| // Copyright 2006-2008 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "v8.h" |
| |
| #include "prettyprinter.h" |
| #include "scopeinfo.h" |
| #include "scopes.h" |
| |
| namespace v8 { namespace internal { |
| |
| // ---------------------------------------------------------------------------- |
| // A Zone allocator for use with LocalsMap. |
| |
| class ZoneAllocator: public Allocator { |
| public: |
| /* nothing to do */ |
| virtual ~ZoneAllocator() {} |
| |
| virtual void* New(size_t size) { return Zone::New(size); } |
| |
| /* ignored - Zone is freed in one fell swoop */ |
| virtual void Delete(void* p) {} |
| }; |
| |
| |
| static ZoneAllocator LocalsMapAllocator; |
| |
| |
| // ---------------------------------------------------------------------------- |
| // Implementation of LocalsMap |
| // |
| // Note: We are storing the handle locations as key values in the hash map. |
| // When inserting a new variable via Declare(), we rely on the fact that |
| // the handle location remains alive for the duration of that variable |
| // use. Because a Variable holding a handle with the same location exists |
| // this is ensured. |
| |
| static bool Match(void* key1, void* key2) { |
| String* name1 = *reinterpret_cast<String**>(key1); |
| String* name2 = *reinterpret_cast<String**>(key2); |
| ASSERT(name1->IsSymbol()); |
| ASSERT(name2->IsSymbol()); |
| return name1 == name2; |
| } |
| |
| |
| // Dummy constructor |
| LocalsMap::LocalsMap(bool gotta_love_static_overloading) : HashMap() {} |
| |
| LocalsMap::LocalsMap() : HashMap(Match, &LocalsMapAllocator, 8) {} |
| LocalsMap::~LocalsMap() {} |
| |
| |
| Variable* LocalsMap::Declare(Scope* scope, |
| Handle<String> name, |
| Variable::Mode mode, |
| bool is_valid_LHS, |
| bool is_this) { |
| HashMap::Entry* p = HashMap::Lookup(name.location(), name->Hash(), true); |
| if (p->value == NULL) { |
| // The variable has not been declared yet -> insert it. |
| ASSERT(p->key == name.location()); |
| p->value = new Variable(scope, name, mode, is_valid_LHS, is_this); |
| } |
| return reinterpret_cast<Variable*>(p->value); |
| } |
| |
| |
| Variable* LocalsMap::Lookup(Handle<String> name) { |
| HashMap::Entry* p = HashMap::Lookup(name.location(), name->Hash(), false); |
| if (p != NULL) { |
| ASSERT(*reinterpret_cast<String**>(p->key) == *name); |
| ASSERT(p->value != NULL); |
| return reinterpret_cast<Variable*>(p->value); |
| } |
| return NULL; |
| } |
| |
| |
| // ---------------------------------------------------------------------------- |
| // Implementation of Scope |
| |
| |
| // Dummy constructor |
| Scope::Scope() |
| : inner_scopes_(0), |
| locals_(false), |
| temps_(0), |
| params_(0), |
| nonlocals_(0), |
| unresolved_(0), |
| decls_(0) { |
| } |
| |
| |
| Scope::Scope(Scope* outer_scope, Type type) |
| : outer_scope_(outer_scope), |
| inner_scopes_(4), |
| type_(type), |
| scope_name_(Factory::empty_symbol()), |
| locals_(), |
| temps_(4), |
| params_(4), |
| nonlocals_(4), |
| unresolved_(16), |
| decls_(4), |
| receiver_(NULL), |
| function_(NULL), |
| arguments_(NULL), |
| arguments_shadow_(NULL), |
| illegal_redecl_(NULL), |
| scope_inside_with_(false), |
| scope_contains_with_(false), |
| scope_calls_eval_(false), |
| outer_scope_calls_eval_(false), |
| inner_scope_calls_eval_(false), |
| force_eager_compilation_(false), |
| num_stack_slots_(0), |
| num_heap_slots_(0) { |
| // At some point we might want to provide outer scopes to |
| // eval scopes (by walking the stack and reading the scope info). |
| // In that case, the ASSERT below needs to be adjusted. |
| ASSERT((type == GLOBAL_SCOPE || type == EVAL_SCOPE) == (outer_scope == NULL)); |
| ASSERT(!HasIllegalRedeclaration()); |
| } |
| |
| |
| void Scope::Initialize(bool inside_with) { |
