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//===-- IGNode.h - Represent a node in an interference graph ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file represents a node in an interference graph.
//
// For efficiency, the AdjList is updated only once - ie. we can add but not
// remove nodes from AdjList.
//
// The removal of nodes from IG is simulated by decrementing the CurDegree.
// If this node is put on stack (that is removed from IG), the CurDegree of all
// the neighbors are decremented and this node is marked OnStack. Hence
// the effective neighbors in the AdjList are the ones that do not have the
// OnStack flag set (therefore, they are in the IG).
//
// The methods that modify/use the CurDegree must be called only
// after all modifications to the IG are over (i.e., all neighbors are fixed).
//
// The vector representation is the most efficient one for adj list.
// Though nodes are removed when coalescing is done, we access it in sequence
// for far many times when coloring (colorNode()).
//
//===----------------------------------------------------------------------===//
#ifndef IGNODE_H
#define IGNODE_H
#include "LiveRange.h"
#include <vector>
namespace llvm {
class RegClass;
//----------------------------------------------------------------------------
// Class IGNode
//
// Represents a node in an interference graph.
//----------------------------------------------------------------------------
class IGNode {
const unsigned Index; // index within IGNodeList
bool OnStack; // this has been pushed on to stack for coloring
std::vector<IGNode *> AdjList;// adjacency list for this live range
int CurDegree;
//
// set by InterferenceGraph::setCurDegreeOfIGNodes() after calculating
// all adjacency lists.
// Decremented when a neighbor is pushed on to the stack.
// After that, never incremented/set again nor used.
LiveRange *const ParentLR;
public:
IGNode(LiveRange *LR, unsigned index) : Index(index), ParentLR(LR) {
OnStack = false;
CurDegree = -1;
ParentLR->setUserIGNode(this);
}
inline unsigned int getIndex() const { return Index; }
// adjLists must be updated only once. However, the CurDegree can be changed
//
inline void addAdjIGNode(IGNode *AdjNode) { AdjList.push_back(AdjNode); }
inline IGNode *getAdjIGNode(unsigned ind) const
{ assert ( ind < AdjList.size()); return AdjList[ind]; }
// delete a node in AdjList - node must be in the list
// should not be called often
//
void delAdjIGNode(const IGNode *Node);
inline unsigned getNumOfNeighbors() const { return AdjList.size(); }
// Get the number of unique neighbors if these two nodes are merged
unsigned getCombinedDegree(const IGNode* otherNode) const;
inline bool isOnStack() const { return OnStack; }
// remove form IG and pushes on to stack (reduce the degree of neighbors)
//
void pushOnStack();
// CurDegree is the effective number of neighbors when neighbors are
// pushed on to the stack during the coloring phase. Must be called
// after all modifications to the IG are over (i.e., all neighbors are
// fixed).
//
inline void setCurDegree() {
assert(CurDegree == -1);
CurDegree = AdjList.size();
}
inline int getCurDegree() const { return CurDegree; }
// called when a neigh is pushed on to stack
//
inline void decCurDegree() { assert(CurDegree > 0); --CurDegree; }
// The following methods call the methods in ParentLR
// They are added to this class for convenience
// If many of these are called within a single scope,
// consider calling the methods directly on LR
inline bool hasColor() const { return ParentLR->hasColor(); }
inline unsigned int getColor() const { return ParentLR->getColor(); }
inline void setColor(unsigned Col) { ParentLR->setColor(Col); }
inline LiveRange *getParentLR() const { return ParentLR; }
};
} // End llvm namespace
#endif
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