Add Zone-based handle allocation interface and reduce use of Isolate-based interfaces.

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/cha.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 29 matching lines @@
     "Optimize left shift to truncate if possible");
 DEFINE_FLAG(bool, use_cha, true, "Use class hierarchy analysis.");
 #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, enable_type_checks);
 DECLARE_FLAG(bool, source_lines);
 DECLARE_FLAG(bool, trace_type_check_elimination);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
 
-// Quick access to the locally defined isolate() method.
+// Quick access to the current isolate and zone.
 #define I (isolate())
+#define Z (zone())
 
 static bool ShouldInlineSimd() {
   return FlowGraphCompiler::SupportsUnboxedSimd128();
 }
 
 
 static bool CanUnboxDouble() {
   return FlowGraphCompiler::SupportsUnboxedDoubles();
 }
 
@@ skipping 108 matching lines @@
     }
   }
 
   for (intptr_t i = 0; i < class_ids.length(); i++) {
     if (class_ids[i] == kDynamicCid) {
       // Not all cid-s known.
       return false;
     }
   }
 
-  const Array& args_desc_array = Array::Handle(I,
+  const Array& args_desc_array = Array::Handle(Z,
       ArgumentsDescriptor::New(call->ArgumentCount(), call->argument_names()));
   ArgumentsDescriptor args_desc(args_desc_array);
-  const Class& receiver_class = Class::Handle(I,
+  const Class& receiver_class = Class::Handle(Z,
       isolate()->class_table()->At(class_ids[0]));
-  const Function& function = Function::Handle(I,
+  const Function& function = Function::Handle(Z,
       Resolver::ResolveDynamicForReceiverClass(
           receiver_class,
           call->function_name(),
           args_desc));
   if (function.IsNull()) {
     return false;
   }
   // Create new ICData, do not modify the one attached to the instruction
   // since it is attached to the assembly instruction itself.
   // TODO(srdjan): Prevent modification of ICData object that is
   // referenced in assembly code.
-  ICData& ic_data = ICData::ZoneHandle(I, ICData::New(
+  ICData& ic_data = ICData::ZoneHandle(Z, ICData::New(
       flow_graph_->parsed_function()->function(),
       call->function_name(),
       args_desc_array,
       call->deopt_id(),
       class_ids.length()));
   if (class_ids.length() > 1) {
     ic_data.AddCheck(class_ids, function);
   } else {
     ASSERT(class_ids.length() == 1);
     ic_data.AddReceiverCheck(class_ids[0], function);
   }
   call->set_ic_data(&ic_data);
   return true;
 }
 
 
 const ICData& FlowGraphOptimizer::TrySpecializeICData(const ICData& ic_data,
                                                       intptr_t cid) {
   ASSERT(ic_data.NumArgsTested() == 1);
 
   if ((ic_data.NumberOfUsedChecks() == 1) && ic_data.HasReceiverClassId(cid)) {
     return ic_data;  // Nothing to do
   }
 
   const Function& function =
-      Function::Handle(I, ic_data.GetTargetForReceiverClassId(cid));
+      Function::Handle(Z, ic_data.GetTargetForReceiverClassId(cid));
   // TODO(fschneider): Try looking up the function on the class if it is
   // not found in the ICData.
   if (!function.IsNull()) {
-    const ICData& new_ic_data = ICData::ZoneHandle(I, ICData::New(
-        Function::Handle(I, ic_data.owner()),
-        String::Handle(I, ic_data.target_name()),
+    const ICData& new_ic_data = ICData::ZoneHandle(Z, ICData::New(
+        Function::Handle(Z, ic_data.owner()),
+        String::Handle(Z, ic_data.target_name()),
         Object::empty_array(),  // Dummy argument descriptor.
         ic_data.deopt_id(),
         ic_data.NumArgsTested()));
     new_ic_data.SetDeoptReasons(ic_data.DeoptReasons());
     new_ic_data.AddReceiverCheck(cid, function);
     return new_ic_data;
   }
 
   return ic_data;
 }
@@ skipping 12 matching lines @@
   }
 
   const ICData& ic_data = TrySpecializeICData(call->ic_data(), receiver_cid);
   if (ic_data.raw() == call->ic_data().raw()) {
     // No specialization.
     return;
   }
 
   const bool with_checks = false;
   PolymorphicInstanceCallInstr* specialized =
-      new(I) PolymorphicInstanceCallInstr(call->instance_call(),
+      new(Z) PolymorphicInstanceCallInstr(call->instance_call(),
                                           ic_data,
                                           with_checks);
   call->ReplaceWith(specialized, current_iterator());
 }
 
 
 static BinarySmiOpInstr* AsSmiShiftLeftInstruction(Definition* d) {
   BinarySmiOpInstr* instr = d->AsBinarySmiOp();
   if ((instr != NULL) && (instr->op_kind() == Token::kSHL)) {
     return instr;
@@ skipping 32 matching lines @@
   if ((smi_shift_left == NULL) && (bit_and_instr->InputAt(1)->IsSingleUse())) {
     smi_shift_left = AsSmiShiftLeftInstruction(right_instr);
   }
   if (smi_shift_left == NULL) return;
 
   // Pattern recognized.
   smi_shift_left->mark_truncating();
   ASSERT(bit_and_instr->IsBinarySmiOp() || bit_and_instr->IsBinaryMintOp());
   if (bit_and_instr->IsBinaryMintOp()) {
     // Replace Mint op with Smi op.
-    BinarySmiOpInstr* smi_op = new(I) BinarySmiOpInstr(
+    BinarySmiOpInstr* smi_op = new(Z) BinarySmiOpInstr(
         Token::kBIT_AND,
-        new(I) Value(left_instr),
-        new(I) Value(right_instr),
+        new(Z) Value(left_instr),
+        new(Z) Value(right_instr),
         Isolate::kNoDeoptId);  // BIT_AND cannot deoptimize.
     bit_and_instr->ReplaceWith(smi_op, current_iterator());
   }
 }
 
 
 
 // Used by TryMergeDivMod.
 // Inserts a load-indexed instruction between a TRUNCDIV or MOD instruction,
 // and the using instruction. This is an intermediate step before merging.
 void FlowGraphOptimizer::AppendLoadIndexedForMerged(Definition* instr,
                                                     intptr_t ix,
                                                     intptr_t cid) {
   const intptr_t index_scale = Instance::ElementSizeFor(cid);
   ConstantInstr* index_instr =
-      flow_graph()->GetConstant(Smi::Handle(I, Smi::New(ix)));
+      flow_graph()->GetConstant(Smi::Handle(Z, Smi::New(ix)));
   LoadIndexedInstr* load =
-      new(I) LoadIndexedInstr(new(I) Value(instr),
-                                      new(I) Value(index_instr),
+      new(Z) LoadIndexedInstr(new(Z) Value(instr),
+                                      new(Z) Value(index_instr),
                                       index_scale,
                                       cid,
                                       Isolate::kNoDeoptId,
                                       instr->token_pos());
   instr->ReplaceUsesWith(load);
   flow_graph()->InsertAfter(instr, load, NULL, FlowGraph::kValue);
 }
 
 
 void FlowGraphOptimizer::AppendExtractNthOutputForMerged(Definition* instr,
                                                          intptr_t index,
                                                          Representation rep,
                                                          intptr_t cid) {
   ExtractNthOutputInstr* extract =
-      new(I) ExtractNthOutputInstr(new(I) Value(instr), index, rep, cid);
+      new(Z) ExtractNthOutputInstr(new(Z) Value(instr), index, rep, cid);
   instr->ReplaceUsesWith(extract);
   flow_graph()->InsertAfter(instr, extract, NULL, FlowGraph::kValue);
 }
 
 
 // Dart:
 //  var x = d % 10;
 //  var y = d ~/ 10;
 //  var z = x + y;
 //
@@ skipping 40 matching lines @@
         AppendExtractNthOutputForMerged(
             curr_instr,
             MergedMathInstr::OutputIndexOf(curr_instr->op_kind()),
             kTagged, kSmiCid);
         ASSERT(other_binop->HasUses());
         AppendExtractNthOutputForMerged(
             other_binop,
             MergedMathInstr::OutputIndexOf(other_binop->op_kind()),
             kTagged, kSmiCid);
 
-        ZoneGrowableArray<Value*>* args = new(I) ZoneGrowableArray<Value*>(2);
-        args->Add(new(I) Value(curr_instr->left()->definition()));
-        args->Add(new(I) Value(curr_instr->right()->definition()));
+        ZoneGrowableArray<Value*>* args = new(Z) ZoneGrowableArray<Value*>(2);
+        args->Add(new(Z) Value(curr_instr->left()->definition()));
+        args->Add(new(Z) Value(curr_instr->right()->definition()));
 
         // Replace with TruncDivMod.
-        MergedMathInstr* div_mod = new(I) MergedMathInstr(
+        MergedMathInstr* div_mod = new(Z) MergedMathInstr(
             args,
             curr_instr->deopt_id(),
             MergedMathInstr::kTruncDivMod);
         curr_instr->ReplaceWith(div_mod, current_iterator());
         other_binop->ReplaceUsesWith(div_mod);
         other_binop->RemoveFromGraph();
         // Only one merge possible. Because canonicalization happens later,
         // more candidates are possible.
         // TODO(srdjan): Allow merging of trunc-div/mod into truncDivMod.
         break;
@@ skipping 34 matching lines @@
         (*merge_candidates)[k] = NULL;  // Clear it.
         ASSERT(curr_instr->HasUses());
         AppendExtractNthOutputForMerged(curr_instr,
                                         MergedMathInstr::OutputIndexOf(kind),
                                         kUnboxedDouble, kDoubleCid);
         ASSERT(other_op->HasUses());
         AppendExtractNthOutputForMerged(
             other_op,
             MergedMathInstr::OutputIndexOf(other_kind),
             kUnboxedDouble, kDoubleCid);
-        ZoneGrowableArray<Value*>* args = new(I) ZoneGrowableArray<Value*>(1);
-        args->Add(new(I) Value(curr_instr->value()->definition()));
+        ZoneGrowableArray<Value*>* args = new(Z) ZoneGrowableArray<Value*>(1);
+        args->Add(new(Z) Value(curr_instr->value()->definition()));
         // Replace with SinCos.
         MergedMathInstr* sin_cos =
-            new(I) MergedMathInstr(args,
+            new(Z) MergedMathInstr(args,
                                    curr_instr->DeoptimizationTarget(),
                                    MergedMathInstr::kSinCos);
         curr_instr->ReplaceWith(sin_cos, current_iterator());
         other_op->ReplaceUsesWith(sin_cos);
         other_op->RemoveFromGraph();
         // Only one merge possible. Because canonicalization happens later,
         // more candidates are possible.
         // TODO(srdjan): Allow merging of sin/cos into sincos.
         break;
       }
@@ skipping 140 matching lines @@
         phi->block()->PredecessorAt(use->use_index())->last_instruction();
     deopt_target = NULL;
   } else {
     deopt_target = insert_before = use->instruction();
   }
 
   Definition* converted = NULL;
   if (IsUnboxedInteger(from) && IsUnboxedInteger(to)) {
     const intptr_t deopt_id = (to == kUnboxedInt32) && (deopt_target != NULL) ?
       deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
-    converted = new(I) UnboxedIntConverterInstr(from,
+    converted = new(Z) UnboxedIntConverterInstr(from,
                                                 to,
                                                 use->CopyWithType(),
                                                 deopt_id);
   } else if ((from == kUnboxedInt32) && (to == kUnboxedDouble)) {
     converted = new Int32ToDoubleInstr(use->CopyWithType());
   } else if ((from == kUnboxedMint) &&
              (to == kUnboxedDouble) &&
              CanConvertUnboxedMintToDouble()) {
     const intptr_t deopt_id = (deopt_target != NULL) ?
       deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
@@ skipping 10 matching lines @@
     // Insert two "dummy" conversion instructions with the correct
     // "from" and "to" representation. The inserted instructions will
     // trigger a deoptimization if executed. See #12417 for a discussion.
     const intptr_t deopt_id = (deopt_target != NULL) ?
       deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
     ASSERT(Boxing::Supports(from));
     ASSERT(Boxing::Supports(to));
     Definition* boxed = BoxInstr::Create(from, use->CopyWithType());
     use->BindTo(boxed);
     InsertBefore(insert_before, boxed, NULL, FlowGraph::kValue);
-    converted = UnboxInstr::Create(to, new(I) Value(boxed), deopt_id);
+    converted = UnboxInstr::Create(to, new(Z) Value(boxed), deopt_id);
   }
   ASSERT(converted != NULL);
   InsertBefore(insert_before, converted, use->instruction()->env(),
                FlowGraph::kValue);
   if (is_environment_use) {
     use->BindToEnvironment(converted);
   } else {
     use->BindTo(converted);
   }
 
@@ skipping 330 matching lines @@
   call->ReplaceWith(replacement, current_iterator());
 }
 
 
 void FlowGraphOptimizer::AddCheckSmi(Definition* to_check,
                                      intptr_t deopt_id,
                                      Environment* deopt_environment,
                                      Instruction* insert_before) {
   if (to_check->Type()->ToCid() != kSmiCid) {
     InsertBefore(insert_before,
-                 new(I) CheckSmiInstr(new(I) Value(to_check),
+                 new(Z) CheckSmiInstr(new(Z) Value(to_check),
                                       deopt_id,
                                       insert_before->token_pos()),
                  deopt_environment,
                  FlowGraph::kEffect);
   }
 }
 
 
 Instruction* FlowGraphOptimizer::GetCheckClass(Definition* to_check,
                                                const ICData& unary_checks,
                                                intptr_t deopt_id,
                                                intptr_t token_pos) {
   if ((unary_checks.NumberOfUsedChecks() == 1) &&
       unary_checks.HasReceiverClassId(kSmiCid)) {
-    return new(I) CheckSmiInstr(new(I) Value(to_check),
+    return new(Z) CheckSmiInstr(new(Z) Value(to_check),
                                 deopt_id,
                                 token_pos);
   }
-  return new(I) CheckClassInstr(
-      new(I) Value(to_check), deopt_id, unary_checks, token_pos);
+  return new(Z) CheckClassInstr(
+      new(Z) Value(to_check), deopt_id, unary_checks, token_pos);
 }
 
 
 void FlowGraphOptimizer::AddCheckClass(Definition* to_check,
                                        const ICData& unary_checks,
                                        intptr_t deopt_id,
                                        Environment* deopt_environment,
                                        Instruction* insert_before) {
   // Type propagation has not run yet, we cannot eliminate the check.
   Instruction* check = GetCheckClass(
       to_check, unary_checks, deopt_id, insert_before->token_pos());
   InsertBefore(insert_before, check, deopt_environment, FlowGraph::kEffect);
 }
 
 
 void FlowGraphOptimizer::AddReceiverCheck(InstanceCallInstr* call) {
   AddCheckClass(call->ArgumentAt(0),
-                ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecks()),
+                ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecks()),
                 call->deopt_id(),
                 call->env(),
                 call);
 }
 
 
 static bool ArgIsAlways(intptr_t cid,
                         const ICData& ic_data,
                         intptr_t arg_number) {
   ASSERT(ic_data.NumArgsTested() > arg_number);
@@ skipping 94 matching lines @@
       break;
   }
   return kIllegalCid;
 }
 
 
 bool FlowGraphOptimizer::TryReplaceWithIndexedOp(InstanceCallInstr* call) {
   // Check for monomorphic IC data.
   if (!call->HasICData()) return false;
   const ICData& ic_data =
-      ICData::Handle(I, call->ic_data()->AsUnaryClassChecks());
+      ICData::Handle(Z, call->ic_data()->AsUnaryClassChecks());
   if (ic_data.NumberOfChecks() != 1) {
     return false;
   }
   return TryReplaceInstanceCallWithInline(call);
 }
 
 
 bool FlowGraphOptimizer::InlineSetIndexed(
     MethodRecognizer::Kind kind,
     const Function& target,
     Instruction* call,
     Definition* receiver,
     intptr_t token_pos,
     const ICData& value_check,
     TargetEntryInstr** entry,
     Definition** last) {
   intptr_t array_cid = MethodKindToCid(kind);
   ASSERT(array_cid != kIllegalCid);
 
   Definition* array = receiver;
   Definition* index = call->ArgumentAt(1);
   Definition* stored_value = call->ArgumentAt(2);
 