| // Add this scope as a new inner scope of the outer scope. |
| if (outer_scope_ != NULL) { |
| outer_scope_->inner_scopes_.Add(this); |
| scope_inside_with_ = outer_scope_->scope_inside_with_ || inside_with; |
| } else { |
| scope_inside_with_ = inside_with; |
| } |
| |
| // Declare convenience variables. |
| // Declare and allocate receiver (even for the global scope, and even |
| // if naccesses_ == 0). |
| // NOTE: When loading parameters in the global scope, we must take |
| // care not to access them as properties of the global object, but |
| // instead load them directly from the stack. Currently, the only |
| // such parameter is 'this' which is passed on the stack when |
| // invoking scripts |
| { Variable* var = |
| locals_.Declare(this, Factory::this_symbol(), Variable::VAR, false, true); |
| var->rewrite_ = new Slot(var, Slot::PARAMETER, -1); |
| receiver_ = new VariableProxy(Factory::this_symbol(), true, false); |
| receiver_->BindTo(var); |
| } |
| |
| if (is_function_scope()) { |
| // Declare 'arguments' variable which exists in all functions. |
| // Note that it may never be accessed, in which case it won't |
| // be allocated during variable allocation. |
| Declare(Factory::arguments_symbol(), Variable::VAR); |
| } |
| } |
| |
| |
| |
| Variable* Scope::LookupLocal(Handle<String> name) { |
| return locals_.Lookup(name); |
| } |
| |
| |
| Variable* Scope::Lookup(Handle<String> name) { |
| for (Scope* scope = this; |
| scope != NULL; |
| scope = scope->outer_scope()) { |
| Variable* var = scope->LookupLocal(name); |
| if (var != NULL) return var; |
| } |
| return NULL; |
| } |
| |
| |
| Variable* Scope::DeclareFunctionVar(Handle<String> name) { |
| ASSERT(is_function_scope() && function_ == NULL); |
| function_ = new Variable(this, name, Variable::CONST, true, false); |
| return function_; |
| } |
| |
| |
| Variable* Scope::Declare(Handle<String> name, Variable::Mode mode) { |
| // DYNAMIC variables are introduces during variable allocation, |
| // INTERNAL variables are allocated explicitly, and TEMPORARY |
| // variables are allocated via NewTemporary(). |
| ASSERT(mode == Variable::VAR || mode == Variable::CONST); |
| return locals_.Declare(this, name, mode, true, false); |
| } |
| |
| |
| void Scope::AddParameter(Variable* var) { |
| ASSERT(is_function_scope()); |
| ASSERT(LookupLocal(var->name()) == var); |
| params_.Add(var); |
| } |
| |
| |
| VariableProxy* Scope::NewUnresolved(Handle<String> name, bool inside_with) { |
| // Note that we must not share the unresolved variables with |
| // the same name because they may be removed selectively via |
| // RemoveUnresolved(). |
| VariableProxy* proxy = new VariableProxy(name, false, inside_with); |
| unresolved_.Add(proxy); |
| return proxy; |
| } |
| |
| |
| void Scope::RemoveUnresolved(VariableProxy* var) { |
| // Most likely (always?) any variable we want to remove |
| // was just added before, so we search backwards. |
| for (int i = unresolved_.length(); i-- > 0;) { |
| if (unresolved_[i] == var) { |
| unresolved_.Remove(i); |
| return; |
| } |
| } |
| } |
| |
| |
| VariableProxy* Scope::NewTemporary(Handle<String> name) { |
| Variable* var = new Variable(this, name, Variable::TEMPORARY, true, false); |
| VariableProxy* tmp = new VariableProxy(name, false, false); |
| tmp->BindTo(var); |
| temps_.Add(var); |
| return tmp; |
| } |
| |
| |
| void Scope::AddDeclaration(Declaration* declaration) { |
| decls_.Add(declaration); |
| } |
| |
| |
| void Scope::SetIllegalRedeclaration(Expression* expression) { |
| // Only set the illegal redeclaration expression the |
| // first time the function is called. |
| if (!HasIllegalRedeclaration()) { |
| illegal_redecl_ = expression; |
| } |
| ASSERT(HasIllegalRedeclaration()); |
| } |
| |
| |
| void Scope::VisitIllegalRedeclaration(AstVisitor* visitor) { |
