lookup(&alias);
-    if (canonical == NULL) {
-      canonical = Place::Wrap(zone_,
-                              alias,
-                              kAnyInstanceAnyIndexAlias + aliases_.length());
-      InsertAlias(canonical);
-    }
-    ASSERT(aliases_map_.Lookup(&alias) == canonical);
-    return canonical;
-  }
-
-  BitVector* GetRepresentativesSet(intptr_t alias) {
-    return (alias < representatives_.length()) ? representatives_[alias] : NULL;
-  }
-
-  BitVector* EnsureSet(GrowableArray<BitVector*>* sets,
-                       intptr_t alias) {
-    while (sets->length() <= alias) {
-      sets->Add(NULL);
-    }
-
-    BitVector* set = (*sets)[alias];
-    if (set == NULL) {
-      (*sets)[alias] = set = new(zone_) BitVector(zone_, max_place_id());
-    }
-    return set;
-  }
-
-  void AddAllRepresentatives(const Place* to, intptr_t from) {
-    AddAllRepresentatives(to->id(), from);
-  }
-
-  void AddAllRepresentatives(intptr_t to, intptr_t from) {
-    BitVector* from_set = GetRepresentativesSet(from);
-    if (from_set != NULL) {
-      EnsureSet(&killed_, to)->AddAll(from_set);
-    }
-  }
-
-  void CrossAlias(const Place* to, const Place& from) {
-    const intptr_t from_id = LookupAliasId(from);
-    if (from_id == kNoAlias) {
-      return;
-    }
-    CrossAlias(to, from_id);
-  }
-
-  void CrossAlias(const Place* to, intptr_t from) {
-    AddAllRepresentatives(to->id(), from);
-    AddAllRepresentatives(from, to->id());
-  }
-
-  // When computing kill sets we let less generic alias insert its
-  // representatives into more generic alias'es kill set. For example
-  // when visiting alias X[*] instead of searching for all aliases X[C]
-  // and inserting their representatives into kill set for X[*] we update
-  // kill set for X[*] each time we visit new X[C] for some C.
-  // There is an exception however: if both aliases are parametric like *[C]
-  // and X[*] which cross alias when X is an aliased allocation then we use
-  // artificial aliases that contain all possible representatives for the given
-  // alias for any value of the parameter to compute resulting kill set.
-  void ComputeKillSet(const Place* alias) {
-    switch (alias->kind()) {
-      case Place::kIndexed:  // Either *[*] or X[*] alias.
-        if (alias->instance() == NULL) {
-          // *[*] aliases with X[*], X[C], *[C].
-          AddAllRepresentatives(alias, kAnyConstantIndexedAlias);
-          AddAllRepresentatives(alias, kAnyAllocationIndexedAlias);
-        } else if (CanBeAliased(alias->instance())) {
-          // X[*] aliases with X[C].
-          // If X can be aliased then X[*] also aliases with *[C], *[*].
-          CrossAlias(alias, kAnyInstanceAnyIndexAlias);
-          AddAllRepresentatives(alias, kUnknownInstanceConstantIndexedAlias);
-        }
-        break;
-
-      case Place::kConstantIndexed:  // Either X[C] or *[C] alias.
-        if (alias->element_size() != Place::kNoSize) {
-          const bool has_aliased_instance =
-              (alias->instance() != NULL) && CanBeAliased(alias->instance());
-
-          // If this is a TypedData access then X[C|S] aliases larger elements
-          // covering this one X[RoundDown(C, S')|S'] for all S' > S and
-          // all smaller elements being covered by this one X[C'|S'] for
-          // some S' < S and all C' such that C = RoundDown(C', S).
-          // In the loop below it's enough to only propagate aliasing to
-          // larger aliases because propagation is symmetric: smaller aliases
-          // (if there are any) would update kill set for this alias when they
-          // are visited.
-          for (intptr_t i = static_cast<intptr_t>(alias->element_size()) + 1;
-               i <= Place::kLargestElementSize;
-               i++) {
-            // Skip element sizes that a guaranteed to have no representatives.
-            if (!typed_data_access_sizes_.Contains(alias->element_size())) {
-              continue;
-            }
-
-            // X[C|S] aliases with X[RoundDown(C, S')|S'] and likewise
-            // *[C|S] aliases with *[RoundDown(C, S')|S'].
-            const Place larger_alias =
-                alias->ToLargerElement(static_cast<Place::ElementSize>(i));
-            CrossAlias(alias, larger_alias);
-            if (has_aliased_instance) {
-              // If X is an aliased instance then X[C|S] aliases
-              // with *[RoundDown(C, S')|S'].
-              CrossAlias(alias, larger_alias.CopyWithoutInstance());
-            }
-          }
-        }
-
-        if (alias->instance() == NULL) {
-          // *[C] aliases with X[C], X[*], *[*].
-          AddAllRepresentatives(alias, kAnyAllocationIndexedAlias);
-          CrossAlias(alias, kAnyInstanceAnyIndexAlias);
-        } else {
-          // X[C] aliases with X[*].
-          // If X can be aliased then X[C] also aliases with *[C], *[*].
-          CrossAlias(alias, alias->CopyWithoutIndex());
-          if (CanBeAliased(alias->instance())) {
-            CrossAlias(alias, alias->CopyWithoutInstance());
-            CrossAlias(alias, kAnyInstanceAnyIndexAlias);
-          }
-        }
-        break;
-
-      case Place::kField:
-      case Place::kVMField:
-        if (CanBeAliased(alias->instance())) {
-          // X.f or X.@offs alias with *.f and *.@offs respectively.
-          CrossAlias(alias, alias->CopyWithoutInstance());
-        }
-        break;
-
-      case Place::kNone:
-        UNREACHABLE();
-    }
-  }
-
-  // Returns true if the given load is unaffected by external side-effects.
-  // This essentially means that no stores to the same location can
-  // occur in other functions.
-  bool IsIndependentFromEffects(Place* place) {
-    if (place->IsImmutableField()) {
-      // Note that we can't use LoadField's is_immutable attribute here because
-      // some VM-fields (those that have no corresponding Field object and
-      // accessed through offset alone) can share offset but have different
-      // immutability properties.
-      // One example is the length property of growable and fixed size list. If
-      // loads of these two properties occur in the same function for the same
-      // receiver then they will get the same expression number. However
-      // immutability of the length of fixed size list does not mean that
-      // growable list also has immutable property. Thus we will make a
-      // conservative assumption for the VM-properties.
-      // TODO(vegorov): disambiguate immutable and non-immutable VM-fields with
-      // the same offset e.g. through recognized kind.
-      return true;
-    }
-
-    return ((place->kind() == Place::kField) ||
-         (place->kind() == Place::kVMField)) &&
-        !CanBeAliased(place->instance());
-  }
-
-  // Returns true if there are direct loads from the given place.
-  bool HasLoadsFromPlace(Definition* defn, const Place* place) {
-    ASSERT((place->kind() == Place::kField) ||
-           (place->kind() == Place::kVMField));
-
-    for (Value* use = defn->input_use_list();
-         use != NULL;
-         use = use->next_use()) {
-      Instruction* instr = use->instruction();
-      if ((instr->IsRedefinition() ||
-           instr->IsAssertAssignable()) &&
-          HasLoadsFromPlace(instr->AsDefinition(), place)) {
-        return true;
-      }
-      bool is_load = false, is_store;
-      Place load_place(instr, &is_load, &is_store);
-
-      if (is_load && load_place.Equals(place)) {
-        return true;
-      }
-    }
-
-    return false;
-  }
-
-  // Check if any use of the definition can create an alias.
-  // Can add more objects into aliasing_worklist_.
-  bool AnyUseCreatesAlias(Definition* defn) {
-    for (Value* use = defn->input_use_list();
-         use != NULL;
-         use = use->next_use()) {
-      Instruction* instr = use->instruction();
-      if (instr->IsPushArgument() ||
-          (instr->IsStoreIndexed()
-           && (use->use_index() == StoreIndexedInstr::kValuePos)) ||
-          instr->IsStoreStaticField() ||
-          instr->IsPhi()) {
-        return true;
-      } else if ((instr->IsAssertAssignable() || instr->IsRedefinition()) &&
-                 AnyUseCreatesAlias(instr->AsDefinition())) {
-        return true;
-      } else if ((instr->IsStoreInstanceField()
-           && (use->use_index() != StoreInstanceFieldInstr::kInstancePos))) {
-        ASSERT(use->use_index() == StoreInstanceFieldInstr::kValuePos);
-        // If we store this value into an object that is not aliased itself
-        // and we never load again then the store does not create an alias.
-        StoreInstanceFieldInstr* store = instr->AsStoreInstanceField();
-        Definition* instance =
-            store->instance()->definition()->OriginalDefinition();
-        if (Place::IsAllocation(instance) &&
-            !instance->Identity().IsAliased()) {
-          bool is_load, is_store;
-          Place store_place(instr, &is_load, &is_store);
-
-          if (!HasLoadsFromPlace(instance, &store_place)) {
-            // No loads found that match this store. If it is yet unknown if
-            // the object is not aliased then optimistically assume this but
-            // add it to the worklist to check its uses transitively.
-            if (instance->Identity().IsUnknown()) {
-              instance->SetIdentity(AliasIdentity::NotAliased());
-              aliasing_worklist_.Add(instance);
-            }
-            continue;
-          }
-        }
-        return true;
-      }
-    }
-    return false;
-  }
-
-  // Mark any value stored into the given object as potentially aliased.
-  void MarkStoredValuesEscaping(Definition* defn) {
-    // Find all stores into this object.
-    for (Value* use = defn->input_use_list();
-         use != NULL;
-         use = use->next_use()) {
-      if (use->instruction()->IsRedefinition() ||
-          use->instruction()->IsAssertAssignable()) {
-        MarkStoredValuesEscaping(use->instruction()->AsDefinition());
-        continue;
-      }
-      if ((use->use_index() == StoreInstanceFieldInstr::kInstancePos) &&
-          use->instruction()->IsStoreInstanceField()) {
-        StoreInstanceFieldInstr* store =
-            use->instruction()->AsStoreInstanceField();
-        Definition* value = store->value()->definition()->OriginalDefinition();
-        if (value->Identity().IsNotAliased()) {
-          value->SetIdentity(AliasIdentity::Aliased());
-          identity_rollback_.Add(value);
-
-          // Add to worklist to propagate the mark transitively.
-          aliasing_worklist_.Add(value);
-        }
-      }
-    }
-  }
-
-  // Determine if the given definition can't be aliased.
-  void ComputeAliasing(Definition* alloc) {
-    ASSERT(Place::IsAllocation(alloc));
-    ASSERT(alloc->Identity().IsUnknown());
-    ASSERT(aliasing_worklist_.is_empty());
-
-    alloc->SetIdentity(AliasIdentity::NotAliased());
-    aliasing_worklist_.Add(alloc);
-
-    while (!aliasing_worklist_.is_empty()) {
-      Definition* defn = aliasing_worklist_.RemoveLast();
-      ASSERT(Place::IsAllocation(defn));
-      // If the definition in the worklist was optimistically marked as
-      // not-aliased check that optimistic assumption still holds: check if
-      // any of its uses can create an alias.
