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/*
* Copyright (C) 2014, 2015 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.
*/
#ifndef CallVariant_h
#define CallVariant_h
#include "Executable.h"
#include "JSCell.h"
#include "JSFunction.h"
namespace JSC {
// The CallVariant class is meant to encapsulate a callee in a way that is useful for call linking
// and inlining. Because JavaScript has closures, and because JSC implements the notion of internal
// non-function objects that nevertheless provide call traps, the call machinery wants to see a
// callee in one of the following four forms:
//
// JSFunction callee: This means that we expect the callsite to always call a particular function
// instance, that is associated with a particular lexical environment. This pinpoints not
// just the code that will be called (i.e. the executable) but also the scope within which
// the code runs.
//
// Executable callee: This corresponds to a call to a closure. In this case, we know that the
// callsite will call a JSFunction, but we do not know which particular JSFunction. We do know
// what code will be called - i.e. we know the executable.
//
// InternalFunction callee: JSC supports a special kind of native functions that support bizarre
// semantics. These are always singletons. If we know that the callee is an InternalFunction
// then we know both the code that will be called and the scope; in fact the "scope" is really
// just the InternalFunction itself.
//
// Something else: It's possible call all manner of rubbish in JavaScript. This implicitly supports
// bizarre object callees, but it can't really tell you anything interesting about them other
// than the fact that they don't fall into any of the above categories.
//
// This class serves as a kind of union over these four things. It does so by just holding a
// JSCell*. We determine which of the modes its in by doing type checks on the cell. Note that we
// cannot use WriteBarrier<> here because this gets used inside the compiler.
class CallVariant {
public:
explicit CallVariant(JSCell* callee = nullptr)
: m_callee(callee)
{
}
CallVariant(WTF::HashTableDeletedValueType)
: m_callee(deletedToken())
{
}
bool operator!() const { return !m_callee; }
// If this variant refers to a function, change it to refer to its executable.
ALWAYS_INLINE CallVariant despecifiedClosure() const
{
if (m_callee->type() == JSFunctionType)
return CallVariant(jsCast<JSFunction*>(m_callee)->executable());
return *this;
}
JSCell* rawCalleeCell() const { return m_callee; }
InternalFunction* internalFunction() const
{
return jsDynamicCast<InternalFunction*>(m_callee);
}
JSFunction* function() const
{
return jsDynamicCast<JSFunction*>(m_callee);
}
bool isClosureCall() const { return !!jsDynamicCast<ExecutableBase*>(m_callee); }
ExecutableBase* executable() const
{
if (JSFunction* function = this->function())
return function->executable();
return jsDynamicCast<ExecutableBase*>(m_callee);
}
JSCell* nonExecutableCallee() const
{
RELEASE_ASSERT(!isClosureCall());
return m_callee;
}
Intrinsic intrinsicFor(CodeSpecializationKind kind) const
{
if (ExecutableBase* executable = this->executable())
return executable->intrinsicFor(kind);
return NoIntrinsic;
}
FunctionExecutable* functionExecutable() const
{
if (ExecutableBase* executable = this->executable())
return jsDynamicCast<FunctionExecutable*>(executable);
return nullptr;
}
void dump(PrintStream& out) const;
bool isHashTableDeletedValue() const
{
return m_callee == deletedToken();
}
bool operator==(const CallVariant& other) const
{
return m_callee == other.m_callee;
}
bool operator!=(const CallVariant& other) const
{
return !(*this == other);
}
bool operator<(const CallVariant& other) const
{
return m_callee < other.m_callee;
}
bool operator>(const CallVariant& other) const
{
return other < *this;
}
bool operator<=(const CallVariant& other) const
{
return !(*this < other);
}
bool operator>=(const CallVariant& other) const
{
return other <= *this;
}
unsigned hash() const
{
return WTF::PtrHash<JSCell*>::hash(m_callee);
}
private:
static JSCell* deletedToken() { return bitwise_cast<JSCell*>(static_cast<uintptr_t>(1)); }
JSCell* m_callee;
};
struct CallVariantHash {
static unsigned hash(const CallVariant& key) { return key.hash(); }
static bool equal(const CallVariant& a, const CallVariant& b) { return a == b; }
static const bool safeToCompareToEmptyOrDeleted = true;
};
typedef Vector<CallVariant, 1> CallVariantList;
// Returns a new variant list by attempting to either append the given variant or merge it with one
// of the variants we already have by despecifying closures.
CallVariantList variantListWithVariant(const CallVariantList&, CallVariant);
// Returns a new list where every element is despecified, and the list is deduplicated.
CallVariantList despecifiedVariantList(const CallVariantList&);
} // namespace JSC
namespace WTF {
template<typename T> struct DefaultHash;
template<> struct DefaultHash<JSC::CallVariant> {
typedef JSC::CallVariantHash Hash;
};
template<typename T> struct HashTraits;
template<> struct HashTraits<JSC::CallVariant> : SimpleClassHashTraits<JSC::CallVariant> { };
} // namespace WTF
#endif // CallVariant_h
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