| ASSERT(HasIllegalRedeclaration()); |
| illegal_redecl_->Accept(visitor); |
| } |
| |
| |
| template<class Allocator> |
| void Scope::CollectUsedVariables(List<Variable*, Allocator>* locals) { |
| // Collect variables in this scope. |
| // Note that the function_ variable - if present - is not |
| // collected here but handled separately in ScopeInfo |
| // which is the current user of this function). |
| for (int i = 0; i < temps_.length(); i++) { |
| Variable* var = temps_[i]; |
| if (var->var_uses()->is_used()) { |
| locals->Add(var); |
| } |
| } |
| for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| Variable* var = reinterpret_cast<Variable*>(p->value); |
| if (var->var_uses()->is_used()) { |
| locals->Add(var); |
| } |
| } |
| } |
| |
| |
| // Make sure the method gets instantiated by the template system. |
| template void Scope::CollectUsedVariables( |
| List<Variable*, FreeStoreAllocationPolicy>* locals); |
| template void Scope::CollectUsedVariables( |
| List<Variable*, PreallocatedStorage>* locals); |
| |
| |
| void Scope::AllocateVariables() { |
| ASSERT(outer_scope_ == NULL); // eval or global scopes only |
| |
| // 1) Propagate scope information. |
| // If we are in an eval scope, we may have other outer scopes about |
| // which we don't know anything at this point. Thus we must be conservative |
| // and assume they may invoke eval themselves. Eventually we could capture |
| // this information in the ScopeInfo and then use it here (by traversing |
| // the call chain stack, at compile time). |
| PropagateScopeInfo(is_eval_scope()); |
| |
| // 2) Resolve variables. |
| Scope* global_scope = NULL; |
| if (is_global_scope()) global_scope = this; |
| ResolveVariablesRecursively(global_scope); |
| |
| // 3) Allocate variables. |
| AllocateVariablesRecursively(); |
| } |
| |
| |
| bool Scope::AllowsLazyCompilation() const { |
| return !force_eager_compilation_ && HasTrivialOuterContext(); |
| } |
| |
| |
| bool Scope::HasTrivialContext() const { |
| // A function scope has a trivial context if it always is the global |
| // context. We iteratively scan out the context chain to see if |
| // there is anything that makes this scope non-trivial; otherwise we |
| // return true. |
| for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) { |
| if (scope->is_eval_scope()) return false; |
| if (scope->scope_inside_with_) return false; |
| if (scope->num_heap_slots_ > 0) return false; |
| } |
| return true; |
| } |
| |
| |
| bool Scope::HasTrivialOuterContext() const { |
| Scope* outer = outer_scope_; |
| if (outer == NULL) return true; |
| // Note that the outer context may be trivial in general, but the current |
| // scope may be inside a 'with' statement in which case the outer context |
| // for this scope is not trivial. |
| return !scope_inside_with_ && outer->HasTrivialContext(); |
| } |
| |
| |
| int Scope::ContextChainLength(Scope* scope) { |
| int n = 0; |
| for (Scope* s = this; s != scope; s = s->outer_scope_) { |
| ASSERT(s != NULL); // scope must be in the scope chain |
| if (s->num_heap_slots() > 0) n++; |
| } |
| return n; |
| } |
| |
| |
| #ifdef DEBUG |
| static const char* Header(Scope::Type type) { |
| switch (type) { |
| case Scope::EVAL_SCOPE: return "eval"; |
| case Scope::FUNCTION_SCOPE: return "function"; |
| case Scope::GLOBAL_SCOPE: return "global"; |
| } |
| UNREACHABLE(); |
| return NULL; |
| } |
| |
| |
| static void Indent(int n, const char* str) { |
| PrintF("%*s%s", n, "", str); |
| } |
| |
| |
| static void PrintName(Handle<String> name) { |
| SmartPointer<char> s = name->ToCString(DISALLOW_NULLS); |
| PrintF("%s", *s); |
| } |
| |
| |
| static void PrintVar(PrettyPrinter* printer, int indent, Variable* var) { |
| if (var->var_uses()->is_used() || var->rewrite() != NULL) { |
