1 //===- DominanceFrontier.cpp - Dominance Frontier Calculation -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Analysis/DominanceFrontier.h"
11 #include "llvm/ADT/SmallPtrSet.h"
12 #include "llvm/Assembly/Writer.h"
13 #include "llvm/Support/Debug.h"
14 #include "llvm/Support/raw_ostream.h"
17 char DominanceFrontier::ID = 0;
18 INITIALIZE_PASS_BEGIN(DominanceFrontier, "domfrontier",
19 "Dominance Frontier Construction", true, true)
20 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
21 INITIALIZE_PASS_END(DominanceFrontier, "domfrontier",
22 "Dominance Frontier Construction", true, true)
25 class DFCalculateWorkObject {
27 DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
29 const DomTreeNode *PN)
30 : currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
31 BasicBlock *currentBB;
33 const DomTreeNode *Node;
34 const DomTreeNode *parentNode;
38 void DominanceFrontier::anchor() { }
40 const DominanceFrontier::DomSetType &
41 DominanceFrontier::calculate(const DominatorTree &DT,
42 const DomTreeNode *Node) {
43 BasicBlock *BB = Node->getBlock();
44 DomSetType *Result = NULL;
46 std::vector<DFCalculateWorkObject> workList;
47 SmallPtrSet<BasicBlock *, 32> visited;
49 workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
51 DFCalculateWorkObject *currentW = &workList.back();
52 assert (currentW && "Missing work object.");
54 BasicBlock *currentBB = currentW->currentBB;
55 BasicBlock *parentBB = currentW->parentBB;
56 const DomTreeNode *currentNode = currentW->Node;
57 const DomTreeNode *parentNode = currentW->parentNode;
58 assert (currentBB && "Invalid work object. Missing current Basic Block");
59 assert (currentNode && "Invalid work object. Missing current Node");
60 DomSetType &S = Frontiers[currentBB];
62 // Visit each block only once.
63 if (visited.count(currentBB) == 0) {
64 visited.insert(currentBB);
66 // Loop over CFG successors to calculate DFlocal[currentNode]
67 for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
69 // Does Node immediately dominate this successor?
70 if (DT[*SI]->getIDom() != currentNode)
75 // At this point, S is DFlocal. Now we union in DFup's of our children...
76 // Loop through and visit the nodes that Node immediately dominates (Node's
77 // children in the IDomTree)
78 bool visitChild = false;
79 for (DomTreeNode::const_iterator NI = currentNode->begin(),
80 NE = currentNode->end(); NI != NE; ++NI) {
81 DomTreeNode *IDominee = *NI;
82 BasicBlock *childBB = IDominee->getBlock();
83 if (visited.count(childBB) == 0) {
84 workList.push_back(DFCalculateWorkObject(childBB, currentBB,
85 IDominee, currentNode));
90 // If all children are visited or there is any child then pop this block
99 DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
100 DomSetType &parentSet = Frontiers[parentBB];
101 for (; CDFI != CDFE; ++CDFI) {
102 if (!DT.properlyDominates(parentNode, DT[*CDFI]))
103 parentSet.insert(*CDFI);
108 } while (!workList.empty());
113 void DominanceFrontierBase::print(raw_ostream &OS, const Module* ) const {
114 for (const_iterator I = begin(), E = end(); I != E; ++I) {
115 OS << " DomFrontier for BB ";
117 WriteAsOperand(OS, I->first, false);
119 OS << " <<exit node>>";
122 const std::set<BasicBlock*> &BBs = I->second;
124 for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
128 WriteAsOperand(OS, *I, false);
130 OS << "<<exit node>>";
136 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
137 void DominanceFrontierBase::dump() const {