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.
7 #include "src/rewriter.h"
10 #include "src/compiler.h"
11 #include "src/scopes.h"
16 class Processor: public AstVisitor {
18 Processor(Variable* result, AstValueFactory* ast_value_factory)
20 result_assigned_(false),
23 factory_(ast_value_factory) {
24 InitializeAstVisitor(ast_value_factory->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) virtual void Visit##type(type* node) OVERRIDE;
63 AST_NODE_LIST(DEF_VISIT)
66 void VisitIterationStatement(IterationStatement* stmt);
68 DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
72 void Processor::Process(ZoneList<Statement*>* statements) {
73 for (int i = statements->length() - 1; i >= 0; --i) {
74 Visit(statements->at(i));
79 void Processor::VisitBlock(Block* node) {
80 // An initializer block is the rewritten form of a variable declaration
81 // with initialization expressions. The initializer block contains the
82 // list of assignments corresponding to the initialization expressions.
83 // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
84 // a variable declaration with initialization expression is 'undefined'
85 // with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
86 // returns 'undefined'. To obtain the same behavior with v8, we need
87 // to prevent rewriting in that case.
88 if (!node->is_initializer_block()) Process(node->statements());
92 void Processor::VisitModuleStatement(ModuleStatement* node) {
93 bool set_after_body = is_set_;
95 is_set_ = is_set_ && set_after_body;
99 void Processor::VisitExpressionStatement(ExpressionStatement* node) {
100 // Rewrite : <x>; -> .result = <x>;
101 if (!is_set_ && !node->expression()->IsThrow()) {
102 node->set_expression(SetResult(node->expression()));
103 if (!in_try_) is_set_ = true;
108 void Processor::VisitIfStatement(IfStatement* node) {
109 // Rewrite both then and else parts (reversed).
111 Visit(node->else_statement());
112 bool set_after_then = is_set_;
114 Visit(node->then_statement());
115 is_set_ = is_set_ && set_after_then;
119 void Processor::VisitIterationStatement(IterationStatement* node) {
121 bool set_after_loop = is_set_;
123 is_set_ = is_set_ && set_after_loop;
127 void Processor::VisitDoWhileStatement(DoWhileStatement* node) {
128 VisitIterationStatement(node);
132 void Processor::VisitWhileStatement(WhileStatement* node) {
133 VisitIterationStatement(node);
137 void Processor::VisitForStatement(ForStatement* node) {
138 VisitIterationStatement(node);
142 void Processor::VisitForInStatement(ForInStatement* node) {
143 VisitIterationStatement(node);
147 void Processor::VisitForOfStatement(ForOfStatement* node) {
148 VisitIterationStatement(node);
152 void Processor::VisitTryCatchStatement(TryCatchStatement* node) {
153 // Rewrite both try and catch blocks (reversed order).
154 bool set_after_catch = is_set_;
155 Visit(node->catch_block());
156 is_set_ = is_set_ && set_after_catch;
159 Visit(node->try_block());
164 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
165 // Rewrite both try and finally block (reversed order).
166 Visit(node->finally_block());
169 Visit(node->try_block());
174 void Processor::VisitSwitchStatement(SwitchStatement* node) {
175 // Rewrite statements in all case clauses in reversed order.
176 ZoneList<CaseClause*>* clauses = node->cases();
177 bool set_after_switch = is_set_;
178 for (int i = clauses->length() - 1; i >= 0; --i) {
179 CaseClause* clause = clauses->at(i);
180 Process(clause->statements());
182 is_set_ = is_set_ && set_after_switch;
186 void Processor::VisitContinueStatement(ContinueStatement* node) {
191 void Processor::VisitBreakStatement(BreakStatement* node) {
196 void Processor::VisitWithStatement(WithStatement* node) {
197 bool set_after_body = is_set_;
198 Visit(node->statement());
199 is_set_ = is_set_ && set_after_body;
204 void Processor::VisitVariableDeclaration(VariableDeclaration* node) {}
205 void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {}
206 void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {}
207 void Processor::VisitImportDeclaration(ImportDeclaration* node) {}
208 void Processor::VisitExportDeclaration(ExportDeclaration* node) {}
209 void Processor::VisitModuleLiteral(ModuleLiteral* node) {}
210 void Processor::VisitModuleVariable(ModuleVariable* node) {}
211 void Processor::VisitModulePath(ModulePath* node) {}
212 void Processor::VisitModuleUrl(ModuleUrl* node) {}
213 void Processor::VisitEmptyStatement(EmptyStatement* node) {}
214 void Processor::VisitReturnStatement(ReturnStatement* node) {}
215 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
218 // Expressions are never visited yet.
219 #define DEF_VISIT(type) \
220 void Processor::Visit##type(type* expr) { UNREACHABLE(); }
221 EXPRESSION_NODE_LIST(DEF_VISIT)
225 // Assumes code has been parsed. Mutates the AST, so the AST should not
226 // continue to be used in the case of failure.
227 bool Rewriter::Rewrite(CompilationInfo* info) {
228 FunctionLiteral* function = info->function();
229 DCHECK(function != NULL);
230 Scope* scope = function->scope();
231 DCHECK(scope != NULL);
232 if (!scope->is_global_scope() && !scope->is_eval_scope()) return true;
234 ZoneList<Statement*>* body = function->body();
235 if (!body->is_empty()) {
237 scope->NewTemporary(info->ast_value_factory()->dot_result_string());
238 // The name string must be internalized at this point.
239 DCHECK(!result->name().is_null());
240 Processor processor(result, info->ast_value_factory());
241 processor.Process(body);
242 if (processor.HasStackOverflow()) return false;
244 if (processor.result_assigned()) {
245 DCHECK(function->end_position() != RelocInfo::kNoPosition);
246 // Set the position of the assignment statement one character past the
247 // source code, such that it definitely is not in the source code range
248 // of an immediate inner scope. For example in
249 // eval('with ({x:1}) x = 1');
250 // the end position of the function generated for executing the eval code
251 // coincides with the end of the with scope which is the position of '1'.
252 int pos = function->end_position();
253 VariableProxy* result_proxy =
254 processor.factory()->NewVariableProxy(result, pos);
255 Statement* result_statement =
256 processor.factory()->NewReturnStatement(result_proxy, pos);
257 body->Add(result_statement, info->zone());
265 } } // namespace v8::internal