Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame^] | 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. |
| 4 | |
| 5 | #include "src/parsing/rewriter.h" |
| 6 | |
| 7 | #include "src/ast/ast.h" |
| 8 | #include "src/ast/scopes.h" |
| 9 | #include "src/parsing/parser.h" |
| 10 | |
| 11 | namespace v8 { |
| 12 | namespace internal { |
| 13 | |
| 14 | class Processor: public AstVisitor { |
| 15 | public: |
| 16 | Processor(Isolate* isolate, Scope* scope, Variable* result, |
| 17 | AstValueFactory* ast_value_factory) |
| 18 | : result_(result), |
| 19 | result_assigned_(false), |
| 20 | replacement_(nullptr), |
| 21 | is_set_(false), |
| 22 | zone_(ast_value_factory->zone()), |
| 23 | scope_(scope), |
| 24 | factory_(ast_value_factory) { |
| 25 | InitializeAstVisitor(isolate); |
| 26 | } |
| 27 | |
| 28 | Processor(Parser* parser, Scope* scope, Variable* result, |
| 29 | AstValueFactory* ast_value_factory) |
| 30 | : result_(result), |
| 31 | result_assigned_(false), |
| 32 | replacement_(nullptr), |
| 33 | is_set_(false), |
| 34 | scope_(scope), |
| 35 | factory_(ast_value_factory) { |
| 36 | InitializeAstVisitor(parser->stack_limit()); |
| 37 | } |
| 38 | |
| 39 | ~Processor() override {} |
| 40 | |
| 41 | void Process(ZoneList<Statement*>* statements); |
| 42 | bool result_assigned() const { return result_assigned_; } |
| 43 | |
| 44 | Zone* zone() { return zone_; } |
| 45 | Scope* scope() { return scope_; } |
| 46 | AstNodeFactory* factory() { return &factory_; } |
| 47 | |
| 48 | // Returns ".result = value" |
| 49 | Expression* SetResult(Expression* value) { |
| 50 | result_assigned_ = true; |
| 51 | VariableProxy* result_proxy = factory()->NewVariableProxy(result_); |
| 52 | return factory()->NewAssignment(Token::ASSIGN, result_proxy, value, |
| 53 | RelocInfo::kNoPosition); |
| 54 | } |
| 55 | |
| 56 | // Inserts '.result = undefined' in front of the given statement. |
| 57 | Statement* AssignUndefinedBefore(Statement* s); |
| 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 | // When visiting a node, we "return" a replacement for that node in |
| 69 | // [replacement_]. In many cases this will just be the original node. |
| 70 | Statement* replacement_; |
| 71 | |
| 72 | // To avoid storing to .result all the time, we eliminate some of |
| 73 | // the stores by keeping track of whether or not we're sure .result |
| 74 | // will be overwritten anyway. This is a bit more tricky than what I |
| 75 | // was hoping for. |
| 76 | bool is_set_; |
| 77 | |
| 78 | Zone* zone_; |
| 79 | Scope* scope_; |
| 80 | AstNodeFactory factory_; |
| 81 | |
| 82 | // Node visitors. |
| 83 | #define DEF_VISIT(type) void Visit##type(type* node) override; |
| 84 | AST_NODE_LIST(DEF_VISIT) |
| 85 | #undef DEF_VISIT |
| 86 | |
| 87 | void VisitIterationStatement(IterationStatement* stmt); |
| 88 | |
| 89 | DEFINE_AST_VISITOR_SUBCLASS_MEMBERS(); |
| 90 | }; |
| 91 | |
| 92 | |
| 93 | Statement* Processor::AssignUndefinedBefore(Statement* s) { |
| 94 | Expression* result_proxy = factory()->NewVariableProxy(result_); |
| 95 | Expression* undef = factory()->NewUndefinedLiteral(RelocInfo::kNoPosition); |
| 96 | Expression* assignment = factory()->NewAssignment( |
| 97 | Token::ASSIGN, result_proxy, undef, RelocInfo::kNoPosition); |
| 98 | Block* b = factory()->NewBlock(NULL, 2, false, RelocInfo::kNoPosition); |
| 99 | b->statements()->Add( |
| 100 | factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition), |
| 101 | zone()); |
| 102 | b->statements()->Add(s, zone()); |
| 103 | return b; |
| 104 | } |
| 105 | |
| 106 | |
| 107 | void Processor::Process(ZoneList<Statement*>* statements) { |
| 108 | for (int i = statements->length() - 1; i >= 0; --i) { |
