christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame^] | 1 | // Copyright 2006-2008 Google Inc. 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 "prettyprinter.h" |
| 31 | #include "scopeinfo.h" |
| 32 | #include "scopes.h" |
| 33 | |
| 34 | namespace v8 { namespace internal { |
| 35 | |
| 36 | // ---------------------------------------------------------------------------- |
| 37 | // A Zone allocator for use with LocalsMap. |
| 38 | |
| 39 | class ZoneAllocator: public Allocator { |
| 40 | public: |
| 41 | /* nothing to do */ |
| 42 | virtual ~ZoneAllocator() {} |
| 43 | |
| 44 | virtual void* New(size_t size) { return Zone::New(size); } |
| 45 | |
| 46 | /* ignored - Zone is freed in one fell swoop */ |
| 47 | virtual void Delete(void* p) {} |
| 48 | }; |
| 49 | |
| 50 | |
| 51 | static ZoneAllocator LocalsMapAllocator; |
| 52 | |
| 53 | |
| 54 | // ---------------------------------------------------------------------------- |
| 55 | // Implementation of LocalsMap |
| 56 | // |
| 57 | // Note: We are storing the handle locations as key values in the hash map. |
| 58 | // When inserting a new variable via Declare(), we rely on the fact that |
| 59 | // the handle location remains alive for the duration of that variable |
| 60 | // use. Because a Variable holding a handle with the same location exists |
| 61 | // this is ensured. |
| 62 | |
| 63 | static bool Match(void* key1, void* key2) { |
| 64 | String* name1 = *reinterpret_cast<String**>(key1); |
| 65 | String* name2 = *reinterpret_cast<String**>(key2); |
| 66 | ASSERT(name1->IsSymbol()); |
| 67 | ASSERT(name2->IsSymbol()); |
| 68 | return name1 == name2; |
| 69 | } |
| 70 | |
| 71 | |
| 72 | // Dummy constructor |
| 73 | LocalsMap::LocalsMap(bool gotta_love_static_overloading) : HashMap() {} |
| 74 | |
| 75 | LocalsMap::LocalsMap() : HashMap(Match, &LocalsMapAllocator, 8) {} |
| 76 | LocalsMap::~LocalsMap() {} |
| 77 | |
| 78 | |
| 79 | Variable* LocalsMap::Declare(Scope* scope, |
| 80 | Handle<String> name, |
| 81 | Variable::Mode mode, |
| 82 | bool is_valid_LHS, |
| 83 | bool is_this) { |
| 84 | HashMap::Entry* p = HashMap::Lookup(name.location(), name->Hash(), true); |
| 85 | if (p->value == NULL) { |
| 86 | // The variable has not been declared yet -> insert it. |
| 87 | ASSERT(p->key == name.location()); |
| 88 | p->value = new Variable(scope, name, mode, is_valid_LHS, is_this); |
| 89 | } |
| 90 | return reinterpret_cast<Variable*>(p->value); |
| 91 | } |
| 92 | |
| 93 | |
| 94 | Variable* LocalsMap::Lookup(Handle<String> name) { |
| 95 | HashMap::Entry* p = HashMap::Lookup(name.location(), name->Hash(), false); |
| 96 | if (p != NULL) { |
| 97 | ASSERT(*reinterpret_cast<String**>(p->key) == *name); |
| 98 | ASSERT(p->value != NULL); |
| 99 | return reinterpret_cast<Variable*>(p->value); |
| 100 | } |
| 101 | return NULL; |
| 102 | } |
| 103 | |
| 104 | |
| 105 | // ---------------------------------------------------------------------------- |
| 106 | // Implementation of Scope |
| 107 | |
| 108 | |
| 109 | // Dummy constructor |
| 110 | Scope::Scope() |
| 111 | : inner_scopes_(0), |
| 112 | locals_(false), |
| 113 | temps_(0), |
| 114 | params_(0), |
| 115 | nonlocals_(0), |
| 116 | unresolved_(0), |
| 117 | decls_(0) { |
| 118 | } |
| 119 | |
| 120 | |
| 121 | Scope::Scope(Scope* outer_scope, Type type) |
| 122 | : outer_scope_(outer_scope), |
| 123 | inner_scopes_(4), |
| 124 | type_(type), |
| 125 | scope_name_(Factory::empty_symbol()), |
| 126 | locals_(), |
| 127 | temps_(4), |
| 128 | params_(4), |
| 129 | nonlocals_(4), |
| 130 | unresolved_(16), |
| 131 | decls_(4), |
| 132 | receiver_(NULL), |
| 133 | function_(NULL), |
| 134 | arguments_(NULL), |
| 135 | arguments_shadow_(NULL), |
| 136 | illegal_redecl_(NULL), |
| 137 | scope_inside_with_(false), |
| 138 | scope_contains_with_(false), |
| 139 | scope_calls_eval_(false), |
| 140 | outer_scope_calls_eval_(false), |
| 141 | inner_scope_calls_eval_(false), |
| 142 | force_eager_compilation_(false), |
| 143 | num_stack_slots_(0), |
| 144 | num_heap_slots_(0) { |
| 145 | // At some point we might want to provide outer scopes to |
| 146 | // eval scopes (by walking the stack and reading the scope info). |
| 147 | // In that case, the ASSERT below needs to be adjusted. |
| 148 | ASSERT((type == GLOBAL_SCOPE || type == EVAL_SCOPE) == (outer_scope == NULL)); |
| 149 | ASSERT(!HasIllegalRedeclaration()); |
| 150 | } |
