1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
16 class Processor: public AstVisitor {
18 Processor(Variable* result, Zone* zone)
20 result_assigned_(false),
24 InitializeAstVisitor(zone);
27 virtual ~Processor() { }
29 void Process(ZoneList<Statement*>* statements);
30 bool result_assigned() const { return result_assigned_; }
32 AstNodeFactory<AstNullVisitor>* factory() {
39 // We are not tracking result usage via the result_'s use
40 // counts (we leave the accurate computation to the
41 // usage analyzer). Instead we simple remember if
42 // there was ever an assignment to result_.
43 bool result_assigned_;
45 // To avoid storing to .result all the time, we eliminate some of
46 // the stores by keeping track of whether or not we're sure .result
47 // will be overwritten anyway. This is a bit more tricky than what I
52 AstNodeFactory<AstNullVisitor> factory_;
54 Expression* SetResult(Expression* value) {
55 result_assigned_ = true;
56 VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
57 return factory()->NewAssignment(
58 Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition);
62 #define DEF_VISIT(type) \
63 virtual void Visit##type(type* node);
64 AST_NODE_LIST(DEF_VISIT)
67 void VisitIterationStatement(IterationStatement* stmt);
69 DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
73 void Processor::Process(ZoneList<Statement*>* statements) {
74 for (int i = statements->length() - 1; i >= 0; --i) {
75 Visit(statements->at(i));
80 void Processor::VisitBlock(Block* node) {
81 // An initializer block is the rewritten form of a variable declaration
82 // with initialization expressions. The initializer block contains the
83 // list of assignments corresponding to the initialization expressions.
84 // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
85 // a variable declaration with initialization expression is 'undefined'
86 // with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
87 // returns 'undefined'. To obtain the same behavior with v8, we need
88 // to prevent rewriting in that case.
89 if (!node->is_initializer_block()) Process(node->statements());
93 void Processor::VisitModuleStatement(ModuleStatement* node) {
94 bool set_after_body = is_set_;
96 is_set_ = is_set_ && set_after_body;
100 void Processor::VisitExpressionStatement(ExpressionStatement* node) {
101 // Rewrite : <x>; -> .result = <x>;
102 if (!is_set_ && !node->expression()->IsThrow()) {
103 node->set_expression(SetResult(node->expression()));
104 if (!in_try_) is_set_ = true;
109 void Processor::VisitIfStatement(IfStatement* node) {
110 // Rewrite both then and else parts (reversed).
112 Visit(node->else_statement());
113 bool set_after_then = is_set_;
115 Visit(node->then_statement());
116 is_set_ = is_set_ && set_after_then;
120 void Processor::VisitIterationStatement(IterationStatement* node) {
122 bool set_after_loop = is_set_;
124 is_set_ = is_set_ && set_after_loop;
128 void Processor::VisitDoWhileStatement(DoWhileStatement* node) {
129 VisitIterationStatement(node);
133 void Processor::VisitWhileStatement(WhileStatement* node) {
134 VisitIterationStatement(node);
138 void Processor::VisitForStatement(ForStatement* node) {
139 VisitIterationStatement(node);
143 void Processor::VisitForInStatement(ForInStatement* node) {
144 VisitIterationStatement(node);
148 void Processor::VisitForOfStatement(ForOfStatement* node) {
149 VisitIterationStatement(node);
153 void Processor::VisitTryCatchStatement(TryCatchStatement* node) {
154 // Rewrite both try and catch blocks (reversed order).
155 bool set_after_catch = is_set_;
156 Visit(node->catch_block());
157 is_set_ = is_set_ && set_after_catch;
160 Visit(node->try_block());
165 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
166 // Rewrite both try and finally block (reversed order).
167 Visit(node->finally_block());
170 Visit(node->try_block());
175 void Processor::VisitSwitchStatement(SwitchStatement* node) {
176 // Rewrite statements in all case clauses in reversed order.
177 ZoneList<CaseClause*>* clauses = node->cases();
178 bool set_after_switch = is_set_;
179 for (int i = clauses->length() - 1; i >= 0; --i) {
180 CaseClause* clause = clauses->at(i);
181 Process(clause->statements());
183 is_set_ = is_set_ && set_after_switch;
187 void Processor::VisitContinueStatement(ContinueStatement* node) {
192 void Processor::VisitBreakStatement(BreakStatement* node) {
197 void Processor::VisitWithStatement(WithStatement* node) {
198 bool set_after_body = is_set_;
199 Visit(node->statement());
200 is_set_ = is_set_ && set_after_body;
205 void Processor::VisitVariableDeclaration(VariableDeclaration* node) {}
206 void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {}
207 void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {}
208 void Processor::VisitImportDeclaration(ImportDeclaration* node) {}
209 void Processor::VisitExportDeclaration(ExportDeclaration* node) {}
210 void Processor::VisitModuleLiteral(ModuleLiteral* node) {}
211 void Processor::VisitModuleVariable(ModuleVariable* node) {}
212 void Processor::VisitModulePath(ModulePath* node) {}
213 void Processor::VisitModuleUrl(ModuleUrl* node) {}
214 void Processor::VisitEmptyStatement(EmptyStatement* node) {}
215 void Processor::VisitReturnStatement(ReturnStatement* node) {}
216 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
219 // Expressions are never visited yet.
220 #define DEF_VISIT(type) \
221 void Processor::Visit##type(type* expr) { UNREACHABLE(); }
222 EXPRESSION_NODE_LIST(DEF_VISIT)
226 // Assumes code has been parsed. Mutates the AST, so the AST should not
227 // continue to be used in the case of failure.
228 bool Rewriter::Rewrite(CompilationInfo* info) {
229 FunctionLiteral* function = info->function();
230 ASSERT(function != NULL);
231 Scope* scope = function->scope();
232 ASSERT(scope != NULL);
233 if (!scope->is_global_scope() && !scope->is_eval_scope()) return true;
235 ZoneList<Statement*>* body = function->body();
236 if (!body->is_empty()) {
237 Variable* result = scope->NewTemporary(
238 info->isolate()->factory()->dot_result_string());
239 Processor processor(result, info->zone());
240 processor.Process(body);
241 if (processor.HasStackOverflow()) return false;
243 if (processor.result_assigned()) {
244 ASSERT(function->end_position() != RelocInfo::kNoPosition);
245 // Set the position of the assignment statement one character past the
246 // source code, such that it definitely is not in the source code range
247 // of an immediate inner scope. For example in
248 // eval('with ({x:1}) x = 1');
249 // the end position of the function generated for executing the eval code
250 // coincides with the end of the with scope which is the position of '1'.
251 int pos = function->end_position();
252 VariableProxy* result_proxy = processor.factory()->NewVariableProxy(
253 result->name(), false, result->interface(), pos);
254 result_proxy->BindTo(result);
255 Statement* result_statement =
256 processor.factory()->NewReturnStatement(result_proxy, pos);
257 body->Add(result_statement, info->zone());
265 } } // namespace v8::internal