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.
8 #include "src/parser.h"
9 #include "src/rewriter.h"
10 #include "src/scopes.h"
15 class Processor: public AstVisitor {
17 Processor(Isolate* isolate, Variable* result,
18 AstValueFactory* ast_value_factory)
20 result_assigned_(false),
23 factory_(ast_value_factory) {
24 InitializeAstVisitor(isolate, ast_value_factory->zone());
27 virtual ~Processor() { }
29 void Process(ZoneList<Statement*>* statements);
30 bool result_assigned() const { return result_assigned_; }
32 AstNodeFactory* factory() { return &factory_; }
37 // We are not tracking result usage via the result_'s use
38 // counts (we leave the accurate computation to the
39 // usage analyzer). Instead we simple remember if
40 // there was ever an assignment to result_.
41 bool result_assigned_;
43 // To avoid storing to .result all the time, we eliminate some of
44 // the stores by keeping track of whether or not we're sure .result
45 // will be overwritten anyway. This is a bit more tricky than what I
50 AstNodeFactory factory_;
52 Expression* SetResult(Expression* value) {
53 result_assigned_ = true;
54 VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
55 return factory()->NewAssignment(
56 Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition);
60 #define DEF_VISIT(type) virtual void Visit##type(type* node) OVERRIDE;
61 AST_NODE_LIST(DEF_VISIT)
64 void VisitIterationStatement(IterationStatement* stmt);
66 DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
70 void Processor::Process(ZoneList<Statement*>* statements) {
71 for (int i = statements->length() - 1; i >= 0; --i) {
72 Visit(statements->at(i));
77 void Processor::VisitBlock(Block* node) {
78 // An initializer block is the rewritten form of a variable declaration
79 // with initialization expressions. The initializer block contains the
80 // list of assignments corresponding to the initialization expressions.
81 // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
82 // a variable declaration with initialization expression is 'undefined'
83 // with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
84 // returns 'undefined'. To obtain the same behavior with v8, we need
85 // to prevent rewriting in that case.
86 if (!node->is_initializer_block()) Process(node->statements());
90 void Processor::VisitModuleStatement(ModuleStatement* node) {
91 bool set_after_body = is_set_;
93 is_set_ = is_set_ && set_after_body;
97 void Processor::VisitExpressionStatement(ExpressionStatement* node) {
98 // Rewrite : <x>; -> .result = <x>;
99 if (!is_set_ && !node->expression()->IsThrow()) {
100 node->set_expression(SetResult(node->expression()));
101 if (!in_try_) is_set_ = true;
106 void Processor::VisitIfStatement(IfStatement* node) {
107 // Rewrite both then and else parts (reversed).
109 Visit(node->else_statement());
110 bool set_after_then = is_set_;
112 Visit(node->then_statement());
113 is_set_ = is_set_ && set_after_then;
117 void Processor::VisitIterationStatement(IterationStatement* node) {
119 bool set_after_loop = is_set_;
121 is_set_ = is_set_ && set_after_loop;
125 void Processor::VisitDoWhileStatement(DoWhileStatement* node) {
126 VisitIterationStatement(node);
130 void Processor::VisitWhileStatement(WhileStatement* node) {
131 VisitIterationStatement(node);
135 void Processor::VisitForStatement(ForStatement* node) {
136 VisitIterationStatement(node);
140 void Processor::VisitForInStatement(ForInStatement* node) {
141 VisitIterationStatement(node);
145 void Processor::VisitForOfStatement(ForOfStatement* node) {
146 VisitIterationStatement(node);
150 void Processor::VisitTryCatchStatement(TryCatchStatement* node) {
151 // Rewrite both try and catch blocks (reversed order).
152 bool set_after_catch = is_set_;
153 Visit(node->catch_block());
154 is_set_ = is_set_ && set_after_catch;
157 Visit(node->try_block());
162 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
163 // Rewrite both try and finally block (reversed order).
164 Visit(node->finally_block());
167 Visit(node->try_block());
172 void Processor::VisitSwitchStatement(SwitchStatement* node) {
173 // Rewrite statements in all case clauses in reversed order.
174 ZoneList<CaseClause*>* clauses = node->cases();
175 bool set_after_switch = is_set_;
176 for (int i = clauses->length() - 1; i >= 0; --i) {
177 CaseClause* clause = clauses->at(i);
178 Process(clause->statements());
180 is_set_ = is_set_ && set_after_switch;
184 void Processor::VisitContinueStatement(ContinueStatement* node) {
189 void Processor::VisitBreakStatement(BreakStatement* node) {
194 void Processor::VisitWithStatement(WithStatement* node) {
195 bool set_after_body = is_set_;
196 Visit(node->statement());
197 is_set_ = is_set_ && set_after_body;
202 void Processor::VisitVariableDeclaration(VariableDeclaration* node) {}
203 void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {}
204 void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {}
205 void Processor::VisitImportDeclaration(ImportDeclaration* node) {}
206 void Processor::VisitExportDeclaration(ExportDeclaration* node) {}
207 void Processor::VisitModuleLiteral(ModuleLiteral* node) {}
208 void Processor::VisitModulePath(ModulePath* node) {}
209 void Processor::VisitModuleUrl(ModuleUrl* node) {}
210 void Processor::VisitEmptyStatement(EmptyStatement* node) {}
211 void Processor::VisitReturnStatement(ReturnStatement* node) {}
212 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
215 // Expressions are never visited yet.
216 #define DEF_VISIT(type) \
217 void Processor::Visit##type(type* expr) { UNREACHABLE(); }
218 EXPRESSION_NODE_LIST(DEF_VISIT)
222 // Assumes code has been parsed. Mutates the AST, so the AST should not
223 // continue to be used in the case of failure.
224 bool Rewriter::Rewrite(ParseInfo* info) {
225 FunctionLiteral* function = info->function();
226 DCHECK(function != NULL);
227 Scope* scope = function->scope();
228 DCHECK(scope != NULL);
229 if (!scope->is_script_scope() && !scope->is_eval_scope()) return true;
231 ZoneList<Statement*>* body = function->body();
232 if (!body->is_empty()) {
234 scope->NewTemporary(info->ast_value_factory()->dot_result_string());
235 // The name string must be internalized at this point.
236 DCHECK(!result->name().is_null());
237 Processor processor(info->isolate(), result, info->ast_value_factory());
238 processor.Process(body);
239 if (processor.HasStackOverflow()) return false;
241 if (processor.result_assigned()) {
242 DCHECK(function->end_position() != RelocInfo::kNoPosition);
243 // Set the position of the assignment statement one character past the
244 // source code, such that it definitely is not in the source code range
245 // of an immediate inner scope. For example in
246 // eval('with ({x:1}) x = 1');
247 // the end position of the function generated for executing the eval code
248 // coincides with the end of the with scope which is the position of '1'.
249 int pos = function->end_position();
250 VariableProxy* result_proxy =
251 processor.factory()->NewVariableProxy(result, pos);
252 Statement* result_statement =
253 processor.factory()->NewReturnStatement(result_proxy, pos);
254 body->Add(result_statement, info->zone());
262 } } // namespace v8::internal