| Indent(indent, Variable::Mode2String(var->mode())); |
| PrintF(" "); |
| PrintName(var->name()); |
| PrintF("; // "); |
| if (var->rewrite() != NULL) PrintF("%s, ", printer->Print(var->rewrite())); |
| if (var->is_accessed_from_inner_scope()) PrintF("inner scope access, "); |
| PrintF("var "); |
| var->var_uses()->Print(); |
| PrintF(", obj "); |
| var->obj_uses()->Print(); |
| PrintF("\n"); |
| } |
| } |
| |
| |
| void Scope::Print(int n) { |
| int n0 = (n > 0 ? n : 0); |
| int n1 = n0 + 2; // indentation |
| |
| // Print header. |
| Indent(n0, Header(type_)); |
| if (scope_name_->length() > 0) { |
| PrintF(" "); |
| PrintName(scope_name_); |
| } |
| |
| // Print parameters, if any. |
| if (is_function_scope()) { |
| PrintF(" ("); |
| for (int i = 0; i < params_.length(); i++) { |
| if (i > 0) PrintF(", "); |
| PrintName(params_[i]->name()); |
| } |
| PrintF(")"); |
| } |
| |
| PrintF(" {\n"); |
| |
| // Function name, if any (named function literals, only). |
| if (function_ != NULL) { |
| Indent(n1, "// (local) function name: "); |
| PrintName(function_->name()); |
| PrintF("\n"); |
| } |
| |
| // Scope info. |
| if (HasTrivialOuterContext()) { |
| Indent(n1, "// scope has trivial outer context\n"); |
| } |
| if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n"); |
| if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n"); |
| if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n"); |
| if (outer_scope_calls_eval_) Indent(n1, "// outer scope calls 'eval'\n"); |
| if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n"); |
| if (num_stack_slots_ > 0) { Indent(n1, "// "); |
| PrintF("%d stack slots\n", num_stack_slots_); } |
| if (num_heap_slots_ > 0) { Indent(n1, "// "); |
| PrintF("%d heap slots\n", num_heap_slots_); } |
| |
| // Print locals. |
| PrettyPrinter printer; |
| Indent(n1, "// function var\n"); |
| if (function_ != NULL) { |
| PrintVar(&printer, n1, function_); |
| } |
| |
| Indent(n1, "// temporary vars\n"); |
| for (int i = 0; i < temps_.length(); i++) { |
| PrintVar(&printer, n1, temps_[i]); |
| } |
| |
| Indent(n1, "// local vars\n"); |
| for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| Variable* var = reinterpret_cast<Variable*>(p->value); |
| PrintVar(&printer, n1, var); |
| } |
| |
| Indent(n1, "// nonlocal vars\n"); |
| for (int i = 0; i < nonlocals_.length(); i++) |
| PrintVar(&printer, n1, nonlocals_[i]); |
| |
| // Print inner scopes (disable by providing negative n). |
| if (n >= 0) { |
| for (int i = 0; i < inner_scopes_.length(); i++) { |
| PrintF("\n"); |
| inner_scopes_[i]->Print(n1); |
| } |
| } |
| |
| Indent(n0, "}\n"); |
| } |
| #endif // DEBUG |
| |
| |
| Variable* Scope::NonLocal(Handle<String> name) { |
| // Space optimization: reuse existing non-local with the same name. |
| for (int i = 0; i < nonlocals_.length(); i++) { |
| Variable* var = nonlocals_[i]; |
| if (var->name().is_identical_to(name)) { |
| ASSERT(var->mode() == Variable::DYNAMIC); |
| return var; |
| } |
| } |
| |
| // Otherwise create a new new-local and add it to the list. |
| Variable* var = new Variable( |
| NULL /* we don't know the scope */, |
| name, Variable::DYNAMIC, true, false); |
| nonlocals_.Add(var); |
| |
| // Allocate it by giving it a dynamic lookup. |
| var->rewrite_ = new Slot(var, Slot::LOOKUP, -1); |
| |
| return var; |
| } |
| |
| |
| // Lookup a variable starting with this scope. The result is either |
| // the statically resolved (local!) variable belonging to an outer scope, |
| // or NULL. It may be NULL because a) we couldn't find a variable, or b) |
| // because the variable is just a guess (and may be shadowed by another |
| // variable that is introduced dynamically via an 'eval' call or a 'with' |
| // statement). |
