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/*
* Copyright (C) 2012, 2013, 2014 Apple 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:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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 "config.h"
#include "JSScope.h"
#include "JSGlobalObject.h"
#include "JSLexicalEnvironment.h"
#include "JSNameScope.h"
#include "JSWithScope.h"
#include "JSCInlines.h"
namespace JSC {
STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(JSScope);
void JSScope::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
JSScope* thisObject = jsCast<JSScope*>(cell);
ASSERT_GC_OBJECT_INHERITS(thisObject, info());
Base::visitChildren(thisObject, visitor);
visitor.append(&thisObject->m_next);
}
// Returns true if we found enough information to terminate optimization.
static inline bool abstractAccess(ExecState* exec, JSScope* scope, const Identifier& ident, GetOrPut getOrPut, size_t depth, bool& needsVarInjectionChecks, ResolveOp& op)
{
if (JSLexicalEnvironment* lexicalEnvironment = jsDynamicCast<JSLexicalEnvironment*>(scope)) {
if (ident == exec->propertyNames().arguments) {
// We know the property will be at this lexical environment scope, but we don't know how to cache it.
op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
return true;
}
SymbolTableEntry entry = lexicalEnvironment->symbolTable()->get(ident.impl());
if (entry.isReadOnly() && getOrPut == Put) {
// We know the property will be at this lexical environment scope, but we don't know how to cache it.
op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
return true;
}
if (!entry.isNull()) {
op = ResolveOp(makeType(ClosureVar, needsVarInjectionChecks), depth, 0, lexicalEnvironment, entry.watchpointSet(), entry.getIndex());
return true;
}
if (lexicalEnvironment->symbolTable()->usesNonStrictEval())
needsVarInjectionChecks = true;
return false;
}
if (JSGlobalObject* globalObject = jsDynamicCast<JSGlobalObject*>(scope)) {
SymbolTableEntry entry = globalObject->symbolTable()->get(ident.impl());
if (!entry.isNull()) {
if (getOrPut == Put && entry.isReadOnly()) {
// We know the property will be at global scope, but we don't know how to cache it.
op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
return true;
}
op = ResolveOp(
makeType(GlobalVar, needsVarInjectionChecks), depth, 0, 0, entry.watchpointSet(),
reinterpret_cast<uintptr_t>(globalObject->registerAt(entry.getIndex()).slot()));
return true;
}
PropertySlot slot(globalObject);
if (!globalObject->getOwnPropertySlot(globalObject, exec, ident, slot)
|| !slot.isCacheableValue()
|| !globalObject->structure()->propertyAccessesAreCacheable()
|| (globalObject->structure()->hasReadOnlyOrGetterSetterPropertiesExcludingProto() && getOrPut == Put)) {
// We know the property will be at global scope, but we don't know how to cache it.
ASSERT(!scope->next());
op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), depth, 0, 0, 0, 0);
return true;
}
WatchpointState state = globalObject->structure()->ensurePropertyReplacementWatchpointSet(exec->vm(), slot.cachedOffset())->state();
if (state == IsWatched && getOrPut == Put) {
// The field exists, but because the replacement watchpoint is still intact. This is
// kind of dangerous. We have two options:
// 1) Invalidate the watchpoint set. That would work, but it's possible that this code
// path never executes - in which case this would be unwise.
// 2) Have the invalidation happen at run-time. All we have to do is leave the code
// uncached. The only downside is slightly more work when this does execute.
// We go with option (2) here because it seems less evil.
op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), depth, 0, 0, 0, 0);
} else
op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), depth, globalObject->structure(), 0, 0, slot.cachedOffset());
return true;
}
op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
return true;
}
JSObject* JSScope::objectAtScope(JSScope* scope)
{
JSObject* object = scope;
if (object->type() == WithScopeType)
return jsCast<JSWithScope*>(object)->object();
return object;
}
int JSScope::depth()
{
int depth = 0;
for (JSScope* scope = this; scope; scope = scope->next())
++depth;
return depth;
}
JSValue JSScope::resolve(ExecState* exec, JSScope* scope, const Identifier& ident)
{
ScopeChainIterator end = scope->end();
ScopeChainIterator it = scope->begin();
while (1) {
JSObject* object = it.get();
if (++it == end) // Global scope.
return object;
if (object->hasProperty(exec, ident))
return object;
}
}
ResolveOp JSScope::abstractResolve(ExecState* exec, bool hasTopActivation, JSScope* scope, const Identifier& ident, GetOrPut getOrPut, ResolveType unlinkedType)
{
ResolveOp op(Dynamic, 0, 0, 0, 0, 0);
if (unlinkedType == Dynamic)
return op;
size_t depth = hasTopActivation ? 1 : 0;
bool needsVarInjectionChecks = JSC::needsVarInjectionChecks(unlinkedType);
for (; scope; scope = scope->next()) {
if (abstractAccess(exec, scope, ident, getOrPut, depth, needsVarInjectionChecks, op))
break;
++depth;
}
return op;
}
const char* resolveModeName(ResolveMode mode)
{
static const char* const names[] = {
"ThrowIfNotFound",
"DoNotThrowIfNotFound"
};
return names[mode];
}
const char* resolveTypeName(ResolveType type)
{
static const char* const names[] = {
"GlobalProperty",
"GlobalVar",
"ClosureVar",
"GlobalPropertyWithVarInjectionChecks",
"GlobalVarWithVarInjectionChecks",
"ClosureVarWithVarInjectionChecks",
"Dynamic"
};
ASSERT(type < sizeof(names) / sizeof(names[0]));
return names[type];
}
} // namespace JSC
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