| 109 | Visit(statements->at(i)); |
| 110 | statements->Set(i, replacement_); |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | |
| 115 | void Processor::VisitBlock(Block* node) { |
| 116 | // An initializer block is the rewritten form of a variable declaration |
| 117 | // with initialization expressions. The initializer block contains the |
| 118 | // list of assignments corresponding to the initialization expressions. |
| 119 | // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of |
| 120 | // a variable declaration with initialization expression is 'undefined' |
| 121 | // with some JS VMs: For instance, using smjs, print(eval('var x = 7')) |
| 122 | // returns 'undefined'. To obtain the same behavior with v8, we need |
| 123 | // to prevent rewriting in that case. |
| 124 | if (!node->ignore_completion_value()) Process(node->statements()); |
| 125 | replacement_ = node; |
| 126 | } |
| 127 | |
| 128 | |
| 129 | void Processor::VisitExpressionStatement(ExpressionStatement* node) { |
| 130 | // Rewrite : <x>; -> .result = <x>; |
| 131 | if (!is_set_) { |
| 132 | node->set_expression(SetResult(node->expression())); |
| 133 | is_set_ = true; |
| 134 | } |
| 135 | replacement_ = node; |
| 136 | } |
| 137 | |
| 138 | |
| 139 | void Processor::VisitIfStatement(IfStatement* node) { |
| 140 | // Rewrite both branches. |
| 141 | bool set_after = is_set_; |
| 142 | Visit(node->then_statement()); |
| 143 | node->set_then_statement(replacement_); |
| 144 | bool set_in_then = is_set_; |
| 145 | is_set_ = set_after; |
| 146 | Visit(node->else_statement()); |
| 147 | node->set_else_statement(replacement_); |
| 148 | is_set_ = is_set_ && set_in_then; |
| 149 | replacement_ = node; |
| 150 | |
| 151 | if (FLAG_harmony_completion && !is_set_) { |
| 152 | is_set_ = true; |
| 153 | replacement_ = AssignUndefinedBefore(node); |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | |
| 158 | void Processor::VisitIterationStatement(IterationStatement* node) { |
| 159 | // Rewrite the body. |
| 160 | bool set_after = is_set_; |
| 161 | is_set_ = false; // We are in a loop, so we can't rely on [set_after]. |
| 162 | Visit(node->body()); |
| 163 | node->set_body(replacement_); |
| 164 | is_set_ = is_set_ && set_after; |
| 165 | replacement_ = node; |
| 166 | |
| 167 | if (FLAG_harmony_completion && !is_set_) { |
| 168 | is_set_ = true; |
| 169 | replacement_ = AssignUndefinedBefore(node); |
| 170 | } |
| 171 | } |
| 172 | |
| 173 | |
| 174 | void Processor::VisitDoWhileStatement(DoWhileStatement* node) { |
| 175 | VisitIterationStatement(node); |
| 176 | } |
| 177 | |
| 178 | |
| 179 | void Processor::VisitWhileStatement(WhileStatement* node) { |
| 180 | VisitIterationStatement(node); |
| 181 | } |
| 182 | |
| 183 | |
| 184 | void Processor::VisitForStatement(ForStatement* node) { |
| 185 | VisitIterationStatement(node); |
| 186 | } |
| 187 | |
| 188 | |
| 189 | void Processor::VisitForInStatement(ForInStatement* node) { |
| 190 | VisitIterationStatement(node); |
| 191 | } |
| 192 | |
| 193 | |
| 194 | void Processor::VisitForOfStatement(ForOfStatement* node) { |
| 195 | VisitIterationStatement(node); |
| 196 | } |
| 197 | |
| 198 | |
| 199 | void Processor::VisitTryCatchStatement(TryCatchStatement* node) { |
| 200 | // Rewrite both try and catch block. |
| 201 | bool set_after = is_set_; |
| 202 | Visit(node->try_block()); |
| 203 | node->set_try_block(static_cast<Block*>(replacement_)); |
| 204 | bool set_in_try = is_set_; |
| 205 | is_set_ = set_after; |
| 206 | Visit(node->catch_block()); |
| 207 | node->set_catch_block(static_cast<Block*>(replacement_)); |
| 208 | is_set_ = is_set_ && set_in_try; |
| 209 | replacement_ = node; |
| 210 | |
| 211 | if (FLAG_harmony_completion && !is_set_) { |
