VM [KERNEL] Avoid emitting :expr_temp and capturing :iterator

runtime/vm/kernel_to_il.cc

Index: runtime/vm/kernel_to_il.cc
diff --git a/runtime/vm/kernel_to_il.cc b/runtime/vm/kernel_to_il.cc
index 40c1cd1fd326c2e9b143e2d75375a447d40675bf..1653061c07ab9624fefbdc97806cd57e696198ac 100644
--- a/runtime/vm/kernel_to_il.cc
+++ b/runtime/vm/kernel_to_il.cc
@@ -31,6 +31,32 @@ namespace kernel {
 #define I Isolate::Current()
 
 
+class NeedExprTempVisitor : public RecursiveVisitor {
+ public:
+  NeedExprTempVisitor() : need_expr_temp_(false) {}
+
+  virtual void VisitConditionalExpression(ConditionalExpression* node) {
+    need_expr_temp_ = true;
+  }
+
+  virtual void VisitLogicalExpression(LogicalExpression* node) {
+    need_expr_temp_ = true;
+  }
+
+  bool NeedTemp() const { return need_expr_temp_; }

[Vyacheslav Egorov (Google), 2017/03/27 14:31:46]

nit: style guide suggests naming simple getters like this:

bool needs_expr_temp() const {  ... }

+
+ private:
+  bool need_expr_temp_;

[Vyacheslav Egorov (Google), 2017/03/27 14:31:46]

better name is needs_expr_temp_.

+};
+
+
+bool NeedExprTemp(TreeNode* node) {

[Vyacheslav Egorov (Google), 2017/03/27 14:31:46]

static bool NeedsExprTemp(...)

+  NeedExprTempVisitor visitor;
+  node->AcceptVisitor(&visitor);
+  return visitor.NeedTemp();
+}
+
+
 static void DiscoverEnclosingElements(Zone* zone,
                                       const Function& function,
                                       Function* outermost_function,
@@ -300,7 +326,11 @@ ScopeBuildingResult* ScopeBuilder::BuildScopes() {
   LocalVariable* context_var = parsed_function->current_context_var();
   context_var->set_is_forced_stack();
   scope_->AddVariable(context_var);
-  scope_->AddVariable(parsed_function->EnsureExpressionTemp());
+  bool has_expr_temp = false;
+  if (node_ != NULL && NeedExprTemp(node_)) {
+    scope_->AddVariable(parsed_function->EnsureExpressionTemp());
+    has_expr_temp = true;
+  }
 
   parsed_function->SetNodeSequence(
       new SequenceNode(TokenPosition::kNoSource, scope_));
@@ -348,6 +378,10 @@ ScopeBuildingResult* ScopeBuilder::BuildScopes() {
             Field* field = klass->fields()[i];
             if (!field->IsStatic() && (field->initializer() != NULL)) {
               EnterScope(field, field->position());
+              if (!has_expr_temp && NeedExprTemp(field->initializer())) {
+                scope_->AddVariable(parsed_function->EnsureExpressionTemp());
+                has_expr_temp = true;
+              }
               field->initializer()->AcceptExpressionVisitor(this);
               ExitScope(field->end_position());
             }