| 151 | |
| 152 | |
| 153 | void Scope::Initialize(bool inside_with) { |
| 154 | // Add this scope as a new inner scope of the outer scope. |
| 155 | if (outer_scope_ != NULL) { |
| 156 | outer_scope_->inner_scopes_.Add(this); |
| 157 | scope_inside_with_ = outer_scope_->scope_inside_with_ || inside_with; |
| 158 | } else { |
| 159 | scope_inside_with_ = inside_with; |
| 160 | } |
| 161 | |
| 162 | // Declare convenience variables. |
| 163 | // Declare and allocate receiver (even for the global scope, and even |
| 164 | // if naccesses_ == 0). |
| 165 | // NOTE: When loading parameters in the global scope, we must take |
| 166 | // care not to access them as properties of the global object, but |
| 167 | // instead load them directly from the stack. Currently, the only |
| 168 | // such parameter is 'this' which is passed on the stack when |
| 169 | // invoking scripts |
| 170 | { Variable* var = |
| 171 | locals_.Declare(this, Factory::this_symbol(), Variable::VAR, false, true); |
| 172 | var->rewrite_ = new Slot(var, Slot::PARAMETER, -1); |
| 173 | receiver_ = new VariableProxy(Factory::this_symbol(), true, false); |
| 174 | receiver_->BindTo(var); |
| 175 | } |
| 176 | |
| 177 | if (is_function_scope()) { |
| 178 | // Declare 'arguments' variable which exists in all functions. |
| 179 | // Note that it may never be accessed, in which case it won't |
| 180 | // be allocated during variable allocation. |
| 181 | Declare(Factory::arguments_symbol(), Variable::VAR); |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | |
| 186 | |
| 187 | Variable* Scope::Lookup(Handle<String> name) { |
| 188 | return locals_.Lookup(name); |
| 189 | } |
| 190 | |
| 191 | |
| 192 | Variable* Scope::DeclareFunctionVar(Handle<String> name) { |
| 193 | ASSERT(is_function_scope() && function_ == NULL); |
| 194 | function_ = new Variable(this, name, Variable::CONST, true, false); |
| 195 | return function_; |
| 196 | } |
| 197 | |
| 198 | |
| 199 | Variable* Scope::Declare(Handle<String> name, Variable::Mode mode) { |
| 200 | // DYNAMIC variables are introduces during variable allocation, |
| 201 | // INTERNAL variables are allocated explicitly, and TEMPORARY |
| 202 | // variables are allocated via NewTemporary(). |
| 203 | ASSERT(mode == Variable::VAR || mode == Variable::CONST); |
| 204 | return locals_.Declare(this, name, mode, true, false); |
| 205 | } |
| 206 | |
| 207 | |
| 208 | void Scope::AddParameter(Variable* var) { |
| 209 | ASSERT(is_function_scope()); |
| 210 | ASSERT(Lookup(var->name()) == var); |
| 211 | params_.Add(var); |
| 212 | } |
| 213 | |
| 214 | |
| 215 | VariableProxy* Scope::NewUnresolved(Handle<String> name, bool inside_with) { |
| 216 | // Note that we must not share the unresolved variables with |
| 217 | // the same name because they may be removed selectively via |
| 218 | // RemoveUnresolved(). |
| 219 | VariableProxy* proxy = new VariableProxy(name, false, inside_with); |
| 220 | unresolved_.Add(proxy); |
| 221 | return proxy; |
| 222 | } |
| 223 | |
| 224 | |
| 225 | void Scope::RemoveUnresolved(VariableProxy* var) { |
| 226 | // Most likely (always?) any variable we want to remove |
| 227 | // was just added before, so we search backwards. |
| 228 | for (int i = unresolved_.length(); i-- > 0;) { |
| 229 | if (unresolved_[i] == var) { |
| 230 | unresolved_.Remove(i); |
| 231 | return; |
| 232 | } |
| 233 | } |
| 234 | } |
| 235 | |
| 236 | |
| 237 | VariableProxy* Scope::NewTemporary(Handle<String> name) { |
| 238 | Variable* var = new Variable(this, name, Variable::TEMPORARY, true, false); |
| 239 | VariableProxy* tmp = new VariableProxy(name, false, false); |
| 240 | tmp->BindTo(var); |
| 241 | temps_.Add(var); |
| 242 | return tmp; |
| 243 | } |
| 244 | |
| 245 | |
| 246 | void Scope::AddDeclaration(Declaration* declaration) { |
| 247 | decls_.Add(declaration); |
| 248 | } |
| 249 | |
| 250 | |
| 251 | void Scope::SetIllegalRedeclaration(Expression* expression) { |
| 252 | // Only set the illegal redeclaration expression the |
| 253 | // first time the function is called. |
| 254 | if (!HasIllegalRedeclaration()) { |
| 255 | illegal_redecl_ = expression; |
| 256 | } |
| 257 | ASSERT(HasIllegalRedeclaration()); |
| 258 | } |
| 259 | |
| 260 | |
| 261 | void Scope::VisitIllegalRedeclaration(Visitor* visitor) { |
| 262 | ASSERT(HasIllegalRedeclaration()); |
| 263 | illegal_redecl_->Accept(visitor); |
| 264 | } |
| 265 | |