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
   Instruction* cursor = *entry;
   if (FLAG_enable_type_checks) {
     // Only type check for the value. A type check for the index is not
     // needed here because we insert a deoptimizing smi-check for the case
     // the index is not a smi.
     const AbstractType& value_type =
-        AbstractType::ZoneHandle(I, target.ParameterTypeAt(2));
+        AbstractType::ZoneHandle(Z, target.ParameterTypeAt(2));
     Definition* instantiator = NULL;
     Definition* type_args = NULL;
     switch (array_cid) {
       case kArrayCid:
       case kGrowableObjectArrayCid: {
-        const Class& instantiator_class =  Class::Handle(I, target.Owner());
+        const Class& instantiator_class =  Class::Handle(Z, target.Owner());
         intptr_t type_arguments_field_offset =
             instantiator_class.type_arguments_field_offset();
         LoadFieldInstr* load_type_args =
-            new(I) LoadFieldInstr(new(I) Value(array),
+            new(Z) LoadFieldInstr(new(Z) Value(array),
                                   type_arguments_field_offset,
-                                  Type::ZoneHandle(I),  // No type.
+                                  Type::ZoneHandle(Z),  // No type.
                                   call->token_pos());
         cursor = flow_graph()->AppendTo(cursor,
                                         load_type_args,
                                         NULL,
                                         FlowGraph::kValue);
 
         instantiator = array;
         type_args = load_type_args;
         break;
       }
@@ skipping 30 matching lines @@
         ASSERT((array_cid != kTypedDataFloat64x2ArrayCid) ||
                value_type.IsFloat64x2Type());
         ASSERT(value_type.IsInstantiated());
         break;
       }
       default:
         // TODO(fschneider): Add support for other array types.
         UNREACHABLE();
     }
     AssertAssignableInstr* assert_value =
-        new(I) AssertAssignableInstr(token_pos,
-                                     new(I) Value(stored_value),
-                                     new(I) Value(instantiator),
-                                     new(I) Value(type_args),
+        new(Z) AssertAssignableInstr(token_pos,
+                                     new(Z) Value(stored_value),
+                                     new(Z) Value(instantiator),
+                                     new(Z) Value(type_args),
                                      value_type,
                                      Symbols::Value(),
                                      call->deopt_id());
     cursor = flow_graph()->AppendTo(cursor,
                                     assert_value,
                                     call->env(),
                                     FlowGraph::kValue);
   }
 
   array_cid = PrepareInlineIndexedOp(call,
@@ skipping 20 matching lines @@
     Instruction* check = GetCheckClass(
         stored_value, value_check, call->deopt_id(), call->token_pos());
     cursor = flow_graph()->AppendTo(cursor,
                                     check,
                                     call->env(),
                                     FlowGraph::kEffect);
   }
 
   if (array_cid == kTypedDataFloat32ArrayCid) {
     stored_value =
-        new(I) DoubleToFloatInstr(
-            new(I) Value(stored_value), call->deopt_id());
+        new(Z) DoubleToFloatInstr(
+            new(Z) Value(stored_value), call->deopt_id());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     NULL,
                                     FlowGraph::kValue);
   } else if (array_cid == kTypedDataInt32ArrayCid) {
-    stored_value = new(I) UnboxInt32Instr(
+    stored_value = new(Z) UnboxInt32Instr(
         UnboxInt32Instr::kTruncate,
-        new(I) Value(stored_value),
+        new(Z) Value(stored_value),
         call->deopt_id());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     call->env(),
                                     FlowGraph::kValue);
   } else if (array_cid == kTypedDataUint32ArrayCid) {
-    stored_value = new(I) UnboxUint32Instr(
-        new(I) Value(stored_value),
+    stored_value = new(Z) UnboxUint32Instr(
+        new(Z) Value(stored_value),
         call->deopt_id());
     ASSERT(stored_value->AsUnboxInteger()->is_truncating());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     call->env(),
                                     FlowGraph::kValue);
   }
 
   const intptr_t index_scale = Instance::ElementSizeFor(array_cid);
-  *last = new(I) StoreIndexedInstr(new(I) Value(array),
-                                   new(I) Value(index),
-                                   new(I) Value(stored_value),
+  *last = new(Z) StoreIndexedInstr(new(Z) Value(array),
+                                   new(Z) Value(index),
+                                   new(Z) Value(stored_value),
                                    needs_store_barrier,
                                    index_scale,
                                    array_cid,
                                    call->deopt_id(),
                                    call->token_pos());
   flow_graph()->AppendTo(cursor,
                          *last,
                          call->env(),
                          FlowGraph::kEffect);
   return true;
 }
 
 
 bool FlowGraphOptimizer::TryInlineRecognizedMethod(intptr_t receiver_cid,
                                                    const Function& target,
                                                    Instruction* call,
                                                    Definition* receiver,
                                                    intptr_t token_pos,
                                                    const ICData& ic_data,
                                                    TargetEntryInstr** entry,
                                                    Definition** last) {
-  ICData& value_check = ICData::ZoneHandle(I);
+  ICData& value_check = ICData::ZoneHandle(Z);
   MethodRecognizer::Kind kind = MethodRecognizer::RecognizeKind(target);
   switch (kind) {
     // Recognized [] operators.
     case MethodRecognizer::kImmutableArrayGetIndexed:
     case MethodRecognizer::kObjectArrayGetIndexed:
     case MethodRecognizer::kGrowableArrayGetIndexed:
     case MethodRecognizer::kInt8ArrayGetIndexed:
     case MethodRecognizer::kUint8ArrayGetIndexed:
     case MethodRecognizer::kUint8ClampedArrayGetIndexed:
     case MethodRecognizer::kExternalUint8ArrayGetIndexed:
@@ skipping 223 matching lines @@
 
 
 intptr_t FlowGraphOptimizer::PrepareInlineIndexedOp(Instruction* call,
                                                     intptr_t array_cid,
                                                     Definition** array,
                                                     Definition* index,
                                                     Instruction** cursor) {
   // Insert index smi check.
   *cursor = flow_graph()->AppendTo(
       *cursor,
-      new(I) CheckSmiInstr(new(I) Value(index),
+      new(Z) CheckSmiInstr(new(Z) Value(index),
                            call->deopt_id(),
                            call->token_pos()),
       call->env(),
       FlowGraph::kEffect);
 
   // Insert array length load and bounds check.
   LoadFieldInstr* length =
-      new(I) LoadFieldInstr(
-          new(I) Value(*array),
+      new(Z) LoadFieldInstr(
+          new(Z) Value(*array),
           CheckArrayBoundInstr::LengthOffsetFor(array_cid),
-          Type::ZoneHandle(I, Type::SmiType()),
+          Type::ZoneHandle(Z, Type::SmiType()),
           call->token_pos());
   length->set_is_immutable(
       CheckArrayBoundInstr::IsFixedLengthArrayType(array_cid));
   length->set_result_cid(kSmiCid);
   length->set_recognized_kind(
       LoadFieldInstr::RecognizedKindFromArrayCid(array_cid));
   *cursor = flow_graph()->AppendTo(*cursor,
                                    length,
                                    NULL,
                                    FlowGraph::kValue);
 
   *cursor = flow_graph()->AppendTo(*cursor,
-                                   new(I) CheckArrayBoundInstr(
-                                       new(I) Value(length),
-                                       new(I) Value(index),
+                                   new(Z) CheckArrayBoundInstr(
+                                       new(Z) Value(length),
+                                       new(Z) Value(index),
                                        call->deopt_id()),
                                    call->env(),
                                    FlowGraph::kEffect);
 
   if (array_cid == kGrowableObjectArrayCid) {
     // Insert data elements load.
     LoadFieldInstr* elements =
-        new(I) LoadFieldInstr(
-            new(I) Value(*array),
+        new(Z) LoadFieldInstr(
+            new(Z) Value(*array),
             GrowableObjectArray::data_offset(),
-            Type::ZoneHandle(I, Type::DynamicType()),
+            Type::ZoneHandle(Z, Type::DynamicType()),
             call->token_pos());
     elements->set_result_cid(kArrayCid);
     *cursor = flow_graph()->AppendTo(*cursor,
                                      elements,
                                      NULL,
                                      FlowGraph::kValue);
     // Load from the data from backing store which is a fixed-length array.
     *array = elements;
     array_cid = kArrayCid;
   } else if (RawObject::IsExternalTypedDataClassId(array_cid)) {
     LoadUntaggedInstr* elements =
-        new(I) LoadUntaggedInstr(new(I) Value(*array),
+        new(Z) LoadUntaggedInstr(new(Z) Value(*array),
                                  ExternalTypedData::data_offset());
     *cursor = flow_graph()->AppendTo(*cursor,
                                      elements,
                                      NULL,
                                      FlowGraph::kValue);
     *array = elements;
   }
   return array_cid;
 }
 
 
 bool FlowGraphOptimizer::InlineGetIndexed(MethodRecognizer::Kind kind,
                                           Instruction* call,
                                           Definition* receiver,
                                           TargetEntryInstr** entry,
                                           Definition** last) {
   intptr_t array_cid = MethodKindToCid(kind);
   ASSERT(array_cid != kIllegalCid);
 
   Definition* array = receiver;
   Definition* index = call->ArgumentAt(1);
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
   Instruction* cursor = *entry;
 
   array_cid = PrepareInlineIndexedOp(call,
                                      array_cid,
                                      &array,
                                      index,
                                      &cursor);
 
   intptr_t deopt_id = Isolate::kNoDeoptId;
   if ((array_cid == kTypedDataInt32ArrayCid) ||
       (array_cid == kTypedDataUint32ArrayCid)) {
     // Deoptimization may be needed if result does not always fit in a Smi.
     deopt_id = (kSmiBits >= 32) ? Isolate::kNoDeoptId : call->deopt_id();
   }
 
   // Array load and return.
   intptr_t index_scale = Instance::ElementSizeFor(array_cid);
-  *last = new(I) LoadIndexedInstr(new(I) Value(array),
-                                  new(I) Value(index),
+  *last = new(Z) LoadIndexedInstr(new(Z) Value(array),
+                                  new(Z) Value(index),
                                   index_scale,
                                   array_cid,
                                   deopt_id,
                                   call->token_pos());
   cursor = flow_graph()->AppendTo(
       cursor,
       *last,
       deopt_id != Isolate::kNoDeoptId ? call->env() : NULL,
       FlowGraph::kValue);
 
   if (array_cid == kTypedDataFloat32ArrayCid) {
-    *last = new(I) FloatToDoubleInstr(new(I) Value(*last), deopt_id);
+    *last = new(Z) FloatToDoubleInstr(new(Z) Value(*last), deopt_id);
     flow_graph()->AppendTo(cursor,
                            *last,
                            deopt_id != Isolate::kNoDeoptId ? call->env() : NULL,
                            FlowGraph::kValue);
   }
   return true;
 }
 
 
 // Return true if d is a string of length one (a constant or result from
@@ skipping 32 matching lines @@
     right = temp;
   }
   if (IsLengthOneString(left)) {
     // Optimize if left is a string with length one (either constant or
     // result of string-from-char-code.
     if (left->IsConstant()) {
       ConstantInstr* left_const = left->AsConstant();
       const String& str = String::Cast(left_const->value());
       ASSERT(str.Length() == 1);
       ConstantInstr* char_code_left = flow_graph()->GetConstant(
-          Smi::ZoneHandle(I, Smi::New(static_cast<intptr_t>(str.CharAt(0)))));
-      left_val = new(I) Value(char_code_left);
+          Smi::ZoneHandle(Z, Smi::New(static_cast<intptr_t>(str.CharAt(0)))));
+      left_val = new(Z) Value(char_code_left);
     } else if (left->IsStringFromCharCode()) {
       // Use input of string-from-charcode as left value.
       StringFromCharCodeInstr* instr = left->AsStringFromCharCode();
-      left_val = new(I) Value(instr->char_code()->definition());
+      left_val = new(Z) Value(instr->char_code()->definition());
       to_remove_left = instr;
     } else {
       // IsLengthOneString(left) should have been false.
       UNREACHABLE();
     }
 
     Definition* to_remove_right = NULL;
     Value* right_val = NULL;
     if (right->IsStringFromCharCode()) {
       // Skip string-from-char-code, and use its input as right value.
       StringFromCharCodeInstr* right_instr = right->AsStringFromCharCode();
-      right_val = new(I) Value(right_instr->char_code()->definition());
+      right_val = new(Z) Value(right_instr->char_code()->definition());
       to_remove_right = right_instr;
     } else {
       const ICData& unary_checks_1 =
-          ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecksForArgNr(1));
+          ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecksForArgNr(1));
       AddCheckClass(right,
                     unary_checks_1,
                     call->deopt_id(),
                     call->env(),
                     call);
       // String-to-char-code instructions returns -1 (illegal charcode) if
       // string is not of length one.
       StringToCharCodeInstr* char_code_right =
-          new(I) StringToCharCodeInstr(new(I) Value(right), kOneByteStringCid);
+          new(Z) StringToCharCodeInstr(new(Z) Value(right), kOneByteStringCid);
       InsertBefore(call, char_code_right, call->env(), FlowGraph::kValue);
-      right_val = new(I) Value(char_code_right);
+      right_val = new(Z) Value(char_code_right);
     }
 
     // Comparing char-codes instead of strings.
     EqualityCompareInstr* comp =
-        new(I) EqualityCompareInstr(call->token_pos(),
+        new(Z) EqualityCompareInstr(call->token_pos(),
                                     op_kind,
                                     left_val,
                                     right_val,
                                     kSmiCid,
                                     call->deopt_id());
     ReplaceCall(call, comp);
 
     // Remove dead instructions.
     if ((to_remove_left != NULL) &&
         (to_remove_left->input_use_list() == NULL)) {
@@ skipping 24 matching lines @@
 
   intptr_t cid = kIllegalCid;
   if (HasOnlyTwoOf(ic_data, kOneByteStringCid)) {
     if (TryStringLengthOneEquality(call, op_kind)) {
       return true;
     } else {
       return false;
     }
   } else if (HasOnlyTwoOf(ic_data, kSmiCid)) {
     InsertBefore(call,
-                 new(I) CheckSmiInstr(new(I) Value(left),
+                 new(Z) CheckSmiInstr(new(Z) Value(left),
                                       call->deopt_id(),
                                       call->token_pos()),
                  call->env(),
                  FlowGraph::kEffect);
     InsertBefore(call,
-                 new(I) CheckSmiInstr(new(I) Value(right),
+                 new(Z) CheckSmiInstr(new(Z) Value(right),
                                       call->deopt_id(),
                                       call->token_pos()),
                  call->env(),
                  FlowGraph::kEffect);
     cid = kSmiCid;
   } else if (HasTwoMintOrSmi(ic_data) &&
              FlowGraphCompiler::SupportsUnboxedMints()) {
     cid = kMintCid;
   } else if (HasTwoDoubleOrSmi(ic_data) && CanUnboxDouble()) {
     // Use double comparison.
     if (SmiFitsInDouble()) {
       cid = kDoubleCid;
     } else {
       if (ICDataHasReceiverArgumentClassIds(ic_data, kSmiCid, kSmiCid)) {
         // We cannot use double comparison on two smis. Need polymorphic
         // call.
         return false;
       } else {
         InsertBefore(call,
-                     new(I) CheckEitherNonSmiInstr(
-                         new(I) Value(left),
-                         new(I) Value(right),
+                     new(Z) CheckEitherNonSmiInstr(
+                         new(Z) Value(left),
+                         new(Z) Value(right),
                          call->deopt_id()),
                      call->env(),
                      FlowGraph::kEffect);
         cid = kDoubleCid;
       }
     }
   } else {
     // Check if ICDData contains checks with Smi/Null combinations. In that case
     // we can still emit the optimized Smi equality operation but need to add
     // checks for null or Smi.
     GrowableArray<intptr_t> smi_or_null(2);
     smi_or_null.Add(kSmiCid);
     smi_or_null.Add(kNullCid);
     if (ICDataHasOnlyReceiverArgumentClassIds(ic_data,
                                               smi_or_null,
                                               smi_or_null)) {
       const ICData& unary_checks_0 =
-          ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecks());
+          ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecks());
       AddCheckClass(left,
                     unary_checks_0,
                     call->deopt_id(),
                     call->env(),
                     call);
 
       const ICData& unary_checks_1 =
-          ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecksForArgNr(1));
+          ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecksForArgNr(1));
       AddCheckClass(right,
                     unary_checks_1,
                     call->deopt_id(),
                     call->env(),
                     call);
       cid = kSmiCid;
     } else {
       // Shortcut for equality with null.
       ConstantInstr* right_const = right->AsConstant();
       ConstantInstr* left_const = left->AsConstant();
       if ((right_const != NULL && right_const->value().IsNull()) ||
           (left_const != NULL && left_const->value().IsNull())) {
         StrictCompareInstr* comp =
-            new(I) StrictCompareInstr(call->token_pos(),
+            new(Z) StrictCompareInstr(call->token_pos(),
                                       Token::kEQ_STRICT,
-                                      new(I) Value(left),
-                                      new(I) Value(right),
+                                      new(Z) Value(left),
+                                      new(Z) Value(right),
                                       false);  // No number check.
         ReplaceCall(call, comp);
         return true;
       }
       return false;
     }
   }
   ASSERT(cid != kIllegalCid);
-  EqualityCompareInstr* comp = new(I) EqualityCompareInstr(call->token_pos(),
+  EqualityCompareInstr* comp = new(Z) EqualityCompareInstr(call->token_pos(),
                                                            op_kind,
-                                                           new(I) Value(left),
-                                                           new(I) Value(right),
+                                                           new(Z) Value(left),
+                                                           new(Z) Value(right),
                                                            cid,
                                                            call->deopt_id());
   ReplaceCall(call, comp);
   return true;
 }
 
 
 bool FlowGraphOptimizer::TryReplaceWithRelationalOp(InstanceCallInstr* call,
                                                     Token::Kind op_kind) {
   const ICData& ic_data = *call->ic_data();
   ASSERT(ic_data.NumArgsTested() == 2);
 