-      if (!defn->Identity().IsAliased() && AnyUseCreatesAlias(defn)) {
-        defn->SetIdentity(AliasIdentity::Aliased());
-        identity_rollback_.Add(defn);
-      }
-
-      // If the allocation site is marked as aliased conservatively mark
-      // any values stored into the object aliased too.
-      if (defn->Identity().IsAliased()) {
-        MarkStoredValuesEscaping(defn);
-      }
-    }
-  }
-
-  Zone* zone_;
-
-  DirectChainedHashMap<PointerKeyValueTrait<Place> >* places_map_;
-
-  const ZoneGrowableArray<Place*>& places_;
-
-  const PhiPlaceMoves* phi_moves_;
-
-  // A list of all seen aliases and a map that allows looking up canonical
-  // alias object.
-  GrowableArray<const Place*> aliases_;
-  DirectChainedHashMap<PointerKeyValueTrait<const Place> > aliases_map_;
-
-  SmallSet<Place::ElementSize> typed_data_access_sizes_;
-
-  // Maps alias id to set of ids of places representing the alias.
-  // Place represents an alias if this alias is least generic alias for
-  // the place.
-  // (see ToAlias for the definition of least generic alias).
-  GrowableArray<BitVector*> representatives_;
-
-  // Maps alias id to set of ids of places aliased.
-  GrowableArray<BitVector*> killed_;
-
-  // Set of ids of places that can be affected by side-effects other than
-  // explicit stores (i.e. through calls).
-  BitVector* aliased_by_effects_;
-
-  // Worklist used during alias analysis.
-  GrowableArray<Definition*> aliasing_worklist_;
-
-  // List of definitions that had their identity set to Aliased. At the end
-  // of load optimization their identity will be rolled back to Unknown to
-  // avoid treating them as Aliased at later stages without checking first
-  // as optimizations can potentially eliminate instructions leading to
-  // aliasing.
-  GrowableArray<Definition*> identity_rollback_;
-};
-
-
-static Definition* GetStoredValue(Instruction* instr) {
-  if (instr->IsStoreIndexed()) {
-    return instr->AsStoreIndexed()->value()->definition();
-  }
-
-  StoreInstanceFieldInstr* store_instance_field = instr->AsStoreInstanceField();
-  if (store_instance_field != NULL) {
-    return store_instance_field->value()->definition();
-  }
-
-  StoreStaticFieldInstr* store_static_field = instr->AsStoreStaticField();
-  if (store_static_field != NULL) {
-    return store_static_field->value()->definition();
-  }
-
-  UNREACHABLE();  // Should only be called for supported store instructions.
-  return NULL;
-}
-
-
-static bool IsPhiDependentPlace(Place* place) {
-  return ((place->kind() == Place::kField) ||
-          (place->kind() == Place::kVMField)) &&
-        (place->instance() != NULL) &&
-        place->instance()->IsPhi();
-}
-
-
-// For each place that depends on a phi ensure that equivalent places
-// corresponding to phi input are numbered and record outgoing phi moves
-// for each block which establish correspondence between phi dependent place
-// and phi input's place that is flowing in.
-static PhiPlaceMoves* ComputePhiMoves(
-    DirectChainedHashMap<PointerKeyValueTrait<Place> >* map,
-    ZoneGrowableArray<Place*>* places) {
-  Thread* thread = Thread::Current();
-  Zone* zone = thread->zone();
-  PhiPlaceMoves* phi_moves = new(zone) PhiPlaceMoves();
-
-  for (intptr_t i = 0; i < places->length(); i++) {
-    Place* place = (*places)[i];
-
-    if (IsPhiDependentPlace(place)) {
-      PhiInstr* phi = place->instance()->AsPhi();
-      BlockEntryInstr* block = phi->GetBlock();
-
-      if (FLAG_trace_optimization) {
-        THR_Print("phi dependent place %s\n", place->ToCString());
-      }
-
-      Place input_place(*place);
-      for (intptr_t j = 0; j < phi->InputCount(); j++) {
-        input_place.set_instance(phi->InputAt(j)->definition());
-
-        Place* result = map->Lookup(&input_place);
-        if (result == NULL) {
-          result = Place::Wrap(zone, input_place, places->length());
-          map->Insert(result);
-          places->Add(result);
-          if (FLAG_trace_optimization) {
-            THR_Print("  adding place %s as %" Pd "\n",
-                      result->ToCString(),
-                      result->id());
-          }
-        }
-        phi_moves->CreateOutgoingMove(zone,
-                                      block->PredecessorAt(j),
-                                      result->id(),
-                                      place->id());
-      }
-    }
-  }
-
-  return phi_moves;
-}
-
-
-enum CSEMode {
-  kOptimizeLoads,
-  kOptimizeStores
-};
-
-
-static AliasedSet* NumberPlaces(
-    FlowGraph* graph,
-    DirectChainedHashMap<PointerKeyValueTrait<Place> >* map,
-    CSEMode mode) {
-  // Loads representing different expression ids will be collected and
-  // used to build per offset kill sets.
-  Zone* zone = graph->zone();
-  ZoneGrowableArray<Place*>* places =
-      new(zone) ZoneGrowableArray<Place*>(10);
-
-  bool has_loads = false;
-  bool has_stores = false;
-  for (BlockIterator it = graph->reverse_postorder_iterator();
-       !it.Done();
-       it.Advance()) {
-    BlockEntryInstr* block = it.Current();
-
-    for (ForwardInstructionIterator instr_it(block);
-         !instr_it.Done();
-         instr_it.Advance()) {
-      Instruction* instr = instr_it.Current();
-      Place place(instr, &has_loads, &has_stores);
-      if (place.kind() == Place::kNone) {
-        continue;
-      }
-
-      Place* result = map->Lookup(&place);
-      if (result == NULL) {
-        result = Place::Wrap(zone, place, places->length());
-        map->Insert(result);
-        places->Add(result);
-
-        if (FLAG_trace_optimization) {
-          THR_Print("numbering %s as %" Pd "\n",
-                    result->ToCString(),
-                    result->id());
-        }
-      }
-
-      instr->set_place_id(result->id());
-    }
-  }
-
-  if ((mode == kOptimizeLoads) && !has_loads) {
-    return NULL;
-  }
-  if ((mode == kOptimizeStores) && !has_stores) {
-    return NULL;
-  }
-
-  PhiPlaceMoves* phi_moves = ComputePhiMoves(map, places);
-
-  // Build aliasing sets mapping aliases to loads.
-  return new(zone) AliasedSet(zone, map, places, phi_moves);
-}
-
-
-class LoadOptimizer : public ValueObject {
- public:
-  LoadOptimizer(FlowGraph* graph, AliasedSet* aliased_set)
-      : graph_(graph),
-        aliased_set_(aliased_set),
-        in_(graph_->preorder().length()),
-        out_(graph_->preorder().length()),
-        gen_(graph_->preorder().length()),
-        kill_(graph_->preorder().length()),
-        exposed_values_(graph_->preorder().length()),
-        out_values_(graph_->preorder().length()),
-        phis_(5),
-        worklist_(5),
-        congruency_worklist_(6),
-        in_worklist_(NULL),
-        forwarded_(false) {
-    const intptr_t num_blocks = graph_->preorder().length();
-    for (intptr_t i = 0; i < num_blocks; i++) {
-      out_.Add(NULL);
-      gen_.Add(new(Z) BitVector(Z, aliased_set_->max_place_id()));
-      kill_.Add(new(Z) BitVector(Z, aliased_set_->max_place_id()));
-      in_.Add(new(Z) BitVector(Z, aliased_set_->max_place_id()));
-
-      exposed_values_.Add(NULL);
-      out_values_.Add(NULL);
-    }
-  }
-
-  ~LoadOptimizer() {
-    aliased_set_->RollbackAliasedIdentites();
-  }
-
-  Isolate* isolate() const { return graph_->isolate(); }
-  Zone* zone() const { return graph_->zone(); }
-
-  static bool OptimizeGraph(FlowGraph* graph) {
-    ASSERT(FLAG_load_cse);
-    if (FLAG_trace_load_optimization) {
-      FlowGraphPrinter::PrintGraph("Before LoadOptimizer", graph);
-    }
-
-    DirectChainedHashMap<PointerKeyValueTrait<Place> > map;
-    AliasedSet* aliased_set = NumberPlaces(graph, &map, kOptimizeLoads);
-    if ((aliased_set != NULL) && !aliased_set->IsEmpty()) {
-      // If any loads were forwarded return true from Optimize to run load
-      // forwarding again. This will allow to forward chains of loads.
-      // This is especially important for context variables as they are built
-      // as loads from loaded context.
-      // TODO(vegorov): renumber newly discovered congruences during the
-      // forwarding to forward chains without running whole pass twice.
-      LoadOptimizer load_optimizer(graph, aliased_set);
-      return load_optimizer.Optimize();
-    }
-    return false;
-  }
-
- private:
-  bool Optimize() {
-    ComputeInitialSets();
-    ComputeOutSets();
-    ComputeOutValues();
-    if (graph_->is_licm_allowed()) {
-      MarkLoopInvariantLoads();
-    }
-    ForwardLoads();
-    EmitPhis();
-
-    if (FLAG_trace_load_optimization) {
-      FlowGraphPrinter::PrintGraph("After LoadOptimizer", graph_);
-    }
-
-    return forwarded_;
-  }
-
-  // Compute sets of loads generated and killed by each block.
-  // Additionally compute upwards exposed and generated loads for each block.
-  // Exposed loads are those that can be replaced if a corresponding
-  // reaching load will be found.
-  // Loads that are locally redundant will be replaced as we go through
-  // instructions.
-  void ComputeInitialSets() {
-    for (BlockIterator block_it = graph_->reverse_postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-      const intptr_t preorder_number = block->preorder_number();
-
-      BitVector* kill = kill_[preorder_number];
-      BitVector* gen = gen_[preorder_number];
-
-      ZoneGrowableArray<Definition*>* exposed_values = NULL;
-      ZoneGrowableArray<Definition*>* out_values = NULL;
-
-      for (ForwardInstructionIterator instr_it(block);
-           !instr_it.Done();
-           instr_it.Advance()) {
-        Instruction* instr = instr_it.Current();
-
-        bool is_load = false, is_store = false;
-        Place place(instr, &is_load, &is_store);
-
-        BitVector* killed = NULL;
-        if (is_store) {
-          const intptr_t alias_id =
-              aliased_set_->LookupAliasId(place.ToAlias());
-          if (alias_id != AliasedSet::kNoAlias) {
-            killed = aliased_set_->GetKilledSet(alias_id);
-          } else if (!place.IsImmutableField()) {
-            // We encountered unknown alias: this means intrablock load
-            // forwarding refined parameter of this store, for example
-            //
-            //     o   <- alloc()
-            //     a.f <- o
-            //     u   <- a.f
-            //     u.x <- null ;; this store alias is *.x
-            //
-            // after intrablock load forwarding
-            //
-            //     o   <- alloc()
-            //     a.f <- o
-            //     o.x <- null ;; this store alias is o.x
-            //
-            // In this case we fallback to using place id recorded in the
-            // instruction that still points to the old place with a more
-            // generic alias.