| 266 | |
| 267 | template<class Allocator> |
| 268 | void Scope::CollectUsedVariables(List<Variable*, Allocator>* locals) { |
| 269 | // Collect variables in this scope. |
| 270 | // Note that the function_ variable - if present - is not |
| 271 | // collected here but handled separately in ScopeInfo |
| 272 | // which is the current user of this function). |
| 273 | for (int i = 0; i < temps_.length(); i++) { |
| 274 | Variable* var = temps_[i]; |
| 275 | if (var->var_uses()->is_used()) { |
| 276 | locals->Add(var); |
| 277 | } |
| 278 | } |
| 279 | for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| 280 | Variable* var = reinterpret_cast<Variable*>(p->value); |
| 281 | if (var->var_uses()->is_used()) { |
| 282 | locals->Add(var); |
| 283 | } |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | |
| 288 | // Make sure the method gets instantiated by the template system. |
| 289 | template void Scope::CollectUsedVariables( |
| 290 | List<Variable*, FreeStoreAllocationPolicy>* locals); |
| 291 | template void Scope::CollectUsedVariables( |
| 292 | List<Variable*, PreallocatedStorage>* locals); |
| 293 | |
| 294 | |
| 295 | void Scope::AllocateVariables() { |
| 296 | ASSERT(outer_scope_ == NULL); // eval or global scopes only |
| 297 | |
| 298 | // 1) Propagate scope information. |
| 299 | // If we are in an eval scope, we may have other outer scopes about |
| 300 | // which we don't know anything at this point. Thus we must be conservative |
| 301 | // and assume they may invoke eval themselves. Eventually we could capture |
| 302 | // this information in the ScopeInfo and then use it here (by traversing |
| 303 | // the call chain stack, at compile time). |
| 304 | PropagateScopeInfo(is_eval_scope()); |
| 305 | |
| 306 | // 2) Resolve variables. |
| 307 | Scope* global_scope = NULL; |
| 308 | if (is_global_scope()) global_scope = this; |
| 309 | ResolveVariablesRecursively(global_scope); |
| 310 | |
| 311 | // 3) Allocate variables. |
| 312 | AllocateVariablesRecursively(); |
| 313 | } |
| 314 | |
| 315 | |
| 316 | bool Scope::SupportsEval() const { |
| 317 | return scope_calls_eval_ || inner_scope_calls_eval_; |
| 318 | } |
| 319 | |
| 320 | |
| 321 | bool Scope::AllowsLazyCompilation() const { |
| 322 | return !force_eager_compilation_ && HasTrivialOuterContext(); |
| 323 | } |
| 324 | |
| 325 | |
| 326 | bool Scope::HasTrivialContext() const { |
| 327 | // A function scope has a trivial context if it always is the global |
| 328 | // context. We iteratively scan out the context chain to see if |
| 329 | // there is anything that makes this scope non-trivial; otherwise we |
| 330 | // return true. |
| 331 | for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) { |
| 332 | if (scope->is_eval_scope()) return false; |
| 333 | if (scope->scope_inside_with_) return false; |
| 334 | if (scope->num_heap_slots_ > 0) return false; |
| 335 | } |
| 336 | return true; |
| 337 | } |
| 338 | |
| 339 | |
| 340 | bool Scope::HasTrivialOuterContext() const { |
| 341 | Scope* outer = outer_scope_; |
| 342 | if (outer == NULL) return true; |
| 343 | // Note that the outer context may be trivial in general, but the current |
| 344 | // scope may be inside a 'with' statement in which case the outer context |
| 345 | // for this scope is not trivial. |
| 346 | return !scope_inside_with_ && outer->HasTrivialContext(); |
| 347 | } |
| 348 | |
| 349 | |
| 350 | int Scope::ContextChainLength(Scope* scope) { |
| 351 | int n = 0; |
| 352 | for (Scope* s = this; s != scope; s = s->outer_scope_) { |
| 353 | ASSERT(s != NULL); // scope must be in the scope chain |
| 354 | if (s->num_heap_slots() > 0) n++; |
| 355 | } |
| 356 | return n; |
| 357 | } |
| 358 | |
| 359 | |
| 360 | #ifdef DEBUG |
| 361 | static const char* Header(Scope::Type type) { |
| 362 | switch (type) { |
| 363 | case Scope::EVAL_SCOPE: return "eval"; |
| 364 | case Scope::FUNCTION_SCOPE: return "function"; |
| 365 | case Scope::GLOBAL_SCOPE: return "global"; |
| 366 | } |
| 367 | UNREACHABLE(); |
| 368 | return NULL; |
| 369 | } |
| 370 | |
| 371 | |
| 372 | static void Indent(int n, const char* str) { |
| 373 | PrintF("%*s%s", n, "", str); |
| 374 | } |
| 375 | |
| 376 | |
| 377 | static void PrintName(Handle<String> name) { |
| 378 | SmartPointer<char> s = name->ToCString(DISALLOW_NULLS); |
| 379 | PrintF("%s", *s); |
| 380 | } |
| 381 | |
| 382 | |
| 383 | static void PrintVar(PrettyPrinter* printer, int indent, Variable* var) { |
