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 explicit Processor(Variable* result) 42 : result_(result), 43 result_assigned_(false), 44 is_set_(false), 45 in_try_(false), 46 factory_(isolate()) { } 47 48 virtual ~Processor() { } 49 50 void Process(ZoneList<Statement*>* statements); 51 bool result_assigned() const { return result_assigned_; } 52 53 AstNodeFactory<AstNullVisitor>* factory() { 54 return &factory_; 55 } 56 57 private: 58 Variable* result_; 59 60 // We are not tracking result usage via the result_'s use 61 // counts (we leave the accurate computation to the 62 // usage analyzer). Instead we simple remember if 63 // there was ever an assignment to result_. 64 bool result_assigned_; 65 66 // To avoid storing to .result all the time, we eliminate some of 67 // the stores by keeping track of whether or not we're sure .result 68 // will be overwritten anyway. This is a bit more tricky than what I 69 // was hoping for 70 bool is_set_; 71 bool in_try_; 72 73 AstNodeFactory<AstNullVisitor> factory_; 74 75 Expression* SetResult(Expression* value) { 76 result_assigned_ = true; 77 VariableProxy* result_proxy = factory()->NewVariableProxy(result_); 78 return factory()->NewAssignment( 79 Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition); 80 } 81 82 // Node visitors. 83 #define DEF_VISIT(type) \ 84 virtual void Visit##type(type* node); 85 AST_NODE_LIST(DEF_VISIT) 86 #undef DEF_VISIT 87 88 void VisitIterationStatement(IterationStatement* stmt); 89 }; 90 91 92 void Processor::Process(ZoneList<Statement*>* statements) { 93 for (int i = statements->length() - 1; i >= 0; --i) { 94 Visit(statements->at(i)); 95 } 96 } 97 98 99 void Processor::VisitBlock(Block* node) { 100 // An initializer block is the rewritten form of a variable declaration 101 // with initialization expressions. The initializer block contains the 102 // list of assignments corresponding to the initialization expressions. 103 // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of 104 // a variable declaration with initialization expression is 'undefined' 105 // with some JS VMs: For instance, using smjs, print(eval('var x = 7')) 106 // returns 'undefined'. To obtain the same behavior with v8, we need 107 // to prevent rewriting in that case. 108 if (!node->is_initializer_block()) Process(node->statements()); 109 } 110 111 112 void Processor::VisitExpressionStatement(ExpressionStatement* node) { 113 // Rewrite : <x>; -> .result = <x>; 114 if (!is_set_) { 115 node->set_expression(SetResult(node->expression())); 116 if (!in_try_) is_set_ = true; 117 } 118 } 119 120 121 void Processor::VisitIfStatement(IfStatement* node) { 122 // Rewrite both then and else parts (reversed). 123 bool save = is_set_; 124 Visit(node->else_statement()); 125 bool set_after_then = is_set_; 126 is_set_ = save; 127 Visit(node->then_statement()); 128 is_set_ = is_set_ && set_after_then; 129 } 130 131 132 void Processor::VisitIterationStatement(IterationStatement* node) { 133 // Rewrite the body. 134 bool set_after_loop = is_set_; 135 Visit(node->body()); 136 is_set_ = is_set_ && set_after_loop; 137 } 138 139 140 void Processor::VisitDoWhileStatement(DoWhileStatement* node) { 141 VisitIterationStatement(node); 142 } 143 144 145 void Processor::VisitWhileStatement(WhileStatement* node) { 146 VisitIterationStatement(node); 147 } 148 149 150 void Processor::VisitForStatement(ForStatement* node) { 151 VisitIterationStatement(node); 152 } 153 154 155 void Processor::VisitForInStatement(ForInStatement* node) { 156 VisitIterationStatement(node); 157 } 158 159 160 void Processor::VisitTryCatchStatement(TryCatchStatement* node) { 161 // Rewrite both try and catch blocks (reversed order). 