| Variable* Scope::LookupRecursive(Handle<String> name, bool inner_lookup) { |
| // If we find a variable, but the current scope calls 'eval', the found |
| // variable may not be the correct one (the 'eval' may introduce a |
| // property with the same name). In that case, remember that the variable |
| // found is just a guess. |
| bool guess = scope_calls_eval_; |
| |
| // Try to find the variable in this scope. |
| Variable* var = LookupLocal(name); |
| |
| if (var != NULL) { |
| // We found a variable. If this is not an inner lookup, we are done. |
| // (Even if there is an 'eval' in this scope which introduces the |
| // same variable again, the resulting variable remains the same. |
| // Note that enclosing 'with' statements are handled at the call site.) |
| if (!inner_lookup) |
| return var; |
| |
| } else { |
| // We did not find a variable locally. Check against the function variable, |
| // if any. We can do this for all scopes, since the function variable is |
| // only present - if at all - for function scopes. |
| // |
| // This lookup corresponds to a lookup in the "intermediate" scope sitting |
| // between this scope and the outer scope. (ECMA-262, 3rd., requires that |
| // the name of named function literal is kept in an intermediate scope |
| // in between this scope and the next outer scope.) |
| if (function_ != NULL && function_->name().is_identical_to(name)) { |
| var = function_; |
| |
| } else if (outer_scope_ != NULL) { |
| var = outer_scope_->LookupRecursive(name, true /* inner lookup */); |
| // We may have found a variable in an outer scope. However, if |
| // the current scope is inside a 'with', the actual variable may |
| // be a property introduced via the 'with' statement. Then, the |
| // variable we may have found is just a guess. |
| if (scope_inside_with_) |
| guess = true; |
| } |
| |
| // If we did not find a variable, we are done. |
| if (var == NULL) |
| return NULL; |
| } |
| |
| ASSERT(var != NULL); |
| |
| // If this is a lookup from an inner scope, mark the variable. |
| if (inner_lookup) |
| var->is_accessed_from_inner_scope_ = true; |
| |
| // If the variable we have found is just a guess, invalidate the result. |
| if (guess) |
| var = NULL; |
| |
| return var; |
| } |
| |
| |
| void Scope::ResolveVariable(Scope* global_scope, VariableProxy* proxy) { |
| ASSERT(global_scope == NULL || global_scope->is_global_scope()); |
| |
| // If the proxy is already resolved there's nothing to do |
| // (functions and consts may be resolved by the parser). |
| if (proxy->var() != NULL) return; |
| |
| // Otherwise, try to resolve the variable. |
| Variable* var = LookupRecursive(proxy->name(), false); |
| |
| if (proxy->inside_with()) { |
| // If we are inside a local 'with' statement, all bets are off |
| // and we cannot resolve the proxy to a local variable even if |
| // we found an outer matching variable. |
| // Note that we must do a lookup anyway, because if we find one, |
| // we must mark that variable as potentially accessed from this |
| // inner scope (the property may not be in the 'with' object). |
| var = NonLocal(proxy->name()); |
| |
| } else { |
| // We are not inside a local 'with' statement. |
| |
| if (var == NULL) { |
| // We did not find the variable. We have a global variable |
| // if we are in the global scope (we know already that we |
| // are outside a 'with' statement) or if there is no way |
| // that the variable might be introduced dynamically (through |
| // a local or outer eval() call, or an outer 'with' statement), |
| // or we don't know about the outer scope (because we are |
| // in an eval scope). |
| if (!is_global_scope() && |
| (is_eval_scope() || outer_scope_calls_eval_ || |
| scope_calls_eval_ || scope_inside_with_)) { |
| // We must look up the variable at runtime, and we don't |