   ASSERT(call->ArgumentCount() == 2);
   Definition* left = call->ArgumentAt(0);
   Definition* right = call->ArgumentAt(1);
 
   intptr_t cid = kIllegalCid;
   if (HasOnlyTwoOf(ic_data, kSmiCid)) {
     InsertBefore(call,
-                 new(I) CheckSmiInstr(new(I) Value(left),
+                 new(Z) CheckSmiInstr(new(Z) Value(left),
                                       call->deopt_id(),
                                       call->token_pos()),
                  call->env(),
                  FlowGraph::kEffect);
     InsertBefore(call,
-                 new(I) CheckSmiInstr(new(I) Value(right),
+                 new(Z) CheckSmiInstr(new(Z) Value(right),
                                       call->deopt_id(),
                                       call->token_pos()),
                  call->env(),
                  FlowGraph::kEffect);
     cid = kSmiCid;
   } else if (HasTwoMintOrSmi(ic_data) &&
              FlowGraphCompiler::SupportsUnboxedMints()) {
     cid = kMintCid;
   } else if (HasTwoDoubleOrSmi(ic_data) && CanUnboxDouble()) {
     // Use double comparison.
     if (SmiFitsInDouble()) {
       cid = kDoubleCid;
     } else {
       if (ICDataHasReceiverArgumentClassIds(ic_data, kSmiCid, kSmiCid)) {
         // We cannot use double comparison on two smis. Need polymorphic
         // call.
         return false;
       } else {
         InsertBefore(call,
-                     new(I) CheckEitherNonSmiInstr(
-                         new(I) Value(left),
-                         new(I) Value(right),
+                     new(Z) CheckEitherNonSmiInstr(
+                         new(Z) Value(left),
+                         new(Z) Value(right),
                          call->deopt_id()),
                      call->env(),
                      FlowGraph::kEffect);
         cid = kDoubleCid;
       }
     }
   } else {
     return false;
   }
   ASSERT(cid != kIllegalCid);
-  RelationalOpInstr* comp = new(I) RelationalOpInstr(call->token_pos(),
+  RelationalOpInstr* comp = new(Z) RelationalOpInstr(call->token_pos(),
                                                      op_kind,
-                                                     new(I) Value(left),
-                                                     new(I) Value(right),
+                                                     new(Z) Value(left),
+                                                     new(Z) Value(right),
                                                      cid,
                                                      call->deopt_id());
   ReplaceCall(call, comp);
   return true;
 }
 
 
 bool FlowGraphOptimizer::TryReplaceWithBinaryOp(InstanceCallInstr* call,
                                                 Token::Kind op_kind) {
   intptr_t operands_type = kIllegalCid;
@@ skipping 59 matching lines @@
         // Left shift may overflow from smi into mint or big ints.
         // Don't generate smi code if the IC data is marked because
         // of an overflow.
         if (ic_data.HasDeoptReason(ICData::kDeoptBinaryMintOp)) {
           return false;
         }
         operands_type = ic_data.HasDeoptReason(ICData::kDeoptBinarySmiOp)
             ? kMintCid
             : kSmiCid;
       } else if (HasTwoMintOrSmi(ic_data) &&
-                 HasOnlyOneSmi(ICData::Handle(I,
+                 HasOnlyOneSmi(ICData::Handle(Z,
                      ic_data.AsUnaryClassChecksForArgNr(1)))) {
         // Don't generate mint code if the IC data is marked because of an
         // overflow.
         if (ic_data.HasDeoptReason(ICData::kDeoptBinaryMintOp)) {
           return false;
         }
         // Check for smi/mint << smi or smi/mint >> smi.
         operands_type = kMintCid;
       } else {
         return false;
@@ skipping 19 matching lines @@
   Definition* right = call->ArgumentAt(1);
   if (operands_type == kDoubleCid) {
     if (!CanUnboxDouble()) {
       return false;
     }
     // Check that either left or right are not a smi.  Result of a
     // binary operation with two smis is a smi not a double, except '/' which
     // returns a double for two smis.
     if (op_kind != Token::kDIV) {
       InsertBefore(call,
-                   new(I) CheckEitherNonSmiInstr(
-                       new(I) Value(left),
-                       new(I) Value(right),
+                   new(Z) CheckEitherNonSmiInstr(
+                       new(Z) Value(left),
+                       new(Z) Value(right),
                        call->deopt_id()),
                    call->env(),
                    FlowGraph::kEffect);
     }
 
     BinaryDoubleOpInstr* double_bin_op =
-        new(I) BinaryDoubleOpInstr(op_kind,
-                                   new(I) Value(left),
-                                   new(I) Value(right),
+        new(Z) BinaryDoubleOpInstr(op_kind,
+                                   new(Z) Value(left),
+                                   new(Z) Value(right),
                                    call->deopt_id(), call->token_pos());
     ReplaceCall(call, double_bin_op);
   } else if (operands_type == kMintCid) {
     if (!FlowGraphCompiler::SupportsUnboxedMints()) return false;
     if ((op_kind == Token::kSHR) || (op_kind == Token::kSHL)) {
       ShiftMintOpInstr* shift_op =
-          new(I) ShiftMintOpInstr(
-              op_kind, new(I) Value(left), new(I) Value(right),
+          new(Z) ShiftMintOpInstr(
+              op_kind, new(Z) Value(left), new(Z) Value(right),
               call->deopt_id());
       ReplaceCall(call, shift_op);
     } else {
       BinaryMintOpInstr* bin_op =
-          new(I) BinaryMintOpInstr(
-              op_kind, new(I) Value(left), new(I) Value(right),
+          new(Z) BinaryMintOpInstr(
+              op_kind, new(Z) Value(left), new(Z) Value(right),
               call->deopt_id());
       ReplaceCall(call, bin_op);
     }
   } else if (operands_type == kFloat32x4Cid) {
     return InlineFloat32x4BinaryOp(call, op_kind);
   } else if (operands_type == kInt32x4Cid) {
     return InlineInt32x4BinaryOp(call, op_kind);
   } else if (operands_type == kFloat64x2Cid) {
     return InlineFloat64x2BinaryOp(call, op_kind);
   } else if (op_kind == Token::kMOD) {
     ASSERT(operands_type == kSmiCid);
     if (right->IsConstant()) {
       const Object& obj = right->AsConstant()->value();
       if (obj.IsSmi() && Utils::IsPowerOfTwo(Smi::Cast(obj).Value())) {
         // Insert smi check and attach a copy of the original environment
         // because the smi operation can still deoptimize.
         InsertBefore(call,
-                     new(I) CheckSmiInstr(new(I) Value(left),
+                     new(Z) CheckSmiInstr(new(Z) Value(left),
                                           call->deopt_id(),
                                           call->token_pos()),
                      call->env(),
                      FlowGraph::kEffect);
         ConstantInstr* constant =
-            flow_graph()->GetConstant(Smi::Handle(I,
+            flow_graph()->GetConstant(Smi::Handle(Z,
                 Smi::New(Smi::Cast(obj).Value() - 1)));
         BinarySmiOpInstr* bin_op =
-            new(I) BinarySmiOpInstr(Token::kBIT_AND,
-                                    new(I) Value(left),
-                                    new(I) Value(constant),
+            new(Z) BinarySmiOpInstr(Token::kBIT_AND,
+                                    new(Z) Value(left),
+                                    new(Z) Value(constant),
                                     call->deopt_id());
         ReplaceCall(call, bin_op);
         return true;
       }
     }
     // Insert two smi checks and attach a copy of the original
     // environment because the smi operation can still deoptimize.
     AddCheckSmi(left, call->deopt_id(), call->env(), call);
     AddCheckSmi(right, call->deopt_id(), call->env(), call);
     BinarySmiOpInstr* bin_op =
-        new(I) BinarySmiOpInstr(op_kind,
-                                new(I) Value(left),
-                                new(I) Value(right),
+        new(Z) BinarySmiOpInstr(op_kind,
+                                new(Z) Value(left),
+                                new(Z) Value(right),
                                 call->deopt_id());
     ReplaceCall(call, bin_op);
   } else {
     ASSERT(operands_type == kSmiCid);
     // Insert two smi checks and attach a copy of the original
     // environment because the smi operation can still deoptimize.
     AddCheckSmi(left, call->deopt_id(), call->env(), call);
     AddCheckSmi(right, call->deopt_id(), call->env(), call);
     if (left->IsConstant() &&
         ((op_kind == Token::kADD) || (op_kind == Token::kMUL))) {
       // Constant should be on the right side.
       Definition* temp = left;
       left = right;
       right = temp;
     }
     BinarySmiOpInstr* bin_op =
-        new(I) BinarySmiOpInstr(
+        new(Z) BinarySmiOpInstr(
             op_kind,
-            new(I) Value(left),
-            new(I) Value(right),
+            new(Z) Value(left),
+            new(Z) Value(right),
             call->deopt_id());
     ReplaceCall(call, bin_op);
   }
   return true;
 }
 
 
 bool FlowGraphOptimizer::TryReplaceWithUnaryOp(InstanceCallInstr* call,
                                                Token::Kind op_kind) {
   ASSERT(call->ArgumentCount() == 1);
   Definition* input = call->ArgumentAt(0);
   Definition* unary_op = NULL;
   if (HasOnlyOneSmi(*call->ic_data())) {
     InsertBefore(call,
-                 new(I) CheckSmiInstr(new(I) Value(input),
+                 new(Z) CheckSmiInstr(new(Z) Value(input),
                                       call->deopt_id(),
                                       call->token_pos()),
                  call->env(),
                  FlowGraph::kEffect);
-    unary_op = new(I) UnarySmiOpInstr(
-        op_kind, new(I) Value(input), call->deopt_id());
+    unary_op = new(Z) UnarySmiOpInstr(
+        op_kind, new(Z) Value(input), call->deopt_id());
   } else if ((op_kind == Token::kBIT_NOT) &&
              HasOnlySmiOrMint(*call->ic_data()) &&
              FlowGraphCompiler::SupportsUnboxedMints()) {
-    unary_op = new(I) UnaryMintOpInstr(
-        op_kind, new(I) Value(input), call->deopt_id());
+    unary_op = new(Z) UnaryMintOpInstr(
+        op_kind, new(Z) Value(input), call->deopt_id());
   } else if (HasOnlyOneDouble(*call->ic_data()) &&
              (op_kind == Token::kNEGATE) &&
              CanUnboxDouble()) {
     AddReceiverCheck(call);
-    unary_op = new(I) UnaryDoubleOpInstr(
-        Token::kNEGATE, new(I) Value(input), call->deopt_id());
+    unary_op = new(Z) UnaryDoubleOpInstr(
+        Token::kNEGATE, new(Z) Value(input), call->deopt_id());
   } else {
     return false;
   }
   ASSERT(unary_op != NULL);
   ReplaceCall(call, unary_op);
   return true;
 }
 
 
 // Using field class
@@ skipping 18 matching lines @@
 bool FlowGraphOptimizer::InstanceCallNeedsClassCheck(
     InstanceCallInstr* call, RawFunction::Kind kind) const {
   if (!FLAG_use_cha) return true;
   Definition* callee_receiver = call->ArgumentAt(0);
   ASSERT(callee_receiver != NULL);
   const Function& function = flow_graph_->parsed_function()->function();
   if (function.IsDynamicFunction() &&
       callee_receiver->IsParameter() &&
       (callee_receiver->AsParameter()->index() == 0)) {
     const String& name = (kind == RawFunction::kMethodExtractor)
-        ? String::Handle(I, Field::NameFromGetter(call->function_name()))
+        ? String::Handle(Z, Field::NameFromGetter(call->function_name()))
         : call->function_name();
-    return isolate()->cha()->HasOverride(Class::Handle(I, function.Owner()),
+    return isolate()->cha()->HasOverride(Class::Handle(Z, function.Owner()),
                                          name);
   }
   return true;
 }
 
 
 void FlowGraphOptimizer::InlineImplicitInstanceGetter(InstanceCallInstr* call) {
   ASSERT(call->HasICData());
   const ICData& ic_data = *call->ic_data();
   ASSERT(ic_data.HasOneTarget());
-  Function& target = Function::Handle(I);
+  Function& target = Function::Handle(Z);
   GrowableArray<intptr_t> class_ids;
   ic_data.GetCheckAt(0, &class_ids, &target);
   ASSERT(class_ids.length() == 1);
   // Inline implicit instance getter.
   const String& field_name =
-      String::Handle(I, Field::NameFromGetter(call->function_name()));
+      String::Handle(Z, Field::NameFromGetter(call->function_name()));
   const Field& field =
-      Field::ZoneHandle(I, GetField(class_ids[0], field_name));
+      Field::ZoneHandle(Z, GetField(class_ids[0], field_name));
   ASSERT(!field.IsNull());
 
   if (InstanceCallNeedsClassCheck(call, RawFunction::kImplicitGetter)) {
     AddReceiverCheck(call);
   }
-  LoadFieldInstr* load = new(I) LoadFieldInstr(
-      new(I) Value(call->ArgumentAt(0)),
+  LoadFieldInstr* load = new(Z) LoadFieldInstr(
+      new(Z) Value(call->ArgumentAt(0)),
       &field,
-      AbstractType::ZoneHandle(I, field.type()),
+      AbstractType::ZoneHandle(Z, field.type()),
       call->token_pos());
   load->set_is_immutable(field.is_final());
   if (field.guarded_cid() != kIllegalCid) {
     if (!field.is_nullable() || (field.guarded_cid() == kNullCid)) {
       load->set_result_cid(field.guarded_cid());
     }
     FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
   }
 
   // Discard the environment from the original instruction because the load
@@ skipping 12 matching lines @@
 }
 
 
 bool FlowGraphOptimizer::InlineFloat32x4Getter(InstanceCallInstr* call,
                                                MethodRecognizer::Kind getter) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   AddCheckClass(call->ArgumentAt(0),
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                 call->deopt_id(),
                 call->env(),
                 call);
   intptr_t mask = 0;
   if ((getter == MethodRecognizer::kFloat32x4Shuffle) ||
       (getter == MethodRecognizer::kFloat32x4ShuffleMix)) {
     // Extract shuffle mask.
     Definition* mask_definition = NULL;
     if (getter == MethodRecognizer::kFloat32x4Shuffle) {
       ASSERT(call->ArgumentCount() == 2);
@@ skipping 13 matching lines @@
       return false;
     }
     ASSERT(constant_mask.IsSmi());
     mask = Smi::Cast(constant_mask).Value();
     if ((mask < 0) || (mask > 255)) {
       // Not a valid mask.
       return false;
     }
   }
   if (getter == MethodRecognizer::kFloat32x4GetSignMask) {
-    Simd32x4GetSignMaskInstr* instr = new(I) Simd32x4GetSignMaskInstr(
+    Simd32x4GetSignMaskInstr* instr = new(Z) Simd32x4GetSignMaskInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   } else if (getter == MethodRecognizer::kFloat32x4ShuffleMix) {
-    Simd32x4ShuffleMixInstr* instr = new(I) Simd32x4ShuffleMixInstr(
+    Simd32x4ShuffleMixInstr* instr = new(Z) Simd32x4ShuffleMixInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
-        new(I) Value(call->ArgumentAt(1)),
+        new(Z) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(1)),
         mask,
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   } else {
     ASSERT((getter == MethodRecognizer::kFloat32x4Shuffle)  ||
            (getter == MethodRecognizer::kFloat32x4ShuffleX) ||
            (getter == MethodRecognizer::kFloat32x4ShuffleY) ||
            (getter == MethodRecognizer::kFloat32x4ShuffleZ) ||
            (getter == MethodRecognizer::kFloat32x4ShuffleW));
-    Simd32x4ShuffleInstr* instr = new(I) Simd32x4ShuffleInstr(
+    Simd32x4ShuffleInstr* instr = new(Z) Simd32x4ShuffleInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         mask,
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   }
   UNREACHABLE();
   return false;
 }
 
 
 bool FlowGraphOptimizer::InlineFloat64x2Getter(InstanceCallInstr* call,
                                                MethodRecognizer::Kind getter) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   AddCheckClass(call->ArgumentAt(0),
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                 call->deopt_id(),
                 call->env(),
                 call);
   if ((getter == MethodRecognizer::kFloat64x2GetX) ||
       (getter == MethodRecognizer::kFloat64x2GetY)) {
-    Simd64x2ShuffleInstr* instr = new(I) Simd64x2ShuffleInstr(
+    Simd64x2ShuffleInstr* instr = new(Z) Simd64x2ShuffleInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         0,
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   }
   UNREACHABLE();
   return false;
 }
 
