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//===- DominanceFrontier.cpp - Dominance Frontier Calculation -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/DominanceFrontier.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
char DominanceFrontier::ID = 0;
INITIALIZE_PASS_BEGIN(DominanceFrontier, "domfrontier",
"Dominance Frontier Construction", true, true)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_END(DominanceFrontier, "domfrontier",
"Dominance Frontier Construction", true, true)
namespace {
class DFCalculateWorkObject {
public:
DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
const DomTreeNode *N,
const DomTreeNode *PN)
: currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
BasicBlock *currentBB;
BasicBlock *parentBB;
const DomTreeNode *Node;
const DomTreeNode *parentNode;
};
}
const DominanceFrontier::DomSetType &
DominanceFrontier::calculate(const DominatorTree &DT,
const DomTreeNode *Node) {
BasicBlock *BB = Node->getBlock();
DomSetType *Result = NULL;
std::vector<DFCalculateWorkObject> workList;
SmallPtrSet<BasicBlock *, 32> visited;
workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
do {
DFCalculateWorkObject *currentW = &workList.back();
assert (currentW && "Missing work object.");
BasicBlock *currentBB = currentW->currentBB;
BasicBlock *parentBB = currentW->parentBB;
const DomTreeNode *currentNode = currentW->Node;
const DomTreeNode *parentNode = currentW->parentNode;
assert (currentBB && "Invalid work object. Missing current Basic Block");
assert (currentNode && "Invalid work object. Missing current Node");
DomSetType &S = Frontiers[currentBB];
// Visit each block only once.
if (visited.count(currentBB) == 0) {
visited.insert(currentBB);
// Loop over CFG successors to calculate DFlocal[currentNode]
for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
SI != SE; ++SI) {
// Does Node immediately dominate this successor?
if (DT[*SI]->getIDom() != currentNode)
S.insert(*SI);
}
}
// At this point, S is DFlocal. Now we union in DFup's of our children...
// Loop through and visit the nodes that Node immediately dominates (Node's
// children in the IDomTree)
bool visitChild = false;
for (DomTreeNode::const_iterator NI = currentNode->begin(),
NE = currentNode->end(); NI != NE; ++NI) {
DomTreeNode *IDominee = *NI;
BasicBlock *childBB = IDominee->getBlock();
if (visited.count(childBB) == 0) {
workList.push_back(DFCalculateWorkObject(childBB, currentBB,
IDominee, currentNode));
visitChild = true;
}
}
// If all children are visited or there is any child then pop this block
// from the workList.
if (!visitChild) {
if (!parentBB) {
Result = &S;
break;
}
DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
DomSetType &parentSet = Frontiers[parentBB];
for (; CDFI != CDFE; ++CDFI) {
if (!DT.properlyDominates(parentNode, DT[*CDFI]))
parentSet.insert(*CDFI);
}
workList.pop_back();
}
} while (!workList.empty());
return *Result;
}
void DominanceFrontierBase::print(raw_ostream &OS, const Module* ) const {
for (const_iterator I = begin(), E = end(); I != E; ++I) {
OS << " DomFrontier for BB ";
if (I->first)
WriteAsOperand(OS, I->first, false);
else
OS << " <<exit node>>";
OS << " is:\t";
const std::set<BasicBlock*> &BBs = I->second;
for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
I != E; ++I) {
OS << ' ';
if (*I)
WriteAsOperand(OS, *I, false);
else
OS << "<<exit node>>";
}
OS << "\n";
}
}
void DominanceFrontierBase::dump() const {
print(dbgs());
}
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