| 384 | if (var->var_uses()->is_used() || var->rewrite() != NULL) { |
| 385 | Indent(indent, Variable::Mode2String(var->mode())); |
| 386 | PrintF(" "); |
| 387 | PrintName(var->name()); |
| 388 | PrintF("; // "); |
| 389 | if (var->rewrite() != NULL) PrintF("%s, ", printer->Print(var->rewrite())); |
| 390 | if (var->is_accessed_from_inner_scope()) PrintF("inner scope access, "); |
| 391 | PrintF("var "); |
| 392 | var->var_uses()->Print(); |
| 393 | PrintF(", obj "); |
| 394 | var->obj_uses()->Print(); |
| 395 | PrintF("\n"); |
| 396 | } |
| 397 | } |
| 398 | |
| 399 | |
| 400 | void Scope::Print(int n) { |
| 401 | int n0 = (n > 0 ? n : 0); |
| 402 | int n1 = n0 + 2; // indentation |
| 403 | |
| 404 | // Print header. |
| 405 | Indent(n0, Header(type_)); |
| 406 | if (scope_name_->length() > 0) { |
| 407 | PrintF(" "); |
| 408 | PrintName(scope_name_); |
| 409 | } |
| 410 | |
| 411 | // Print parameters, if any. |
| 412 | if (is_function_scope()) { |
| 413 | PrintF(" ("); |
| 414 | for (int i = 0; i < params_.length(); i++) { |
| 415 | if (i > 0) PrintF(", "); |
| 416 | PrintName(params_[i]->name()); |
| 417 | } |
| 418 | PrintF(")"); |
| 419 | } |
| 420 | |
| 421 | PrintF(" {\n"); |
| 422 | |
| 423 | // Function name, if any (named function literals, only). |
| 424 | if (function_ != NULL) { |
| 425 | Indent(n1, "// (local) function name: "); |
| 426 | PrintName(function_->name()); |
| 427 | PrintF("\n"); |
| 428 | } |
| 429 | |
| 430 | // Scope info. |
| 431 | if (HasTrivialOuterContext()) { |
| 432 | Indent(n1, "// scope has trivial outer context\n"); |
| 433 | } |
| 434 | if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n"); |
| 435 | if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n"); |
| 436 | if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n"); |
| 437 | if (outer_scope_calls_eval_) Indent(n1, "// outer scope calls 'eval'\n"); |
| 438 | if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n"); |
| 439 | if (num_stack_slots_ > 0) { Indent(n1, "// "); |
| 440 | PrintF("%d stack slots\n", num_stack_slots_); } |
| 441 | if (num_heap_slots_ > 0) { Indent(n1, "// "); |
| 442 | PrintF("%d heap slots\n", num_heap_slots_); } |
| 443 | |
| 444 | // Print locals. |
| 445 | PrettyPrinter printer; |
| 446 | Indent(n1, "// function var\n"); |
| 447 | if (function_ != NULL) { |
| 448 | PrintVar(&printer, n1, function_); |
| 449 | } |
| 450 | |
| 451 | Indent(n1, "// temporary vars\n"); |
| 452 | for (int i = 0; i < temps_.length(); i++) { |
| 453 | PrintVar(&printer, n1, temps_[i]); |
| 454 | } |
| 455 | |
| 456 | Indent(n1, "// local vars\n"); |
| 457 | for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| 458 | Variable* var = reinterpret_cast<Variable*>(p->value); |
| 459 | PrintVar(&printer, n1, var); |
| 460 | } |
| 461 | |
| 462 | Indent(n1, "// nonlocal vars\n"); |
| 463 | for (int i = 0; i < nonlocals_.length(); i++) |
| 464 | PrintVar(&printer, n1, nonlocals_[i]); |
| 465 | |
| 466 | // Print inner scopes (disable by providing negative n). |
| 467 | if (n >= 0) { |
| 468 | for (int i = 0; i < inner_scopes_.length(); i++) { |
| 469 | PrintF("\n"); |
| 470 | inner_scopes_[i]->Print(n1); |
| 471 | } |
| 472 | } |
| 473 | |
| 474 | Indent(n0, "}\n"); |
| 475 | } |
| 476 | #endif // DEBUG |
| 477 | |
| 478 | |
| 479 | Variable* Scope::NonLocal(Handle<String> name) { |
| 480 | // Space optimization: reuse existing non-local with the same name. |
| 481 | for (int i = 0; i < nonlocals_.length(); i++) { |
| 482 | Variable* var = nonlocals_[i]; |
| 483 | if (var->name().is_identical_to(name)) { |
| 484 | ASSERT(var->mode() == Variable::DYNAMIC); |
| 485 | return var; |
| 486 | } |
| 487 | } |
| 488 | |
| 489 | // Otherwise create a new new-local and add it to the list. |
| 490 | Variable* var = new Variable( |
| 491 | NULL /* we don't know the scope */, |
| 492 | name, Variable::DYNAMIC, true, false); |
| 493 | nonlocals_.Add(var); |
| 494 | |
| 495 | // Allocate it by giving it a dynamic lookup. |
| 496 | var->rewrite_ = new Slot(var, Slot::LOOKUP, -1); |
| 497 | |
| 498 | return var; |
| 499 | } |
| 500 | |
| 501 | |
| 502 | // Lookup a variable starting with this scope. The result is either |
| 503 | // the statically resolved (local!) variable belonging to an outer scope, |
| 504 | // or NULL. It may be NULL because a) we couldn't find a variable, or b) |
