| // 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/parsing/rewriter.h" |
| |
| #include "src/ast/ast.h" |
| #include "src/ast/scopes.h" |
| #include "src/parsing/parser.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), |
| zone_(ast_value_factory->zone()), |
| scope_(scope), |
| factory_(ast_value_factory) { |
| InitializeAstVisitor(isolate); |
| } |
| |
| Processor(Parser* parser, Scope* scope, Variable* result, |
| AstValueFactory* ast_value_factory) |
| : result_(result), |
| result_assigned_(false), |
| replacement_(nullptr), |
| is_set_(false), |
| zone_(ast_value_factory->zone()), |
| scope_(scope), |
| factory_(ast_value_factory) { |
| InitializeAstVisitor(parser->stack_limit()); |
| } |
| |
| ~Processor() override {} |
| |
| void Process(ZoneList<Statement*>* statements); |
| bool result_assigned() const { return result_assigned_; } |
| |
| Zone* zone() { return zone_; } |
| Scope* scope() { return scope_; } |
| AstNodeFactory* factory() { return &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); |
| |
| 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_; |
| |
| Zone* zone_; |
| Scope* scope_; |
| AstNodeFactory factory_; |
| |
| // Node visitors. |
| #define DEF_VISIT(type) void Visit##type(type* node) override; |
| AST_NODE_LIST(DEF_VISIT) |
| #undef DEF_VISIT |
| |
| void VisitIterationStatement(IterationStatement* stmt); |
| |
| DEFINE_AST_VISITOR_SUBCLASS_MEMBERS(); |
| }; |
| |
| |
| 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( |
| factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition), |
| zone()); |
| b->statements()->Add(s, zone()); |
| return b; |
| } |
| |
| |
| 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 |
| // with initialization expressions. The initializer block contains the |
| // list of assignments corresponding to the initialization expressions. |
| // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of |
| // a variable declaration with initialization expression is 'undefined' |
| // with some JS VMs: For instance, using smjs, print(eval('var x = 7')) |
| // returns 'undefined'. To obtain the same behavior with v8, we need |
| // to prevent rewriting in that case. |
| if (!node->ignore_completion_value()) Process(node->statements()); |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitExpressionStatement(ExpressionStatement* node) { |
| // Rewrite : <x>; -> .result = <x>; |
| if (!is_set_) { |
| node->set_expression(SetResult(node->expression())); |
| is_set_ = true; |
| } |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitIfStatement(IfStatement* node) { |
| // Rewrite both branches. |
| bool set_after = is_set_; |
| Visit(node->then_statement()); |
| node->set_then_statement(replacement_); |
| bool set_in_then = is_set_; |
| is_set_ = set_after; |
| Visit(node->else_statement()); |
| node->set_else_statement(replacement_); |
| is_set_ = is_set_ && set_in_then; |
| replacement_ = node; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(node); |
| } |
| } |
| |
| |
| void Processor::VisitIterationStatement(IterationStatement* node) { |
| // Rewrite the body. |
| bool set_after = is_set_; |
| is_set_ = false; // We are in a loop, so we can't rely on [set_after]. |
| Visit(node->body()); |
| node->set_body(replacement_); |
| is_set_ = is_set_ && set_after; |
| replacement_ = node; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(node); |
| } |
| } |
| |
| |
| void Processor::VisitDoWhileStatement(DoWhileStatement* node) { |
| VisitIterationStatement(node); |
| } |
| |
| |
| void Processor::VisitWhileStatement(WhileStatement* node) { |
| VisitIterationStatement(node); |
| } |
| |
| |
| void Processor::VisitForStatement(ForStatement* node) { |
| VisitIterationStatement(node); |
| } |
| |
| |
| void Processor::VisitForInStatement(ForInStatement* node) { |
| VisitIterationStatement(node); |
| } |
| |
| |
| void Processor::VisitForOfStatement(ForOfStatement* node) { |
| VisitIterationStatement(node); |
| } |
| |
| |
