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v8/src/scopes.cc
kasperl@chromium.org 15fe7a8ad6 Make the ResolvePossiblyDirectEval faster by avoiding the 
stack traversal code.
Review URL: http://codereview.chromium.org/523051

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3533 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
2010-01-05 09:38:02 +00:00

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// 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(static_cast<int>(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
VariableMap::VariableMap(bool gotta_love_static_overloading) : HashMap() {}
VariableMap::VariableMap() : HashMap(Match, &LocalsMapAllocator, 8) {}
VariableMap::~VariableMap() {}
Variable* VariableMap::Declare(Scope* scope,
Handle<String> name,
Variable::Mode mode,
bool is_valid_lhs,
Variable::Kind kind) {
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, kind);
}
return reinterpret_cast<Variable*>(p->value);
}
Variable* VariableMap::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(Type type)
: outer_scope_(NULL),
inner_scopes_(0),
type_(type),
scope_name_(Factory::empty_symbol()),
variables_(false),
temps_(0),
params_(0),
dynamics_(NULL),
unresolved_(0),
decls_(0),
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),
outer_scope_is_eval_scope_(false),
force_eager_compilation_(false),
num_stack_slots_(0),
num_heap_slots_(0) {
}
Scope::Scope(Scope* outer_scope, Type type)
: outer_scope_(outer_scope),
inner_scopes_(4),
type_(type),
scope_name_(Factory::empty_symbol()),
temps_(4),
params_(4),
dynamics_(NULL),
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),
outer_scope_is_eval_scope_(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 =
variables_.Declare(this, Factory::this_symbol(), Variable::VAR,
false, Variable::THIS);
var->rewrite_ = new Slot(var, Slot::PARAMETER, -1);
receiver_ = var;
if (is_function_scope()) {
// Declare 'arguments' variable which exists in all functions.
// Note that it might never be accessed, in which case it won't be
// allocated during variable allocation.
variables_.Declare(this, Factory::arguments_symbol(), Variable::VAR,
true, Variable::ARGUMENTS);
}
}
Variable* Scope::LocalLookup(Handle<String> name) {
return variables_.Lookup(name);
}
Variable* Scope::Lookup(Handle<String> name) {
for (Scope* scope = this;
scope != NULL;
scope = scope->outer_scope()) {
Variable* var = scope->LocalLookup(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, Variable::NORMAL);
return function_;
}
Variable* Scope::DeclareLocal(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 variables_.Declare(this, name, mode, true, Variable::NORMAL);
}
Variable* Scope::DeclareGlobal(Handle<String> name) {
ASSERT(is_global_scope());
return variables_.Declare(this, name, Variable::DYNAMIC_GLOBAL, true,
Variable::NORMAL);
}
void Scope::AddParameter(Variable* var) {
ASSERT(is_function_scope());
ASSERT(LocalLookup(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,
Variable::NORMAL);
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 (VariableMap::Entry* p = variables_.Start();
p != NULL;
p = variables_.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);
template void Scope::CollectUsedVariables(
List<Variable*, ZoneListAllocationPolicy>* locals);
void Scope::AllocateVariables(Handle<Context> context) {
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).
bool eval_scope = is_eval_scope();
PropagateScopeInfo(eval_scope, eval_scope);
// 2) Resolve variables.
Scope* global_scope = NULL;
if (is_global_scope()) global_scope = this;
ResolveVariablesRecursively(global_scope, context);
// 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");
}
}
static void PrintMap(PrettyPrinter* printer, int indent, VariableMap* map) {
for (VariableMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
Variable* var = reinterpret_cast<Variable*>(p->value);
PrintVar(printer, indent, var);
}
}
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 (outer_scope_is_eval_scope_) {
Indent(n1, "// outer scope is 'eval' scope\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");
PrintMap(&printer, n1, &variables_);
Indent(n1, "// dynamic vars\n");
if (dynamics_ != NULL) {
PrintMap(&printer, n1, dynamics_->GetMap(Variable::DYNAMIC));
PrintMap(&printer, n1, dynamics_->GetMap(Variable::DYNAMIC_LOCAL));
PrintMap(&printer, n1, dynamics_->GetMap(Variable::DYNAMIC_GLOBAL));
}
// 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, Variable::Mode mode) {
if (dynamics_ == NULL) dynamics_ = new DynamicScopePart();
VariableMap* map = dynamics_->GetMap(mode);
Variable* var = map->Lookup(name);
if (var == NULL) {
// Declare a new non-local.