-            const intptr_t old_alias_id = aliased_set_->LookupAliasId(
-                aliased_set_->places()[instr->place_id()]->ToAlias());
-            killed = aliased_set_->GetKilledSet(old_alias_id);
-          }
-
-          if (killed != NULL) {
-            kill->AddAll(killed);
-            // There is no need to clear out_values when clearing GEN set
-            // because only those values that are in the GEN set
-            // will ever be used.
-            gen->RemoveAll(killed);
-          }
-
-          // Only forward stores to normal arrays, float64, and simd arrays
-          // to loads because other array stores (intXX/uintXX/float32)
-          // may implicitly convert the value stored.
-          StoreIndexedInstr* array_store = instr->AsStoreIndexed();
-          if ((array_store == NULL) ||
-              (array_store->class_id() == kArrayCid) ||
-              (array_store->class_id() == kTypedDataFloat64ArrayCid) ||
-              (array_store->class_id() == kTypedDataFloat32ArrayCid) ||
-              (array_store->class_id() == kTypedDataFloat32x4ArrayCid)) {
-            Place* canonical_place = aliased_set_->LookupCanonical(&place);
-            if (canonical_place != NULL) {
-              // Store has a corresponding numbered place that might have a
-              // load. Try forwarding stored value to it.
-              gen->Add(canonical_place->id());
-              if (out_values == NULL) out_values = CreateBlockOutValues();
-              (*out_values)[canonical_place->id()] = GetStoredValue(instr);
-            }
-          }
-
-          ASSERT(!instr->IsDefinition() ||
-                 !IsLoadEliminationCandidate(instr->AsDefinition()));
-          continue;
-        } else if (is_load) {
-          // Check if this load needs renumbering because of the intrablock
-          // load forwarding.
-          const Place* canonical = aliased_set_->LookupCanonical(&place);
-          if ((canonical != NULL) &&
-            (canonical->id() != instr->AsDefinition()->place_id())) {
-            instr->AsDefinition()->set_place_id(canonical->id());
-          }
-        }
-
-        // If instruction has effects then kill all loads affected.
-        if (!instr->Effects().IsNone()) {
-          kill->AddAll(aliased_set_->aliased_by_effects());
-          // There is no need to clear out_values when removing values from GEN
-          // set because only those values that are in the GEN set
-          // will ever be used.
-          gen->RemoveAll(aliased_set_->aliased_by_effects());
-          continue;
-        }
-
-        Definition* defn = instr->AsDefinition();
-        if (defn == NULL) {
-          continue;
-        }
-
-        // For object allocation forward initial values of the fields to
-        // subsequent loads. For skip final fields.  Final fields are
-        // initialized in constructor that potentially can be not inlined into
-        // the function that we are currently optimizing. However at the same
-        // time we assume that values of the final fields can be forwarded
-        // across side-effects. If we add 'null' as known values for these
-        // fields here we will incorrectly propagate this null across
-        // constructor invocation.
-        AllocateObjectInstr* alloc = instr->AsAllocateObject();
-        if ((alloc != NULL)) {
-          for (Value* use = alloc->input_use_list();
-               use != NULL;
-               use = use->next_use()) {
-            // Look for all immediate loads from this object.
-            if (use->use_index() != 0) {
-              continue;
-            }
-
-            LoadFieldInstr* load = use->instruction()->AsLoadField();
-            if (load != NULL) {
-              // Found a load. Initialize current value of the field to null for
-              // normal fields, or with type arguments.
-
-              // Forward for all fields for non-escaping objects and only
-              // non-final fields and type arguments for escaping ones.
-              if (aliased_set_->CanBeAliased(alloc) &&
-                  (load->field() != NULL) &&
-                  load->field()->is_final()) {
-                continue;
-              }
-
-              Definition* forward_def = graph_->constant_null();
-              if (alloc->ArgumentCount() > 0) {
-                ASSERT(alloc->ArgumentCount() == 1);
-                intptr_t type_args_offset =
-                    alloc->cls().type_arguments_field_offset();
-                if (load->offset_in_bytes() == type_args_offset) {
-                  forward_def = alloc->PushArgumentAt(0)->value()->definition();
-                }
-              }
-              gen->Add(load->place_id());
-              if (out_values == NULL) out_values = CreateBlockOutValues();
-              (*out_values)[load->place_id()] = forward_def;
-            }
-          }
-          continue;
-        }
-
-        if (!IsLoadEliminationCandidate(defn)) {
-          continue;
-        }
-
-        const intptr_t place_id = defn->place_id();
-        if (gen->Contains(place_id)) {
-          // This is a locally redundant load.
-          ASSERT((out_values != NULL) && ((*out_values)[place_id] != NULL));
-
-          Definition* replacement = (*out_values)[place_id];
-          EnsureSSATempIndex(graph_, defn, replacement);
-          if (FLAG_trace_optimization) {
-            THR_Print("Replacing load v%" Pd " with v%" Pd "\n",
-                      defn->ssa_temp_index(),
-                      replacement->ssa_temp_index());
-          }
-
-          defn->ReplaceUsesWith(replacement);
-          instr_it.RemoveCurrentFromGraph();
-          forwarded_ = true;
-          continue;
-        } else if (!kill->Contains(place_id)) {
-          // This is an exposed load: it is the first representative of a
-          // given expression id and it is not killed on the path from
-          // the block entry.
-          if (exposed_values == NULL) {
-            static const intptr_t kMaxExposedValuesInitialSize = 5;
-            exposed_values = new(Z) ZoneGrowableArray<Definition*>(
-                Utils::Minimum(kMaxExposedValuesInitialSize,
-                               aliased_set_->max_place_id()));
-          }
-
-          exposed_values->Add(defn);
-        }
-
-        gen->Add(place_id);
-
-        if (out_values == NULL) out_values = CreateBlockOutValues();
-        (*out_values)[place_id] = defn;
-      }
-
-      exposed_values_[preorder_number] = exposed_values;
-      out_values_[preorder_number] = out_values;
-    }
-  }
-
-  static void PerformPhiMoves(PhiPlaceMoves::MovesList phi_moves,
-                              BitVector* out,
-                              BitVector* forwarded_loads) {
-    forwarded_loads->Clear();
-
-    for (intptr_t i = 0; i < phi_moves->length(); i++) {
-      const intptr_t from = (*phi_moves)[i].from();
-      const intptr_t to = (*phi_moves)[i].to();
-      if (from == to) continue;
-
-      if (out->Contains(from)) {
-        forwarded_loads->Add(to);
-      }
-    }
-
-    for (intptr_t i = 0; i < phi_moves->length(); i++) {
-      const intptr_t from = (*phi_moves)[i].from();
-      const intptr_t to = (*phi_moves)[i].to();
-      if (from == to) continue;
-
-      out->Remove(to);
-    }
-
-    out->AddAll(forwarded_loads);
-  }
-
-  // Compute OUT sets by propagating them iteratively until fix point
-  // is reached.
-  void ComputeOutSets() {
-    BitVector* temp = new(Z) BitVector(Z, aliased_set_->max_place_id());
-    BitVector* forwarded_loads =
-        new(Z) BitVector(Z, aliased_set_->max_place_id());
-    BitVector* temp_out = new(Z) BitVector(Z, aliased_set_->max_place_id());
-
-    bool changed = true;
-    while (changed) {
-      changed = false;
-
-      for (BlockIterator block_it = graph_->reverse_postorder_iterator();
-           !block_it.Done();
-           block_it.Advance()) {
-        BlockEntryInstr* block = block_it.Current();
-
-        const intptr_t preorder_number = block->preorder_number();
-
-        BitVector* block_in = in_[preorder_number];
-        BitVector* block_out = out_[preorder_number];
-        BitVector* block_kill = kill_[preorder_number];
-        BitVector* block_gen = gen_[preorder_number];
-
-        // Compute block_in as the intersection of all out(p) where p
-        // is a predecessor of the current block.
-        if (block->IsGraphEntry()) {
-          temp->Clear();
-        } else {
-          temp->SetAll();
-          ASSERT(block->PredecessorCount() > 0);
-          for (intptr_t i = 0; i < block->PredecessorCount(); i++) {
-            BlockEntryInstr* pred = block->PredecessorAt(i);
-            BitVector* pred_out = out_[pred->preorder_number()];
-            if (pred_out == NULL) continue;
-            PhiPlaceMoves::MovesList phi_moves =
-                aliased_set_->phi_moves()->GetOutgoingMoves(pred);
-            if (phi_moves != NULL) {
-              // If there are phi moves, perform intersection with
-              // a copy of pred_out where the phi moves are applied.
-              temp_out->CopyFrom(pred_out);
-              PerformPhiMoves(phi_moves, temp_out, forwarded_loads);
-              pred_out = temp_out;
-            }
-            temp->Intersect(pred_out);
-          }
-        }
-
-        if (!temp->Equals(*block_in) || (block_out == NULL)) {
-          // If IN set has changed propagate the change to OUT set.
-          block_in->CopyFrom(temp);
-
-          temp->RemoveAll(block_kill);
-          temp->AddAll(block_gen);
-
-          if ((block_out == NULL) || !block_out->Equals(*temp)) {
-            if (block_out == NULL) {
-              block_out = out_[preorder_number] =
-                  new(Z) BitVector(Z, aliased_set_->max_place_id());
-            }
-            block_out->CopyFrom(temp);
-            changed = true;
-          }
-        }
-      }
-    }
-  }
-
-  // Compute out_values mappings by propagating them in reverse postorder once
-  // through the graph. Generate phis on back edges where eager merge is
-  // impossible.
-  // No replacement is done at this point and thus any out_value[place_id] is
-  // changed at most once: from NULL to an actual value.
-  // When merging incoming loads we might need to create a phi.
-  // These phis are not inserted at the graph immediately because some of them
-  // might become redundant after load forwarding is done.
-  void ComputeOutValues() {
-    GrowableArray<PhiInstr*> pending_phis(5);
-    ZoneGrowableArray<Definition*>* temp_forwarded_values = NULL;
-
-    for (BlockIterator block_it = graph_->reverse_postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-
-      const bool can_merge_eagerly = CanMergeEagerly(block);
-
-      const intptr_t preorder_number = block->preorder_number();
-
-      ZoneGrowableArray<Definition*>* block_out_values =
-          out_values_[preorder_number];
-
-
-      // If OUT set has changed then we have new values available out of
-      // the block. Compute these values creating phi where necessary.
-      for (BitVector::Iterator it(out_[preorder_number]);
-           !it.Done();
-           it.Advance()) {
-        const intptr_t place_id = it.Current();
-
-        if (block_out_values == NULL) {
-          out_values_[preorder_number] = block_out_values =
-              CreateBlockOutValues();
-        }
-
-        if ((*block_out_values)[place_id] == NULL) {
-          ASSERT(block->PredecessorCount() > 0);
-          Definition* in_value = can_merge_eagerly ?
-              MergeIncomingValues(block, place_id) : NULL;
-          if ((in_value == NULL) &&
-              (in_[preorder_number]->Contains(place_id))) {
-            PhiInstr* phi = new(Z) PhiInstr(block->AsJoinEntry(),
-                                            block->PredecessorCount());
-            phi->set_place_id(place_id);
-            pending_phis.Add(phi);
-            in_value = phi;
-          }
-          (*block_out_values)[place_id] = in_value;
-        }
-      }
-
-      // If the block has outgoing phi moves perform them. Use temporary list
-      // of values to ensure that cyclic moves are performed correctly.
