Initial export.
git-svn-id: http://v8.googlecode.com/svn/trunk@2 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
diff --git a/src/scopes.cc b/src/scopes.cc
new file mode 100644
index 0000000..b2b8f65
--- /dev/null
+++ b/src/scopes.cc
@@ -0,0 +1,897 @@
+// Copyright 2006-2008 Google Inc. 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::Lookup(Handle<String> name) {
+ return locals_.Lookup(name);
+}
+
+
+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(Lookup(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(Visitor* 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::SupportsEval() const {
+ return scope_calls_eval_ || inner_scope_calls_eval_;
+}
+
+
+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 = Lookup(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
+ // inbetween 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 = Lookup(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))),
+ 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);
+ }
+ }
+}
+
+
+DECLARE_bool(usage_computation);
+
+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