 
 bool FlowGraphOptimizer::InlineInt32x4Getter(InstanceCallInstr* call,
                                               MethodRecognizer::Kind getter) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   AddCheckClass(call->ArgumentAt(0),
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                 call->deopt_id(),
                 call->env(),
                 call);
   intptr_t mask = 0;
   if ((getter == MethodRecognizer::kInt32x4Shuffle) ||
       (getter == MethodRecognizer::kInt32x4ShuffleMix)) {
     // Extract shuffle mask.
     Definition* mask_definition = NULL;
     if (getter == MethodRecognizer::kInt32x4Shuffle) {
       ASSERT(call->ArgumentCount() == 2);
@@ skipping 13 matching lines @@
       return false;
     }
     ASSERT(constant_mask.IsSmi());
     mask = Smi::Cast(constant_mask).Value();
     if ((mask < 0) || (mask > 255)) {
       // Not a valid mask.
       return false;
     }
   }
   if (getter == MethodRecognizer::kInt32x4GetSignMask) {
-    Simd32x4GetSignMaskInstr* instr = new(I) Simd32x4GetSignMaskInstr(
+    Simd32x4GetSignMaskInstr* instr = new(Z) Simd32x4GetSignMaskInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   } else if (getter == MethodRecognizer::kInt32x4ShuffleMix) {
-    Simd32x4ShuffleMixInstr* instr = new(I) Simd32x4ShuffleMixInstr(
+    Simd32x4ShuffleMixInstr* instr = new(Z) Simd32x4ShuffleMixInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
-        new(I) Value(call->ArgumentAt(1)),
+        new(Z) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(1)),
         mask,
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   } else if (getter == MethodRecognizer::kInt32x4Shuffle) {
-    Simd32x4ShuffleInstr* instr = new(I) Simd32x4ShuffleInstr(
+    Simd32x4ShuffleInstr* instr = new(Z) Simd32x4ShuffleInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         mask,
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   } else {
-    Int32x4GetFlagInstr* instr = new(I) Int32x4GetFlagInstr(
+    Int32x4GetFlagInstr* instr = new(Z) Int32x4GetFlagInstr(
         getter,
-        new(I) Value(call->ArgumentAt(0)),
+        new(Z) Value(call->ArgumentAt(0)),
         call->deopt_id());
     ReplaceCall(call, instr);
     return true;
   }
 }
 
 
 bool FlowGraphOptimizer::InlineFloat32x4BinaryOp(InstanceCallInstr* call,
                                                  Token::Kind op_kind) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   ASSERT(call->ArgumentCount() == 2);
   Definition* left = call->ArgumentAt(0);
   Definition* right = call->ArgumentAt(1);
   // Type check left.
   AddCheckClass(left,
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                 call->deopt_id(),
                 call->env(),
                 call);
   // Type check right.
   AddCheckClass(right,
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(1)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(1)),
                 call->deopt_id(),
                 call->env(),
                 call);
   // Replace call.
   BinaryFloat32x4OpInstr* float32x4_bin_op =
-      new(I) BinaryFloat32x4OpInstr(
-          op_kind, new(I) Value(left), new(I) Value(right),
+      new(Z) BinaryFloat32x4OpInstr(
+          op_kind, new(Z) Value(left), new(Z) Value(right),
           call->deopt_id());
   ReplaceCall(call, float32x4_bin_op);
 
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineInt32x4BinaryOp(InstanceCallInstr* call,
                                                 Token::Kind op_kind) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   ASSERT(call->ArgumentCount() == 2);
   Definition* left = call->ArgumentAt(0);
   Definition* right = call->ArgumentAt(1);
   // Type check left.
   AddCheckClass(left,
                 ICData::ZoneHandle(
-                    I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                    Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                 call->deopt_id(),
                 call->env(),
                 call);
   // Type check right.
   AddCheckClass(right,
-                ICData::ZoneHandle(I,
+                ICData::ZoneHandle(Z,
                     call->ic_data()->AsUnaryClassChecksForArgNr(1)),
                 call->deopt_id(),
                 call->env(),
                 call);
   // Replace call.
   BinaryInt32x4OpInstr* int32x4_bin_op =
-      new(I) BinaryInt32x4OpInstr(
-          op_kind, new(I) Value(left), new(I) Value(right),
+      new(Z) BinaryInt32x4OpInstr(
+          op_kind, new(Z) Value(left), new(Z) Value(right),
           call->deopt_id());
   ReplaceCall(call, int32x4_bin_op);
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineFloat64x2BinaryOp(InstanceCallInstr* call,
                                                  Token::Kind op_kind) {
   if (!ShouldInlineSimd()) {
     return false;
@@ skipping 10 matching lines @@
                 call);
   // Type check right.
   AddCheckClass(right,
                 ICData::ZoneHandle(
                     call->ic_data()->AsUnaryClassChecksForArgNr(1)),
                 call->deopt_id(),
                 call->env(),
                 call);
   // Replace call.
   BinaryFloat64x2OpInstr* float64x2_bin_op =
-      new(I) BinaryFloat64x2OpInstr(
-          op_kind, new(I) Value(left), new(I) Value(right),
+      new(Z) BinaryFloat64x2OpInstr(
+          op_kind, new(Z) Value(left), new(Z) Value(right),
           call->deopt_id());
   ReplaceCall(call, float64x2_bin_op);
   return true;
 }
 
 
 // Only unique implicit instance getters can be currently handled.
 bool FlowGraphOptimizer::TryInlineInstanceGetter(InstanceCallInstr* call) {
   ASSERT(call->HasICData());
   const ICData& ic_data = *call->ic_data();
   if (ic_data.NumberOfUsedChecks() == 0) {
     // No type feedback collected.
     return false;
   }
 
   if (!ic_data.HasOneTarget()) {
     // Polymorphic sites are inlined like normal methods by conventional
     // inlining in FlowGraphInliner.
     return false;
   }
 
-  const Function& target = Function::Handle(I, ic_data.GetTargetAt(0));
+  const Function& target = Function::Handle(Z, ic_data.GetTargetAt(0));
   if (target.kind() != RawFunction::kImplicitGetter) {
     // Non-implicit getters are inlined like normal methods by conventional
     // inlining in FlowGraphInliner.
     return false;
   }
   InlineImplicitInstanceGetter(call);
   return true;
 }
 
 
 bool FlowGraphOptimizer::TryReplaceInstanceCallWithInline(
     InstanceCallInstr* call) {
-  Function& target = Function::Handle(I);
+  Function& target = Function::Handle(Z);
   GrowableArray<intptr_t> class_ids;
   call->ic_data()->GetCheckAt(0, &class_ids, &target);
   const intptr_t receiver_cid = class_ids[0];
 
   TargetEntryInstr* entry;
   Definition* last;
   if (!TryInlineRecognizedMethod(receiver_cid,
                                  target,
                                  call,
                                  call->ArgumentAt(0),
@@ skipping 29 matching lines @@
 
 // Returns the LoadIndexedInstr.
 Definition* FlowGraphOptimizer::PrepareInlineStringIndexOp(
     Instruction* call,
     intptr_t cid,
     Definition* str,
     Definition* index,
     Instruction* cursor) {
 
   cursor = flow_graph()->AppendTo(cursor,
-                                  new(I) CheckSmiInstr(
-                                      new(I) Value(index),
+                                  new(Z) CheckSmiInstr(
+                                      new(Z) Value(index),
                                       call->deopt_id(),
                                       call->token_pos()),
                                   call->env(),
                                   FlowGraph::kEffect);
 
   // Load the length of the string.
   // Treat length loads as mutable (i.e. affected by side effects) to avoid
   // hoisting them since we can't hoist the preceding class-check. This
   // is because of externalization of strings that affects their class-id.
-  LoadFieldInstr* length = new(I) LoadFieldInstr(
-      new(I) Value(str),
+  LoadFieldInstr* length = new(Z) LoadFieldInstr(
+      new(Z) Value(str),
       String::length_offset(),
-      Type::ZoneHandle(I, Type::SmiType()),
+      Type::ZoneHandle(Z, Type::SmiType()),
       str->token_pos());
   length->set_result_cid(kSmiCid);
   length->set_recognized_kind(MethodRecognizer::kStringBaseLength);
 
   cursor = flow_graph()->AppendTo(cursor, length, NULL, FlowGraph::kValue);
   // Bounds check.
   cursor = flow_graph()->AppendTo(cursor,
-                                   new(I) CheckArrayBoundInstr(
-                                       new(I) Value(length),
-                                       new(I) Value(index),
+                                   new(Z) CheckArrayBoundInstr(
+                                       new(Z) Value(length),
+                                       new(Z) Value(index),
                                        call->deopt_id()),
                                    call->env(),
                                    FlowGraph::kEffect);
 
-  LoadIndexedInstr* load_indexed = new(I) LoadIndexedInstr(
-      new(I) Value(str),
-      new(I) Value(index),
+  LoadIndexedInstr* load_indexed = new(Z) LoadIndexedInstr(
+      new(Z) Value(str),
+      new(Z) Value(index),
       Instance::ElementSizeFor(cid),
       cid,
       Isolate::kNoDeoptId,
       call->token_pos());
 
   cursor = flow_graph()->AppendTo(cursor,
                                   load_indexed,
                                   NULL,
                                   FlowGraph::kValue);
   ASSERT(cursor == load_indexed);
   return load_indexed;
 }
 
 
 bool FlowGraphOptimizer::InlineStringCodeUnitAt(
     Instruction* call,
     intptr_t cid,
     TargetEntryInstr** entry,
     Definition** last) {
   // TODO(johnmccutchan): Handle external strings in PrepareInlineStringIndexOp.
   if (RawObject::IsExternalStringClassId(cid)) {
     return false;
   }
 
   Definition* str = call->ArgumentAt(0);
   Definition* index = call->ArgumentAt(1);
 
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
 
   *last = PrepareInlineStringIndexOp(call, cid, str, index, *entry);
 
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineStringBaseCharAt(
     Instruction* call,
     intptr_t cid,
     TargetEntryInstr** entry,
     Definition** last) {
   // TODO(johnmccutchan): Handle external strings in PrepareInlineStringIndexOp.
   if (RawObject::IsExternalStringClassId(cid) || cid != kOneByteStringCid) {
     return false;
   }
   Definition* str = call->ArgumentAt(0);
   Definition* index = call->ArgumentAt(1);
 
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
 
   *last = PrepareInlineStringIndexOp(call, cid, str, index, *entry);
 
-  StringFromCharCodeInstr* char_at = new(I) StringFromCharCodeInstr(
-      new(I) Value(*last), cid);
+  StringFromCharCodeInstr* char_at = new(Z) StringFromCharCodeInstr(
+      new(Z) Value(*last), cid);
 
   flow_graph()->AppendTo(*last, char_at, NULL, FlowGraph::kValue);
   *last = char_at;
 
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineDoubleOp(
     Token::Kind op_kind,
     Instruction* call,
     TargetEntryInstr** entry,
     Definition** last) {
   Definition* left = call->ArgumentAt(0);
   Definition* right = call->ArgumentAt(1);
 
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
   // Arguments are checked. No need for class check.
   BinaryDoubleOpInstr* double_bin_op =
-      new(I) BinaryDoubleOpInstr(op_kind,
-                                 new(I) Value(left),
-                                 new(I) Value(right),
+      new(Z) BinaryDoubleOpInstr(op_kind,
+                                 new(Z) Value(left),
+                                 new(Z) Value(right),
                                  call->deopt_id(), call->token_pos());
   flow_graph()->AppendTo(*entry, double_bin_op, call->env(), FlowGraph::kValue);
   *last = double_bin_op;
 
   return true;
 }
 
 
 void FlowGraphOptimizer::ReplaceWithMathCFunction(
     InstanceCallInstr* call,
     MethodRecognizer::Kind recognized_kind) {
   AddReceiverCheck(call);
   ZoneGrowableArray<Value*>* args =
-      new(I) ZoneGrowableArray<Value*>(call->ArgumentCount());
+      new(Z) ZoneGrowableArray<Value*>(call->ArgumentCount());
   for (intptr_t i = 0; i < call->ArgumentCount(); i++) {
-    args->Add(new(I) Value(call->ArgumentAt(i)));
+    args->Add(new(Z) Value(call->ArgumentAt(i)));
   }
   InvokeMathCFunctionInstr* invoke =
-      new(I) InvokeMathCFunctionInstr(args,
+      new(Z) InvokeMathCFunctionInstr(args,
                                       call->deopt_id(),
                                       recognized_kind,
                                       call->token_pos());
   ReplaceCall(call, invoke);
 }
 
 
 static bool IsSupportedByteArrayViewCid(intptr_t cid) {
   switch (cid) {
     case kTypedDataInt8ArrayCid:
@@ skipping 18 matching lines @@
 
 // Inline only simple, frequently called core library methods.
 bool FlowGraphOptimizer::TryInlineInstanceMethod(InstanceCallInstr* call) {
   ASSERT(call->HasICData());
   const ICData& ic_data = *call->ic_data();
   if ((ic_data.NumberOfUsedChecks() == 0) || !ic_data.HasOneTarget()) {
     // No type feedback collected or multiple targets found.
     return false;
   }
 
-  Function& target = Function::Handle(I);
+  Function& target = Function::Handle(Z);
   GrowableArray<intptr_t> class_ids;
   ic_data.GetCheckAt(0, &class_ids, &target);
   MethodRecognizer::Kind recognized_kind =
       MethodRecognizer::RecognizeKind(target);
 
   if ((recognized_kind == MethodRecognizer::kGrowableArraySetData) &&
       (ic_data.NumberOfChecks() == 1) &&
       (class_ids[0] == kGrowableObjectArrayCid)) {
     // This is an internal method, no need to check argument types.
     Definition* array = call->ArgumentAt(0);
     Definition* value = call->ArgumentAt(1);
-    StoreInstanceFieldInstr* store = new(I) StoreInstanceFieldInstr(
+    StoreInstanceFieldInstr* store = new(Z) StoreInstanceFieldInstr(
         GrowableObjectArray::data_offset(),
-        new(I) Value(array),
-        new(I) Value(value),
+        new(Z) Value(array),
+        new(Z) Value(value),
         kEmitStoreBarrier,
         call->token_pos());
     ReplaceCall(call, store);
     return true;
   }
 
   if ((recognized_kind == MethodRecognizer::kGrowableArraySetLength) &&
       (ic_data.NumberOfChecks() == 1) &&
       (class_ids[0] == kGrowableObjectArrayCid)) {
     // This is an internal method, no need to check argument types nor
     // range.
     Definition* array = call->ArgumentAt(0);
     Definition* value = call->ArgumentAt(1);
-    StoreInstanceFieldInstr* store = new(I) StoreInstanceFieldInstr(
+    StoreInstanceFieldInstr* store = new(Z) StoreInstanceFieldInstr(
         GrowableObjectArray::length_offset(),
-        new(I) Value(array),
-        new(I) Value(value),
+        new(Z) Value(array),
+        new(Z) Value(value),
         kNoStoreBarrier,
         call->token_pos());
     ReplaceCall(call, store);
     return true;
   }
 
   if (((recognized_kind == MethodRecognizer::kStringBaseCodeUnitAt) ||
        (recognized_kind == MethodRecognizer::kStringBaseCharAt)) &&
       (ic_data.NumberOfChecks() == 1) &&
       ((class_ids[0] == kOneByteStringCid) ||
        (class_ids[0] == kTwoByteStringCid))) {
     return TryReplaceInstanceCallWithInline(call);
   }
 
   if ((class_ids[0] == kOneByteStringCid) && (ic_data.NumberOfChecks() == 1)) {
     if (recognized_kind == MethodRecognizer::kOneByteStringSetAt) {
       // This is an internal method, no need to check argument types nor
       // range.
       Definition* str = call->ArgumentAt(0);
       Definition* index = call->ArgumentAt(1);
       Definition* value = call->ArgumentAt(2);
-      StoreIndexedInstr* store_op = new(I) StoreIndexedInstr(
-          new(I) Value(str),
-          new(I) Value(index),
-          new(I) Value(value),
+      StoreIndexedInstr* store_op = new(Z) StoreIndexedInstr(
+          new(Z) Value(str),
+          new(Z) Value(index),
+          new(Z) Value(value),
           kNoStoreBarrier,
           1,  // Index scale
           kOneByteStringCid,
           call->deopt_id(),
           call->token_pos());
       ReplaceCall(call, store_op);
       return true;
     }
     return false;
   }
 
   if (CanUnboxDouble() &&
       (recognized_kind == MethodRecognizer::kIntegerToDouble) &&
       (ic_data.NumberOfChecks() == 1)) {
     if (class_ids[0] == kSmiCid) {
       AddReceiverCheck(call);
       ReplaceCall(call,
-                  new(I) SmiToDoubleInstr(
-                      new(I) Value(call->ArgumentAt(0)),
+                  new(Z) SmiToDoubleInstr(
+                      new(Z) Value(call->ArgumentAt(0)),
                       call->token_pos()));
       return true;
     } else if ((class_ids[0] == kMintCid) && CanConvertUnboxedMintToDouble()) {
       AddReceiverCheck(call);
       ReplaceCall(call,
-                  new(I) MintToDoubleInstr(new(I) Value(call->ArgumentAt(0)),
+                  new(Z) MintToDoubleInstr(new(Z) Value(call->ArgumentAt(0)),
                                            call->deopt_id()));
       return true;
     }
   }
 