| 212 | is_set_ = true; |
| 213 | replacement_ = AssignUndefinedBefore(node); |
| 214 | } |
| 215 | } |
| 216 | |
| 217 | |
| 218 | void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) { |
| 219 | // Rewrite both try and finally block (in reverse order). |
| 220 | bool set_after = is_set_; |
| 221 | is_set_ = true; // Don't normally need to assign in finally block. |
| 222 | Visit(node->finally_block()); |
| 223 | node->set_finally_block(replacement_->AsBlock()); |
| 224 | { // Save .result value at the beginning of the finally block and restore it |
| 225 | // at the end again: ".backup = .result; ...; .result = .backup" |
| 226 | // This is necessary because the finally block does not normally contribute |
| 227 | // to the completion value. |
| 228 | Variable* backup = scope()->NewTemporary( |
| 229 | factory()->ast_value_factory()->dot_result_string()); |
| 230 | Expression* backup_proxy = factory()->NewVariableProxy(backup); |
| 231 | Expression* result_proxy = factory()->NewVariableProxy(result_); |
| 232 | Expression* save = factory()->NewAssignment( |
| 233 | Token::ASSIGN, backup_proxy, result_proxy, RelocInfo::kNoPosition); |
| 234 | Expression* restore = factory()->NewAssignment( |
| 235 | Token::ASSIGN, result_proxy, backup_proxy, RelocInfo::kNoPosition); |
| 236 | node->finally_block()->statements()->InsertAt( |
| 237 | 0, factory()->NewExpressionStatement(save, RelocInfo::kNoPosition), |
| 238 | zone()); |
| 239 | node->finally_block()->statements()->Add( |
| 240 | factory()->NewExpressionStatement(restore, RelocInfo::kNoPosition), |
| 241 | zone()); |
| 242 | } |
| 243 | is_set_ = set_after; |
| 244 | Visit(node->try_block()); |
| 245 | node->set_try_block(replacement_->AsBlock()); |
| 246 | replacement_ = node; |
| 247 | |
| 248 | if (FLAG_harmony_completion && !is_set_) { |
| 249 | is_set_ = true; |
| 250 | replacement_ = AssignUndefinedBefore(node); |
| 251 | } |
| 252 | } |
| 253 | |
| 254 | |
| 255 | void Processor::VisitSwitchStatement(SwitchStatement* node) { |
| 256 | // Rewrite statements in all case clauses (in reverse order). |
| 257 | ZoneList<CaseClause*>* clauses = node->cases(); |
| 258 | bool set_after = is_set_; |
| 259 | for (int i = clauses->length() - 1; i >= 0; --i) { |
| 260 | CaseClause* clause = clauses->at(i); |
| 261 | Process(clause->statements()); |
| 262 | } |
| 263 | is_set_ = is_set_ && set_after; |
| 264 | replacement_ = node; |
| 265 | |
| 266 | if (FLAG_harmony_completion && !is_set_) { |
| 267 | is_set_ = true; |
| 268 | replacement_ = AssignUndefinedBefore(node); |
| 269 | } |
| 270 | } |
| 271 | |
| 272 | |
| 273 | void Processor::VisitContinueStatement(ContinueStatement* node) { |
| 274 | is_set_ = false; |
| 275 | replacement_ = node; |
| 276 | } |
| 277 | |
| 278 | |
| 279 | void Processor::VisitBreakStatement(BreakStatement* node) { |
| 280 | is_set_ = false; |
| 281 | replacement_ = node; |
| 282 | } |
| 283 | |
| 284 | |
| 285 | void Processor::VisitWithStatement(WithStatement* node) { |
| 286 | Visit(node->statement()); |
| 287 | node->set_statement(replacement_); |
| 288 | replacement_ = node; |
| 289 | |
| 290 | if (FLAG_harmony_completion && !is_set_) { |
| 291 | is_set_ = true; |
| 292 | replacement_ = AssignUndefinedBefore(node); |
| 293 | } |
| 294 | } |
| 295 | |
| 296 | |
| 297 | void Processor::VisitSloppyBlockFunctionStatement( |
| 298 | SloppyBlockFunctionStatement* node) { |
| 299 | Visit(node->statement()); |
| 300 | node->set_statement(replacement_); |
| 301 | replacement_ = node; |
| 302 | } |
| 303 | |
| 304 | |
| 305 | void Processor::VisitEmptyStatement(EmptyStatement* node) { |
| 306 | replacement_ = node; |
| 307 | } |
| 308 | |
| 309 | |
| 310 | void Processor::VisitReturnStatement(ReturnStatement* node) { |