-      PhiPlaceMoves::MovesList phi_moves =
-          aliased_set_->phi_moves()->GetOutgoingMoves(block);
-      if ((phi_moves != NULL) && (block_out_values != NULL)) {
-        if (temp_forwarded_values == NULL) {
-          temp_forwarded_values = CreateBlockOutValues();
-        }
-
-        for (intptr_t i = 0; i < phi_moves->length(); i++) {
-          const intptr_t from = (*phi_moves)[i].from();
-          const intptr_t to = (*phi_moves)[i].to();
-          if (from == to) continue;
-
-          (*temp_forwarded_values)[to] = (*block_out_values)[from];
-        }
-
-        for (intptr_t i = 0; i < phi_moves->length(); i++) {
-          const intptr_t from = (*phi_moves)[i].from();
-          const intptr_t to = (*phi_moves)[i].to();
-          if (from == to) continue;
-
-          (*block_out_values)[to] = (*temp_forwarded_values)[to];
-        }
-      }
-
-      if (FLAG_trace_load_optimization) {
-        THR_Print("B%" Pd "\n", block->block_id());
-        THR_Print("  IN: ");
-        aliased_set_->PrintSet(in_[preorder_number]);
-        THR_Print("\n");
-
-        THR_Print("  KILL: ");
-        aliased_set_->PrintSet(kill_[preorder_number]);
-        THR_Print("\n");
-
-        THR_Print("  OUT: ");
-        aliased_set_->PrintSet(out_[preorder_number]);
-        THR_Print("\n");
-      }
-    }
-
-    // All blocks were visited. Fill pending phis with inputs
-    // that flow on back edges.
-    for (intptr_t i = 0; i < pending_phis.length(); i++) {
-      FillPhiInputs(pending_phis[i]);
-    }
-  }
-
-  bool CanMergeEagerly(BlockEntryInstr* block) {
-    for (intptr_t i = 0; i < block->PredecessorCount(); i++) {
-      BlockEntryInstr* pred = block->PredecessorAt(i);
-      if (pred->postorder_number() < block->postorder_number()) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  void MarkLoopInvariantLoads() {
-    const ZoneGrowableArray<BlockEntryInstr*>& loop_headers =
-        graph_->LoopHeaders();
-
-    ZoneGrowableArray<BitVector*>* invariant_loads =
-        new(Z) ZoneGrowableArray<BitVector*>(loop_headers.length());
-
-    for (intptr_t i = 0; i < loop_headers.length(); i++) {
-      BlockEntryInstr* header = loop_headers[i];
-      BlockEntryInstr* pre_header = header->ImmediateDominator();
-      if (pre_header == NULL) {
-        invariant_loads->Add(NULL);
-        continue;
-      }
-
-      BitVector* loop_gen = new(Z) BitVector(Z, aliased_set_->max_place_id());
-      for (BitVector::Iterator loop_it(header->loop_info());
-           !loop_it.Done();
-           loop_it.Advance()) {
-        const intptr_t preorder_number = loop_it.Current();
-        loop_gen->AddAll(gen_[preorder_number]);
-      }
-
-      for (BitVector::Iterator loop_it(header->loop_info());
-           !loop_it.Done();
-           loop_it.Advance()) {
-        const intptr_t preorder_number = loop_it.Current();
-        loop_gen->RemoveAll(kill_[preorder_number]);
-      }
-
-      if (FLAG_trace_optimization) {
-        for (BitVector::Iterator it(loop_gen); !it.Done(); it.Advance()) {
-          THR_Print("place %s is loop invariant for B%" Pd "\n",
-                    aliased_set_->places()[it.Current()]->ToCString(),
-                    header->block_id());
-        }
-      }
-
-      invariant_loads->Add(loop_gen);
-    }
-
-    graph_->set_loop_invariant_loads(invariant_loads);
-  }
-
-  // Compute incoming value for the given expression id.
-  // Will create a phi if different values are incoming from multiple
-  // predecessors.
-  Definition* MergeIncomingValues(BlockEntryInstr* block, intptr_t place_id) {
-    // First check if the same value is coming in from all predecessors.
-    static Definition* const kDifferentValuesMarker =
-        reinterpret_cast<Definition*>(-1);
-    Definition* incoming = NULL;
-    for (intptr_t i = 0; i < block->PredecessorCount(); i++) {
-      BlockEntryInstr* pred = block->PredecessorAt(i);
-      ZoneGrowableArray<Definition*>* pred_out_values =
-          out_values_[pred->preorder_number()];
-      if ((pred_out_values == NULL) || ((*pred_out_values)[place_id] == NULL)) {
-        return NULL;
-      } else if (incoming == NULL) {
-        incoming = (*pred_out_values)[place_id];
-      } else if (incoming != (*pred_out_values)[place_id]) {
-        incoming = kDifferentValuesMarker;
-      }
-    }
-
-    if (incoming != kDifferentValuesMarker) {
-      ASSERT(incoming != NULL);
-      return incoming;
-    }
-
-    // Incoming values are different. Phi is required to merge.
-    PhiInstr* phi = new(Z) PhiInstr(
-        block->AsJoinEntry(), block->PredecessorCount());
-    phi->set_place_id(place_id);
-    FillPhiInputs(phi);
-    return phi;
-  }
-
-  void FillPhiInputs(PhiInstr* phi) {
-    BlockEntryInstr* block = phi->GetBlock();
-    const intptr_t place_id = phi->place_id();
-
-    for (intptr_t i = 0; i < block->PredecessorCount(); i++) {
-      BlockEntryInstr* pred = block->PredecessorAt(i);
-      ZoneGrowableArray<Definition*>* pred_out_values =
-          out_values_[pred->preorder_number()];
-      ASSERT((*pred_out_values)[place_id] != NULL);
-
-      // Sets of outgoing values are not linked into use lists so
-      // they might contain values that were replaced and removed
-      // from the graph by this iteration.
-      // To prevent using them we additionally mark definitions themselves
-      // as replaced and store a pointer to the replacement.
-      Definition* replacement = (*pred_out_values)[place_id]->Replacement();
-      Value* input = new(Z) Value(replacement);
-      phi->SetInputAt(i, input);
-      replacement->AddInputUse(input);
-    }
-
-    graph_->AllocateSSAIndexes(phi);
-    phis_.Add(phi);  // Postpone phi insertion until after load forwarding.
-
-    if (FLAG_trace_load_optimization) {
-      THR_Print("created pending phi %s for %s at B%" Pd "\n",
-                phi->ToCString(),
-                aliased_set_->places()[place_id]->ToCString(),
-                block->block_id());
-    }
-  }
-
-  // Iterate over basic blocks and replace exposed loads with incoming
-  // values.
-  void ForwardLoads() {
-    for (BlockIterator block_it = graph_->reverse_postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-
-      ZoneGrowableArray<Definition*>* loads =
-          exposed_values_[block->preorder_number()];
-      if (loads == NULL) continue;  // No exposed loads.
-
-      BitVector* in = in_[block->preorder_number()];
-
-      for (intptr_t i = 0; i < loads->length(); i++) {
-        Definition* load = (*loads)[i];
-        if (!in->Contains(load->place_id())) continue;  // No incoming value.
-
-        Definition* replacement = MergeIncomingValues(block, load->place_id());
-        ASSERT(replacement != NULL);
-
-        // Sets of outgoing values are not linked into use lists so
-        // they might contain values that were replace and removed
-        // from the graph by this iteration.
-        // To prevent using them we additionally mark definitions themselves
-        // as replaced and store a pointer to the replacement.
-        replacement = replacement->Replacement();
-
-        if (load != replacement) {
-          EnsureSSATempIndex(graph_, load, replacement);
-
-          if (FLAG_trace_optimization) {
-            THR_Print("Replacing load v%" Pd " with v%" Pd "\n",
-                      load->ssa_temp_index(),
-                      replacement->ssa_temp_index());
-          }
-
-          load->ReplaceUsesWith(replacement);
-          load->RemoveFromGraph();
-          load->SetReplacement(replacement);
-          forwarded_ = true;
-        }
-      }
-    }
-  }
-
-  // Check if the given phi take the same value on all code paths.
-  // Eliminate it as redundant if this is the case.
-  // When analyzing phi operands assumes that only generated during
-  // this load phase can be redundant. They can be distinguished because
-  // they are not marked alive.
-  // TODO(vegorov): move this into a separate phase over all phis.
-  bool EliminateRedundantPhi(PhiInstr* phi) {
-    Definition* value = NULL;  // Possible value of this phi.
-
-    worklist_.Clear();
-    if (in_worklist_ == NULL) {
-      in_worklist_ = new(Z) BitVector(Z, graph_->current_ssa_temp_index());
-    } else {
-      in_worklist_->Clear();
-    }
-
-    worklist_.Add(phi);
-    in_worklist_->Add(phi->ssa_temp_index());
-
-    for (intptr_t i = 0; i < worklist_.length(); i++) {
-      PhiInstr* phi = worklist_[i];
-
-      for (intptr_t i = 0; i < phi->InputCount(); i++) {
-        Definition* input = phi->InputAt(i)->definition();
-        if (input == phi) continue;
-
-        PhiInstr* phi_input = input->AsPhi();
-        if ((phi_input != NULL) && !phi_input->is_alive()) {
-          if (!in_worklist_->Contains(phi_input->ssa_temp_index())) {
-            worklist_.Add(phi_input);
-            in_worklist_->Add(phi_input->ssa_temp_index());
-          }
-          continue;
-        }
-
-        if (value == NULL) {
-          value = input;
-        } else if (value != input) {
-          return false;  // This phi is not redundant.
-        }
-      }
-    }
-
-    // All phis in the worklist are redundant and have the same computed
-    // value on all code paths.
-    ASSERT(value != NULL);
-    for (intptr_t i = 0; i < worklist_.length(); i++) {
-      worklist_[i]->ReplaceUsesWith(value);
-    }
-
-    return true;
-  }
-
-  // Returns true if definitions are congruent assuming their inputs
-  // are congruent.
-  bool CanBeCongruent(Definition* a, Definition* b) {
-    return (a->tag() == b->tag()) &&
-       ((a->IsPhi() && (a->GetBlock() == b->GetBlock())) ||
-        (a->AllowsCSE() && a->Dependencies().IsNone() &&
-         a->AttributesEqual(b)));
-  }
-
-  // Given two definitions check if they are congruent under assumption that
-  // their inputs will be proven congruent. If they are - add them to the
-  // worklist to check their inputs' congruency.
-  // Returns true if pair was added to the worklist or is already in the
-  // worklist and false if a and b are not congruent.
-  bool AddPairToCongruencyWorklist(Definition* a, Definition* b) {
-    if (!CanBeCongruent(a, b)) {
-      return false;
-    }
-
-    // If a is already in the worklist check if it is being compared to b.
-    // Give up if it is not.