| // know anything else. |
| var = NonLocal(proxy->name()); |
| |
| } else { |
| // We must have a global variable. |
| ASSERT(global_scope != NULL); |
| var = new Variable(global_scope, proxy->name(), |
| Variable::DYNAMIC, true, false); |
| // Ideally we simply rewrite these variables into property |
| // accesses. Unfortunately, we cannot do this here at the |
| // moment because then we can't differentiate between |
| // global variable ('x') and global property ('this.x') access. |
| // If 'x' doesn't exist, the former leads to an error, while the |
| // latter returns undefined. Sigh... |
| // var->rewrite_ = new Property(new Literal(env_->global()), |
| // new Literal(proxy->name())); |
| } |
| } |
| } |
| |
| proxy->BindTo(var); |
| } |
| |
| |
| void Scope::ResolveVariablesRecursively(Scope* global_scope) { |
| ASSERT(global_scope == NULL || global_scope->is_global_scope()); |
| |
| // Resolve unresolved variables for this scope. |
| for (int i = 0; i < unresolved_.length(); i++) { |
| ResolveVariable(global_scope, unresolved_[i]); |
| } |
| |
| // Resolve unresolved variables for inner scopes. |
| for (int i = 0; i < inner_scopes_.length(); i++) { |
| inner_scopes_[i]->ResolveVariablesRecursively(global_scope); |
| } |
| } |
| |
| |
| bool Scope::PropagateScopeInfo(bool outer_scope_calls_eval) { |
| if (outer_scope_calls_eval) { |
| outer_scope_calls_eval_ = true; |
| } |
| |
| bool b = scope_calls_eval_ || outer_scope_calls_eval_; |
| for (int i = 0; i < inner_scopes_.length(); i++) { |
| Scope* inner_scope = inner_scopes_[i]; |
| if (inner_scope->PropagateScopeInfo(b)) { |
| inner_scope_calls_eval_ = true; |
| } |
| if (inner_scope->force_eager_compilation_) { |
| force_eager_compilation_ = true; |
| } |
| } |
| |
| return scope_calls_eval_ || inner_scope_calls_eval_; |
| } |
| |
| |
| bool Scope::MustAllocate(Variable* var) { |
| // Give var a read/write use if there is a chance it might be |
| // accessed via an eval() call, or if it is a global variable. |
| // This is only possible if the variable has a visible name. |
| if ((var->is_this() || var->name()->length() > 0) && |
| (var->is_accessed_from_inner_scope_ || |
| scope_calls_eval_ || inner_scope_calls_eval_ || |
| scope_contains_with_ || var->is_global())) { |
| var->var_uses()->RecordAccess(1); |
| } |
| return var->var_uses()->is_used(); |
| } |
| |
| |
| bool Scope::MustAllocateInContext(Variable* var) { |
| // If var is accessed from an inner scope, or if there is a |
| // possibility that it might be accessed from the current or |
| // an inner scope (through an eval() call), it must be allocated |
| // in the context. |
| // Exceptions: Global variables and temporary variables must |
| // never be allocated in the (FixedArray part of the) context. |
| return |
| var->mode() != Variable::TEMPORARY && |
| (var->is_accessed_from_inner_scope_ || |
| scope_calls_eval_ || inner_scope_calls_eval_ || |
| scope_contains_with_ || var->is_global()); |
| } |
| |
| |
| bool Scope::HasArgumentsParameter() { |
| for (int i = 0; i < params_.length(); i++) { |
| if (params_[i]->name().is_identical_to(Factory::arguments_symbol())) |
| return true; |
| } |
| return false; |
| } |
| |
| |
| void Scope::AllocateStackSlot(Variable* var) { |
| var->rewrite_ = new Slot(var, Slot::LOCAL, num_stack_slots_++); |
| } |
| |
| |
| void Scope::AllocateHeapSlot(Variable* var) { |
| var->rewrite_ = new Slot(var, Slot::CONTEXT, num_heap_slots_++); |
| } |
| |
| |
| void Scope::AllocateParameterLocals() { |
| ASSERT(is_function_scope()); |
| Variable* arguments = LookupLocal(Factory::arguments_symbol()); |
| ASSERT(arguments != NULL); // functions have 'arguments' declared implicitly |
| if (MustAllocate(arguments) && !HasArgumentsParameter()) { |
