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//===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- 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 defines the following classes:
// 1. DominatorTree: Represent dominators as an explicit tree structure.
// 2. DominanceFrontier: Calculate and hold the dominance frontier for a
// function.
//
// These data structures are listed in increasing order of complexity. It
// takes longer to calculate the dominator frontier, for example, than the
// DominatorTree mapping.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_DOMINATORS_H
#define LLVM_ANALYSIS_DOMINATORS_H
#include "llvm/Pass.h"
#include <set>
#include "llvm/ADT/DenseMap.h"
namespace llvm {
class Instruction;
template <typename GraphType> struct GraphTraits;
//===----------------------------------------------------------------------===//
/// DominatorBase - Base class that other, more interesting dominator analyses
/// inherit from.
///
class DominatorBase : public FunctionPass {
protected:
std::vector<BasicBlock*> Roots;
const bool IsPostDominators;
inline DominatorBase(intptr_t ID, bool isPostDom) :
FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {}
public:
/// getRoots - Return the root blocks of the current CFG. This may include
/// multiple blocks if we are computing post dominators. For forward
/// dominators, this will always be a single block (the entry node).
///
inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
/// isPostDominator - Returns true if analysis based of postdoms
///
bool isPostDominator() const { return IsPostDominators; }
};
//===----------------------------------------------------------------------===//
// DomTreeNode - Dominator Tree Node
class DominatorTreeBase;
class PostDominatorTree;
class DomTreeNode {
BasicBlock *TheBB;
DomTreeNode *IDom;
std::vector<DomTreeNode*> Children;
int DFSNumIn, DFSNumOut;
friend class DominatorTreeBase;
friend class PostDominatorTree;
public:
typedef std::vector<DomTreeNode*>::iterator iterator;
typedef std::vector<DomTreeNode*>::const_iterator const_iterator;
iterator begin() { return Children.begin(); }
iterator end() { return Children.end(); }
const_iterator begin() const { return Children.begin(); }
const_iterator end() const { return Children.end(); }
BasicBlock *getBlock() const { return TheBB; }
DomTreeNode *getIDom() const { return IDom; }
const std::vector<DomTreeNode*> &getChildren() const { return Children; }
DomTreeNode(BasicBlock *BB, DomTreeNode *iDom)
: TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { }
DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; }
void setIDom(DomTreeNode *NewIDom);
/// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
/// not call them.
unsigned getDFSNumIn() const { return DFSNumIn; }
unsigned getDFSNumOut() const { return DFSNumOut; }
private:
// Return true if this node is dominated by other. Use this only if DFS info
// is valid.
bool DominatedBy(const DomTreeNode *other) const {
return this->DFSNumIn >= other->DFSNumIn &&
this->DFSNumOut <= other->DFSNumOut;
}
};
//===----------------------------------------------------------------------===//
/// DominatorTree - Calculate the immediate dominator tree for a function.
///
class DominatorTreeBase : public DominatorBase {
protected:
void reset();
typedef DenseMap<BasicBlock*, DomTreeNode*> DomTreeNodeMapType;
DomTreeNodeMapType DomTreeNodes;
DomTreeNode *RootNode;
bool DFSInfoValid;
unsigned int SlowQueries;
// Information record used during immediate dominators computation.
struct InfoRec {
unsigned Semi;
unsigned Size;
BasicBlock *Label, *Parent, *Child, *Ancestor;
std::vector<BasicBlock*> Bucket;
InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0) {}
};
DenseMap<BasicBlock*, BasicBlock*> IDoms;
// Vertex - Map the DFS number to the BasicBlock*
std::vector<BasicBlock*> Vertex;
// Info - Collection of information used during the computation of idoms.
DenseMap<BasicBlock*, InfoRec> Info;
public:
DominatorTreeBase(intptr_t ID, bool isPostDom)
: DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {}
~DominatorTreeBase() { reset(); }
virtual void releaseMemory() { reset(); }
/// getNode - return the (Post)DominatorTree node for the specified basic
/// block. This is the same as using operator[] on this class.
