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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
/*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XX XX
XX ObjectAllocator XX
XX XX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
*/
/*****************************************************************************/
#ifndef OBJECTALLOC_H
#define OBJECTALLOC_H
/*****************************************************************************/
//===============================================================================
#include "phase.h"
#include "smallhash.h"
class ObjectAllocator final : public Phase
{
typedef SmallHashTable<unsigned int, unsigned int, 8U> LocalToLocalMap;
//===============================================================================
// Data members
bool m_IsObjectStackAllocationEnabled;
bool m_AnalysisDone;
BitVecTraits m_bitVecTraits;
BitVec m_EscapingPointers;
// We keep the set of possibly-stack-pointing pointers as a superset of the set of
// definitely-stack-pointing pointers. All definitely-stack-pointing pointers are in both sets.
BitVec m_PossiblyStackPointingPointers;
BitVec m_DefinitelyStackPointingPointers;
LocalToLocalMap m_HeapLocalToStackLocalMap;
BitSetShortLongRep* m_ConnGraphAdjacencyMatrix;
//===============================================================================
// Methods
public:
ObjectAllocator(Compiler* comp);
bool IsObjectStackAllocationEnabled() const;
void EnableObjectStackAllocation();
protected:
virtual void DoPhase() override;
private:
bool CanAllocateLclVarOnStack(unsigned int lclNum, CORINFO_CLASS_HANDLE clsHnd);
bool CanLclVarEscape(unsigned int lclNum);
void MarkLclVarAsPossiblyStackPointing(unsigned int lclNum);
void MarkLclVarAsDefinitelyStackPointing(unsigned int lclNum);
bool MayLclVarPointToStack(unsigned int lclNum);
bool DoesLclVarPointToStack(unsigned int lclNum);
void DoAnalysis();
void MarkLclVarAsEscaping(unsigned int lclNum);
void MarkEscapingVarsAndBuildConnGraph();
void AddConnGraphEdge(unsigned int sourceLclNum, unsigned int targetLclNum);
void ComputeEscapingNodes(BitVecTraits* bitVecTraits, BitVec& escapingNodes);
void ComputeStackObjectPointers(BitVecTraits* bitVecTraits);
bool MorphAllocObjNodes();
void RewriteUses();
GenTree* MorphAllocObjNodeIntoHelperCall(GenTreeAllocObj* allocObj);
unsigned int MorphAllocObjNodeIntoStackAlloc(GenTreeAllocObj* allocObj, BasicBlock* block, GenTreeStmt* stmt);
struct BuildConnGraphVisitorCallbackData;
bool CanLclVarEscapeViaParentStack(ArrayStack<GenTree*>* parentStack, unsigned int lclNum);
void UpdateAncestorTypes(GenTree* tree, ArrayStack<GenTree*>* parentStack, var_types newType);
#ifdef DEBUG
static Compiler::fgWalkResult AssertWhenAllocObjFoundVisitor(GenTree** pTree, Compiler::fgWalkData* data);
#endif // DEBUG
static const unsigned int s_StackAllocMaxSize = 0x2000U;
};
//===============================================================================
inline ObjectAllocator::ObjectAllocator(Compiler* comp)
: Phase(comp, "Allocate Objects", PHASE_ALLOCATE_OBJECTS)
, m_IsObjectStackAllocationEnabled(false)
, m_AnalysisDone(false)
, m_bitVecTraits(comp->lvaCount, comp)
, m_HeapLocalToStackLocalMap(comp->getAllocator())
{
// Disable checks since this phase runs before fgComputePreds phase.
// Checks are not expected to pass before fgComputePreds.
doChecks = false;
m_EscapingPointers = BitVecOps::UninitVal();
m_PossiblyStackPointingPointers = BitVecOps::UninitVal();
m_DefinitelyStackPointingPointers = BitVecOps::UninitVal();
m_ConnGraphAdjacencyMatrix = nullptr;
}
//------------------------------------------------------------------------
// IsObjectStackAllocationEnabled: Returns true iff object stack allocation is enabled
//
// Return Value:
// Returns true iff object stack allocation is enabled
inline bool ObjectAllocator::IsObjectStackAllocationEnabled() const
{
return m_IsObjectStackAllocationEnabled;
}
//------------------------------------------------------------------------
// EnableObjectStackAllocation: Enable object stack allocation.
inline void ObjectAllocator::EnableObjectStackAllocation()
{
m_IsObjectStackAllocationEnabled = true;
}
//------------------------------------------------------------------------
// CanAllocateLclVarOnStack: Returns true iff local variable can be
// allocated on the stack.
//
// Arguments:
// lclNum - Local variable number
// clsHnd - Class handle of the variable class
//
// Return Value:
// Returns true iff local variable can be allocated on the stack.
//
// Notes:
// Stack allocation of objects with gc fields and boxed objects is currently disabled.
inline bool ObjectAllocator::CanAllocateLclVarOnStack(unsigned int lclNum, CORINFO_CLASS_HANDLE clsHnd)
{
assert(m_AnalysisDone);
DWORD classAttribs = comp->info.compCompHnd->getClassAttribs(clsHnd);
if ((classAttribs & CORINFO_FLG_VALUECLASS) != 0)
{
// TODO-ObjectStackAllocation: enable stack allocation of boxed structs
return false;
}
if (!comp->info.compCompHnd->canAllocateOnStack(clsHnd))
{
return false;
}
const unsigned int classSize = comp->info.compCompHnd->getHeapClassSize(clsHnd);
return !CanLclVarEscape(lclNum) && (classSize <= s_StackAllocMaxSize);
}
//------------------------------------------------------------------------
// CanLclVarEscape: Returns true iff local variable can
// potentially escape from the method
//
// Arguments:
// lclNum - Local variable number
//
// Return Value:
// Returns true iff local variable can potentially escape from the method
inline bool ObjectAllocator::CanLclVarEscape(unsigned int lclNum)
{
return BitVecOps::IsMember(&m_bitVecTraits, m_EscapingPointers, lclNum);
}
//------------------------------------------------------------------------
// MayLclVarPointToStack: Returns true iff local variable may
// point to a stack-allocated object
//
// Arguments:
// lclNum - Local variable number
//
// Return Value:
// Returns true iff local variable may point to a stack-allocated object
inline bool ObjectAllocator::MayLclVarPointToStack(unsigned int lclNum)
{
assert(m_AnalysisDone);
return BitVecOps::IsMember(&m_bitVecTraits, m_PossiblyStackPointingPointers, lclNum);
}
//------------------------------------------------------------------------
// DoesLclVarPointToStack: Returns true iff local variable definitely
// points to a stack-allocated object (or is null)
//
// Arguments:
// lclNum - Local variable number
//
// Return Value:
// Returns true iff local variable definitely points to a stack-allocated object
// (or is null)
inline bool ObjectAllocator::DoesLclVarPointToStack(unsigned int lclNum)
{
assert(m_AnalysisDone);
return BitVecOps::IsMember(&m_bitVecTraits, m_DefinitelyStackPointingPointers, lclNum);
}
//===============================================================================
#endif // OBJECTALLOC_H
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