| void Processor::VisitTryCatchStatement(TryCatchStatement* node) { |
| // Rewrite both try and catch block. |
| bool set_after = is_set_; |
| Visit(node->try_block()); |
| node->set_try_block(static_cast<Block*>(replacement_)); |
| bool set_in_try = is_set_; |
| 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; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(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()); |
| { // Save .result value at the beginning of the finally block and restore it |
| // at the end again: ".backup = .result; ...; .result = .backup" |
| // This is necessary because the finally block does not normally contribute |
| // to the completion value. |
| CHECK(scope() != nullptr); |
| Variable* backup = scope()->NewTemporary( |
| factory()->ast_value_factory()->dot_result_string()); |
| Expression* backup_proxy = factory()->NewVariableProxy(backup); |
| Expression* result_proxy = factory()->NewVariableProxy(result_); |
| Expression* save = factory()->NewAssignment( |
| Token::ASSIGN, backup_proxy, result_proxy, RelocInfo::kNoPosition); |
| Expression* restore = factory()->NewAssignment( |
| Token::ASSIGN, result_proxy, backup_proxy, RelocInfo::kNoPosition); |
| node->finally_block()->statements()->InsertAt( |
| 0, factory()->NewExpressionStatement(save, RelocInfo::kNoPosition), |
| zone()); |
| node->finally_block()->statements()->Add( |
| factory()->NewExpressionStatement(restore, RelocInfo::kNoPosition), |
| zone()); |
| } |
| is_set_ = set_after; |
| Visit(node->try_block()); |
| node->set_try_block(replacement_->AsBlock()); |
| replacement_ = node; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(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) { |
| CaseClause* clause = clauses->at(i); |
| Process(clause->statements()); |
| } |
| is_set_ = is_set_ && set_after; |
| replacement_ = node; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(node); |
| } |
| } |
| |
| |
| void Processor::VisitContinueStatement(ContinueStatement* node) { |
| is_set_ = false; |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitBreakStatement(BreakStatement* node) { |
| is_set_ = false; |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitWithStatement(WithStatement* node) { |
| Visit(node->statement()); |
| node->set_statement(replacement_); |
| replacement_ = node; |
| |
| if (!is_set_) { |
| is_set_ = true; |
| replacement_ = AssignUndefinedBefore(node); |
| } |
| } |
| |
| |
| void Processor::VisitSloppyBlockFunctionStatement( |
| SloppyBlockFunctionStatement* node) { |
| Visit(node->statement()); |
| node->set_statement(replacement_); |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitEmptyStatement(EmptyStatement* node) { |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitReturnStatement(ReturnStatement* node) { |
| is_set_ = true; |
| replacement_ = node; |
| } |
| |
| |
| void Processor::VisitDebuggerStatement(DebuggerStatement* node) { |
| replacement_ = node; |
| } |
| |
| |
| // Expressions are never visited. |
| #define DEF_VISIT(type) \ |
| void Processor::Visit##type(type* expr) { UNREACHABLE(); } |
| EXPRESSION_NODE_LIST(DEF_VISIT) |
| #undef DEF_VISIT |
| |
| |
| // Declarations are never visited. |
| #define DEF_VISIT(type) \ |
| void Processor::Visit##type(type* expr) { UNREACHABLE(); } |
| DECLARATION_NODE_LIST(DEF_VISIT) |
| #undef DEF_VISIT |
| |
| |
| // Assumes code has been parsed. Mutates the AST, so the AST should not |
| // continue to be used in the case of failure. |
| bool Rewriter::Rewrite(ParseInfo* info) { |
| FunctionLiteral* function = info->literal(); |
| DCHECK(function != NULL); |
| 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(), scope, result, |
| info->ast_value_factory()); |
| processor.Process(body); |
| if (processor.HasStackOverflow()) return false; |
| |
| if (processor.result_assigned()) { |
| int pos = RelocInfo::kNoPosition; |
| 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; |
| } |
| |
| |
| 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 |