///
inline DomTreeNode *getNode(BasicBlock *BB) const {
DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB);
return I != DomTreeNodes.end() ? I->second : 0;
}
inline DomTreeNode *operator[](BasicBlock *BB) const {
return getNode(BB);
}
/// getRootNode - This returns the entry node for the CFG of the function. If
/// this tree represents the post-dominance relations for a function, however,
/// this root may be a node with the block == NULL. This is the case when
/// there are multiple exit nodes from a particular function. Consumers of
/// post-dominance information must be capable of dealing with this
/// possibility.
///
DomTreeNode *getRootNode() { return RootNode; }
const DomTreeNode *getRootNode() const { return RootNode; }
/// properlyDominates - Returns true iff this dominates N and this != N.
/// Note that this is not a constant time operation!
///
bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const {
if (A == 0 || B == 0) return false;
return dominatedBySlowTreeWalk(A, B);
}
inline bool properlyDominates(BasicBlock *A, BasicBlock *B) {
return properlyDominates(getNode(A), getNode(B));
}
bool dominatedBySlowTreeWalk(const DomTreeNode *A,
const DomTreeNode *B) const {
const DomTreeNode *IDom;
if (A == 0 || B == 0) return false;
while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B)
B = IDom; // Walk up the tree
return IDom != 0;
}
/// isReachableFromEntry - Return true if A is dominated by the entry
/// block of the function containing it.
const bool isReachableFromEntry(BasicBlock* A);
/// dominates - Returns true iff A dominates B. Note that this is not a
/// constant time operation!
///
inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
if (B == A)
return true; // A node trivially dominates itself.
if (A == 0 || B == 0)
return false;
if (DFSInfoValid)
return B->DominatedBy(A);
// If we end up with too many slow queries, just update the
// DFS numbers on the theory that we are going to keep querying.
SlowQueries++;
if (SlowQueries > 32) {
updateDFSNumbers();
return B->DominatedBy(A);
}
return dominatedBySlowTreeWalk(A, B);
}
inline bool dominates(BasicBlock *A, BasicBlock *B) {
if (A == B)
return true;
return dominates(getNode(A), getNode(B));
}
/// findNearestCommonDominator - Find nearest common dominator basic block
/// for basic block A and B. If there is no such block then return NULL.
BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B);
// dominates - Return true if A dominates B. This performs the
// special checks necessary if A and B are in the same basic block.
bool dominates(Instruction *A, Instruction *B);
//===--------------------------------------------------------------------===//
// API to update (Post)DominatorTree information based on modifications to
// the CFG...
/// addNewBlock - Add a new node to the dominator tree information. This
/// creates a new node as a child of DomBB dominator node,linking it into
/// the children list of the immediate dominator.
DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
assert(getNode(BB) == 0 && "Block already in dominator tree!");
DomTreeNode *IDomNode = getNode(DomBB);
assert(IDomNode && "Not immediate dominator specified for block!");
DFSInfoValid = false;
return DomTreeNodes[BB] =
IDomNode->addChild(new DomTreeNode(BB, IDomNode));
}
/// changeImmediateDominator - This method is used to update the dominator
/// tree information when a node's immediate dominator changes.
///
void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
assert(N && NewIDom && "Cannot change null node pointers!");
DFSInfoValid = false;
N->setIDom(NewIDom);
}
void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
changeImmediateDominator(getNode(BB), getNode(NewBB));
}
/// removeNode - Removes a node from the dominator tree. Block must not
/// dominate any other blocks. Invalidates any node pointing to removed
/// block.
void removeNode(BasicBlock *BB) {
assert(getNode(BB) && "Removing node that isn't in dominator tree.");
DomTreeNodes.erase(BB);
}
/// print - Convert to human readable form
///
virtual void print(std::ostream &OS, const Module* = 0) const;
void print(std::ostream *OS, const Module* M = 0) const {
if (OS) print(*OS, M);
}
virtual void dump();
protected:
/// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
/// dominator tree in dfs order.
void updateDFSNumbers();
};
//===-------------------------------------
/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
/// compute a normal dominator tree.