| 505 | // because the variable is just a guess (and may be shadowed by another |
| 506 | // variable that is introduced dynamically via an 'eval' call or a 'with' |
| 507 | // statement). |
| 508 | Variable* Scope::LookupRecursive(Handle<String> name, bool inner_lookup) { |
| 509 | // If we find a variable, but the current scope calls 'eval', the found |
| 510 | // variable may not be the correct one (the 'eval' may introduce a |
| 511 | // property with the same name). In that case, remember that the variable |
| 512 | // found is just a guess. |
| 513 | bool guess = scope_calls_eval_; |
| 514 | |
| 515 | // Try to find the variable in this scope. |
| 516 | Variable* var = Lookup(name); |
| 517 | |
| 518 | if (var != NULL) { |
| 519 | // We found a variable. If this is not an inner lookup, we are done. |
| 520 | // (Even if there is an 'eval' in this scope which introduces the |
| 521 | // same variable again, the resulting variable remains the same. |
| 522 | // Note that enclosing 'with' statements are handled at the call site.) |
| 523 | if (!inner_lookup) |
| 524 | return var; |
| 525 | |
| 526 | } else { |
| 527 | // We did not find a variable locally. Check against the function variable, |
| 528 | // if any. We can do this for all scopes, since the function variable is |
| 529 | // only present - if at all - for function scopes. |
| 530 | // |
| 531 | // This lookup corresponds to a lookup in the "intermediate" scope sitting |
| 532 | // between this scope and the outer scope. (ECMA-262, 3rd., requires that |
| 533 | // the name of named function literal is kept in an intermediate scope |
| 534 | // inbetween this scope and the next outer scope.) |
| 535 | if (function_ != NULL && function_->name().is_identical_to(name)) { |
| 536 | var = function_; |
| 537 | |
| 538 | } else if (outer_scope_ != NULL) { |
| 539 | var = outer_scope_->LookupRecursive(name, true /* inner lookup */); |
| 540 | // We may have found a variable in an outer scope. However, if |
| 541 | // the current scope is inside a 'with', the actual variable may |
| 542 | // be a property introduced via the 'with' statement. Then, the |
| 543 | // variable we may have found is just a guess. |
| 544 | if (scope_inside_with_) |
| 545 | guess = true; |
| 546 | } |
| 547 | |
| 548 | // If we did not find a variable, we are done. |
| 549 | if (var == NULL) |
| 550 | return NULL; |
| 551 | } |
| 552 | |
| 553 | ASSERT(var != NULL); |
| 554 | |
| 555 | // If this is a lookup from an inner scope, mark the variable. |
| 556 | if (inner_lookup) |
| 557 | var->is_accessed_from_inner_scope_ = true; |
| 558 | |
| 559 | // If the variable we have found is just a guess, invalidate the result. |
| 560 | if (guess) |
| 561 | var = NULL; |
| 562 | |
| 563 | return var; |
| 564 | } |
| 565 | |
| 566 | |
| 567 | void Scope::ResolveVariable(Scope* global_scope, VariableProxy* proxy) { |
| 568 | ASSERT(global_scope == NULL || global_scope->is_global_scope()); |
| 569 | |
| 570 | // If the proxy is already resolved there's nothing to do |
| 571 | // (functions and consts may be resolved by the parser). |
| 572 | if (proxy->var() != NULL) return; |
| 573 | |
| 574 | // Otherwise, try to resolve the variable. |
| 575 | Variable* var = LookupRecursive(proxy->name(), false); |
| 576 | |
| 577 | if (proxy->inside_with()) { |
| 578 | // If we are inside a local 'with' statement, all bets are off |
| 579 | // and we cannot resolve the proxy to a local variable even if |
| 580 | // we found an outer matching variable. |
| 581 | // Note that we must do a lookup anyway, because if we find one, |
| 582 | // we must mark that variable as potentially accessed from this |
| 583 | // inner scope (the property may not be in the 'with' object). |
| 584 | var = NonLocal(proxy->name()); |
| 585 | |
| 586 | } else { |
| 587 | // We are not inside a local 'with' statement. |
| 588 | |
| 589 | if (var == NULL) { |
| 590 | // We did not find the variable. We have a global variable |
| 591 | // if we are in the global scope (we know already that we |
| 592 | // are outside a 'with' statement) or if there is no way |
| 593 | // that the variable might be introduced dynamically (through |
| 594 | // a local or outer eval() call, or an outer 'with' statement), |
| 595 | // or we don't know about the outer scope (because we are |
| 596 | // in an eval scope). |
| 597 | if (!is_global_scope() && |
| 598 | (is_eval_scope() || outer_scope_calls_eval_ || |