| // 'arguments' is used. Unless there is also a parameter called |
| // 'arguments', we must be conservative and access all parameters via |
| // the arguments object: The i'th parameter is rewritten into |
| // '.arguments[i]' (*). If we have a parameter named 'arguments', a |
| // (new) value is always assigned to it via the function |
| // invocation. Then 'arguments' denotes that specific parameter value |
| // and cannot be used to access the parameters, which is why we don't |
| // need to rewrite in that case. |
| // |
| // (*) Instead of having a parameter called 'arguments', we may have an |
| // assignment to 'arguments' in the function body, at some arbitrary |
| // point in time (possibly through an 'eval()' call!). After that |
| // assignment any re-write of parameters would be invalid (was bug |
| // 881452). Thus, we introduce a shadow '.arguments' |
| // variable which also points to the arguments object. For rewrites we |
| // use '.arguments' which remains valid even if we assign to |
| // 'arguments'. To summarize: If we need to rewrite, we allocate an |
| // 'arguments' object dynamically upon function invocation. The compiler |
| // introduces 2 local variables 'arguments' and '.arguments', both of |
| // which originally point to the arguments object that was |
| // allocated. All parameters are rewritten into property accesses via |
| // the '.arguments' variable. Thus, any changes to properties of |
| // 'arguments' are reflected in the variables and vice versa. If the |
| // 'arguments' variable is changed, '.arguments' still points to the |
| // correct arguments object and the rewrites still work. |
| |
| // We are using 'arguments'. Tell the code generator that is needs to |
| // allocate the arguments object by setting 'arguments_'. |
| arguments_ = new VariableProxy(Factory::arguments_symbol(), false, false); |
| arguments_->BindTo(arguments); |
| |
| // We also need the '.arguments' shadow variable. Declare it and create |
| // and bind the corresponding proxy. It's ok to declare it only now |
| // because it's a local variable that is allocated after the parameters |
| // have been allocated. |
| // |
| // Note: This is "almost" at temporary variable but we cannot use |
| // NewTemporary() because the mode needs to be INTERNAL since this |
| // variable may be allocated in the heap-allocated context (temporaries |
| // are never allocated in the context). |
| Variable* arguments_shadow = |
| new Variable(this, Factory::arguments_shadow_symbol(), |
| Variable::INTERNAL, true, false); |
| arguments_shadow_ = |
| new VariableProxy(Factory::arguments_shadow_symbol(), false, false); |
| arguments_shadow_->BindTo(arguments_shadow); |
| temps_.Add(arguments_shadow); |
| |
| // Allocate the parameters by rewriting them into '.arguments[i]' accesses. |
| for (int i = 0; i < params_.length(); i++) { |
| Variable* var = params_[i]; |
| ASSERT(var->scope() == this); |
| if (MustAllocate(var)) { |
| if (MustAllocateInContext(var)) { |
| // It is ok to set this only now, because arguments is a local |
| // variable that is allocated after the parameters have been |
| // allocated. |
| arguments_shadow->is_accessed_from_inner_scope_ = true; |
| } |
| var->rewrite_ = |
| new Property(arguments_shadow_, |
| new Literal(Handle<Object>(Smi::FromInt(i))), |
| RelocInfo::kNoPosition); |
| arguments_shadow->var_uses()->RecordUses(var->var_uses()); |
| } |
| } |
| |
| } else { |
| // The arguments object is not used, so we can access parameters directly. |
| // The same parameter may occur multiple times in the parameters_ list. |
| // If it does, and if it is not copied into the context object, it must |
| // receive the highest parameter index for that parameter; thus iteration |
| // order is relevant! |
