1 // Copyright 2012 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #include "v8.h" 29 30 #include "rewriter.h" 31 32 #include "ast.h" 33 #include "compiler.h" 34 #include "scopes.h" 35 36 namespace v8 { 37 namespace internal { 38 39 class Processor: public AstVisitor { 40 public: 41 Processor(Variable* result, Zone* zone) 42 : result_(result), 43 result_assigned_(false), 44 is_set_(false), 45 in_try_(false), 46 factory_(Isolate::Current(), zone) { 47 InitializeAstVisitor(); 48 } 49 50 virtual ~Processor() { } 51 52 void Process(ZoneList<Statement*>* statements); 53 bool result_assigned() const { return result_assigned_; } 54 55 AstNodeFactory<AstNullVisitor>* factory() { 56 return &factory_; 57 } 58 59 private: 60 Variable* result_; 61 62 // We are not tracking result usage via the result_'s use 63 // counts (we leave the accurate computation to the 64 // usage analyzer). Instead we simple remember if 65 // there was ever an assignment to result_. 66 bool result_assigned_; 67 68 // To avoid storing to .result all the time, we eliminate some of 69 // the stores by keeping track of whether or not we're sure .result 70 // will be overwritten anyway. This is a bit more tricky than what I 71 // was hoping for 72 bool is_set_; 73 bool in_try_; 74 75 AstNodeFactory<AstNullVisitor> factory_; 76 77 Expression* SetResult(Expression* value) { 78 result_assigned_ = true; 79 VariableProxy* result_proxy = factory()->NewVariableProxy(result_); 80 return factory()->NewAssignment( 81 Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition); 82 } 83 84 // Node visitors. 85 #define DEF_VISIT(type) \ 86 virtual void Visit##type(type* node); 87 AST_NODE_LIST(DEF_VISIT) 88 #undef DEF_VISIT 89 90 void VisitIterationStatement(IterationStatement* stmt); 91 92 DEFINE_AST_VISITOR_SUBCLASS_MEMBERS(); 93 }; 94 95 96 void Processor::Process(ZoneList<Statement*>* statements) { 97 for (int i = statements->length() - 1; i >= 0; --i) { 98 Visit(statements->at(i)); 99 } 100 } 101 102 103 void Processor::VisitBlock(Block* node) { 104 // An initializer block is the rewritten form of a variable declaration 105 // with initialization expressions. The initializer block contains the 106 // list of assignments corresponding to the initialization expressions. 107 // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of 108 // a variable declaration with initialization expression is 'undefined' 109 // with some JS VMs: For instance, using smjs, print(eval('var x = 7')) 110 // returns 'undefined'. To obtain the same behavior with v8, we need 111 // to prevent rewriting in that case. 112 if (!node->is_initializer_block()) Process(node->statements()); 113 } 114 115 116 void Processor::VisitModuleStatement(ModuleStatement* node) { 117 bool set_after_body = is_set_; 118 Visit(node->body()); 119 is_set_ = is_set_ && set_after_body; 120 } 121 122 123 void Processor::VisitExpressionStatement(ExpressionStatement* node) { 124 // Rewrite : <x>; -> .result = <x>; 125 if (!is_set_ && !node->expression()->IsThrow()) { 126 node->set_expression(SetResult(node->expression())); 127 if (!in_try_) is_set_ = true; 128 } 129 } 130 131 132 void Processor::VisitIfStatement(IfStatement* node) { 133 // Rewrite both then and else parts (reversed). 134 bool save = is_set_; 135 Visit(node->else_statement()); 136 bool set_after_then = is_set_; 137 is_set_ = save; 138 Visit(node->then_statement()); 139 is_set_ = is_set_ && set_after_then; 140 } 141 142 143 void Processor::VisitIterationStatement(IterationStatement* node) { 144 // Rewrite the body. 145 bool set_after_loop = is_set_; 146 Visit(node->body()); 147 is_set_ = is_set_ && set_after_loop; 148 } 149 150 151 void Processor::VisitDoWhileStatement(DoWhileStatement* node) { 152 VisitIterationStatement(node); 153 } 154 155 156 void Processor::VisitWhileStatement(WhileStatement* node) { 157 VisitIterationStatement(node); 158 } 159 160 161 void Processor::VisitForStatement(ForStatement* node) { 162 VisitIterationStatement(node); 163 } 164 165 166 void Processor::VisitForInStatement(ForInStatement* node) { 167 VisitIterationStatement(node); 168 } 169 170 171 void Processor::VisitForOfStatement(ForOfStatement* node) { 172 VisitIterationStatement(node); 173 } 174 175 176 void Processor::VisitTryCatchStatement(TryCatchStatement* node) { 177 // Rewrite both try and catch blocks (reversed order). 