| 599 | scope_calls_eval_ || scope_inside_with_)) { |
| 600 | // We must look up the variable at runtime, and we don't |
| 601 | // know anything else. |
| 602 | var = NonLocal(proxy->name()); |
| 603 | |
| 604 | } else { |
| 605 | // We must have a global variable. |
| 606 | ASSERT(global_scope != NULL); |
| 607 | var = new Variable(global_scope, proxy->name(), |
| 608 | Variable::DYNAMIC, true, false); |
| 609 | // Ideally we simply rewrite these variables into property |
| 610 | // accesses. Unfortunately, we cannot do this here at the |
| 611 | // moment because then we can't differentiate between |
| 612 | // global variable ('x') and global property ('this.x') access. |
| 613 | // If 'x' doesn't exist, the former leads to an error, while the |
| 614 | // latter returns undefined. Sigh... |
| 615 | // var->rewrite_ = new Property(new Literal(env_->global()), |
| 616 | // new Literal(proxy->name())); |
| 617 | } |
| 618 | } |
| 619 | } |
| 620 | |
| 621 | proxy->BindTo(var); |
| 622 | } |
| 623 | |
| 624 | |
| 625 | void Scope::ResolveVariablesRecursively(Scope* global_scope) { |
| 626 | ASSERT(global_scope == NULL || global_scope->is_global_scope()); |
| 627 | |
| 628 | // Resolve unresolved variables for this scope. |
| 629 | for (int i = 0; i < unresolved_.length(); i++) { |
| 630 | ResolveVariable(global_scope, unresolved_[i]); |
| 631 | } |
| 632 | |
| 633 | // Resolve unresolved variables for inner scopes. |
| 634 | for (int i = 0; i < inner_scopes_.length(); i++) { |
| 635 | inner_scopes_[i]->ResolveVariablesRecursively(global_scope); |
| 636 | } |
| 637 | } |
| 638 | |
| 639 | |
| 640 | bool Scope::PropagateScopeInfo(bool outer_scope_calls_eval) { |
| 641 | if (outer_scope_calls_eval) { |
| 642 | outer_scope_calls_eval_ = true; |
| 643 | } |
| 644 | |
| 645 | bool b = scope_calls_eval_ || outer_scope_calls_eval_; |
| 646 | for (int i = 0; i < inner_scopes_.length(); i++) { |
| 647 | Scope* inner_scope = inner_scopes_[i]; |
| 648 | if (inner_scope->PropagateScopeInfo(b)) { |
| 649 | inner_scope_calls_eval_ = true; |
| 650 | } |
| 651 | if (inner_scope->force_eager_compilation_) { |
| 652 | force_eager_compilation_ = true; |
| 653 | } |
| 654 | } |
| 655 | |
| 656 | return scope_calls_eval_ || inner_scope_calls_eval_; |
| 657 | } |
| 658 | |
| 659 | |
| 660 | bool Scope::MustAllocate(Variable* var) { |
| 661 | // Give var a read/write use if there is a chance it might be |
| 662 | // accessed via an eval() call, or if it is a global variable. |
| 663 | // This is only possible if the variable has a visible name. |
| 664 | if ((var->is_this() || var->name()->length() > 0) && |
| 665 | (var->is_accessed_from_inner_scope_ || |
| 666 | scope_calls_eval_ || inner_scope_calls_eval_ || |
| 667 | scope_contains_with_ || var->is_global())) { |
| 668 | var->var_uses()->RecordAccess(1); |
| 669 | } |
| 670 | return var->var_uses()->is_used(); |
| 671 | } |
| 672 | |
| 673 | |
| 674 | bool Scope::MustAllocateInContext(Variable* var) { |
| 675 | // If var is accessed from an inner scope, or if there is a |
| 676 | // possibility that it might be accessed from the current or |
| 677 | // an inner scope (through an eval() call), it must be allocated |
| 678 | // in the context. |
| 679 | // Exceptions: Global variables and temporary variables must |
| 680 | // never be allocated in the (FixedArray part of the) context. |
| 681 | return |
| 682 | var->mode() != Variable::TEMPORARY && |
| 683 | (var->is_accessed_from_inner_scope_ || |
| 684 | scope_calls_eval_ || inner_scope_calls_eval_ || |
| 685 | scope_contains_with_ || var->is_global()); |
| 686 | } |
| 687 | |
| 688 | |
| 689 | bool Scope::HasArgumentsParameter() { |
| 690 | for (int i = 0; i < params_.length(); i++) { |
| 691 | if (params_[i]->name().is_identical_to(Factory::arguments_symbol())) |
| 692 | return true; |
| 693 | } |
| 694 | return false; |
| 695 | } |
| 696 | |
| 697 | |
| 698 | void Scope::AllocateStackSlot(Variable* var) { |
| 699 | var->rewrite_ = new Slot(var, Slot::LOCAL, num_stack_slots_++); |
| 700 | } |
| 701 | |
| 702 | |
| 703 | void Scope::AllocateHeapSlot(Variable* var) { |
| 704 | var->rewrite_ = new Slot(var, Slot::CONTEXT, num_heap_slots_++); |
| 705 | } |
| 706 | |
| 707 | |
| 708 | void Scope::AllocateParameterLocals() { |
| 709 | ASSERT(is_function_scope()); |
| 710 | Variable* arguments = Lookup(Factory::arguments_symbol()); |