| 311 | is_set_ = true; |
| 312 | replacement_ = node; |
| 313 | } |
| 314 | |
| 315 | |
| 316 | void Processor::VisitDebuggerStatement(DebuggerStatement* node) { |
| 317 | replacement_ = node; |
| 318 | } |
| 319 | |
| 320 | |
| 321 | // Expressions are never visited. |
| 322 | #define DEF_VISIT(type) \ |
| 323 | void Processor::Visit##type(type* expr) { UNREACHABLE(); } |
| 324 | EXPRESSION_NODE_LIST(DEF_VISIT) |
| 325 | #undef DEF_VISIT |
| 326 | |
| 327 | |
| 328 | // Declarations are never visited. |
| 329 | #define DEF_VISIT(type) \ |
| 330 | void Processor::Visit##type(type* expr) { UNREACHABLE(); } |
| 331 | DECLARATION_NODE_LIST(DEF_VISIT) |
| 332 | #undef DEF_VISIT |
| 333 | |
| 334 | |
| 335 | // Assumes code has been parsed. Mutates the AST, so the AST should not |
| 336 | // continue to be used in the case of failure. |
| 337 | bool Rewriter::Rewrite(ParseInfo* info) { |
| 338 | FunctionLiteral* function = info->literal(); |
| 339 | DCHECK(function != NULL); |
| 340 | Scope* scope = function->scope(); |
| 341 | DCHECK(scope != NULL); |
| 342 | if (!scope->is_script_scope() && !scope->is_eval_scope()) return true; |
| 343 | |
| 344 | ZoneList<Statement*>* body = function->body(); |
| 345 | if (!body->is_empty()) { |
| 346 | Variable* result = |
| 347 | scope->NewTemporary(info->ast_value_factory()->dot_result_string()); |
| 348 | // The name string must be internalized at this point. |
| 349 | DCHECK(!result->name().is_null()); |
| 350 | Processor processor(info->isolate(), scope, result, |
| 351 | info->ast_value_factory()); |
| 352 | processor.Process(body); |
| 353 | if (processor.HasStackOverflow()) return false; |
| 354 | |
| 355 | if (processor.result_assigned()) { |
| 356 | DCHECK(function->end_position() != RelocInfo::kNoPosition); |
| 357 | // Set the position of the assignment statement one character past the |
| 358 | // source code, such that it definitely is not in the source code range |
| 359 | // of an immediate inner scope. For example in |
| 360 | // eval('with ({x:1}) x = 1'); |
| 361 | // the end position of the function generated for executing the eval code |
| 362 | // coincides with the end of the with scope which is the position of '1'. |
| 363 | int pos = function->end_position(); |
| 364 | VariableProxy* result_proxy = |
| 365 | processor.factory()->NewVariableProxy(result, pos); |
| 366 | Statement* result_statement = |
| 367 | processor.factory()->NewReturnStatement(result_proxy, pos); |
| 368 | body->Add(result_statement, info->zone()); |
| 369 | } |
| 370 | } |
| 371 | |
| 372 | return true; |
| 373 | } |
| 374 | |
| 375 | |
| 376 | bool Rewriter::Rewrite(Parser* parser, DoExpression* expr, |
| 377 | AstValueFactory* factory) { |
| 378 | Block* block = expr->block(); |
| 379 | Scope* scope = block->scope(); |
| 380 | ZoneList<Statement*>* body = block->statements(); |
| 381 | VariableProxy* result = expr->result(); |
| 382 | Variable* result_var = result->var(); |
| 383 | |
| 384 | if (!body->is_empty()) { |
| 385 | Processor processor(parser, scope, result_var, factory); |
| 386 | processor.Process(body); |
| 387 | if (processor.HasStackOverflow()) return false; |
| 388 | |
| 389 | if (!processor.result_assigned()) { |
| 390 | AstNodeFactory* node_factory = processor.factory(); |
| 391 | Expression* undef = |
| 392 | node_factory->NewUndefinedLiteral(RelocInfo::kNoPosition); |
| 393 | Statement* completion = node_factory->NewExpressionStatement( |
| 394 | processor.SetResult(undef), expr->position()); |
| 395 | body->Add(completion, factory->zone()); |
| 396 | } |
| 397 | } |
| 398 | return true; |
| 399 | } |
| 400 | |
| 401 | |
| 402 | } // namespace internal |
| 403 | } // namespace v8 |