   if (class_ids[0] == kDoubleCid) {
     if (!CanUnboxDouble()) {
       return false;
     }
     switch (recognized_kind) {
       case MethodRecognizer::kDoubleToInteger: {
         AddReceiverCheck(call);
         ASSERT(call->HasICData());
         const ICData& ic_data = *call->ic_data();
         Definition* input = call->ArgumentAt(0);
         Definition* d2i_instr = NULL;
         if (ic_data.HasDeoptReason(ICData::kDeoptDoubleToSmi)) {
           // Do not repeatedly deoptimize because result didn't fit into Smi.
-          d2i_instr =  new(I) DoubleToIntegerInstr(
-              new(I) Value(input), call);
+          d2i_instr =  new(Z) DoubleToIntegerInstr(
+              new(Z) Value(input), call);
         } else {
           // Optimistically assume result fits into Smi.
-          d2i_instr = new(I) DoubleToSmiInstr(
-              new(I) Value(input), call->deopt_id());
+          d2i_instr = new(Z) DoubleToSmiInstr(
+              new(Z) Value(input), call->deopt_id());
         }
         ReplaceCall(call, d2i_instr);
         return true;
       }
       case MethodRecognizer::kDoubleMod:
       case MethodRecognizer::kDoubleRound:
         ReplaceWithMathCFunction(call, recognized_kind);
         return true;
       case MethodRecognizer::kDoubleTruncate:
       case MethodRecognizer::kDoubleFloor:
       case MethodRecognizer::kDoubleCeil:
         if (!TargetCPUFeatures::double_truncate_round_supported()) {
           ReplaceWithMathCFunction(call, recognized_kind);
         } else {
           AddReceiverCheck(call);
           DoubleToDoubleInstr* d2d_instr =
-              new(I) DoubleToDoubleInstr(new(I) Value(call->ArgumentAt(0)),
+              new(Z) DoubleToDoubleInstr(new(Z) Value(call->ArgumentAt(0)),
                                          recognized_kind, call->deopt_id());
           ReplaceCall(call, d2d_instr);
         }
         return true;
       case MethodRecognizer::kDoubleAdd:
       case MethodRecognizer::kDoubleSub:
       case MethodRecognizer::kDoubleMul:
       case MethodRecognizer::kDoubleDiv:
         return TryReplaceInstanceCallWithInline(call);
       default:
@@ skipping 102 matching lines @@
       ASSERT(int32_mask->IsConstant());
       const Integer& mask_literal = Integer::Cast(
           int32_mask->AsConstant()->value());
       const int64_t mask_value = mask_literal.AsInt64Value();
       ASSERT(mask_value >= 0);
       if (mask_value > Smi::kMaxValue) {
         // The result will not be Smi.
         return false;
       }
       BinarySmiOpInstr* left_shift =
-          new(I) BinarySmiOpInstr(Token::kSHL,
-                                  new(I) Value(value),
-                                  new(I) Value(count),
+          new(Z) BinarySmiOpInstr(Token::kSHL,
+                                  new(Z) Value(value),
+                                  new(Z) Value(count),
                                   call->deopt_id());
       left_shift->mark_truncating();
       if ((kBitsPerWord == 32) && (mask_value == 0xffffffffLL)) {
         // No BIT_AND operation needed.
         ReplaceCall(call, left_shift);
       } else {
         InsertBefore(call, left_shift, call->env(), FlowGraph::kValue);
         BinarySmiOpInstr* bit_and =
-            new(I) BinarySmiOpInstr(Token::kBIT_AND,
-                                    new(I) Value(left_shift),
-                                    new(I) Value(int32_mask),
+            new(Z) BinarySmiOpInstr(Token::kBIT_AND,
+                                    new(Z) Value(left_shift),
+                                    new(Z) Value(int32_mask),
                                     call->deopt_id());
         ReplaceCall(call, bit_and);
       }
       return true;
     }
 
     if (HasTwoMintOrSmi(ic_data) &&
-        HasOnlyOneSmi(ICData::Handle(I,
+        HasOnlyOneSmi(ICData::Handle(Z,
                                      ic_data.AsUnaryClassChecksForArgNr(1)))) {
       if (!FlowGraphCompiler::SupportsUnboxedMints() ||
           ic_data.HasDeoptReason(ICData::kDeoptBinaryMintOp)) {
         return false;
       }
       ShiftMintOpInstr* left_shift =
-          new(I) ShiftMintOpInstr(Token::kSHL,
-                                  new(I) Value(value),
-                                  new(I) Value(count),
+          new(Z) ShiftMintOpInstr(Token::kSHL,
+                                  new(Z) Value(value),
+                                  new(Z) Value(count),
                                   call->deopt_id());
       InsertBefore(call, left_shift, call->env(), FlowGraph::kValue);
       BinaryMintOpInstr* bit_and =
-          new(I) BinaryMintOpInstr(Token::kBIT_AND,
-                                   new(I) Value(left_shift),
-                                   new(I) Value(int32_mask),
+          new(Z) BinaryMintOpInstr(Token::kBIT_AND,
+                                   new(Z) Value(left_shift),
+                                   new(Z) Value(int32_mask),
                                    call->deopt_id());
       ReplaceCall(call, bit_and);
       return true;
     }
   }
   return false;
 }
 
 
 bool FlowGraphOptimizer::TryInlineFloat32x4Constructor(
     StaticCallInstr* call,
     MethodRecognizer::Kind recognized_kind) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   if (recognized_kind == MethodRecognizer::kFloat32x4Zero) {
-    Float32x4ZeroInstr* zero = new(I) Float32x4ZeroInstr();
+    Float32x4ZeroInstr* zero = new(Z) Float32x4ZeroInstr();
     ReplaceCall(call, zero);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat32x4Splat) {
     Float32x4SplatInstr* splat =
-        new(I) Float32x4SplatInstr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Float32x4SplatInstr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, splat);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat32x4Constructor) {
     Float32x4ConstructorInstr* con =
-        new(I) Float32x4ConstructorInstr(
-            new(I) Value(call->ArgumentAt(1)),
-            new(I) Value(call->ArgumentAt(2)),
-            new(I) Value(call->ArgumentAt(3)),
-            new(I) Value(call->ArgumentAt(4)),
+        new(Z) Float32x4ConstructorInstr(
+            new(Z) Value(call->ArgumentAt(1)),
+            new(Z) Value(call->ArgumentAt(2)),
+            new(Z) Value(call->ArgumentAt(3)),
+            new(Z) Value(call->ArgumentAt(4)),
             call->deopt_id());
     ReplaceCall(call, con);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat32x4FromInt32x4Bits) {
     Int32x4ToFloat32x4Instr* cast =
-        new(I) Int32x4ToFloat32x4Instr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Int32x4ToFloat32x4Instr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, cast);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat32x4FromFloat64x2) {
     Float64x2ToFloat32x4Instr* cast =
-        new(I) Float64x2ToFloat32x4Instr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Float64x2ToFloat32x4Instr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, cast);
     return true;
   }
   return false;
 }
 
 
 bool FlowGraphOptimizer::TryInlineFloat64x2Constructor(
     StaticCallInstr* call,
     MethodRecognizer::Kind recognized_kind) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   if (recognized_kind == MethodRecognizer::kFloat64x2Zero) {
-    Float64x2ZeroInstr* zero = new(I) Float64x2ZeroInstr();
+    Float64x2ZeroInstr* zero = new(Z) Float64x2ZeroInstr();
     ReplaceCall(call, zero);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat64x2Splat) {
     Float64x2SplatInstr* splat =
-        new(I) Float64x2SplatInstr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Float64x2SplatInstr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, splat);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat64x2Constructor) {
     Float64x2ConstructorInstr* con =
-        new(I) Float64x2ConstructorInstr(
-            new(I) Value(call->ArgumentAt(1)),
-            new(I) Value(call->ArgumentAt(2)),
+        new(Z) Float64x2ConstructorInstr(
+            new(Z) Value(call->ArgumentAt(1)),
+            new(Z) Value(call->ArgumentAt(2)),
             call->deopt_id());
     ReplaceCall(call, con);
     return true;
   } else if (recognized_kind == MethodRecognizer::kFloat64x2FromFloat32x4) {
     Float32x4ToFloat64x2Instr* cast =
-        new(I) Float32x4ToFloat64x2Instr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Float32x4ToFloat64x2Instr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, cast);
     return true;
   }
   return false;
 }
 
 
 bool FlowGraphOptimizer::TryInlineInt32x4Constructor(
     StaticCallInstr* call,
     MethodRecognizer::Kind recognized_kind) {
   if (!ShouldInlineSimd()) {
     return false;
   }
   if (recognized_kind == MethodRecognizer::kInt32x4BoolConstructor) {
     Int32x4BoolConstructorInstr* con =
-        new(I) Int32x4BoolConstructorInstr(
-            new(I) Value(call->ArgumentAt(1)),
-            new(I) Value(call->ArgumentAt(2)),
-            new(I) Value(call->ArgumentAt(3)),
-            new(I) Value(call->ArgumentAt(4)),
+        new(Z) Int32x4BoolConstructorInstr(
+            new(Z) Value(call->ArgumentAt(1)),
+            new(Z) Value(call->ArgumentAt(2)),
+            new(Z) Value(call->ArgumentAt(3)),
+            new(Z) Value(call->ArgumentAt(4)),
             call->deopt_id());
     ReplaceCall(call, con);
     return true;
   } else if (recognized_kind == MethodRecognizer::kInt32x4FromFloat32x4Bits) {
     Float32x4ToInt32x4Instr* cast =
-        new(I) Float32x4ToInt32x4Instr(
-            new(I) Value(call->ArgumentAt(1)), call->deopt_id());
+        new(Z) Float32x4ToInt32x4Instr(
+            new(Z) Value(call->ArgumentAt(1)), call->deopt_id());
     ReplaceCall(call, cast);
     return true;
   } else if (recognized_kind == MethodRecognizer::kInt32x4Constructor) {
     Int32x4ConstructorInstr* con =
-        new(I) Int32x4ConstructorInstr(
-            new(I) Value(call->ArgumentAt(1)),
-            new(I) Value(call->ArgumentAt(2)),
-            new(I) Value(call->ArgumentAt(3)),
-            new(I) Value(call->ArgumentAt(4)),
+        new(Z) Int32x4ConstructorInstr(
+            new(Z) Value(call->ArgumentAt(1)),
+            new(Z) Value(call->ArgumentAt(2)),
+            new(Z) Value(call->ArgumentAt(3)),
+            new(Z) Value(call->ArgumentAt(4)),
             call->deopt_id());
     ReplaceCall(call, con);
     return true;
   }
   return false;
 }
 
 
 bool FlowGraphOptimizer::TryInlineFloat32x4Method(
     InstanceCallInstr* call,
@@ skipping 16 matching lines @@
     case MethodRecognizer::kFloat32x4GreaterThan:
     case MethodRecognizer::kFloat32x4GreaterThanOrEqual:
     case MethodRecognizer::kFloat32x4LessThan:
     case MethodRecognizer::kFloat32x4LessThanOrEqual:
     case MethodRecognizer::kFloat32x4NotEqual: {
       Definition* left = call->ArgumentAt(0);
       Definition* right = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       // Replace call.
       Float32x4ComparisonInstr* cmp =
-          new(I) Float32x4ComparisonInstr(recognized_kind,
-                                          new(I) Value(left),
-                                          new(I) Value(right),
+          new(Z) Float32x4ComparisonInstr(recognized_kind,
+                                          new(Z) Value(left),
+                                          new(Z) Value(right),
                                           call->deopt_id());
       ReplaceCall(call, cmp);
       return true;
     }
     case MethodRecognizer::kFloat32x4Min:
     case MethodRecognizer::kFloat32x4Max: {
       Definition* left = call->ArgumentAt(0);
       Definition* right = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       Float32x4MinMaxInstr* minmax =
-          new(I) Float32x4MinMaxInstr(
+          new(Z) Float32x4MinMaxInstr(
               recognized_kind,
-              new(I) Value(left),
-              new(I) Value(right),
+              new(Z) Value(left),
+              new(Z) Value(right),
               call->deopt_id());
       ReplaceCall(call, minmax);
       return true;
     }
     case MethodRecognizer::kFloat32x4Scale: {
       Definition* left = call->ArgumentAt(0);
       Definition* right = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       // Left and right values are swapped when handed to the instruction,
       // this is done so that the double value is loaded into the output
       // register and can be destroyed.
       Float32x4ScaleInstr* scale =
-          new(I) Float32x4ScaleInstr(recognized_kind,
-                                     new(I) Value(right),
-                                     new(I) Value(left),
+          new(Z) Float32x4ScaleInstr(recognized_kind,
+                                     new(Z) Value(right),
+                                     new(Z) Value(left),
                                      call->deopt_id());
       ReplaceCall(call, scale);
       return true;
     }
     case MethodRecognizer::kFloat32x4Sqrt:
     case MethodRecognizer::kFloat32x4ReciprocalSqrt:
     case MethodRecognizer::kFloat32x4Reciprocal: {
       Definition* left = call->ArgumentAt(0);
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       Float32x4SqrtInstr* sqrt =
-          new(I) Float32x4SqrtInstr(recognized_kind,
-                                    new(I) Value(left),
+          new(Z) Float32x4SqrtInstr(recognized_kind,
+                                    new(Z) Value(left),
                                     call->deopt_id());
       ReplaceCall(call, sqrt);
       return true;
     }
     case MethodRecognizer::kFloat32x4WithX:
     case MethodRecognizer::kFloat32x4WithY:
     case MethodRecognizer::kFloat32x4WithZ:
     case MethodRecognizer::kFloat32x4WithW: {
       Definition* left = call->ArgumentAt(0);
       Definition* right = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
-      Float32x4WithInstr* with = new(I) Float32x4WithInstr(recognized_kind,
-                                                           new(I) Value(left),
-                                                           new(I) Value(right),
+      Float32x4WithInstr* with = new(Z) Float32x4WithInstr(recognized_kind,
+                                                           new(Z) Value(left),
+                                                           new(Z) Value(right),
                                                            call->deopt_id());
       ReplaceCall(call, with);
       return true;
     }
     case MethodRecognizer::kFloat32x4Absolute:
     case MethodRecognizer::kFloat32x4Negate: {
       Definition* left = call->ArgumentAt(0);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       Float32x4ZeroArgInstr* zeroArg =
-          new(I) Float32x4ZeroArgInstr(
-              recognized_kind, new(I) Value(left), call->deopt_id());
+          new(Z) Float32x4ZeroArgInstr(
+              recognized_kind, new(Z) Value(left), call->deopt_id());
       ReplaceCall(call, zeroArg);
       return true;
     }
     case MethodRecognizer::kFloat32x4Clamp: {
       Definition* left = call->ArgumentAt(0);
       Definition* lower = call->ArgumentAt(1);
       Definition* upper = call->ArgumentAt(2);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
-      Float32x4ClampInstr* clamp = new(I) Float32x4ClampInstr(
-          new(I) Value(left),
-          new(I) Value(lower),
-          new(I) Value(upper),
+      Float32x4ClampInstr* clamp = new(Z) Float32x4ClampInstr(
+          new(Z) Value(left),
+          new(Z) Value(lower),
+          new(Z) Value(upper),
           call->deopt_id());
       ReplaceCall(call, clamp);
       return true;
     }
     case MethodRecognizer::kFloat32x4ShuffleMix:
     case MethodRecognizer::kFloat32x4Shuffle: {
       return InlineFloat32x4Getter(call, recognized_kind);
     }
     default:
       return false;
@@ skipping 15 matching lines @@
       ASSERT(call->ic_data()->HasOneTarget());
       return InlineFloat64x2Getter(call, recognized_kind);
     case MethodRecognizer::kFloat64x2Negate:
     case MethodRecognizer::kFloat64x2Abs:
     case MethodRecognizer::kFloat64x2Sqrt:
     case MethodRecognizer::kFloat64x2GetSignMask: {
       Definition* left = call->ArgumentAt(0);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       Float64x2ZeroArgInstr* zeroArg =
-          new(I) Float64x2ZeroArgInstr(
-              recognized_kind, new(I) Value(left), call->deopt_id());
+          new(Z) Float64x2ZeroArgInstr(
+              recognized_kind, new(Z) Value(left), call->deopt_id());
       ReplaceCall(call, zeroArg);
       return true;
     }
     case MethodRecognizer::kFloat64x2Scale:
     case MethodRecognizer::kFloat64x2WithX:
     case MethodRecognizer::kFloat64x2WithY:
     case MethodRecognizer::kFloat64x2Min:
     case MethodRecognizer::kFloat64x2Max: {
       Definition* left = call->ArgumentAt(0);
       Definition* right = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
       Float64x2OneArgInstr* zeroArg =
-          new(I) Float64x2OneArgInstr(recognized_kind,
-                                      new(I) Value(left),
-                                      new(I) Value(right),
+          new(Z) Float64x2OneArgInstr(recognized_kind,
+                                      new(Z) Value(left),
+                                      new(Z) Value(right),
                                       call->deopt_id());
       ReplaceCall(call, zeroArg);
       return true;
     }
     default:
       return false;
   }
 }
 