| 711 | ASSERT(arguments != NULL); // functions have 'arguments' declared implicitly |
| 712 | if (MustAllocate(arguments) && !HasArgumentsParameter()) { |
| 713 | // 'arguments' is used. Unless there is also a parameter called |
| 714 | // 'arguments', we must be conservative and access all parameters via |
| 715 | // the arguments object: The i'th parameter is rewritten into |
| 716 | // '.arguments[i]' (*). If we have a parameter named 'arguments', a |
| 717 | // (new) value is always assigned to it via the function |
| 718 | // invocation. Then 'arguments' denotes that specific parameter value |
| 719 | // and cannot be used to access the parameters, which is why we don't |
| 720 | // need to rewrite in that case. |
| 721 | // |
| 722 | // (*) Instead of having a parameter called 'arguments', we may have an |
| 723 | // assignment to 'arguments' in the function body, at some arbitrary |
| 724 | // point in time (possibly through an 'eval()' call!). After that |
| 725 | // assignment any re-write of parameters would be invalid (was bug |
| 726 | // 881452). Thus, we introduce a shadow '.arguments' |
| 727 | // variable which also points to the arguments object. For rewrites we |
| 728 | // use '.arguments' which remains valid even if we assign to |
| 729 | // 'arguments'. To summarize: If we need to rewrite, we allocate an |
| 730 | // 'arguments' object dynamically upon function invocation. The compiler |
| 731 | // introduces 2 local variables 'arguments' and '.arguments', both of |
| 732 | // which originally point to the arguments object that was |
| 733 | // allocated. All parameters are rewritten into property accesses via |
| 734 | // the '.arguments' variable. Thus, any changes to properties of |
| 735 | // 'arguments' are reflected in the variables and vice versa. If the |
| 736 | // 'arguments' variable is changed, '.arguments' still points to the |
| 737 | // correct arguments object and the rewrites still work. |
| 738 | |
| 739 | // We are using 'arguments'. Tell the code generator that is needs to |
| 740 | // allocate the arguments object by setting 'arguments_'. |
| 741 | arguments_ = new VariableProxy(Factory::arguments_symbol(), false, false); |
| 742 | arguments_->BindTo(arguments); |
| 743 | |
| 744 | // We also need the '.arguments' shadow variable. Declare it and create |
| 745 | // and bind the corresponding proxy. It's ok to declare it only now |
| 746 | // because it's a local variable that is allocated after the parameters |
| 747 | // have been allocated. |
| 748 | // |
| 749 | // Note: This is "almost" at temporary variable but we cannot use |
| 750 | // NewTemporary() because the mode needs to be INTERNAL since this |
| 751 | // variable may be allocated in the heap-allocated context (temporaries |
| 752 | // are never allocated in the context). |
| 753 | Variable* arguments_shadow = |
| 754 | new Variable(this, Factory::arguments_shadow_symbol(), |
| 755 | Variable::INTERNAL, true, false); |
| 756 | arguments_shadow_ = |
| 757 | new VariableProxy(Factory::arguments_shadow_symbol(), false, false); |
| 758 | arguments_shadow_->BindTo(arguments_shadow); |
| 759 | temps_.Add(arguments_shadow); |
| 760 | |
| 761 | // Allocate the parameters by rewriting them into '.arguments[i]' accesses. |
| 762 | for (int i = 0; i < params_.length(); i++) { |
| 763 | Variable* var = params_[i]; |
| 764 | ASSERT(var->scope() == this); |
| 765 | if (MustAllocate(var)) { |
| 766 | if (MustAllocateInContext(var)) { |
| 767 | // It is ok to set this only now, because arguments is a local |
| 768 | // variable that is allocated after the parameters have been |
| 769 | // allocated. |
| 770 | arguments_shadow->is_accessed_from_inner_scope_ = true; |
| 771 | } |
| 772 | var->rewrite_ = |
| 773 | new Property(arguments_shadow_, |
| 774 | new Literal(Handle<Object>(Smi::FromInt(i))), |
| 775 | kNoPosition); |
| 776 | arguments_shadow->var_uses()->RecordUses(var->var_uses()); |
| 777 | } |
| 778 | } |
| 779 | |
| 780 | } else { |
| 781 | // The arguments object is not used, so we can access parameters directly. |
| 782 | // The same parameter may occur multiple times in the parameters_ list. |
| 783 | // If it does, and if it is not copied into the context object, it must |
| 784 | // receive the highest parameter index for that parameter; thus iteration |
| 785 | // order is relevant! |
| 786 | for (int i = 0; i < params_.length(); i++) { |
| 787 | Variable* var = params_[i]; |
