Introduce nested deoptimization environments.

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index 71c6c31ad2f070f2584d6c781551e7281c022cbb..583858919d4a855f43c83d7728ece5a2181f291f 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -94,8 +94,8 @@ static void ResetUseListsInInstruction(Instruction* instr) {
     use->set_next_use(NULL);
   }
   if (instr->env() != NULL) {
-    for (intptr_t i = 0; i < instr->env()->values().length(); ++i) {
-      Value* use = instr->env()->values()[i];
+    for (Environment::DeepIterator it(instr->env()); !it.Done(); it.Advance()) {
+      Value* use = it.CurrentValue();
       use->set_instruction(NULL);
       use->set_use_index(-1);
       use->set_next_use(NULL);
@@ -109,8 +109,8 @@ bool FlowGraph::ResetUseLists() {
   ResetUseListsInInstruction(graph_entry_->constant_null());
 
   // Reset definitions referenced from the start environment.
-  for (intptr_t i = 0; i < graph_entry_->start_env()->values().length(); ++i) {
-    Value* env_use = graph_entry_->start_env()->values()[i];
+  for (intptr_t i = 0; i < graph_entry_->start_env()->Length(); ++i) {
+    Value* env_use = graph_entry_->start_env()->ValueAt(i);
     ResetUseListsInInstruction(env_use->definition());
   }
 
@@ -140,11 +140,11 @@ static void ValidateUseListsInInstruction(Instruction* instr) {
     ASSERT(use->use_index() == i);
     ASSERT(1 == MembershipCount(use, use->definition()->input_use_list()));
   }
-  Environment* env = instr->env();
-  if (env != NULL) {
-    for (intptr_t i = 0; i < env->values().length(); ++i) {
-      Value* use = env->values()[i];
-      ASSERT(use->use_index() == i);
+  if (instr->env() != NULL) {
+    intptr_t use_index = 0;
+    for (Environment::DeepIterator it(instr->env()); !it.Done(); it.Advance()) {
+      Value* use = it.CurrentValue();
+      ASSERT(use->use_index() == use_index++);
       ASSERT(1 == MembershipCount(use, use->definition()->env_use_list()));
     }
   }
@@ -160,7 +160,8 @@ static void ValidateUseListsInInstruction(Instruction* instr) {
          use != NULL;
          use = use->next_use()) {
       ASSERT(defn == use->definition());
-      ASSERT(use == use->instruction()->env()->values()[use->use_index()]);
+      ASSERT(use ==
+             use->instruction()->env()->ValueAtUseIndex(use->use_index()));
     }
   }
 }
@@ -171,8 +172,8 @@ bool FlowGraph::ValidateUseLists() {
   ValidateUseListsInInstruction(graph_entry_->constant_null());
 
   // Validate definitions referenced from the start environment.
-  for (intptr_t i = 0; i < graph_entry_->start_env()->values().length(); ++i) {
-    Value* env_use = graph_entry_->start_env()->values()[i];
+  for (intptr_t i = 0; i < graph_entry_->start_env()->Length(); ++i) {
+    Value* env_use = graph_entry_->start_env()->ValueAt(i);
     ValidateUseListsInInstruction(env_use->definition());
   }
 
@@ -223,14 +224,15 @@ static void RecordInputUses(Instruction* instr) {
 static void RecordEnvUses(Instruction* instr) {
   ASSERT(instr != NULL);
   if (instr->env() == NULL) return;
-  for (intptr_t i = 0; i < instr->env()->values().length(); ++i) {
-    Value* use = instr->env()->values()[i];
+  intptr_t use_index = 0;
+  for (Environment::DeepIterator it(instr->env()); !it.Done(); it.Advance()) {
+    Value* use = it.CurrentValue();
     DEBUG_ASSERT(use->instruction() == NULL);
     DEBUG_ASSERT(use->use_index() == -1);
     DEBUG_ASSERT(use->next_use() == NULL);
     DEBUG_ASSERT(0 == MembershipCount(use, use->definition()->env_use_list()));
     use->set_instruction(instr);
-    use->set_use_index(i);
+    use->set_use_index(use_index++);
     use->AddToEnvUseList();
   }
 }
@@ -286,8 +288,8 @@ void FlowGraph::ComputeUseLists() {
   DEBUG_ASSERT(ResetUseLists());
   // Clear global constants and definitions in the start environment.
   ClearUseLists(graph_entry_->constant_null());
-  for (intptr_t i = 0; i < graph_entry_->start_env()->values().length(); ++i) {
-    ClearUseLists(graph_entry_->start_env()->values()[i]->definition());
+  for (intptr_t i = 0; i < graph_entry_->start_env()->Length(); ++i) {
+    ClearUseLists(graph_entry_->start_env()->ValueAt(i)->definition());
   }
   ComputeUseListsRecursive(graph_entry_);
   DEBUG_ASSERT(ValidateUseLists());
@@ -512,7 +514,7 @@ void FlowGraph::Rename(GrowableArray<PhiInstr*>* live_phis) {
     start_env.Add(graph_entry_->constant_null());
   }
   graph_entry_->set_start_env(
-      new Environment(start_env, num_non_copied_params_));
+      Environment::From(start_env, num_non_copied_params_, NULL));
 
   BlockEntryInstr* normal_entry = graph_entry_->SuccessorAt(0);
   ASSERT(normal_entry != NULL);  // Must have entry.
@@ -545,7 +547,8 @@ void FlowGraph::RenameRecursive(BlockEntryInstr* block_entry,
     // Attach current environment to the instruction. First, each instruction
     // gets a full copy of the environment. Later we optimize this by
     // eliminating unnecessary environments.
-    current->set_env(new Environment(*env, num_non_copied_params_));
+    current->set_env(
+        Environment::From(*env, num_non_copied_params_, NULL));
 
     // 2a. Handle uses:
     // Update expression stack environment for each use.