178 bool set_after_catch = is_set_; 179 Visit(node->catch_block()); 180 is_set_ = is_set_ && set_after_catch; 181 bool save = in_try_; 182 in_try_ = true; 183 Visit(node->try_block()); 184 in_try_ = save; 185 } 186 187 188 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) { 189 // Rewrite both try and finally block (reversed order). 190 Visit(node->finally_block()); 191 bool save = in_try_; 192 in_try_ = true; 193 Visit(node->try_block()); 194 in_try_ = save; 195 } 196 197 198 void Processor::VisitSwitchStatement(SwitchStatement* node) { 199 // Rewrite statements in all case clauses in reversed order. 200 ZoneList<CaseClause*>* clauses = node->cases(); 201 bool set_after_switch = is_set_; 202 for (int i = clauses->length() - 1; i >= 0; --i) { 203 CaseClause* clause = clauses->at(i); 204 Process(clause->statements()); 205 } 206 is_set_ = is_set_ && set_after_switch; 207 } 208 209 210 void Processor::VisitContinueStatement(ContinueStatement* node) { 211 is_set_ = false; 212 } 213 214 215 void Processor::VisitBreakStatement(BreakStatement* node) { 216 is_set_ = false; 217 } 218 219 220 void Processor::VisitWithStatement(WithStatement* node) { 221 bool set_after_body = is_set_; 222 Visit(node->statement()); 223 is_set_ = is_set_ && set_after_body; 224 } 225 226 227 // Do nothing: 228 void Processor::VisitVariableDeclaration(VariableDeclaration* node) {} 229 void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {} 230 void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {} 231 void Processor::VisitImportDeclaration(ImportDeclaration* node) {} 232 void Processor::VisitExportDeclaration(ExportDeclaration* node) {} 233 void Processor::VisitModuleLiteral(ModuleLiteral* node) {} 234 void Processor::VisitModuleVariable(ModuleVariable* node) {} 235 void Processor::VisitModulePath(ModulePath* node) {} 236 void Processor::VisitModuleUrl(ModuleUrl* node) {} 237 void Processor::VisitEmptyStatement(EmptyStatement* node) {} 238 void Processor::VisitReturnStatement(ReturnStatement* node) {} 239 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {} 240 241 242 // Expressions are never visited yet. 243 #define DEF_VISIT(type) \ 244 void Processor::Visit##type(type* expr) { UNREACHABLE(); } 245 EXPRESSION_NODE_LIST(DEF_VISIT) 246 #undef DEF_VISIT 247 248 249 // Assumes code has been parsed. Mutates the AST, so the AST should not 250 // continue to be used in the case of failure. 251 bool Rewriter::Rewrite(CompilationInfo* info) { 252 FunctionLiteral* function = info->function(); 253 ASSERT(function != NULL); 254 Scope* scope = function->scope(); 255 ASSERT(scope != NULL); 256 if (!scope->is_global_scope() && !scope->is_eval_scope()) return true; 257 258 ZoneList<Statement*>* body = function->body(); 259 if (!body->is_empty()) { 260 Variable* result = scope->NewTemporary( 261 info->isolate()->factory()->result_string()); 262 Processor processor(result, info->zone()); 263 processor.Process(body); 264 if (processor.HasStackOverflow()) return false; 265 266 if (processor.result_assigned()) { 267 ASSERT(function->end_position() != RelocInfo::kNoPosition); 268 // Set the position of the assignment statement one character past the 269 // source code, such that it definitely is not in the source code range 270 // of an immediate inner scope. For example in 271 // eval('with ({x:1}) x = 1'); 272 // the end position of the function generated for executing the eval code 273 // coincides with the end of the with scope which is the position of '1'. 274 int position = function->end_position(); 275 VariableProxy* result_proxy = processor.factory()->NewVariableProxy( 276 result->name(), false, result->interface(), position); 277 result_proxy->BindTo(result); 278 Statement* result_statement = 279 processor.factory()->NewReturnStatement(result_proxy); 280 result_statement->set_statement_pos(position); 281 body->Add(result_statement, info->zone()); 282 } 283 } 284 285 return true; 286 } 287 288 289 } } // namespace v8::internal 290