 
@@ skipping 16 matching lines @@
       ASSERT(call->ic_data()->HasOneTarget());
       return InlineInt32x4Getter(call, recognized_kind);
 
     case MethodRecognizer::kInt32x4Select: {
       Definition* mask = call->ArgumentAt(0);
       Definition* trueValue = call->ArgumentAt(1);
       Definition* falseValue = call->ArgumentAt(2);
       // Type check left.
       AddCheckClass(mask,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
-      Int32x4SelectInstr* select = new(I) Int32x4SelectInstr(
-          new(I) Value(mask),
-          new(I) Value(trueValue),
-          new(I) Value(falseValue),
+      Int32x4SelectInstr* select = new(Z) Int32x4SelectInstr(
+          new(Z) Value(mask),
+          new(Z) Value(trueValue),
+          new(Z) Value(falseValue),
           call->deopt_id());
       ReplaceCall(call, select);
       return true;
     }
     case MethodRecognizer::kInt32x4WithFlagX:
     case MethodRecognizer::kInt32x4WithFlagY:
     case MethodRecognizer::kInt32x4WithFlagZ:
     case MethodRecognizer::kInt32x4WithFlagW: {
       Definition* left = call->ArgumentAt(0);
       Definition* flag = call->ArgumentAt(1);
       // Type check left.
       AddCheckClass(left,
                     ICData::ZoneHandle(
-                        I, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
+                        Z, call->ic_data()->AsUnaryClassChecksForArgNr(0)),
                     call->deopt_id(),
                     call->env(),
                     call);
-      Int32x4SetFlagInstr* setFlag = new(I) Int32x4SetFlagInstr(
+      Int32x4SetFlagInstr* setFlag = new(Z) Int32x4SetFlagInstr(
           recognized_kind,
-          new(I) Value(left),
-          new(I) Value(flag),
+          new(Z) Value(left),
+          new(Z) Value(flag),
           call->deopt_id());
       ReplaceCall(call, setFlag);
       return true;
     }
     default:
       return false;
   }
 }
 
 
 bool FlowGraphOptimizer::InlineByteArrayBaseLoad(Instruction* call,
                                                  Definition* receiver,
                                                  intptr_t array_cid,
                                                  intptr_t view_cid,
                                                  const ICData& ic_data,
                                                  TargetEntryInstr** entry,
                                                  Definition** last) {
   ASSERT(array_cid != kIllegalCid);
   Definition* array = receiver;
   Definition* index = call->ArgumentAt(1);
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
   Instruction* cursor = *entry;
 
   array_cid = PrepareInlineByteArrayBaseOp(call,
                                            array_cid,
                                            view_cid,
                                            &array,
                                            index,
                                            &cursor);
 
   intptr_t deopt_id = Isolate::kNoDeoptId;
   if ((array_cid == kTypedDataInt32ArrayCid) ||
       (array_cid == kTypedDataUint32ArrayCid)) {
     // Deoptimization may be needed if result does not always fit in a Smi.
     deopt_id = (kSmiBits >= 32) ? Isolate::kNoDeoptId : call->deopt_id();
   }
 
-  *last = new(I) LoadIndexedInstr(new(I) Value(array),
-                                  new(I) Value(index),
+  *last = new(Z) LoadIndexedInstr(new(Z) Value(array),
+                                  new(Z) Value(index),
                                   1,
                                   view_cid,
                                   deopt_id,
                                   call->token_pos());
   cursor = flow_graph()->AppendTo(
       cursor,
       *last,
       deopt_id != Isolate::kNoDeoptId ? call->env() : NULL,
       FlowGraph::kValue);
 
   if (view_cid == kTypedDataFloat32ArrayCid) {
-    *last = new(I) FloatToDoubleInstr(new(I) Value(*last), deopt_id);
+    *last = new(Z) FloatToDoubleInstr(new(Z) Value(*last), deopt_id);
     flow_graph()->AppendTo(cursor,
                            *last,
                            deopt_id != Isolate::kNoDeoptId ? call->env() : NULL,
                            FlowGraph::kValue);
   }
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineByteArrayBaseStore(const Function& target,
                                                   Instruction* call,
                                                   Definition* receiver,
                                                   intptr_t array_cid,
                                                   intptr_t view_cid,
                                                   const ICData& ic_data,
                                                   TargetEntryInstr** entry,
                                                   Definition** last) {
   ASSERT(array_cid != kIllegalCid);
   Definition* array = receiver;
   Definition* index = call->ArgumentAt(1);
-  *entry = new(I) TargetEntryInstr(flow_graph()->allocate_block_id(),
+  *entry = new(Z) TargetEntryInstr(flow_graph()->allocate_block_id(),
                                    call->GetBlock()->try_index());
   (*entry)->InheritDeoptTarget(I, call);
   Instruction* cursor = *entry;
 
   array_cid = PrepareInlineByteArrayBaseOp(call,
                                            array_cid,
                                            view_cid,
                                            &array,
                                            index,
                                            &cursor);
 
   // Extract the instance call so we can use the function_name in the stored
   // value check ICData.
   InstanceCallInstr* i_call = NULL;
   if (call->IsPolymorphicInstanceCall()) {
     i_call = call->AsPolymorphicInstanceCall()->instance_call();
   } else {
     ASSERT(call->IsInstanceCall());
     i_call = call->AsInstanceCall();
   }
   ASSERT(i_call != NULL);
-  ICData& value_check = ICData::ZoneHandle(I);
+  ICData& value_check = ICData::ZoneHandle(Z);
   switch (view_cid) {
     case kTypedDataInt8ArrayCid:
     case kTypedDataUint8ArrayCid:
     case kTypedDataUint8ClampedArrayCid:
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kTypedDataInt16ArrayCid:
     case kTypedDataUint16ArrayCid: {
       // Check that value is always smi.
       value_check = ICData::New(flow_graph_->parsed_function()->function(),
@@ skipping 52 matching lines @@
       UNREACHABLE();
   }
 
   Definition* stored_value = call->ArgumentAt(2);
   if (!value_check.IsNull()) {
     AddCheckClass(stored_value, value_check, call->deopt_id(), call->env(),
                   call);
   }
 
   if (view_cid == kTypedDataFloat32ArrayCid) {
-    stored_value = new(I) DoubleToFloatInstr(
-        new(I) Value(stored_value), call->deopt_id());
+    stored_value = new(Z) DoubleToFloatInstr(
+        new(Z) Value(stored_value), call->deopt_id());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     NULL,
                                     FlowGraph::kValue);
   } else if (view_cid == kTypedDataInt32ArrayCid) {
-    stored_value = new(I) UnboxInt32Instr(
+    stored_value = new(Z) UnboxInt32Instr(
         UnboxInt32Instr::kTruncate,
-        new(I) Value(stored_value),
+        new(Z) Value(stored_value),
         call->deopt_id());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     call->env(),
                                     FlowGraph::kValue);
   } else if (view_cid == kTypedDataUint32ArrayCid) {
-    stored_value = new(I) UnboxUint32Instr(
-        new(I) Value(stored_value),
+    stored_value = new(Z) UnboxUint32Instr(
+        new(Z) Value(stored_value),
         call->deopt_id());
     ASSERT(stored_value->AsUnboxInteger()->is_truncating());
     cursor = flow_graph()->AppendTo(cursor,
                                     stored_value,
                                     call->env(),
                                     FlowGraph::kValue);
   }
 
   StoreBarrierType needs_store_barrier = kNoStoreBarrier;
-  *last = new(I) StoreIndexedInstr(new(I) Value(array),
-                                   new(I) Value(index),
-                                   new(I) Value(stored_value),
+  *last = new(Z) StoreIndexedInstr(new(Z) Value(array),
+                                   new(Z) Value(index),
+                                   new(Z) Value(stored_value),
                                    needs_store_barrier,
                                    1,  // Index scale
                                    view_cid,
                                    call->deopt_id(),
                                    call->token_pos());
 
   flow_graph()->AppendTo(cursor,
                          *last,
                          call->deopt_id() != Isolate::kNoDeoptId ?
                             call->env() : NULL,
                          FlowGraph::kEffect);
   return true;
 }
 
 
 
 intptr_t FlowGraphOptimizer::PrepareInlineByteArrayBaseOp(
     Instruction* call,
     intptr_t array_cid,
     intptr_t view_cid,
     Definition** array,
     Definition* byte_index,
     Instruction** cursor) {
   // Insert byte_index smi check.
   *cursor = flow_graph()->AppendTo(*cursor,
-                                   new(I) CheckSmiInstr(
-                                       new(I) Value(byte_index),
+                                   new(Z) CheckSmiInstr(
+                                       new(Z) Value(byte_index),
                                        call->deopt_id(),
                                        call->token_pos()),
                                    call->env(),
                                    FlowGraph::kEffect);
 
   LoadFieldInstr* length =
-      new(I) LoadFieldInstr(
-          new(I) Value(*array),
+      new(Z) LoadFieldInstr(
+          new(Z) Value(*array),
           CheckArrayBoundInstr::LengthOffsetFor(array_cid),
-          Type::ZoneHandle(I, Type::SmiType()),
+          Type::ZoneHandle(Z, Type::SmiType()),
           call->token_pos());
   length->set_is_immutable(true);
   length->set_result_cid(kSmiCid);
   length->set_recognized_kind(
       LoadFieldInstr::RecognizedKindFromArrayCid(array_cid));
   *cursor = flow_graph()->AppendTo(*cursor,
                                    length,
                                    NULL,
                                    FlowGraph::kValue);
 
   intptr_t element_size = Instance::ElementSizeFor(array_cid);
   ConstantInstr* bytes_per_element =
-      flow_graph()->GetConstant(Smi::Handle(I, Smi::New(element_size)));
+      flow_graph()->GetConstant(Smi::Handle(Z, Smi::New(element_size)));
   BinarySmiOpInstr* len_in_bytes =
-      new(I) BinarySmiOpInstr(Token::kMUL,
-                              new(I) Value(length),
-                              new(I) Value(bytes_per_element),
+      new(Z) BinarySmiOpInstr(Token::kMUL,
+                              new(Z) Value(length),
+                              new(Z) Value(bytes_per_element),
                               call->deopt_id());
   *cursor = flow_graph()->AppendTo(*cursor, len_in_bytes, call->env(),
                                    FlowGraph::kValue);
 
   // adjusted_length = len_in_bytes - (element_size - 1).
   Definition* adjusted_length = len_in_bytes;
   intptr_t adjustment = Instance::ElementSizeFor(view_cid) - 1;
   if (adjustment > 0) {
     ConstantInstr* length_adjustment =
-        flow_graph()->GetConstant(Smi::Handle(I, Smi::New(adjustment)));
+        flow_graph()->GetConstant(Smi::Handle(Z, Smi::New(adjustment)));
     adjusted_length =
-        new(I) BinarySmiOpInstr(Token::kSUB,
-                                new(I) Value(len_in_bytes),
-                                new(I) Value(length_adjustment),
+        new(Z) BinarySmiOpInstr(Token::kSUB,
+                                new(Z) Value(len_in_bytes),
+                                new(Z) Value(length_adjustment),
                                 call->deopt_id());
     *cursor = flow_graph()->AppendTo(*cursor, adjusted_length, call->env(),
                                      FlowGraph::kValue);
   }
 
   // Check adjusted_length > 0.
   ConstantInstr* zero =
-      flow_graph()->GetConstant(Smi::Handle(I, Smi::New(0)));
+      flow_graph()->GetConstant(Smi::Handle(Z, Smi::New(0)));
   *cursor = flow_graph()->AppendTo(*cursor,
-                                   new(I) CheckArrayBoundInstr(
-                                       new(I) Value(adjusted_length),
-                                       new(I) Value(zero),
+                                   new(Z) CheckArrayBoundInstr(
+                                       new(Z) Value(adjusted_length),
+                                       new(Z) Value(zero),
                                        call->deopt_id()),
                                    call->env(),
                                    FlowGraph::kEffect);
   // Check 0 <= byte_index < adjusted_length.
   *cursor = flow_graph()->AppendTo(*cursor,
-                                   new(I) CheckArrayBoundInstr(
-                                       new(I) Value(adjusted_length),
-                                       new(I) Value(byte_index),
+                                   new(Z) CheckArrayBoundInstr(
+                                       new(Z) Value(adjusted_length),
+                                       new(Z) Value(byte_index),
                                        call->deopt_id()),
                                    call->env(),
                                    FlowGraph::kEffect);
 
   if (RawObject::IsExternalTypedDataClassId(array_cid)) {
     LoadUntaggedInstr* elements =
-        new(I) LoadUntaggedInstr(new(I) Value(*array),
+        new(Z) LoadUntaggedInstr(new(Z) Value(*array),
                                  ExternalTypedData::data_offset());
     *cursor = flow_graph()->AppendTo(*cursor,
                                      elements,
                                      NULL,
                                      FlowGraph::kValue);
     *array = elements;
   }
   return array_cid;
 }
 
@@ skipping 38 matching lines @@
 // check.
 RawBool* FlowGraphOptimizer::InstanceOfAsBool(
     const ICData& ic_data,
     const AbstractType& type,
     ZoneGrowableArray<intptr_t>* results) const {
   ASSERT(results->is_empty());
   ASSERT(ic_data.NumArgsTested() == 1);  // Unary checks only.
   if (!type.IsInstantiated() || type.IsMalformedOrMalbounded()) {
     return Bool::null();
   }
-  const Class& type_class = Class::Handle(I, type.type_class());
+  const Class& type_class = Class::Handle(Z, type.type_class());
   const intptr_t num_type_args = type_class.NumTypeArguments();
   if (num_type_args > 0) {
     // Only raw types can be directly compared, thus disregarding type
     // arguments.
     const intptr_t num_type_params = type_class.NumTypeParameters();
     const intptr_t from_index = num_type_args - num_type_params;
     const TypeArguments& type_arguments =
-        TypeArguments::Handle(I, type.arguments());
+        TypeArguments::Handle(Z, type.arguments());
     const bool is_raw_type = type_arguments.IsNull() ||
         type_arguments.IsRaw(from_index, num_type_params);
     if (!is_raw_type) {
       // Unknown result.
       return Bool::null();
     }
   }
 
   const ClassTable& class_table = *isolate()->class_table();
-  Bool& prev = Bool::Handle(I);
-  Class& cls = Class::Handle(I);
+  Bool& prev = Bool::Handle(Z);
+  Class& cls = Class::Handle(Z);
 
   bool results_differ = false;
   for (int i = 0; i < ic_data.NumberOfChecks(); i++) {
     cls = class_table.At(ic_data.GetReceiverClassIdAt(i));
     if (cls.NumTypeArguments() > 0) {
       return Bool::null();
     }
     const bool is_subtype = cls.IsSubtypeOf(
-        TypeArguments::Handle(I),
+        TypeArguments::Handle(Z),
         type_class,
-        TypeArguments::Handle(I),
+        TypeArguments::Handle(Z),
         NULL);
     results->Add(cls.id());
     results->Add(is_subtype);
     if (prev.IsNull()) {
       prev = Bool::Get(is_subtype).raw();
     } else {
       if (is_subtype != prev.value()) {
         results_differ = true;
       }
     }
@@ skipping 91 matching lines @@
 void FlowGraphOptimizer::ReplaceWithInstanceOf(InstanceCallInstr* call) {
   ASSERT(Token::IsTypeTestOperator(call->token_kind()));
   Definition* left = call->ArgumentAt(0);
   Definition* instantiator = call->ArgumentAt(1);
   Definition* type_args = call->ArgumentAt(2);
   const AbstractType& type =
       AbstractType::Cast(call->ArgumentAt(3)->AsConstant()->value());
   const bool negate = Bool::Cast(
       call->ArgumentAt(4)->OriginalDefinition()->AsConstant()->value()).value();
   const ICData& unary_checks =
-      ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecks());
+      ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecks());
   if (FLAG_warn_on_javascript_compatibility &&
       !unary_checks.IssuedJSWarning() &&
       (type.IsIntType() || type.IsDoubleType() || !type.IsInstantiated())) {
     // No warning was reported yet for this type check, either because it has
     // not been executed yet, or because no problematic combinations of instance
     // type and test type have been encountered so far. A warning may still be
     // reported, so do not replace the instance call.
     return;
   }
   if (unary_checks.NumberOfChecks() <= FLAG_max_polymorphic_checks) {
     ZoneGrowableArray<intptr_t>* results =
-        new(I) ZoneGrowableArray<intptr_t>(unary_checks.NumberOfChecks() * 2);
+        new(Z) ZoneGrowableArray<intptr_t>(unary_checks.NumberOfChecks() * 2);
     Bool& as_bool =
-        Bool::ZoneHandle(I, InstanceOfAsBool(unary_checks, type, results));
+        Bool::ZoneHandle(Z, InstanceOfAsBool(unary_checks, type, results));
     if (as_bool.IsNull()) {
       if (results->length() == unary_checks.NumberOfChecks() * 2) {
         const bool can_deopt = TryExpandTestCidsResult(results, type);
-        TestCidsInstr* test_cids = new(I) TestCidsInstr(
+        TestCidsInstr* test_cids = new(Z) TestCidsInstr(
             call->token_pos(),
             negate ? Token::kISNOT : Token::kIS,
-            new(I) Value(left),
+            new(Z) Value(left),
             *results,
             can_deopt ? call->deopt_id() : Isolate::kNoDeoptId);
         // Remove type.
         ReplaceCall(call, test_cids);
         return;
       }
     } else {
       // TODO(srdjan): Use TestCidsInstr also for this case.
       // One result only.
       AddReceiverCheck(call);
       if (negate) {
         as_bool = Bool::Get(!as_bool.value()).raw();
       }
       ConstantInstr* bool_const = flow_graph()->GetConstant(as_bool);
       for (intptr_t i = 0; i < call->ArgumentCount(); ++i) {
         PushArgumentInstr* push = call->PushArgumentAt(i);
         push->ReplaceUsesWith(push->value()->definition());
         push->RemoveFromGraph();
       }
       call->ReplaceUsesWith(bool_const);
       ASSERT(current_iterator()->Current() == call);
       current_iterator()->RemoveCurrentFromGraph();
       return;
     }
   }
 
   if (TypeCheckAsClassEquality(type)) {
-    LoadClassIdInstr* left_cid = new(I) LoadClassIdInstr(new(I) Value(left));
+    LoadClassIdInstr* left_cid = new(Z) LoadClassIdInstr(new(Z) Value(left));
     InsertBefore(call,
                  left_cid,
                  NULL,
                  FlowGraph::kValue);
-    const intptr_t type_cid = Class::Handle(I, type.type_class()).id();
+    const intptr_t type_cid = Class::Handle(Z, type.type_class()).id();
     ConstantInstr* cid =
-        flow_graph()->GetConstant(Smi::Handle(I, Smi::New(type_cid)));
+        flow_graph()->GetConstant(Smi::Handle(Z, Smi::New(type_cid)));
 