-    if (in_worklist_->Contains(a->ssa_temp_index())) {
-      for (intptr_t i = 0; i < congruency_worklist_.length(); i += 2) {
-        if (a == congruency_worklist_[i]) {
-          return (b == congruency_worklist_[i + 1]);
-        }
-      }
-      UNREACHABLE();
-    } else if (in_worklist_->Contains(b->ssa_temp_index())) {
-      return AddPairToCongruencyWorklist(b, a);
-    }
-
-    congruency_worklist_.Add(a);
-    congruency_worklist_.Add(b);
-    in_worklist_->Add(a->ssa_temp_index());
-    return true;
-  }
-
-  bool AreInputsCongruent(Definition* a, Definition* b) {
-    ASSERT(a->tag() == b->tag());
-    ASSERT(a->InputCount() == b->InputCount());
-    for (intptr_t j = 0; j < a->InputCount(); j++) {
-      Definition* inputA = a->InputAt(j)->definition();
-      Definition* inputB = b->InputAt(j)->definition();
-
-      if (inputA != inputB) {
-        if (!AddPairToCongruencyWorklist(inputA, inputB)) {
-          return false;
-        }
-      }
-    }
-    return true;
-  }
-
-  // Returns true if instruction dom dominates instruction other.
-  static bool Dominates(Instruction* dom, Instruction* other) {
-    BlockEntryInstr* dom_block = dom->GetBlock();
-    BlockEntryInstr* other_block = other->GetBlock();
-
-    if (dom_block == other_block) {
-      for (Instruction* current = dom->next();
-           current != NULL;
-           current = current->next()) {
-        if (current == other) {
-          return true;
-        }
-      }
-      return false;
-    }
-
-    return dom_block->Dominates(other_block);
-  }
-
-  // Replace the given phi with another if they are congruent.
-  // Returns true if succeeds.
-  bool ReplacePhiWith(PhiInstr* phi, PhiInstr* replacement) {
-    ASSERT(phi->InputCount() == replacement->InputCount());
-    ASSERT(phi->block() == replacement->block());
-
-    congruency_worklist_.Clear();
-    if (in_worklist_ == NULL) {
-      in_worklist_ = new(Z) BitVector(Z, graph_->current_ssa_temp_index());
-    } else {
-      in_worklist_->Clear();
-    }
-
-    // During the comparison worklist contains pairs of definitions to be
-    // compared.
-    if (!AddPairToCongruencyWorklist(phi, replacement)) {
-      return false;
-    }
-
-    // Process the worklist. It might grow during each comparison step.
-    for (intptr_t i = 0; i < congruency_worklist_.length(); i += 2) {
-      if (!AreInputsCongruent(congruency_worklist_[i],
-                              congruency_worklist_[i + 1])) {
-        return false;
-      }
-    }
-
-    // At this point worklist contains pairs of congruent definitions.
-    // Replace the one member of the pair with another maintaining proper
-    // domination relation between definitions and uses.
-    for (intptr_t i = 0; i < congruency_worklist_.length(); i += 2) {
-      Definition* a = congruency_worklist_[i];
-      Definition* b = congruency_worklist_[i + 1];
-
-      // If these definitions are not phis then we need to pick up one
-      // that dominates another as the replacement: if a dominates b swap them.
-      // Note: both a and b are used as a phi input at the same block B which
-      // means a dominates B and b dominates B, which guarantees that either
-      // a dominates b or b dominates a.
-      if (!a->IsPhi()) {
-        if (Dominates(a, b)) {
-          Definition* t = a;
-          a = b;
-          b = t;
-        }
-        ASSERT(Dominates(b, a));
-      }
-
-      if (FLAG_trace_load_optimization) {
-        THR_Print("Replacing %s with congruent %s\n",
-                  a->ToCString(),
-                  b->ToCString());
-      }
-
-      a->ReplaceUsesWith(b);
-      if (a->IsPhi()) {
-        // We might be replacing a phi introduced by the load forwarding
-        // that is not inserted in the graph yet.
-        ASSERT(b->IsPhi());
-        PhiInstr* phi_a = a->AsPhi();
-        if (phi_a->is_alive()) {
-          phi_a->mark_dead();
-          phi_a->block()->RemovePhi(phi_a);
-          phi_a->UnuseAllInputs();
-        }
-      } else {
-        a->RemoveFromGraph();
-      }
-    }
-
-    return true;
-  }
-
-  // Insert the given phi into the graph. Attempt to find an equal one in the
-  // target block first.
-  // Returns true if the phi was inserted and false if it was replaced.
-  bool EmitPhi(PhiInstr* phi) {
-    for (PhiIterator it(phi->block()); !it.Done(); it.Advance()) {
-      if (ReplacePhiWith(phi, it.Current())) {
-        return false;
-      }
-    }
-
-    phi->mark_alive();
-    phi->block()->InsertPhi(phi);
-    return true;
-  }
-
-  // Phis have not yet been inserted into the graph but they have uses of
-  // their inputs.  Insert the non-redundant ones and clear the input uses
-  // of the redundant ones.
-  void EmitPhis() {
-    // First eliminate all redundant phis.
-    for (intptr_t i = 0; i < phis_.length(); i++) {
-      PhiInstr* phi = phis_[i];
-      if (!phi->HasUses() || EliminateRedundantPhi(phi)) {
-        phi->UnuseAllInputs();
-        phis_[i] = NULL;
-      }
-    }
-
-    // Now emit phis or replace them with equal phis already present in the
-    // graph.
-    for (intptr_t i = 0; i < phis_.length(); i++) {
-      PhiInstr* phi = phis_[i];
-      if ((phi != NULL) && (!phi->HasUses() || !EmitPhi(phi))) {
-        phi->UnuseAllInputs();
-      }
-    }
-  }
-
-  ZoneGrowableArray<Definition*>* CreateBlockOutValues() {
-    ZoneGrowableArray<Definition*>* out =
-        new(Z) ZoneGrowableArray<Definition*>(aliased_set_->max_place_id());
-    for (intptr_t i = 0; i < aliased_set_->max_place_id(); i++) {
-      out->Add(NULL);
-    }
-    return out;
-  }
-
-  FlowGraph* graph_;
-  DirectChainedHashMap<PointerKeyValueTrait<Place> >* map_;
-
-  // Mapping between field offsets in words and expression ids of loads from
-  // that offset.
-  AliasedSet* aliased_set_;
-
-  // Per block sets of expression ids for loads that are: incoming (available
-  // on the entry), outgoing (available on the exit), generated and killed.
-  GrowableArray<BitVector*> in_;
-  GrowableArray<BitVector*> out_;
-  GrowableArray<BitVector*> gen_;
-  GrowableArray<BitVector*> kill_;
-
-  // Per block list of upwards exposed loads.
-  GrowableArray<ZoneGrowableArray<Definition*>*> exposed_values_;
-
-  // Per block mappings between expression ids and outgoing definitions that
-  // represent those ids.
-  GrowableArray<ZoneGrowableArray<Definition*>*> out_values_;
-
-  // List of phis generated during ComputeOutValues and ForwardLoads.
-  // Some of these phis might be redundant and thus a separate pass is
-  // needed to emit only non-redundant ones.
-  GrowableArray<PhiInstr*> phis_;
-
-  // Auxiliary worklist used by redundant phi elimination.
-  GrowableArray<PhiInstr*> worklist_;
-  GrowableArray<Definition*> congruency_worklist_;
-  BitVector* in_worklist_;
-
-
-  // True if any load was eliminated.
-  bool forwarded_;
-
-  DISALLOW_COPY_AND_ASSIGN(LoadOptimizer);
-};
-
-
-class StoreOptimizer : public LivenessAnalysis {
- public:
-  StoreOptimizer(FlowGraph* graph,
-                 AliasedSet* aliased_set,
-                 DirectChainedHashMap<PointerKeyValueTrait<Place> >* map)
-      : LivenessAnalysis(aliased_set->max_place_id(), graph->postorder()),
-        graph_(graph),
-        map_(map),
-        aliased_set_(aliased_set),
-        exposed_stores_(graph_->postorder().length()) {
-    const intptr_t num_blocks = graph_->postorder().length();
-    for (intptr_t i = 0; i < num_blocks; i++) {
-      exposed_stores_.Add(NULL);
-    }
-  }
-
-  static void OptimizeGraph(FlowGraph* graph) {
-    ASSERT(FLAG_load_cse);
-    if (FLAG_trace_load_optimization) {
-      FlowGraphPrinter::PrintGraph("Before StoreOptimizer", graph);
-    }
-
-    DirectChainedHashMap<PointerKeyValueTrait<Place> > map;
-    AliasedSet* aliased_set = NumberPlaces(graph, &map, kOptimizeStores);
-    if ((aliased_set != NULL) && !aliased_set->IsEmpty()) {
-      StoreOptimizer store_optimizer(graph, aliased_set, &map);
-      store_optimizer.Optimize();
-    }
-  }
-
- private:
-  void Optimize() {
-    Analyze();
-    if (FLAG_trace_load_optimization) {
-      Dump();
-    }
-    EliminateDeadStores();
-    if (FLAG_trace_load_optimization) {
-      FlowGraphPrinter::PrintGraph("After StoreOptimizer", graph_);
-    }
-  }
-
-  bool CanEliminateStore(Instruction* instr) {
-    switch (instr->tag()) {
-      case Instruction::kStoreInstanceField: {
-        StoreInstanceFieldInstr* store_instance = instr->AsStoreInstanceField();
-        // Can't eliminate stores that initialize fields.
-        return !(store_instance->is_potential_unboxed_initialization() ||
-                 store_instance->is_object_reference_initialization());
-      }
-      case Instruction::kStoreIndexed:
-      case Instruction::kStoreStaticField:
-        return true;
-      default:
-        UNREACHABLE();
-        return false;
-    }
-  }
-
-  virtual void ComputeInitialSets() {
-    Zone* zone = graph_->zone();
-    BitVector* all_places = new(zone) BitVector(zone,
-        aliased_set_->max_place_id());
-    all_places->SetAll();
-    for (BlockIterator block_it = graph_->postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-      const intptr_t postorder_number = block->postorder_number();
-
-      BitVector* kill = kill_[postorder_number];
-      BitVector* live_in = live_in_[postorder_number];
-      BitVector* live_out = live_out_[postorder_number];
-
-      ZoneGrowableArray<Instruction*>* exposed_stores = NULL;
-
-      // Iterate backwards starting at the last instruction.
-      for (BackwardInstructionIterator instr_it(block);
-           !instr_it.Done();
-           instr_it.Advance()) {
-        Instruction* instr = instr_it.Current();
-
-        bool is_load = false;
-        bool is_store = false;
-        Place place(instr, &is_load, &is_store);
-        if (place.IsImmutableField()) {
-          // Loads/stores of final fields do not participate.
-          continue;
-        }
-
-        // Handle stores.
-        if (is_store) {
-          if (kill->Contains(instr->place_id())) {
-            if (!live_in->Contains(instr->place_id()) &&
-                CanEliminateStore(instr)) {
-              if (FLAG_trace_optimization) {
-                THR_Print(
-                    "Removing dead store to place %" Pd " in block B%" Pd "\n",
-                    instr->place_id(), block->block_id());
-              }
-              instr_it.RemoveCurrentFromGraph();
-            }
-          } else if (!live_in->Contains(instr->place_id())) {
-            // Mark this store as down-ward exposed: They are the only
-            // candidates for the global store elimination.
