[es7] implement |do| expressions proposal

src/rewriter.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/rewriter.h"
 
 #include "src/ast.h"
 #include "src/parser.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 
 class Processor: public AstVisitor {
  public:
   Processor(Isolate* isolate, Scope* scope, Variable* result,
             AstValueFactory* ast_value_factory)
       : result_(result),
         result_assigned_(false),
         replacement_(nullptr),
         is_set_(false),
         scope_(scope),
         factory_(ast_value_factory) {
     InitializeAstVisitor(isolate, ast_value_factory->zone());
   }
 
+  Processor(Parser* parser, Scope* scope, Variable* result,
+            AstValueFactory* ast_value_factory)
+      : result_(result),
+        result_assigned_(false),
+        replacement_(nullptr),
+        is_set_(false),
+        scope_(scope),
+        factory_(ast_value_factory) {
+    InitializeAstVisitor(nullptr, ast_value_factory->zone());
+    parser_ = parser;
+  }
+
   virtual ~Processor() { }
 
   void Process(ZoneList<Statement*>* statements);
   bool result_assigned() const { return result_assigned_; }
 
   Scope* scope() { return scope_; }
   AstNodeFactory* factory() { return &factory_; }
 
+  // Returns ".result = value"

[rossberg, 2015/10/13 10:44:33]

Why are these public now?

[caitp (gmail), 2015/10/13 15:05:59]

SetResult is used by the do expression rewriter, instead of duplicating code.
There isn't much point in making them private, tbh.

+  Expression* SetResult(Expression* value) {
+    result_assigned_ = true;
+    VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
+    return factory()->NewAssignment(Token::ASSIGN, result_proxy, value,
+                                    RelocInfo::kNoPosition);
+  }
+
+  // Inserts '.result = undefined' in front of the given statement.
+  Statement* AssignUndefinedBefore(Statement* s);
+
  private:
   Variable* result_;
 
   // We are not tracking result usage via the result_'s use
   // counts (we leave the accurate computation to the
   // usage analyzer). Instead we simple remember if
   // there was ever an assignment to result_.
   bool result_assigned_;
 
   // When visiting a node, we "return" a replacement for that node in
   // [replacement_].  In many cases this will just be the original node.
   Statement* replacement_;
 
   // To avoid storing to .result all the time, we eliminate some of
   // the stores by keeping track of whether or not we're sure .result
   // will be overwritten anyway. This is a bit more tricky than what I
   // was hoping for.
   bool is_set_;
 
   Scope* scope_;
   AstNodeFactory factory_;
 
-  // Returns ".result = value"
-  Expression* SetResult(Expression* value) {
-    result_assigned_ = true;
-    VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
-    return factory()->NewAssignment(
-        Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition);
-  }
-
-  // Inserts '.result = undefined' in front of the given statement.
-  Statement* AssignUndefinedBefore(Statement* s);
-
   // Node visitors.
 #define DEF_VISIT(type) virtual void Visit##type(type* node) override;
   AST_NODE_LIST(DEF_VISIT)
 #undef DEF_VISIT
 
   void VisitIterationStatement(IterationStatement* stmt);
 
-  DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
+ public:
+  void Visit(AstNode* node) final {
+    if (!CheckStackOverflow()) node->Accept(this);
+  }
+
+  void SetStackOverflow() { stack_overflow_ = true; }
+  void ClearStackOverflow() { stack_overflow_ = false; }
+  bool HasStackOverflow() const { return stack_overflow_; }
+
+  bool CheckStackOverflow() {
+    if (stack_overflow_) return true;
+    if (isolate_) {
+      StackLimitCheck check(isolate_);
+      if (!check.HasOverflowed()) return false;
+      stack_overflow_ = true;
+    } else {
+      if (!parser_->CheckStackOverflow()) return false;
+      stack_overflow_ = true;
+    }
+    return true;
+  }
+
+ private:
+  void InitializeAstVisitor(Isolate* isolate, Zone* zone) {
+    isolate_ = isolate;
+    zone_ = zone;
+    stack_overflow_ = false;
+  }
+  Zone* zone() { return zone_; }
+  Isolate* isolate() { return isolate_; }
+
+  Isolate* isolate_;
+  Parser* parser_;
+  Zone* zone_;
+  bool stack_overflow_;
 };
 
 
 Statement* Processor::AssignUndefinedBefore(Statement* s) {
   Expression* result_proxy = factory()->NewVariableProxy(result_);
   Expression* undef = factory()->NewUndefinedLiteral(RelocInfo::kNoPosition);
   Expression* assignment = factory()->NewAssignment(
       Token::ASSIGN, result_proxy, undef, RelocInfo::kNoPosition);
   Block* b = factory()->NewBlock(NULL, 2, false, RelocInfo::kNoPosition);
   b->statements()->Add(
@@ skipping 266 matching lines @@
       Statement* result_statement =
           processor.factory()->NewReturnStatement(result_proxy, pos);
       body->Add(result_statement, info->zone());
     }
   }
 
   return true;
 }
 
 
+bool Rewriter::Rewrite(Parser* parser, DoExpression* expr,
+                       AstValueFactory* factory) {
+  Block* block = expr->block();
+  Scope* scope = block->scope();
+  ZoneList<Statement*>* body = block->statements();
+  VariableProxy* result = expr->result();
+  Variable* result_var = result->var();
+
+  if (!body->is_empty()) {
+    Processor processor(parser, scope, result_var, factory);
+    processor.Process(body);
+    if (processor.HasStackOverflow()) return false;
+
+    if (!processor.result_assigned()) {
+      AstNodeFactory* node_factory = processor.factory();
+      Expression* undef =
+          node_factory->NewUndefinedLiteral(RelocInfo::kNoPosition);
+      Statement* completion = node_factory->NewExpressionStatement(
+          processor.SetResult(undef), expr->position());
+      body->Add(completion, factory->zone());
+    }
+  }
+  return true;
+}
+
+
 }  // namespace internal
 }  // namespace v8