| 788 | ASSERT(var->scope() == this); |
| 789 | if (MustAllocate(var)) { |
| 790 | if (MustAllocateInContext(var)) { |
| 791 | ASSERT(var->rewrite_ == NULL || |
| 792 | (var->slot() != NULL && var->slot()->type() == Slot::CONTEXT)); |
| 793 | if (var->rewrite_ == NULL) { |
| 794 | // Only set the heap allocation if the parameter has not |
| 795 | // been allocated yet. |
| 796 | AllocateHeapSlot(var); |
| 797 | } |
| 798 | } else { |
| 799 | ASSERT(var->rewrite_ == NULL || |
| 800 | (var->slot() != NULL && |
| 801 | var->slot()->type() == Slot::PARAMETER)); |
| 802 | // Set the parameter index always, even if the parameter |
| 803 | // was seen before! (We need to access the actual parameter |
| 804 | // supplied for the last occurrence of a multiply declared |
| 805 | // parameter.) |
| 806 | var->rewrite_ = new Slot(var, Slot::PARAMETER, i); |
| 807 | } |
| 808 | } |
| 809 | } |
| 810 | } |
| 811 | } |
| 812 | |
| 813 | |
| 814 | void Scope::AllocateNonParameterLocal(Variable* var) { |
| 815 | ASSERT(var->scope() == this); |
| 816 | ASSERT(var->rewrite_ == NULL || |
| 817 | (!var->IsVariable(Factory::result_symbol())) || |
| 818 | (var->slot() == NULL || var->slot()->type() != Slot::LOCAL)); |
| 819 | if (MustAllocate(var) && var->rewrite_ == NULL) { |
| 820 | if (MustAllocateInContext(var)) { |
| 821 | AllocateHeapSlot(var); |
| 822 | } else { |
| 823 | AllocateStackSlot(var); |
| 824 | } |
| 825 | } |
| 826 | } |
| 827 | |
| 828 | |
| 829 | DECLARE_bool(usage_computation); |
| 830 | |
| 831 | void Scope::AllocateNonParameterLocals() { |
| 832 | // Each variable occurs exactly once in the locals_ list; all |
| 833 | // variables that have no rewrite yet are non-parameter locals. |
| 834 | |
| 835 | // Sort them according to use such that the locals with more uses |
| 836 | // get allocated first. |
| 837 | if (FLAG_usage_computation) { |
| 838 | // This is currently not implemented. |
| 839 | } |
| 840 | |
| 841 | for (int i = 0; i < temps_.length(); i++) { |
| 842 | AllocateNonParameterLocal(temps_[i]); |
| 843 | } |
| 844 | |
| 845 | for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| 846 | Variable* var = reinterpret_cast<Variable*>(p->value); |
| 847 | AllocateNonParameterLocal(var); |
| 848 | } |
| 849 | |
| 850 | // Note: For now, function_ must be allocated at the very end. If |
| 851 | // it gets allocated in the context, it must be the last slot in the |
| 852 | // context, because of the current ScopeInfo implementation (see |
| 853 | // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor). |
| 854 | if (function_ != NULL) { |
| 855 | AllocateNonParameterLocal(function_); |
| 856 | } |
| 857 | } |
| 858 | |
| 859 | |
| 860 | void Scope::AllocateVariablesRecursively() { |
| 861 | // The number of slots required for variables. |
| 862 | num_stack_slots_ = 0; |
| 863 | num_heap_slots_ = Context::MIN_CONTEXT_SLOTS; |
| 864 | |
| 865 | // Allocate variables for inner scopes. |
| 866 | for (int i = 0; i < inner_scopes_.length(); i++) { |
| 867 | inner_scopes_[i]->AllocateVariablesRecursively(); |
| 868 | } |
| 869 | |
| 870 | // Allocate variables for this scope. |
| 871 | // Parameters must be allocated first, if any. |
| 872 | if (is_function_scope()) AllocateParameterLocals(); |
| 873 | AllocateNonParameterLocals(); |
| 874 | |
| 875 | // Allocate context if necessary. |
| 876 | bool must_have_local_context = false; |
| 877 | if (scope_calls_eval_ || scope_contains_with_) { |
| 878 | // The context for the eval() call or 'with' statement in this scope. |
| 879 | // Unless we are in the global or an eval scope, we need a local |
| 880 | // context even if we didn't statically allocate any locals in it, |
| 881 | // and the compiler will access the context variable. If we are |
| 882 | // not in an inner scope, the scope is provided from the outside. |
| 883 | must_have_local_context = is_function_scope(); |
| 884 | } |
| 885 | |
| 886 | // If we didn't allocate any locals in the local context, then we only |
| 887 | // need the minimal number of slots if we must have a local context. |
| 888 | if (num_heap_slots_ == Context::MIN_CONTEXT_SLOTS && |
| 889 | !must_have_local_context) { |
| 890 | num_heap_slots_ = 0; |
| 891 | } |
| 892 | |
| 893 | // Allocation done. |
| 894 | ASSERT(num_heap_slots_ == 0 || num_heap_slots_ >= Context::MIN_CONTEXT_SLOTS); |
| 895 | } |
| 896 | |
| 897 | } } // namespace v8::internal |