-            if (exposed_stores == NULL) {
-              const intptr_t kMaxExposedStoresInitialSize = 5;
-              exposed_stores = new(zone) ZoneGrowableArray<Instruction*>(
-                  Utils::Minimum(kMaxExposedStoresInitialSize,
-                                 aliased_set_->max_place_id()));
-            }
-            exposed_stores->Add(instr);
-          }
-          // Interfering stores kill only loads from the same place.
-          kill->Add(instr->place_id());
-          live_in->Remove(instr->place_id());
-          continue;
-        }
-
-        // Handle side effects, deoptimization and function return.
-        if (!instr->Effects().IsNone() ||
-            instr->CanDeoptimize() ||
-            instr->IsThrow() ||
-            instr->IsReThrow() ||
-            instr->IsReturn()) {
-          // Instructions that return from the function, instructions with side
-          // effects and instructions that can deoptimize are considered as
-          // loads from all places.
-          live_in->CopyFrom(all_places);
-          if (instr->IsThrow() || instr->IsReThrow() || instr->IsReturn()) {
-            // Initialize live-out for exit blocks since it won't be computed
-            // otherwise during the fixed point iteration.
-            live_out->CopyFrom(all_places);
-          }
-          continue;
-        }
-
-        // Handle loads.
-        Definition* defn = instr->AsDefinition();
-        if ((defn != NULL) && IsLoadEliminationCandidate(defn)) {
-          const intptr_t alias = aliased_set_->LookupAliasId(place.ToAlias());
-          live_in->AddAll(aliased_set_->GetKilledSet(alias));
-          continue;
-        }
-      }
-      exposed_stores_[postorder_number] = exposed_stores;
-    }
-    if (FLAG_trace_load_optimization) {
-      Dump();
-      THR_Print("---\n");
-    }
-  }
-
-  void EliminateDeadStores() {
-    // Iteration order does not matter here.
-    for (BlockIterator block_it = graph_->postorder_iterator();
-         !block_it.Done();
-         block_it.Advance()) {
-      BlockEntryInstr* block = block_it.Current();
-      const intptr_t postorder_number = block->postorder_number();
-
-      BitVector* live_out = live_out_[postorder_number];
-
-      ZoneGrowableArray<Instruction*>* exposed_stores =
-        exposed_stores_[postorder_number];
-      if (exposed_stores == NULL) continue;  // No exposed stores.
-
-      // Iterate over candidate stores.
-      for (intptr_t i = 0; i < exposed_stores->length(); ++i) {
-        Instruction* instr = (*exposed_stores)[i];
-        bool is_load = false;
-        bool is_store = false;
-        Place place(instr, &is_load, &is_store);
-        ASSERT(!is_load && is_store);
-        if (place.IsImmutableField()) {
-          // Final field do not participate in dead store elimination.
-          continue;
-        }
-        // Eliminate a downward exposed store if the corresponding place is not
-        // in live-out.
-        if (!live_out->Contains(instr->place_id()) &&
-            CanEliminateStore(instr)) {
-          if (FLAG_trace_optimization) {
-            THR_Print("Removing dead store to place %" Pd " block B%" Pd "\n",
-                      instr->place_id(), block->block_id());
-          }
-          instr->RemoveFromGraph(/* ignored */ false);
-        }
-      }
-    }
-  }
-
-  FlowGraph* graph_;
-  DirectChainedHashMap<PointerKeyValueTrait<Place> >* map_;
-
-  // Mapping between field offsets in words and expression ids of loads from
-  // that offset.
-  AliasedSet* aliased_set_;
-
-  // Per block list of downward exposed stores.
-  GrowableArray<ZoneGrowableArray<Instruction*>*> exposed_stores_;
-
-  DISALLOW_COPY_AND_ASSIGN(StoreOptimizer);
-};
-
-
-void DeadStoreElimination::Optimize(FlowGraph* graph) {
-  if (FLAG_dead_store_elimination) {
-    StoreOptimizer::OptimizeGraph(graph);
-  }
-}
-
-
-// Returns true iff this definition is used in a non-phi instruction.
-static bool HasRealUse(Definition* def) {
-  // Environment uses are real (non-phi) uses.
-  if (def->env_use_list() != NULL) return true;
-
-  for (Value::Iterator it(def->input_use_list());
-       !it.Done();
-       it.Advance()) {
-    if (!it.Current()->instruction()->IsPhi()) return true;
-  }
-  return false;
-}
-
-
-void DeadCodeElimination::EliminateDeadPhis(FlowGraph* flow_graph) {
-  GrowableArray<PhiInstr*> live_phis;
-  for (BlockIterator b = flow_graph->postorder_iterator();
-       !b.Done();
-       b.Advance()) {
-    JoinEntryInstr* join = b.Current()->AsJoinEntry();
-    if (join != NULL) {
-      for (PhiIterator it(join); !it.Done(); it.Advance()) {
-        PhiInstr* phi = it.Current();
-        // Phis that have uses and phis inside try blocks are
-        // marked as live.
-        if (HasRealUse(phi) || join->InsideTryBlock()) {
-          live_phis.Add(phi);
-          phi->mark_alive();
-        } else {
-          phi->mark_dead();
-        }
-      }
-    }
-  }
-
-  while (!live_phis.is_empty()) {
-    PhiInstr* phi = live_phis.RemoveLast();
-    for (intptr_t i = 0; i < phi->InputCount(); i++) {
-      Value* val = phi->InputAt(i);
-      PhiInstr* used_phi = val->definition()->AsPhi();
-      if ((used_phi != NULL) && !used_phi->is_alive()) {
-        used_phi->mark_alive();
-        live_phis.Add(used_phi);
-      }
-    }
-  }
-
-  for (BlockIterator it(flow_graph->postorder_iterator());
-       !it.Done();
-       it.Advance()) {
-    JoinEntryInstr* join = it.Current()->AsJoinEntry();
-    if (join != NULL) {
-      if (join->phis_ == NULL) continue;
-
-      // Eliminate dead phis and compact the phis_ array of the block.
-      intptr_t to_index = 0;
-      for (intptr_t i = 0; i < join->phis_->length(); ++i) {
-        PhiInstr* phi = (*join->phis_)[i];
-        if (phi != NULL) {
-          if (!phi->is_alive()) {
-            phi->ReplaceUsesWith(flow_graph->constant_null());
-            phi->UnuseAllInputs();
-            (*join->phis_)[i] = NULL;
-            if (FLAG_trace_optimization) {
-              THR_Print("Removing dead phi v%" Pd "\n", phi->ssa_temp_index());
-            }
-          } else if (phi->IsRedundant()) {
-            phi->ReplaceUsesWith(phi->InputAt(0)->definition());
-            phi->UnuseAllInputs();
-            (*join->phis_)[i] = NULL;
-            if (FLAG_trace_optimization) {
-              THR_Print("Removing redundant phi v%" Pd "\n",
-                         phi->ssa_temp_index());
-            }
-          } else {
-            (*join->phis_)[to_index++] = phi;
-          }
-        }
-      }
-      if (to_index == 0) {
-        join->phis_ = NULL;
-      } else {
-        join->phis_->TruncateTo(to_index);
-      }
-    }
-  }
-}
-
-
-class CSEInstructionMap : public ValueObject {
- public:
-  // Right now CSE and LICM track a single effect: possible externalization of
-  // strings.
-  // Other effects like modifications of fields are tracked in a separate load
-  // forwarding pass via Alias structure.
-  COMPILE_ASSERT(EffectSet::kLastEffect == 1);
-
-  CSEInstructionMap() : independent_(), dependent_() { }
-  explicit CSEInstructionMap(const CSEInstructionMap& other)
-      : ValueObject(),
-        independent_(other.independent_),
-        dependent_(other.dependent_) {
-  }
-
-  void RemoveAffected(EffectSet effects) {
-    if (!effects.IsNone()) {
-      dependent_.Clear();
-    }
-  }
-
-  Instruction* Lookup(Instruction* other) const {
-    return GetMapFor(other)->Lookup(other);
-  }
-
-  void Insert(Instruction* instr) {
-    return GetMapFor(instr)->Insert(instr);
-  }
-
- private:
-  typedef DirectChainedHashMap<PointerKeyValueTrait<Instruction> >  Map;
-
-  Map* GetMapFor(Instruction* instr) {
-    return instr->Dependencies().IsNone() ? &independent_ : &dependent_;
-  }
-
-  const Map* GetMapFor(Instruction* instr) const {
-    return instr->Dependencies().IsNone() ? &independent_ : &dependent_;
-  }
-
-  // All computations that are not affected by any side-effect.
-  // Majority of computations are not affected by anything and will be in
-  // this map.
-  Map independent_;
-
-  // All computations that are affected by side effect.
-  Map dependent_;
-};
-
-
-bool DominatorBasedCSE::Optimize(FlowGraph* graph) {
-  bool changed = false;
-  if (FLAG_load_cse) {
-    changed = LoadOptimizer::OptimizeGraph(graph) || changed;
-  }
-
-  CSEInstructionMap map;
-  changed = OptimizeRecursive(graph, graph->graph_entry(), &map) || changed;
-
-  return changed;
-}
-
-
-bool DominatorBasedCSE::OptimizeRecursive(
-    FlowGraph* graph,
-    BlockEntryInstr* block,
-    CSEInstructionMap* map) {
-  bool changed = false;
-  for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
-    Instruction* current = it.Current();
-    if (current->AllowsCSE()) {
-      Instruction* replacement = map->Lookup(current);
-      if ((replacement != NULL) &&
-          graph->block_effects()->IsAvailableAt(replacement, block)) {
-        // Replace current with lookup result.
-        ReplaceCurrentInstruction(&it, current, replacement, graph);
-        changed = true;
-        continue;
-      }
-
-      // For simplicity we assume that instruction either does not depend on
-      // anything or does not affect anything. If this is not the case then
-      // we should first remove affected instructions from the map and
-      // then add instruction to the map so that it does not kill itself.
-      ASSERT(current->Effects().IsNone() || current->Dependencies().IsNone());
-      map->Insert(current);
-    }
-
-    map->RemoveAffected(current->Effects());
-  }
-
-  // Process children in the dominator tree recursively.
-  intptr_t num_children = block->dominated_blocks().length();
-  for (intptr_t i = 0; i < num_children; ++i) {
-    BlockEntryInstr* child = block->dominated_blocks()[i];
-    if (i  < num_children - 1) {
-      // Copy map.
-      CSEInstructionMap child_map(*map);
-      changed = OptimizeRecursive(graph, child, &child_map) || changed;
-    } else {
-      // Reuse map for the last child.
-      changed = OptimizeRecursive(graph, child, map) || changed;
-    }
-  }
-  return changed;
-}
-
-
 void FlowGraphOptimizer::EliminateEnvironments() {
   // After this pass we can no longer perform LICM and hoist instructions
   // that can deoptimize.