///
class DominatorTree : public DominatorTreeBase {
public:
static char ID; // Pass ID, replacement for typeid
DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {}
BasicBlock *getRoot() const {
assert(Roots.size() == 1 && "Should always have entry node!");
return Roots[0];
}
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
/// splitBlock
/// BB is split and now it has one successor. Update dominator tree to
/// reflect this change.
void splitBlock(BasicBlock *BB);
private:
void calculate(Function& F);
DomTreeNode *getNodeForBlock(BasicBlock *BB);
unsigned DFSPass(BasicBlock *V, unsigned N);
void Compress(BasicBlock *V);
BasicBlock *Eval(BasicBlock *v);
void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
inline BasicBlock *getIDom(BasicBlock *BB) const {
DenseMap<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB);
return I != IDoms.end() ? I->second : 0;
}
};
//===-------------------------------------
/// DominatorTree GraphTraits specialization so the DominatorTree can be
/// iterable by generic graph iterators.
///
template <> struct GraphTraits<DomTreeNode*> {
typedef DomTreeNode NodeType;
typedef NodeType::iterator ChildIteratorType;
static NodeType *getEntryNode(NodeType *N) {
return N;
}
static inline ChildIteratorType child_begin(NodeType* N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType* N) {
return N->end();
}
};
template <> struct GraphTraits<DominatorTree*>
: public GraphTraits<DomTreeNode*> {
static NodeType *getEntryNode(DominatorTree *DT) {
return DT->getRootNode();
}
};
//===----------------------------------------------------------------------===//
/// DominanceFrontierBase - Common base class for computing forward and inverse
/// dominance frontiers for a function.
///
class DominanceFrontierBase : public DominatorBase {
public:
typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
protected:
DomSetMapType Frontiers;
public:
DominanceFrontierBase(intptr_t ID, bool isPostDom)
: DominatorBase(ID, isPostDom) {}
virtual void releaseMemory() { Frontiers.clear(); }
// Accessor interface:
typedef DomSetMapType::iterator iterator;
typedef DomSetMapType::const_iterator const_iterator;
iterator begin() { return Frontiers.begin(); }
const_iterator begin() const { return Frontiers.begin(); }
iterator end() { return Frontiers.end(); }
const_iterator end() const { return Frontiers.end(); }
iterator find(BasicBlock *B) { return Frontiers.find(B); }
const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
assert(find(BB) == end() && "Block already in DominanceFrontier!");
Frontiers.insert(std::make_pair(BB, frontier));
}
void addToFrontier(iterator I, BasicBlock *Node) {
assert(I != end() && "BB is not in DominanceFrontier!");
I->second.insert(Node);
}
void removeFromFrontier(iterator I, BasicBlock *Node) {
assert(I != end() && "BB is not in DominanceFrontier!");
assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
I->second.erase(Node);
}
/// print - Convert to human readable form
///
virtual void print(std::ostream &OS, const Module* = 0) const;
void print(std::ostream *OS, const Module* M = 0) const {
if (OS) print(*OS, M);
}
virtual void dump();
};
//===-------------------------------------
/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
/// used to compute a forward dominator frontiers.
///
class DominanceFrontier : public DominanceFrontierBase {
public:
static char ID; // Pass ID, replacement for typeid
DominanceFrontier() :
DominanceFrontierBase((intptr_t)& ID, false) {}
BasicBlock *getRoot() const {
assert(Roots.size() == 1 && "Should always have entry node!");
return Roots[0];
}
virtual bool runOnFunction(Function &) {
Frontiers.clear();
DominatorTree &DT = getAnalysis<DominatorTree>();
Roots = DT.getRoots();
assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
calculate(DT, DT[Roots[0]]);
return false;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<DominatorTree>();
}
/// splitBlock - BB is split and now it has one successor. Update dominance
/// frontier to reflect this change.
void splitBlock(BasicBlock *BB);
private:
const DomSetType &calculate(const DominatorTree &DT,
const DomTreeNode *Node);
};
} // End llvm namespace
#endif
|