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//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
// Defines the type "ValueNum".
// This file exists only to break an include file cycle -- had been in ValueNum.h. But that
// file wanted to include gentree.h to get GT_COUNT, and gentree.h wanted ton include ValueNum.h to
// the ValueNum type.
/*****************************************************************************/
#ifndef _VALUENUMTYPE_H_
#define _VALUENUMTYPE_H_
/*****************************************************************************/
// We will represent ValueNum's as unsigned integers.
typedef UINT32 ValueNum;
// There are two "kinds" of value numbers, which differ in their modeling of the actions of other threads.
// "Liberal" value numbers assume that the other threads change contents of heap locations only at
// synchronization points. Liberal VNs are appropriate, for example, in identifying CSE opportunities.
// "Conservative" value numbers assume that the contents of heap locations change arbitrarily between
// every two accesses. Conservative VNs are appropriate, for example, in assertion prop, where an observation
// of a property of the value in some storage location is used to perform an optimization downstream on
// an operation involving the contents of that storage location. If other threads may modify the storage
// location between the two accesses, the observed property may no longer hold -- and conservative VNs make
// it clear that the values need not be the same.
//
enum ValueNumKind { VNK_Liberal, VNK_Conservative };
struct ValueNumPair
{
private:
ValueNum m_liberal;
ValueNum m_conservative;
public:
ValueNum GetLiberal() const { return m_liberal; }
void SetLiberal(ValueNum vn) { m_liberal = vn; }
ValueNum GetConservative() const { return m_conservative; }
void SetConservative(ValueNum vn) { m_conservative = vn; }
ValueNum* GetLiberalAddr() { return &m_liberal; }
ValueNum* GetConservativeAddr() { return &m_conservative; }
ValueNum Get(ValueNumKind vnk) { return vnk == VNK_Liberal ? m_liberal : m_conservative; }
void SetBoth(ValueNum vn)
{
m_liberal = vn;
m_conservative = vn;
}
void operator=(const ValueNumPair& vn2)
{
m_liberal = vn2.m_liberal;
m_conservative = vn2.m_conservative;
}
// Initializes both elements to "NoVN". Defined in ValueNum.cpp.
ValueNumPair();
ValueNumPair(ValueNum lib, ValueNum cons) : m_liberal(lib), m_conservative(cons) {}
// True iff neither element is "NoVN". Defined in ValueNum.cpp.
bool BothDefined() const;
bool BothEqual() const { return m_liberal == m_conservative; }
};
#endif // _VALUENUMTYPE_H_
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