 
   flow_graph_->disallow_licm();
   for (intptr_t i = 0; i < block_order_.length(); ++i) {
     BlockEntryInstr* block = block_order_[i];
     block->RemoveEnvironment();
     for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
       Instruction* current = it.Current();
       if (!current->CanDeoptimize()) {
         // TODO(srdjan): --source-lines needs deopt environments to get at
         // the code for this instruction, however, leaving the environment
         // changes code.
         current->RemoveEnvironment();
       }
     }
   }
 }
 
 
-enum SafeUseCheck { kOptimisticCheck, kStrictCheck };
-
-// Check if the use is safe for allocation sinking. Allocation sinking
-// candidates can only be used at store instructions:
-//
-//     - any store into the allocation candidate itself is unconditionally safe
-//       as it just changes the rematerialization state of this candidate;
-//     - store into another object is only safe if another object is allocation
-//       candidate.
-//
-// We use a simple fix-point algorithm to discover the set of valid candidates
-// (see CollectCandidates method), that's why this IsSafeUse can operate in two
-// modes:
-//
-//     - optimistic, when every allocation is assumed to be an allocation
-//       sinking candidate;
-//     - strict, when only marked allocations are assumed to be allocation
-//       sinking candidates.
-//
-// Fix-point algorithm in CollectCandiates first collects a set of allocations
-// optimistically and then checks each collected candidate strictly and unmarks
-// invalid candidates transitively until only strictly valid ones remain.
-static bool IsSafeUse(Value* use, SafeUseCheck check_type) {
-  if (use->instruction()->IsMaterializeObject()) {
-    return true;
-  }
-
-  StoreInstanceFieldInstr* store = use->instruction()->AsStoreInstanceField();
-  if (store != NULL) {
-    if (use == store->value()) {
-      Definition* instance = store->instance()->definition();
-      return instance->IsAllocateObject() &&
-          ((check_type == kOptimisticCheck) ||
-           instance->Identity().IsAllocationSinkingCandidate());
-    }
-    return true;
-  }
-
-  return false;
-}
-
-
-// Right now we are attempting to sink allocation only into
-// deoptimization exit. So candidate should only be used in StoreInstanceField
-// instructions that write into fields of the allocated object.
-// We do not support materialization of the object that has type arguments.
-static bool IsAllocationSinkingCandidate(Definition* alloc,
-                                         SafeUseCheck check_type) {
-  for (Value* use = alloc->input_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    if (!IsSafeUse(use, check_type)) {
-      if (FLAG_trace_optimization) {
-        THR_Print("use of %s at %s is unsafe for allocation sinking\n",
-                  alloc->ToCString(),
-                  use->instruction()->ToCString());
-      }
-      return false;
-    }
-  }
-
-  return true;
-}
-
-
-// If the given use is a store into an object then return an object we are
-// storing into.
-static Definition* StoreInto(Value* use) {
-  StoreInstanceFieldInstr* store = use->instruction()->AsStoreInstanceField();
-  if (store != NULL) {
-    return store->instance()->definition();
-  }
-
-  return NULL;
-}
-
-
-// Remove the given allocation from the graph. It is not observable.
-// If deoptimization occurs the object will be materialized.
-void AllocationSinking::EliminateAllocation(Definition* alloc) {
-  ASSERT(IsAllocationSinkingCandidate(alloc, kStrictCheck));
-
-  if (FLAG_trace_optimization) {
-    THR_Print("removing allocation from the graph: v%" Pd "\n",
-              alloc->ssa_temp_index());
-  }
-
-  // As an allocation sinking candidate it is only used in stores to its own
-  // fields. Remove these stores.
-  for (Value* use = alloc->input_use_list();
-       use != NULL;
-       use = alloc->input_use_list()) {
-    use->instruction()->RemoveFromGraph();
-  }
-
-  // There should be no environment uses. The pass replaced them with
-  // MaterializeObject instructions.
-#ifdef DEBUG
-  for (Value* use = alloc->env_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    ASSERT(use->instruction()->IsMaterializeObject());
-  }
-#endif
-  ASSERT(alloc->input_use_list() == NULL);
-  alloc->RemoveFromGraph();
-  if (alloc->ArgumentCount() > 0) {
-    ASSERT(alloc->ArgumentCount() == 1);
-    for (intptr_t i = 0; i < alloc->ArgumentCount(); ++i) {
-      alloc->PushArgumentAt(i)->RemoveFromGraph();
-    }
-  }
-}
-
-
-// Find allocation instructions that can be potentially eliminated and
-// rematerialized at deoptimization exits if needed. See IsSafeUse
-// for the description of algorithm used below.
-void AllocationSinking::CollectCandidates() {
-  // Optimistically collect all potential candidates.
-  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
-       !block_it.Done();
-       block_it.Advance()) {
-    BlockEntryInstr* block = block_it.Current();
-    for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
-      { AllocateObjectInstr* alloc = it.Current()->AsAllocateObject();
-        if ((alloc != NULL) &&
-            IsAllocationSinkingCandidate(alloc, kOptimisticCheck)) {
-          alloc->SetIdentity(AliasIdentity::AllocationSinkingCandidate());
-          candidates_.Add(alloc);
-        }
-      }
-      { AllocateUninitializedContextInstr* alloc =
-            it.Current()->AsAllocateUninitializedContext();
-        if ((alloc != NULL) &&
-            IsAllocationSinkingCandidate(alloc, kOptimisticCheck)) {
-          alloc->SetIdentity(AliasIdentity::AllocationSinkingCandidate());
-          candidates_.Add(alloc);
-        }
-      }
-    }
-  }
-
-  // Transitively unmark all candidates that are not strictly valid.
-  bool changed;
-  do {
-    changed = false;
-    for (intptr_t i = 0; i < candidates_.length(); i++) {
-      Definition* alloc = candidates_[i];
-      if (alloc->Identity().IsAllocationSinkingCandidate()) {
-        if (!IsAllocationSinkingCandidate(alloc, kStrictCheck)) {
-          alloc->SetIdentity(AliasIdentity::Unknown());
-          changed = true;
-        }
-      }
-    }
-  } while (changed);
-
-  // Shrink the list of candidates removing all unmarked ones.
-  intptr_t j = 0;
-  for (intptr_t i = 0; i < candidates_.length(); i++) {
-    Definition* alloc = candidates_[i];
-    if (alloc->Identity().IsAllocationSinkingCandidate()) {
-      if (FLAG_trace_optimization) {
-        THR_Print("discovered allocation sinking candidate: v%" Pd "\n",
-                  alloc->ssa_temp_index());
-      }
-
-      if (j != i) {
-        candidates_[j] = alloc;
-      }
-      j++;
-    }
-  }
-  candidates_.TruncateTo(j);
-}
-
-
-// If materialization references an allocation sinking candidate then replace
-// this reference with a materialization which should have been computed for
-// this side-exit. CollectAllExits should have collected this exit.
-void AllocationSinking::NormalizeMaterializations() {
-  for (intptr_t i = 0; i < candidates_.length(); i++) {
-    Definition* alloc = candidates_[i];
-
-    Value* next_use;
-    for (Value* use = alloc->input_use_list();
-         use != NULL;
-         use = next_use) {
-      next_use = use->next_use();
-      if (use->instruction()->IsMaterializeObject()) {
-        use->BindTo(MaterializationFor(alloc, use->instruction()));
-      }
-    }
-  }
-}
-
-
-// We transitively insert materializations at each deoptimization exit that
-// might see the given allocation (see ExitsCollector). Some of this
-// materializations are not actually used and some fail to compute because
-// they are inserted in the block that is not dominated by the allocation.
-// Remove them unused materializations from the graph.
-void AllocationSinking::RemoveUnusedMaterializations() {
-  intptr_t j = 0;
-  for (intptr_t i = 0; i < materializations_.length(); i++) {
-    MaterializeObjectInstr* mat = materializations_[i];
-    if ((mat->input_use_list() == NULL) && (mat->env_use_list() == NULL)) {
-      // Check if this materialization failed to compute and remove any
-      // unforwarded loads. There were no loads from any allocation sinking
-      // candidate in the beggining so it is safe to assume that any encountered
-      // load was inserted by CreateMaterializationAt.
-      for (intptr_t i = 0; i < mat->InputCount(); i++) {
-        LoadFieldInstr* load = mat->InputAt(i)->definition()->AsLoadField();
-        if ((load != NULL) &&
-            (load->instance()->definition() == mat->allocation())) {
-          load->ReplaceUsesWith(flow_graph_->constant_null());
-          load->RemoveFromGraph();
-        }
-      }
-      mat->RemoveFromGraph();
-    } else {
-      if (j != i) {
-        materializations_[j] = mat;
-      }
-      j++;
-    }
-  }
-  materializations_.TruncateTo(j);
-}
-
-
-// Some candidates might stop being eligible for allocation sinking after
-// the load forwarding because they flow into phis that load forwarding
-// inserts. Discover such allocations and remove them from the list
-// of allocation sinking candidates undoing all changes that we did
-// in preparation for sinking these allocations.
-void AllocationSinking::DiscoverFailedCandidates() {
-  // Transitively unmark all candidates that are not strictly valid.
-  bool changed;
-  do {
-    changed = false;
-    for (intptr_t i = 0; i < candidates_.length(); i++) {
-      Definition* alloc = candidates_[i];
-      if (alloc->Identity().IsAllocationSinkingCandidate()) {
-        if (!IsAllocationSinkingCandidate(alloc, kStrictCheck)) {
-          alloc->SetIdentity(AliasIdentity::Unknown());
-          changed = true;
-        }
-      }
-    }
-  } while (changed);
-
-  // Remove all failed candidates from the candidates list.
-  intptr_t j = 0;
-  for (intptr_t i = 0; i < candidates_.length(); i++) {
-    Definition* alloc = candidates_[i];
-    if (!alloc->Identity().IsAllocationSinkingCandidate()) {
-      if (FLAG_trace_optimization) {
-        THR_Print("allocation v%" Pd " can't be eliminated\n",
-                  alloc->ssa_temp_index());
-      }
-
-#ifdef DEBUG
-      for (Value* use = alloc->env_use_list();
-           use != NULL;
-           use = use->next_use()) {
-        ASSERT(use->instruction()->IsMaterializeObject());
-      }
-#endif
-
-      // All materializations will be removed from the graph. Remove inserted
-      // loads first and detach materializations from allocation's environment
-      // use list: we will reconstruct it when we start removing
-      // materializations.
-      alloc->set_env_use_list(NULL);
-      for (Value* use = alloc->input_use_list();
-           use != NULL;
-           use = use->next_use()) {
-        if (use->instruction()->IsLoadField()) {
-          LoadFieldInstr* load = use->instruction()->AsLoadField();
-          load->ReplaceUsesWith(flow_graph_->constant_null());
-          load->RemoveFromGraph();
-        } else {
-          ASSERT(use->instruction()->IsMaterializeObject() ||
-                 use->instruction()->IsPhi() ||
-                 use->instruction()->IsStoreInstanceField());
-        }
-      }
-    } else {
-      if (j != i) {
-        candidates_[j] = alloc;
-      }
-      j++;
-    }
-  }
-
-  if (j != candidates_.length()) {  // Something was removed from candidates.
