Fix completion of try..finally.

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, Variable* result,
+  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());
   }
 
   virtual ~Processor() { }
 
   void Process(ZoneList<Statement*>* statements);
   bool result_assigned() const { return result_assigned_; }
 
+  Scope* scope() { return scope_; }
   AstNodeFactory* factory() { return &factory_; }
 
  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);
   }
 
+  // Changes b to ".backup = .result; b; .result = .backup"
+  void BackupAndRestore(Block* b);

[rossberg, 2015/10/01 09:59:24]

Nit: SaveAndRestore would sound more like the typical phrase. But in fact, I'd
just inline this function

[neis, 2015/10/01 10:56:48]

Did that, but I don't think it improved readability.

+
   // 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();
 };
 
 
+void Processor::BackupAndRestore(Block* b) {
+  Variable* backup = scope()->NewTemporary(
+      factory()->ast_value_factory()->dot_result_string());
+  Expression* backup_proxy = factory()->NewVariableProxy(backup);
+  Expression* result_proxy = factory()->NewVariableProxy(result_);
+  Expression* assignment1 = factory()->NewAssignment(
+      Token::ASSIGN, backup_proxy, result_proxy, RelocInfo::kNoPosition);
+  Expression* assignment2 = factory()->NewAssignment(
+      Token::ASSIGN, result_proxy, backup_proxy, RelocInfo::kNoPosition);
+  b->InsertStatementAt(
+      0, factory()->NewExpressionStatement(assignment1, RelocInfo::kNoPosition),
+      zone());
+  b->AddStatement(
+      factory()->NewExpressionStatement(assignment2, RelocInfo::kNoPosition),
+      zone());
+}
+
+
 void Processor::Process(ZoneList<Statement*>* statements) {
   for (int i = statements->length() - 1; i >= 0; --i) {
     Visit(statements->at(i));
     statements->Set(i, replacement_);
   }
 }
 
 
 void Processor::VisitBlock(Block* node) {
   // An initializer block is the rewritten form of a variable declaration
@@ skipping 78 matching lines @@
   is_set_ = set_after;
   Visit(node->catch_block());
   node->set_catch_block(static_cast<Block*>(replacement_));
   is_set_ = is_set_ && set_in_try;
   replacement_ = node;
 }
 
 
 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
   // Rewrite both try and finally block (in reverse order).
+  bool set_after = is_set_;
+  is_set_ = true;  // Don't normally need to assign in finally block.
   Visit(node->finally_block());
   node->set_finally_block(replacement_->AsBlock());
-  Visit(node->try_block());  // Exception will not be caught.
+  BackupAndRestore(node->finally_block());
+  is_set_ = set_after;
+  Visit(node->try_block());
   node->set_try_block(replacement_->AsBlock());
   replacement_ = node;
 }
 
 
 void Processor::VisitSwitchStatement(SwitchStatement* node) {
   // Rewrite statements in all case clauses (in reverse order).
   ZoneList<CaseClause*>* clauses = node->cases();
   bool set_after = is_set_;
   for (int i = clauses->length() - 1; i >= 0; --i) {
@@ skipping 70 matching lines @@
   Scope* scope = function->scope();
   DCHECK(scope != NULL);
   if (!scope->is_script_scope() && !scope->is_eval_scope()) return true;
 
   ZoneList<Statement*>* body = function->body();
   if (!body->is_empty()) {
     Variable* result =
         scope->NewTemporary(info->ast_value_factory()->dot_result_string());
     // The name string must be internalized at this point.
     DCHECK(!result->name().is_null());
-    Processor processor(info->isolate(), result, info->ast_value_factory());
+    Processor processor(info->isolate(), scope, result,
+                        info->ast_value_factory());
     processor.Process(body);
     if (processor.HasStackOverflow()) return false;
 
     if (processor.result_assigned()) {
       DCHECK(function->end_position() != RelocInfo::kNoPosition);
       // Set the position of the assignment statement one character past the
       // source code, such that it definitely is not in the source code range
       // of an immediate inner scope. For example in
       //   eval('with ({x:1}) x = 1');
       // the end position of the function generated for executing the eval code
       // coincides with the end of the with scope which is the position of '1'.
       int pos = function->end_position();
       VariableProxy* result_proxy =
           processor.factory()->NewVariableProxy(result, pos);
       Statement* result_statement =
           processor.factory()->NewReturnStatement(result_proxy, pos);
       body->Add(result_statement, info->zone());
     }
   }
 
   return true;
 }
 
 
 }  // namespace internal
 }  // namespace v8