     StrictCompareInstr* check_cid =
-        new(I) StrictCompareInstr(
+        new(Z) StrictCompareInstr(
             call->token_pos(),
             negate ? Token::kNE_STRICT : Token::kEQ_STRICT,
-            new(I) Value(left_cid),
-            new(I) Value(cid),
+            new(Z) Value(left_cid),
+            new(Z) Value(cid),
             false);  // No number check.
     ReplaceCall(call, check_cid);
     return;
   }
 
   InstanceOfInstr* instance_of =
-      new(I) InstanceOfInstr(call->token_pos(),
-                             new(I) Value(left),
-                             new(I) Value(instantiator),
-                             new(I) Value(type_args),
+      new(Z) InstanceOfInstr(call->token_pos(),
+                             new(Z) Value(left),
+                             new(Z) Value(instantiator),
+                             new(Z) Value(type_args),
                              type,
                              negate,
                              call->deopt_id());
   ReplaceCall(call, instance_of);
 }
 
 
 // TODO(srdjan): Apply optimizations as in ReplaceWithInstanceOf (TestCids).
 void FlowGraphOptimizer::ReplaceWithTypeCast(InstanceCallInstr* call) {
   ASSERT(Token::IsTypeCastOperator(call->token_kind()));
   Definition* left = call->ArgumentAt(0);
   Definition* instantiator = call->ArgumentAt(1);
   Definition* type_args = call->ArgumentAt(2);
   const AbstractType& type =
       AbstractType::Cast(call->ArgumentAt(3)->AsConstant()->value());
   ASSERT(!type.IsMalformedOrMalbounded());
   const ICData& unary_checks =
-      ICData::ZoneHandle(I, call->ic_data()->AsUnaryClassChecks());
+      ICData::ZoneHandle(Z, call->ic_data()->AsUnaryClassChecks());
   if (FLAG_warn_on_javascript_compatibility &&
       !unary_checks.IssuedJSWarning() &&
       (type.IsIntType() || type.IsDoubleType() || !type.IsInstantiated())) {
     // No warning was reported yet for this type check, either because it has
     // not been executed yet, or because no problematic combinations of instance
     // type and test type have been encountered so far. A warning may still be
     // reported, so do not replace the instance call.
     return;
   }
   if (unary_checks.NumberOfChecks() <= FLAG_max_polymorphic_checks) {
     ZoneGrowableArray<intptr_t>* results =
-        new(I) ZoneGrowableArray<intptr_t>(unary_checks.NumberOfChecks() * 2);
-    const Bool& as_bool = Bool::ZoneHandle(I,
+        new(Z) ZoneGrowableArray<intptr_t>(unary_checks.NumberOfChecks() * 2);
+    const Bool& as_bool = Bool::ZoneHandle(Z,
         InstanceOfAsBool(unary_checks, type, results));
     if (as_bool.raw() == Bool::True().raw()) {
       AddReceiverCheck(call);
       // Remove the original push arguments.
       for (intptr_t i = 0; i < call->ArgumentCount(); ++i) {
         PushArgumentInstr* push = call->PushArgumentAt(i);
         push->ReplaceUsesWith(push->value()->definition());
         push->RemoveFromGraph();
       }
       // Remove call, replace it with 'left'.
       call->ReplaceUsesWith(left);
       ASSERT(current_iterator()->Current() == call);
       current_iterator()->RemoveCurrentFromGraph();
       return;
     }
   }
-  const String& dst_name = String::ZoneHandle(I,
+  const String& dst_name = String::ZoneHandle(Z,
       Symbols::New(Exceptions::kCastErrorDstName));
   AssertAssignableInstr* assert_as =
-      new(I) AssertAssignableInstr(call->token_pos(),
-                                   new(I) Value(left),
-                                   new(I) Value(instantiator),
-                                   new(I) Value(type_args),
+      new(Z) AssertAssignableInstr(call->token_pos(),
+                                   new(Z) Value(left),
+                                   new(Z) Value(instantiator),
+                                   new(Z) Value(type_args),
                                    type,
                                    dst_name,
                                    call->deopt_id());
   ReplaceCall(call, assert_as);
 }
 
 
 // Tries to optimize instance call by replacing it with a faster instruction
 // (e.g, binary op, field load, ..).
 void FlowGraphOptimizer::VisitInstanceCall(InstanceCallInstr* instr) {
   if (!instr->HasICData() || (instr->ic_data()->NumberOfUsedChecks() == 0)) {
     return;
   }
 
   const Token::Kind op_kind = instr->token_kind();
   // Type test is special as it always gets converted into inlined code.
   if (Token::IsTypeTestOperator(op_kind)) {
     ReplaceWithInstanceOf(instr);
     return;
   }
 
   if (Token::IsTypeCastOperator(op_kind)) {
     ReplaceWithTypeCast(instr);
     return;
   }
 
   const ICData& unary_checks =
-      ICData::ZoneHandle(I, instr->ic_data()->AsUnaryClassChecks());
+      ICData::ZoneHandle(Z, instr->ic_data()->AsUnaryClassChecks());
 
   const intptr_t max_checks = (op_kind == Token::kEQ)
       ? FLAG_max_equality_polymorphic_checks
       : FLAG_max_polymorphic_checks;
   if ((unary_checks.NumberOfChecks() > max_checks) &&
       InstanceCallNeedsClassCheck(instr, RawFunction::kRegularFunction)) {
     // Too many checks, it will be megamorphic which needs unary checks.
     instr->set_ic_data(&unary_checks);
     return;
   }
@@ skipping 32 matching lines @@
   if (TryInlineInstanceMethod(instr)) {
     return;
   }
 
   bool has_one_target = unary_checks.HasOneTarget();
 
   if (has_one_target) {
     // Check if the single target is a polymorphic target, if it is,
     // we don't have one target.
     const Function& target =
-        Function::Handle(I, unary_checks.GetTargetAt(0));
+        Function::Handle(Z, unary_checks.GetTargetAt(0));
     const bool polymorphic_target = MethodRecognizer::PolymorphicTarget(target);
     has_one_target = !polymorphic_target;
   }
 
   if (has_one_target) {
     RawFunction::Kind function_kind =
-        Function::Handle(I, unary_checks.GetTargetAt(0)).kind();
+        Function::Handle(Z, unary_checks.GetTargetAt(0)).kind();
     if (!InstanceCallNeedsClassCheck(instr, function_kind)) {
       const bool call_with_checks = false;
       PolymorphicInstanceCallInstr* call =
-          new(I) PolymorphicInstanceCallInstr(instr, unary_checks,
+          new(Z) PolymorphicInstanceCallInstr(instr, unary_checks,
                                               call_with_checks);
       instr->ReplaceWith(call, current_iterator());
       return;
     }
   }
 
   if (unary_checks.NumberOfChecks() <= FLAG_max_polymorphic_checks) {
     bool call_with_checks;
     if (has_one_target) {
       // Type propagation has not run yet, we cannot eliminate the check.
       AddReceiverCheck(instr);
       // Call can still deoptimize, do not detach environment from instr.
       call_with_checks = false;
     } else {
       call_with_checks = true;
     }
     PolymorphicInstanceCallInstr* call =
-        new(I) PolymorphicInstanceCallInstr(instr, unary_checks,
+        new(Z) PolymorphicInstanceCallInstr(instr, unary_checks,
                                             call_with_checks);
     instr->ReplaceWith(call, current_iterator());
   }
 }
 
 
 void FlowGraphOptimizer::VisitStaticCall(StaticCallInstr* call) {
   if (!CanUnboxDouble()) {
     return;
   }
   MethodRecognizer::Kind recognized_kind =
       MethodRecognizer::RecognizeKind(call->function());
   MathUnaryInstr::MathUnaryKind unary_kind;
   switch (recognized_kind) {
     case MethodRecognizer::kMathSqrt:
       unary_kind = MathUnaryInstr::kSqrt;
       break;
     case MethodRecognizer::kMathSin:
       unary_kind = MathUnaryInstr::kSin;
       break;
     case MethodRecognizer::kMathCos:
       unary_kind = MathUnaryInstr::kCos;
       break;
     default:
       unary_kind = MathUnaryInstr::kIllegal;
       break;
   }
   if (unary_kind != MathUnaryInstr::kIllegal) {
     MathUnaryInstr* math_unary =
-        new(I) MathUnaryInstr(unary_kind,
-                              new(I) Value(call->ArgumentAt(0)),
+        new(Z) MathUnaryInstr(unary_kind,
+                              new(Z) Value(call->ArgumentAt(0)),
                               call->deopt_id());
     ReplaceCall(call, math_unary);
   } else if ((recognized_kind == MethodRecognizer::kFloat32x4Zero) ||
              (recognized_kind == MethodRecognizer::kFloat32x4Splat) ||
              (recognized_kind == MethodRecognizer::kFloat32x4Constructor) ||
              (recognized_kind == MethodRecognizer::kFloat32x4FromFloat64x2)) {
     TryInlineFloat32x4Constructor(call, recognized_kind);
   } else if ((recognized_kind == MethodRecognizer::kFloat64x2Constructor) ||
              (recognized_kind == MethodRecognizer::kFloat64x2Zero) ||
              (recognized_kind == MethodRecognizer::kFloat64x2Splat) ||
@@ skipping 20 matching lines @@
     // being either doubles or smis.
     if (call->HasICData() && (call->ic_data()->NumberOfChecks() == 1)) {
       const ICData& ic_data = *call->ic_data();
       intptr_t result_cid = kIllegalCid;
       if (ICDataHasReceiverArgumentClassIds(ic_data, kDoubleCid, kDoubleCid)) {
         result_cid = kDoubleCid;
       } else if (ICDataHasReceiverArgumentClassIds(ic_data, kSmiCid, kSmiCid)) {
         result_cid = kSmiCid;
       }
       if (result_cid != kIllegalCid) {
-        MathMinMaxInstr* min_max = new(I) MathMinMaxInstr(
+        MathMinMaxInstr* min_max = new(Z) MathMinMaxInstr(
             recognized_kind,
-            new(I) Value(call->ArgumentAt(0)),
-            new(I) Value(call->ArgumentAt(1)),
+            new(Z) Value(call->ArgumentAt(0)),
+            new(Z) Value(call->ArgumentAt(1)),
             call->deopt_id(),
             result_cid);
         const ICData& unary_checks =
-            ICData::ZoneHandle(I, ic_data.AsUnaryClassChecks());
+            ICData::ZoneHandle(Z, ic_data.AsUnaryClassChecks());
         AddCheckClass(min_max->left()->definition(),
                       unary_checks,
                       call->deopt_id(),
                       call->env(),
                       call);
         AddCheckClass(min_max->right()->definition(),
                       unary_checks,
                       call->deopt_id(),
                       call->env(),
                       call);
         ReplaceCall(call, min_max);
       }
     }
   } else if (recognized_kind == MethodRecognizer::kMathDoublePow) {
     // We know that first argument is double, the second is num.
     // InvokeMathCFunctionInstr requires unboxed doubles. UnboxDouble
     // instructions contain type checks and conversions to double.
     ZoneGrowableArray<Value*>* args =
-        new(I) ZoneGrowableArray<Value*>(call->ArgumentCount());
+        new(Z) ZoneGrowableArray<Value*>(call->ArgumentCount());
     for (intptr_t i = 0; i < call->ArgumentCount(); i++) {
-      args->Add(new(I) Value(call->ArgumentAt(i)));
+      args->Add(new(Z) Value(call->ArgumentAt(i)));
     }
     InvokeMathCFunctionInstr* invoke =
-        new(I) InvokeMathCFunctionInstr(args,
+        new(Z) InvokeMathCFunctionInstr(args,
                                         call->deopt_id(),
                                         recognized_kind,
                                         call->token_pos());
     ReplaceCall(call, invoke);
   } else if (recognized_kind == MethodRecognizer::kDoubleFromInteger) {
     if (call->HasICData() && (call->ic_data()->NumberOfChecks() == 1)) {
       const ICData& ic_data = *call->ic_data();
       if (CanUnboxDouble()) {
         if (ArgIsAlways(kSmiCid, ic_data, 1)) {
           Definition* arg = call->ArgumentAt(1);
           AddCheckSmi(arg, call->deopt_id(), call->env(), call);
           ReplaceCall(call,
-                      new(I) SmiToDoubleInstr(new(I) Value(arg),
+                      new(Z) SmiToDoubleInstr(new(Z) Value(arg),
                                               call->token_pos()));
         } else if (ArgIsAlways(kMintCid, ic_data, 1) &&
                    CanConvertUnboxedMintToDouble()) {
           Definition* arg = call->ArgumentAt(1);
           ReplaceCall(call,
-                      new(I) MintToDoubleInstr(new(I) Value(arg),
+                      new(Z) MintToDoubleInstr(new(Z) Value(arg),
                                                call->deopt_id()));
         }
       }
     }
   } else if (call->function().IsFactory()) {
     const Class& function_class =
-        Class::Handle(I, call->function().Owner());
+        Class::Handle(Z, call->function().Owner());
     if ((function_class.library() == Library::CoreLibrary()) ||
         (function_class.library() == Library::TypedDataLibrary())) {
       intptr_t cid = FactoryRecognizer::ResultCid(call->function());
       switch (cid) {
         case kArrayCid: {
-          Value* type = new(I) Value(call->ArgumentAt(0));
-          Value* num_elements = new(I) Value(call->ArgumentAt(1));
+          Value* type = new(Z) Value(call->ArgumentAt(0));
+          Value* num_elements = new(Z) Value(call->ArgumentAt(1));
           if (num_elements->BindsToConstant() &&
               num_elements->BoundConstant().IsSmi()) {
             intptr_t length = Smi::Cast(num_elements->BoundConstant()).Value();
             if (length >= 0 && length <= Array::kMaxElements) {
               CreateArrayInstr* create_array =
-                  new(I) CreateArrayInstr(
+                  new(Z) CreateArrayInstr(
                       call->token_pos(), type, num_elements);
               ReplaceCall(call, create_array);
             }
           }
         }
         default:
           break;
       }
     }
   }
 }
 
 
 void FlowGraphOptimizer::VisitStoreInstanceField(
     StoreInstanceFieldInstr* instr) {
   if (instr->IsUnboxedStore()) {
     ASSERT(instr->is_potential_unboxed_initialization_);
     // Determine if this field should be unboxed based on the usage of getter
     // and setter functions: The heuristic requires that the setter has a
     // usage count of at least 1/kGetterSetterRatio of the getter usage count.
     // This is to avoid unboxing fields where the setter is never or rarely
     // executed.
-    const Field& field = Field::ZoneHandle(I, instr->field().raw());
-    const String& field_name = String::Handle(I, field.name());
-    const Class& owner = Class::Handle(I, field.owner());
+    const Field& field = Field::ZoneHandle(Z, instr->field().raw());
+    const String& field_name = String::Handle(Z, field.name());
+    const Class& owner = Class::Handle(Z, field.owner());
     const Function& getter =
-        Function::Handle(I, owner.LookupGetterFunction(field_name));
+        Function::Handle(Z, owner.LookupGetterFunction(field_name));
     const Function& setter =
-        Function::Handle(I, owner.LookupSetterFunction(field_name));
+        Function::Handle(Z, owner.LookupSetterFunction(field_name));
     bool result = !getter.IsNull()
                && !setter.IsNull()
                && (setter.usage_counter() > 0)
                && (FLAG_getter_setter_ratio * setter.usage_counter() >=
                    getter.usage_counter());
     if (!result) {
       if (FLAG_trace_optimization) {
         OS::Print("Disabling unboxing of %s\n", field.ToCString());
       }
       field.set_is_unboxing_candidate(false);
       field.DeoptimizeDependentCode();
     } else {
       FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
     }
   }
 }
 
 
 void FlowGraphOptimizer::VisitAllocateContext(AllocateContextInstr* instr) {
   // Replace generic allocation with a sequence of inlined allocation and
   // explicit initalizing stores.
   AllocateUninitializedContextInstr* replacement =
       new AllocateUninitializedContextInstr(instr->token_pos(),
                                             instr->num_context_variables());
   instr->ReplaceWith(replacement, current_iterator());
 