var = map->Declare(NULL, name, mode, true, Variable::NORMAL);
// 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 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,
Variable** invalidated_local) {
// 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 = LocalLookup(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, invalidated_local);
// 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 the found variable is local, record that fact so we
// can generate fast code to get it if it is not shadowed by eval.
if (guess) {
if (!var->is_global()) *invalidated_local = var;
var = NULL;
}
return var;
}
void Scope::ResolveVariable(Scope* global_scope,
Handle<Context> context,
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* invalidated_local = NULL;
Variable* var = LookupRecursive(proxy->name(), false, &invalidated_local);
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(), Variable::DYNAMIC);
} 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() ||
!(scope_inside_with_ || outer_scope_is_eval_scope_ ||
scope_calls_eval_ || outer_scope_calls_eval_)) {
// We must have a global variable.
ASSERT(global_scope != NULL);
var = global_scope->DeclareGlobal(proxy->name());
} else if (scope_inside_with_) {
// If we are inside a with statement we give up and look up
// the variable at runtime.
var = NonLocal(proxy->name(), Variable::DYNAMIC);
} else if (invalidated_local != NULL) {
// No with statements are involved and we found a local
// variable that might be shadowed by eval introduced
// variables.
var = NonLocal(proxy->name(), Variable::DYNAMIC_LOCAL);
var->set_local_if_not_shadowed(invalidated_local);
} else if (outer_scope_is_eval_scope_) {
// No with statements and we did not find a local and the code
// is executed with a call to eval. The context contains
// scope information that we can use to determine if the
// variable is global if it is not shadowed by eval-introduced
// variables.
if (context->GlobalIfNotShadowedByEval(proxy->name())) {
var = NonLocal(proxy->name(), Variable::DYNAMIC_GLOBAL);
} else {
var = NonLocal(proxy->name(), Variable::DYNAMIC);
}
} else {
// No with statements and we did not find a local and the code
// is not executed with a call to eval. We know that this
// variable is global unless it is shadowed by eval-introduced
// variables.
var = NonLocal(proxy->name(), Variable::DYNAMIC_GLOBAL);
}
}
}
proxy->BindTo(var);
}
void Scope::ResolveVariablesRecursively(Scope* global_scope,
Handle<Context> context) {
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, context, unresolved_[i]);
}
// Resolve unresolved variables for inner scopes.
for (int i = 0; i < inner_scopes_.length(); i++) {
inner_scopes_[i]->ResolveVariablesRecursively(global_scope, context);
}
}
bool Scope::PropagateScopeInfo(bool outer_scope_calls_eval,
bool outer_scope_is_eval_scope) {
if (outer_scope_calls_eval) {
outer_scope_calls_eval_ = true;
}
if (outer_scope_is_eval_scope) {
outer_scope_is_eval_scope_ = true;
}
bool calls_eval = scope_calls_eval_ || outer_scope_calls_eval_;
bool is_eval = is_eval_scope() || outer_scope_is_eval_scope_;
for (int i = 0; i < inner_scopes_.length(); i++) {
Scope* inner_scope = inner_scopes_[i];
if (inner_scope->PropagateScopeInfo(calls_eval, is_eval)) {
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. 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->var_uses()->RecordAccess(1);
}
// Global variables do not need to be allocated.
return !var->is_global() && 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. Exception: temporary variables are not allocated in 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 = LocalLookup(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, Variable::ARGUMENTS);
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,
Property::SYNTHETIC);
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 (var->rewrite_ == NULL && MustAllocate(var)) {
if (MustAllocateInContext(var)) {
AllocateHeapSlot(var);
} else {
AllocateStackSlot(var);
}
}
}
void Scope::AllocateNonParameterLocals() {
// All variables that have no rewrite yet are non-parameter locals.
for (int i = 0; i < temps_.length(); i++) {
AllocateNonParameterLocal(temps_[i]);
}
for (VariableMap::Entry* p = variables_.Start();
p != NULL;
p = variables_.Next(p)) {
Variable* var = reinterpret_cast<Variable*>(p->value);
AllocateNonParameterLocal(var);
}
// 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
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