162 bool set_after_catch = is_set_; 163 Visit(node->catch_block()); 164 is_set_ = is_set_ && set_after_catch; 165 bool save = in_try_; 166 in_try_ = true; 167 Visit(node->try_block()); 168 in_try_ = save; 169 } 170 171 172 void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) { 173 // Rewrite both try and finally block (reversed order). 174 Visit(node->finally_block()); 175 bool save = in_try_; 176 in_try_ = true; 177 Visit(node->try_block()); 178 in_try_ = save; 179 } 180 181 182 void Processor::VisitSwitchStatement(SwitchStatement* node) { 183 // Rewrite statements in all case clauses in reversed order. 184 ZoneList<CaseClause*>* clauses = node->cases(); 185 bool set_after_switch = is_set_; 186 for (int i = clauses->length() - 1; i >= 0; --i) { 187 CaseClause* clause = clauses->at(i); 188 Process(clause->statements()); 189 } 190 is_set_ = is_set_ && set_after_switch; 191 } 192 193 194 void Processor::VisitContinueStatement(ContinueStatement* node) { 195 is_set_ = false; 196 } 197 198 199 void Processor::VisitBreakStatement(BreakStatement* node) { 200 is_set_ = false; 201 } 202 203 204 void Processor::VisitWithStatement(WithStatement* node) { 205 bool set_after_body = is_set_; 206 Visit(node->statement()); 207 is_set_ = is_set_ && set_after_body; 208 } 209 210 211 // Do nothing: 212 void Processor::VisitVariableDeclaration(VariableDeclaration* node) {} 213 void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {} 214 void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {} 215 void Processor::VisitImportDeclaration(ImportDeclaration* node) {} 216 void Processor::VisitExportDeclaration(ExportDeclaration* node) {} 217 void Processor::VisitModuleLiteral(ModuleLiteral* node) {} 218 void Processor::VisitModuleVariable(ModuleVariable* node) {} 219 void Processor::VisitModulePath(ModulePath* node) {} 220 void Processor::VisitModuleUrl(ModuleUrl* node) {} 221 void Processor::VisitEmptyStatement(EmptyStatement* node) {} 222 void Processor::VisitReturnStatement(ReturnStatement* node) {} 223 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {} 224 225 226 // Expressions are never visited yet. 227 #define DEF_VISIT(type) \ 228 void Processor::Visit##type(type* expr) { UNREACHABLE(); } 229 EXPRESSION_NODE_LIST(DEF_VISIT) 230 #undef DEF_VISIT 231 232 233 // Assumes code has been parsed and scopes have been analyzed. Mutates the 234 // AST, so the AST should not continue to be used in the case of failure. 235 bool Rewriter::Rewrite(CompilationInfo* info) { 236 FunctionLiteral* function = info->function(); 237 ASSERT(function != NULL); 238 Scope* scope = function->scope(); 239 ASSERT(scope != NULL); 240 if (!scope->is_global_scope() && !scope->is_eval_scope()) return true; 241 242 ZoneList<Statement*>* body = function->body(); 243 if (!body->is_empty()) { 244 Variable* result = scope->NewTemporary( 245 info->isolate()->factory()->result_symbol()); 246 Processor processor(result); 247 processor.Process(body); 248 if (processor.HasStackOverflow()) return false; 249 250 if (processor.result_assigned()) { 251 ASSERT(function->end_position() != RelocInfo::kNoPosition); 252 // Set the position of the assignment statement one character past the 253 // source code, such that it definitely is not in the source code range 254 // of an immediate inner scope. For example in 255 // eval('with ({x:1}) x = 1'); 256 // the end position of the function generated for executing the eval code 257 // coincides with the end of the with scope which is the position of '1'. 258 int position = function->end_position(); 259 VariableProxy* result_proxy = processor.factory()->NewVariableProxy( 260 result->name(), false, position); 261 result_proxy->BindTo(result); 262 Statement* result_statement = 263 processor.factory()->NewReturnStatement(result_proxy); 264 result_statement->set_statement_pos(position); 265 body->Add(result_statement); 266 } 267 } 268 269 return true; 270 } 271 272 273 } } // namespace v8::internal 274