| for (int i = 0; i < params_.length(); i++) { |
| Variable* var = params_[i]; |
| ASSERT(var->scope() == this); |
| if (MustAllocate(var)) { |
| if (MustAllocateInContext(var)) { |
| ASSERT(var->rewrite_ == NULL || |
| (var->slot() != NULL && var->slot()->type() == Slot::CONTEXT)); |
| if (var->rewrite_ == NULL) { |
| // Only set the heap allocation if the parameter has not |
| // been allocated yet. |
| AllocateHeapSlot(var); |
| } |
| } else { |
| ASSERT(var->rewrite_ == NULL || |
| (var->slot() != NULL && |
| var->slot()->type() == Slot::PARAMETER)); |
| // Set the parameter index always, even if the parameter |
| // was seen before! (We need to access the actual parameter |
| // supplied for the last occurrence of a multiply declared |
| // parameter.) |
| var->rewrite_ = new Slot(var, Slot::PARAMETER, i); |
| } |
| } |
| } |
| } |
| } |
| |
| |
| void Scope::AllocateNonParameterLocal(Variable* var) { |
| ASSERT(var->scope() == this); |
| ASSERT(var->rewrite_ == NULL || |
| (!var->IsVariable(Factory::result_symbol())) || |
| (var->slot() == NULL || var->slot()->type() != Slot::LOCAL)); |
| if (MustAllocate(var) && var->rewrite_ == NULL) { |
| if (MustAllocateInContext(var)) { |
| AllocateHeapSlot(var); |
| } else { |
| AllocateStackSlot(var); |
| } |
| } |
| } |
| |
| |
| void Scope::AllocateNonParameterLocals() { |
| // Each variable occurs exactly once in the locals_ list; all |
| // variables that have no rewrite yet are non-parameter locals. |
| |
| // Sort them according to use such that the locals with more uses |
| // get allocated first. |
| if (FLAG_usage_computation) { |
| // This is currently not implemented. |
| } |
| |
| for (int i = 0; i < temps_.length(); i++) { |
| AllocateNonParameterLocal(temps_[i]); |
| } |
| |
| for (LocalsMap::Entry* p = locals_.Start(); p != NULL; p = locals_.Next(p)) { |
| Variable* var = reinterpret_cast<Variable*>(p->value); |
| AllocateNonParameterLocal(var); |
| } |
| |
| // Note: For now, function_ must be allocated at the very end. If |
| // it gets allocated in the context, it must be the last slot in the |
| // context, because of the current ScopeInfo implementation (see |
| // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor). |
| if (function_ != NULL) { |
| AllocateNonParameterLocal(function_); |
| } |
| } |
| |
| |
| void Scope::AllocateVariablesRecursively() { |
| // The number of slots required for variables. |
| num_stack_slots_ = 0; |
| num_heap_slots_ = Context::MIN_CONTEXT_SLOTS; |
| |
| // Allocate variables for inner scopes. |
| for (int i = 0; i < inner_scopes_.length(); i++) { |
| inner_scopes_[i]->AllocateVariablesRecursively(); |
| } |
| |
| // Allocate variables for this scope. |
| // Parameters must be allocated first, if any. |
| if (is_function_scope()) AllocateParameterLocals(); |
| AllocateNonParameterLocals(); |
| |
| // Allocate context if necessary. |
| bool must_have_local_context = false; |
| if (scope_calls_eval_ || scope_contains_with_) { |
| // The context for the eval() call or 'with' statement in this scope. |
| // Unless we are in the global or an eval scope, we need a local |
| // context even if we didn't statically allocate any locals in it, |
| // and the compiler will access the context variable. If we are |
| // not in an inner scope, the scope is provided from the outside. |
| must_have_local_context = is_function_scope(); |
| } |
| |
| // If we didn't allocate any locals in the local context, then we only |
| // need the minimal number of slots if we must have a local context. |
| if (num_heap_slots_ == Context::MIN_CONTEXT_SLOTS && |
| !must_have_local_context) { |
| num_heap_slots_ = 0; |
| } |
| |
| // Allocation done. |
| ASSERT(num_heap_slots_ == 0 || num_heap_slots_ >= Context::MIN_CONTEXT_SLOTS); |
| } |
| |
| } } // namespace v8::internal |