-    intptr_t k = 0;
-    for (intptr_t i = 0; i < materializations_.length(); i++) {
-      MaterializeObjectInstr* mat = materializations_[i];
-      if (!mat->allocation()->Identity().IsAllocationSinkingCandidate()) {
-        // Restore environment uses of the allocation that were replaced
-        // by this materialization and drop materialization.
-        mat->ReplaceUsesWith(mat->allocation());
-        mat->RemoveFromGraph();
-      } else {
-        if (k != i) {
-          materializations_[k] = mat;
-        }
-        k++;
-      }
-    }
-    materializations_.TruncateTo(k);
-  }
-
-  candidates_.TruncateTo(j);
-}
-
-
-void AllocationSinking::Optimize() {
-  CollectCandidates();
-
-  // Insert MaterializeObject instructions that will describe the state of the
-  // object at all deoptimization points. Each inserted materialization looks
-  // like this (where v_0 is allocation that we are going to eliminate):
-  //   v_1     <- LoadField(v_0, field_1)
-  //           ...
-  //   v_N     <- LoadField(v_0, field_N)
-  //   v_{N+1} <- MaterializeObject(field_1 = v_1, ..., field_N = v_{N})
-  for (intptr_t i = 0; i < candidates_.length(); i++) {
-    InsertMaterializations(candidates_[i]);
-  }
-
-  // Run load forwarding to eliminate LoadField instructions inserted above.
-  // All loads will be successfully eliminated because:
-  //   a) they use fields (not offsets) and thus provide precise aliasing
-  //      information
-  //   b) candidate does not escape and thus its fields is not affected by
-  //      external effects from calls.
-  LoadOptimizer::OptimizeGraph(flow_graph_);
-
-  NormalizeMaterializations();
-
-  RemoveUnusedMaterializations();
-
-  // If any candidates are no longer eligible for allocation sinking abort
-  // the optimization for them and undo any changes we did in preparation.
-  DiscoverFailedCandidates();
-
-  // At this point we have computed the state of object at each deoptimization
-  // point and we can eliminate it. Loads inserted above were forwarded so there
-  // are no uses of the allocation just as in the begging of the pass.
-  for (intptr_t i = 0; i < candidates_.length(); i++) {
-    EliminateAllocation(candidates_[i]);
-  }
-
-  // Process materializations and unbox their arguments: materializations
-  // are part of the environment and can materialize boxes for double/mint/simd
-  // values when needed.
-  // TODO(vegorov): handle all box types here.
-  for (intptr_t i = 0; i < materializations_.length(); i++) {
-    MaterializeObjectInstr* mat = materializations_[i];
-    for (intptr_t j = 0; j < mat->InputCount(); j++) {
-      Definition* defn = mat->InputAt(j)->definition();
-      if (defn->IsBox()) {
-        mat->InputAt(j)->BindTo(defn->InputAt(0)->definition());
-      }
-    }
-  }
-}
-
-
-// Remove materializations from the graph. Register allocator will treat them
-// as part of the environment not as a real instruction.
-void AllocationSinking::DetachMaterializations() {
-  for (intptr_t i = 0; i < materializations_.length(); i++) {
-    materializations_[i]->previous()->LinkTo(materializations_[i]->next());
-  }
-}
-
-
-// Add a field/offset to the list of fields if it is not yet present there.
-static bool AddSlot(ZoneGrowableArray<const Object*>* slots,
-                    const Object& slot) {
-  for (intptr_t i = 0; i < slots->length(); i++) {
-    if ((*slots)[i]->raw() == slot.raw()) {
-      return false;
-    }
-  }
-  slots->Add(&slot);
-  return true;
-}
-
-
-// Find deoptimization exit for the given materialization assuming that all
-// materializations are emitted right before the instruction which is a
-// deoptimization exit.
-static Instruction* ExitForMaterialization(MaterializeObjectInstr* mat) {
-  while (mat->next()->IsMaterializeObject()) {
-    mat = mat->next()->AsMaterializeObject();
-  }
-  return mat->next();
-}
-
-
-// Given the deoptimization exit find first materialization that was inserted
-// before it.
-static Instruction* FirstMaterializationAt(Instruction* exit) {
-  while (exit->previous()->IsMaterializeObject()) {
-    exit = exit->previous();
-  }
-  return exit;
-}
-
-
-// Given the allocation and deoptimization exit try to find MaterializeObject
-// instruction corresponding to this allocation at this exit.
-MaterializeObjectInstr* AllocationSinking::MaterializationFor(
-    Definition* alloc, Instruction* exit) {
-  if (exit->IsMaterializeObject()) {
-    exit = ExitForMaterialization(exit->AsMaterializeObject());
-  }
-
-  for (MaterializeObjectInstr* mat = exit->previous()->AsMaterializeObject();
-       mat != NULL;
-       mat = mat->previous()->AsMaterializeObject()) {
-    if (mat->allocation() == alloc) {
-      return mat;
-    }
-  }
-
-  return NULL;
-}
-
-
-// Insert MaterializeObject instruction for the given allocation before
-// the given instruction that can deoptimize.
-void AllocationSinking::CreateMaterializationAt(
-    Instruction* exit,
-    Definition* alloc,
-    const ZoneGrowableArray<const Object*>& slots) {
-  ZoneGrowableArray<Value*>* values =
-      new(Z) ZoneGrowableArray<Value*>(slots.length());
-
-  // All loads should be inserted before the first materialization so that
-  // IR follows the following pattern: loads, materializations, deoptimizing
-  // instruction.
-  Instruction* load_point = FirstMaterializationAt(exit);
-
-  // Insert load instruction for every field.
-  for (intptr_t i = 0; i < slots.length(); i++) {
-    LoadFieldInstr* load = slots[i]->IsField()
-        ? new(Z) LoadFieldInstr(
-            new(Z) Value(alloc),
-            &Field::Cast(*slots[i]),
-            AbstractType::ZoneHandle(Z),
-            alloc->token_pos())
-        : new(Z) LoadFieldInstr(
-            new(Z) Value(alloc),
-            Smi::Cast(*slots[i]).Value(),
-            AbstractType::ZoneHandle(Z),
-            alloc->token_pos());
-    flow_graph_->InsertBefore(
-        load_point, load, NULL, FlowGraph::kValue);
-    values->Add(new(Z) Value(load));
-  }
-
-  MaterializeObjectInstr* mat = NULL;
-  if (alloc->IsAllocateObject()) {
-    mat = new(Z) MaterializeObjectInstr(
-        alloc->AsAllocateObject(), slots, values);
-  } else {
-    ASSERT(alloc->IsAllocateUninitializedContext());
-    mat = new(Z) MaterializeObjectInstr(
-        alloc->AsAllocateUninitializedContext(), slots, values);
-  }
-
-  flow_graph_->InsertBefore(exit, mat, NULL, FlowGraph::kValue);
-
-  // Replace all mentions of this allocation with a newly inserted
-  // MaterializeObject instruction.
-  // We must preserve the identity: all mentions are replaced by the same
-  // materialization.
-  for (Environment::DeepIterator env_it(exit->env());
-       !env_it.Done();
-       env_it.Advance()) {
-    Value* use = env_it.CurrentValue();
-    if (use->definition() == alloc) {
-      use->RemoveFromUseList();
-      use->set_definition(mat);
-      mat->AddEnvUse(use);
-    }
-  }
-
-  // Mark MaterializeObject as an environment use of this allocation.
-  // This will allow us to discover it when we are looking for deoptimization
-  // exits for another allocation that potentially flows into this one.
-  Value* val = new(Z) Value(alloc);
-  val->set_instruction(mat);
-  alloc->AddEnvUse(val);
-
-  // Record inserted materialization.
-  materializations_.Add(mat);
-}
-
-
-// Add given instruction to the list of the instructions if it is not yet
-// present there.
-template<typename T>
-void AddInstruction(GrowableArray<T*>* list, T* value) {
-  ASSERT(!value->IsGraphEntry());
-  for (intptr_t i = 0; i < list->length(); i++) {
-    if ((*list)[i] == value) {
-      return;
-    }
-  }
-  list->Add(value);
-}
-
-
-// Transitively collect all deoptimization exits that might need this allocation
-// rematerialized. It is not enough to collect only environment uses of this
-// allocation because it can flow into other objects that will be
-// dematerialized and that are referenced by deopt environments that
-// don't contain this allocation explicitly.
-void AllocationSinking::ExitsCollector::Collect(Definition* alloc) {
-  for (Value* use = alloc->env_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    if (use->instruction()->IsMaterializeObject()) {
-      AddInstruction(&exits_, ExitForMaterialization(
-          use->instruction()->AsMaterializeObject()));
-    } else {
-      AddInstruction(&exits_, use->instruction());
-    }
-  }
-
-  // Check if this allocation is stored into any other allocation sinking
-  // candidate and put it on worklist so that we conservatively collect all
-  // exits for that candidate as well because they potentially might see
-  // this object.
-  for (Value* use = alloc->input_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    Definition* obj = StoreInto(use);
-    if ((obj != NULL) && (obj != alloc)) {
-      AddInstruction(&worklist_, obj);
-    }
-  }
-}
-
-
-void AllocationSinking::ExitsCollector::CollectTransitively(Definition* alloc) {
-  exits_.TruncateTo(0);
-  worklist_.TruncateTo(0);
-
-  worklist_.Add(alloc);
-
-  // Note: worklist potentially will grow while we are iterating over it.
-  // We are not removing allocations from the worklist not to waste space on
-  // the side maintaining BitVector of already processed allocations: worklist
-  // is expected to be very small thus linear search in it is just as effecient
-  // as a bitvector.
-  for (intptr_t i = 0; i < worklist_.length(); i++) {
-    Collect(worklist_[i]);
-  }
-}
-
-
-void AllocationSinking::InsertMaterializations(Definition* alloc) {
-  // Collect all fields that are written for this instance.
-  ZoneGrowableArray<const Object*>* slots =
-      new(Z) ZoneGrowableArray<const Object*>(5);
-
-  for (Value* use = alloc->input_use_list();
-       use != NULL;
-       use = use->next_use()) {
-    StoreInstanceFieldInstr* store = use->instruction()->AsStoreInstanceField();
-    if ((store != NULL) && (store->instance()->definition() == alloc)) {
-      if (!store->field().IsNull()) {
-        AddSlot(slots, store->field());
-      } else {
-        AddSlot(slots, Smi::ZoneHandle(Z, Smi::New(store->offset_in_bytes())));
-      }
-    }
-  }
-
-  if (alloc->ArgumentCount() > 0) {
-    AllocateObjectInstr* alloc_object = alloc->AsAllocateObject();
-    ASSERT(alloc_object->ArgumentCount() == 1);
-    intptr_t type_args_offset =
-        alloc_object->cls().type_arguments_field_offset();
-    AddSlot(slots, Smi::ZoneHandle(Z, Smi::New(type_args_offset)));
-  }
-
-  // Collect all instructions that mention this object in the environment.
-  exits_collector_.CollectTransitively(alloc);
-
-  // Insert materializations at environment uses.
-  for (intptr_t i = 0; i < exits_collector_.exits().length(); i++) {
-    CreateMaterializationAt(
-        exits_collector_.exits()[i], alloc, *slots);
-  }
-}
-
-
 }  // namespace dart