   StoreInstanceFieldInstr* store =
-      new(I) StoreInstanceFieldInstr(Context::parent_offset(),
+      new(Z) StoreInstanceFieldInstr(Context::parent_offset(),
                                      new Value(replacement),
                                      new Value(flow_graph_->constant_null()),
                                      kNoStoreBarrier,
                                      instr->token_pos());
   // Storing into uninitialized memory; remember to prevent dead store
   // elimination and ensure proper GC barrier.
   store->set_is_object_reference_initialization(true);
   flow_graph_->InsertAfter(replacement, store, NULL, FlowGraph::kEffect);
   Definition* cursor = store;
   for (intptr_t i = 0; i < instr->num_context_variables(); ++i) {
     store =
-        new(I) StoreInstanceFieldInstr(Context::variable_offset(i),
+        new(Z) StoreInstanceFieldInstr(Context::variable_offset(i),
                                        new Value(replacement),
                                        new Value(flow_graph_->constant_null()),
                                        kNoStoreBarrier,
                                        instr->token_pos());
     // Storing into uninitialized memory; remember to prevent dead store
     // elimination and ensure proper GC barrier.
     store->set_is_object_reference_initialization(true);
     flow_graph_->InsertAfter(cursor, store, NULL, FlowGraph::kEffect);
     cursor = store;
   }
@@ skipping 22 matching lines @@
   ASSERT(instr->HasICData());
   if (unary_ic_data.NumberOfChecks() == 0) {
     // No type feedback collected.
     return false;
   }
   if (!unary_ic_data.HasOneTarget()) {
     // Polymorphic sites are inlined like normal method calls by conventional
     // inlining.
     return false;
   }
-  Function& target = Function::Handle(I);
+  Function& target = Function::Handle(Z);
   intptr_t class_id;
   unary_ic_data.GetOneClassCheckAt(0, &class_id, &target);
   if (target.kind() != RawFunction::kImplicitSetter) {
     // Non-implicit setter are inlined like normal method calls.
     return false;
   }
   // Inline implicit instance setter.
   const String& field_name =
-      String::Handle(I, Field::NameFromSetter(instr->function_name()));
+      String::Handle(Z, Field::NameFromSetter(instr->function_name()));
   const Field& field =
-      Field::ZoneHandle(I, GetField(class_id, field_name));
+      Field::ZoneHandle(Z, GetField(class_id, field_name));
   ASSERT(!field.IsNull());
 
   if (InstanceCallNeedsClassCheck(instr, RawFunction::kImplicitSetter)) {
     AddReceiverCheck(instr);
   }
   StoreBarrierType needs_store_barrier = kEmitStoreBarrier;
   if (ArgIsAlways(kSmiCid, *instr->ic_data(), 1)) {
     InsertBefore(instr,
-                 new(I) CheckSmiInstr(
-                     new(I) Value(instr->ArgumentAt(1)),
+                 new(Z) CheckSmiInstr(
+                     new(Z) Value(instr->ArgumentAt(1)),
                      instr->deopt_id(),
                      instr->token_pos()),
                  instr->env(),
                  FlowGraph::kEffect);
     needs_store_barrier = kNoStoreBarrier;
   }
 
   if (field.guarded_cid() != kDynamicCid) {
     InsertBefore(instr,
-                 new(I) GuardFieldClassInstr(
-                     new(I) Value(instr->ArgumentAt(1)),
+                 new(Z) GuardFieldClassInstr(
+                     new(Z) Value(instr->ArgumentAt(1)),
                       field,
                       instr->deopt_id()),
                  instr->env(),
                  FlowGraph::kEffect);
   }
 
   if (field.needs_length_check()) {
     InsertBefore(instr,
-                 new(I) GuardFieldLengthInstr(
-                     new(I) Value(instr->ArgumentAt(1)),
+                 new(Z) GuardFieldLengthInstr(
+                     new(Z) Value(instr->ArgumentAt(1)),
                       field,
                       instr->deopt_id()),
                  instr->env(),
                  FlowGraph::kEffect);
   }
 
   // Field guard was detached.
-  StoreInstanceFieldInstr* store = new(I) StoreInstanceFieldInstr(
+  StoreInstanceFieldInstr* store = new(Z) StoreInstanceFieldInstr(
       field,
-      new(I) Value(instr->ArgumentAt(0)),
-      new(I) Value(instr->ArgumentAt(1)),
+      new(Z) Value(instr->ArgumentAt(0)),
+      new(Z) Value(instr->ArgumentAt(1)),
       needs_store_barrier,
       instr->token_pos());
 
   if (store->IsUnboxedStore()) {
     FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
   }
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
@@ skipping 75 matching lines @@
 
   // Step 3. For each candidate transitively collect all other BinarySmiOpInstr
   // and PhiInstr that depend on it and that it depends on and count amount of
   // untagging operations that we save in assumption that this whole graph of
   // values is using kUnboxedInt32 representation instead of kTagged.
   // Convert those graphs that have positive gain to kUnboxedInt32.
 
   // BitVector containing SSA indexes of all processed definitions. Used to skip
   // those candidates that belong to dependency graph of another candidate.
   BitVector* processed =
-      new(I) BitVector(I, flow_graph_->current_ssa_temp_index());
+      new(Z) BitVector(Z, flow_graph_->current_ssa_temp_index());
 
   // Worklist used to collect dependency graph.
   DefinitionWorklist worklist(flow_graph_, candidates.length());
   for (intptr_t i = 0; i < candidates.length(); i++) {
     BinarySmiOpInstr* op = candidates[i];
     if (op->WasEliminated() || processed->Contains(op->ssa_temp_index())) {
       continue;
     }
 
     if (FLAG_trace_smi_widening) {
@@ skipping 103 matching lines @@
 
     if (gain > 0) {
       // We have positive gain from widening. Convert all BinarySmiOpInstr into
       // BinaryInt32OpInstr and set representation of all phis to kUnboxedInt32.
       for (intptr_t j = 0; j < worklist.definitions().length(); j++) {
         Definition* defn = worklist.definitions()[j];
         ASSERT(defn->IsPhi() || defn->IsBinarySmiOp());
 
         if (defn->IsBinarySmiOp()) {
           BinarySmiOpInstr* smi_op = defn->AsBinarySmiOp();
-          BinaryInt32OpInstr* int32_op = new(I) BinaryInt32OpInstr(
+          BinaryInt32OpInstr* int32_op = new(Z) BinaryInt32OpInstr(
             smi_op->op_kind(),
             smi_op->left()->CopyWithType(),
             smi_op->right()->CopyWithType(),
             smi_op->DeoptimizationTarget());
 
           smi_op->ReplaceWith(int32_op, NULL);
         } else if (defn->IsPhi()) {
           defn->AsPhi()->set_representation(kUnboxedInt32);
           ASSERT(defn->Type()->IsInt());
         }
@@ skipping 405 matching lines @@
         *is_store = true;
         break;
       }
 
       default:
         break;
     }
   }
 
   // Create object representing *[*] alias.
-  static Place* CreateAnyInstanceAnyIndexAlias(Isolate* isolate,
+  static Place* CreateAnyInstanceAnyIndexAlias(Zone* zone,
                                                intptr_t id) {
-    return Wrap(isolate, Place(kIndexed, NULL, 0), id);
+    return Wrap(zone, Place(kIndexed, 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
@@ skipping 131 matching lines @@
   }
 
   bool Equals(const Place* other) const {
     return (kind_ == other->kind_) &&
         (representation_ == other->representation_) &&
         (instance_ == other->instance_) &&
         SameField(other);
   }
 
   // Create a zone allocated copy of this place and assign given id to it.
-  static Place* Wrap(Isolate* isolate, const Place& place, intptr_t id);
+  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()));
   }
 
@@ skipping 46 matching lines @@
  public:
   explicit ZonePlace(const Place& place) : place_(place) { }
 
   Place* place() { return &place_; }
 
  private:
   Place place_;
 };
 
 
-Place* Place::Wrap(Isolate* isolate, const Place& place, intptr_t id) {
-  Place* wrapped = (new(isolate) ZonePlace(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
@@ skipping 35 matching lines @@
  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(Isolate* isolate,
+  AliasedSet(Zone* zone,
              DirectChainedHashMap<PointerKeyValueTrait<Place> >* places_map,
              ZoneGrowableArray<Place*>* places,
              PhiPlaceMoves* phi_moves)
-      : isolate_(isolate),
+      : zone_(zone),
         places_map_(places_map),
         places_(*places),
         phi_moves_(phi_moves),
         aliases_(5),
         aliases_map_(),
         representatives_(),
         killed_(),
-        aliased_by_effects_(new(isolate) BitVector(isolate, places->length())) {
-    InsertAlias(Place::CreateAnyInstanceAnyIndexAlias(isolate_,
+        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);
@@ skipping 127 matching lines @@
   }
 
   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(isolate_,
+      canonical = Place::Wrap(zone_,
                               alias,
                               kAnyInstanceAnyIndexAlias + aliases_.length());
       InsertAlias(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(isolate_) BitVector(isolate_, max_place_id());
+      (*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);
@@ skipping 212 matching lines @@
       }
 
       // If the allocation site is marked as aliased conservatively mark
       // any values stored into the object aliased too.
       if (defn->Identity().IsAliased()) {
         MarkStoredValuesEscaping(defn);
       }
     }
   }
 
-  Isolate* isolate_;
+  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_;
@@ skipping 52 matching lines @@
 }
 
 
 // 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) {
-  Isolate* isolate = Isolate::Current();
-  PhiPlaceMoves* phi_moves = new(isolate) PhiPlaceMoves();
+  Thread* thread = Thread::Current();
+  Isolate* isolate = thread->isolate();
+  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) {
         OS::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(isolate, input_place, places->length());
+          result = Place::Wrap(zone, input_place, places->length());
           map->Insert(result);
           places->Add(result);
           if (FLAG_trace_optimization) {
             OS::Print("  adding place %s as %" Pd "\n",
                       result->ToCString(),
                       result->id());
           }
         }
         phi_moves->CreateOutgoingMove(isolate,
                                       block->PredecessorAt(j),
@@ skipping 12 matching lines @@
   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.
-  Isolate* isolate = graph->isolate();
+  Zone* zone = graph->zone();
   ZoneGrowableArray<Place*>* places =
-      new(isolate) ZoneGrowableArray<Place*>(10);
+      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(isolate, place, places->length());
+        result = Place::Wrap(zone, place, places->length());
         map->Insert(result);
         places->Add(result);
 
         if (FLAG_trace_optimization) {
           OS::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(isolate) AliasedSet(isolate, map, places, phi_moves);
+  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(I) BitVector(I, aliased_set_->max_place_id()));
-      kill_.Add(new(I) BitVector(I, aliased_set_->max_place_id()));
-      in_.Add(new(I) BitVector(I, aliased_set_->max_place_id()));
+      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()) {
@@ skipping 206 matching lines @@
           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(I) ZoneGrowableArray<Definition*>(
+            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();
@@ skipping 27 matching lines @@
 
       out->Remove(to);
     }
 
     out->AddAll(forwarded_loads);
   }
 
   // Compute OUT sets by propagating them iteratively until fix point
   // is reached.
   void ComputeOutSets() {
-    BitVector* temp = new(I) BitVector(I, aliased_set_->max_place_id());
+    BitVector* temp = new(Z) BitVector(Z, aliased_set_->max_place_id());
     BitVector* forwarded_loads =
-        new(I) BitVector(I, aliased_set_->max_place_id());
-    BitVector* temp_out = new(I) BitVector(I, aliased_set_->max_place_id());
+        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();
 
@@ skipping 31 matching lines @@
         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(I) BitVector(I, aliased_set_->max_place_id());
+                  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
@@ skipping 32 matching lines @@
           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(I) PhiInstr(block->AsJoinEntry(),
+            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
@@ skipping 53 matching lines @@
       }
     }
     return true;
   }
 
   void MarkLoopInvariantLoads() {
     const ZoneGrowableArray<BlockEntryInstr*>& loop_headers =
         graph_->LoopHeaders();
 
     ZoneGrowableArray<BitVector*>* invariant_loads =
-        new(I) ZoneGrowableArray<BitVector*>(loop_headers.length());
+        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(I) BitVector(I, aliased_set_->max_place_id());
+      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()) {
@@ skipping 35 matching lines @@
         incoming = kDifferentValuesMarker;
       }
     }
 
     if (incoming != kDifferentValuesMarker) {
       ASSERT(incoming != NULL);
       return incoming;
     }
 
     // Incoming values are different. Phi is required to merge.
-    PhiInstr* phi = new(I) PhiInstr(
+    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(I) Value(replacement);
+      Value* input = new(Z) Value(replacement);
       phi->SetInputAt(i, input);
       replacement->AddInputUse(input);
     }
 
     phi->set_ssa_temp_index(graph_->alloc_ssa_temp_index());
     phis_.Add(phi);  // Postpone phi insertion until after load forwarding.
 
     if (FLAG_trace_load_optimization) {
       OS::Print("created pending phi %s for %s at B%" Pd "\n",
                 phi->ToCString(),
@@ skipping 52 matching lines @@
   // 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(I) BitVector(I, graph_->current_ssa_temp_index());
+      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];
 
@@ skipping 102 matching lines @@
   }
 
   // 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(I) BitVector(I, graph_->current_ssa_temp_index());
+      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;
     }
 
@@ skipping 84 matching lines @@
     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(I) ZoneGrowableArray<Definition*>(aliased_set_->max_place_id());
+        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
@@ skipping 85 matching lines @@
       case Instruction::kStoreIndexed:
       case Instruction::kStoreStaticField:
         return true;
       default:
         UNREACHABLE();
         return false;
     }
   }
 
   virtual void ComputeInitialSets() {
-    Isolate* isolate = graph_->isolate();
-    BitVector* all_places = new(isolate) BitVector(isolate,
+    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];
@@ skipping 25 matching lines @@
                     "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(isolate) ZoneGrowableArray<Instruction*>(
+              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;
         }
@@ skipping 1089 matching lines @@
 }
 
 
 // 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(I) ZoneGrowableArray<Value*>(slots.length());
+      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(I) LoadFieldInstr(
-            new(I) Value(alloc),
+        ? new(Z) LoadFieldInstr(
+            new(Z) Value(alloc),
             &Field::Cast(*slots[i]),
-            AbstractType::ZoneHandle(I),
+            AbstractType::ZoneHandle(Z),
             alloc->token_pos())
-        : new(I) LoadFieldInstr(
-            new(I) Value(alloc),
+        : new(Z) LoadFieldInstr(
+            new(Z) Value(alloc),
             Smi::Cast(*slots[i]).Value(),
-            AbstractType::ZoneHandle(I),
+            AbstractType::ZoneHandle(Z),
             alloc->token_pos());
     flow_graph_->InsertBefore(
         load_point, load, NULL, FlowGraph::kValue);
-    values->Add(new(I) Value(load));
+    values->Add(new(Z) Value(load));
   }
 
   MaterializeObjectInstr* mat = NULL;
   if (alloc->IsAllocateObject()) {
-    mat = new(I) MaterializeObjectInstr(
+    mat = new(Z) MaterializeObjectInstr(
         alloc->AsAllocateObject(), slots, values);
   } else {
     ASSERT(alloc->IsAllocateUninitializedContext());
-    mat = new(I) MaterializeObjectInstr(
+    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(I) Value(alloc);
+  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.
@@ skipping 54 matching lines @@
   // 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(I) ZoneGrowableArray<const Object*>(5);
+      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(I, Smi::New(store->offset_in_bytes())));
+        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(I, Smi::New(type_args_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