PostDominators.cpp revision 9491195710811cfe2413bbcd04bce2ed56ea121a 
1//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the post-dominator construction algorithms.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "postdomtree"
15
16#include "llvm/Analysis/PostDominators.h"
17#include "llvm/Instructions.h"
18#include "llvm/Support/CFG.h"
19#include "llvm/Support/Debug.h"
20#include "llvm/ADT/DepthFirstIterator.h"
21#include "llvm/ADT/SetOperations.h"
22#include "llvm/Analysis/DominatorInternals.h"
23using namespace llvm;
24
25//===----------------------------------------------------------------------===//
26//  PostDominatorTree Implementation
27//===----------------------------------------------------------------------===//
28
29char PostDominatorTree::ID = 0;
30char PostDominanceFrontier::ID = 0;
31static RegisterPass<PostDominatorTree>
32F("postdomtree", "Post-Dominator Tree Construction", true, true);
33
34bool PostDominatorTree::runOnFunction(Function &F) {
35  DT->recalculate(F);
36  DEBUG(DT->dump());
37  return false;
38}
39
40PostDominatorTree::~PostDominatorTree()
41{
42  delete DT;
43}
44
45FunctionPass* llvm::createPostDomTree() {
46  return new PostDominatorTree();
47}
48
49//===----------------------------------------------------------------------===//
50//  PostDominanceFrontier Implementation
51//===----------------------------------------------------------------------===//
52
53static RegisterPass<PostDominanceFrontier>
54H("postdomfrontier", "Post-Dominance Frontier Construction", true, true);
55
56const DominanceFrontier::DomSetType &
57PostDominanceFrontier::calculate(const PostDominatorTree &DT,
58                                 const DomTreeNode *Node) {
59  // Loop over CFG successors to calculate DFlocal[Node]
60  BasicBlock *BB = Node->getBlock();
61  DomSetType &S = Frontiers[BB];       // The new set to fill in...
62  if (getRoots().empty()) return S;
63
64  if (BB)
65    for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
66         SI != SE; ++SI) {
67      // Does Node immediately dominate this predecessor?
68      DomTreeNode *SINode = DT[*SI];
69      if (SINode && SINode->getIDom() != Node)
70        S.insert(*SI);
71    }
72
73  // At this point, S is DFlocal.  Now we union in DFup's of our children...
74  // Loop through and visit the nodes that Node immediately dominates (Node's
75  // children in the IDomTree)
76  //
77  for (DomTreeNode::const_iterator
78         NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
79    DomTreeNode *IDominee = *NI;
80    const DomSetType &ChildDF = calculate(DT, IDominee);
81
82    DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
83    for (; CDFI != CDFE; ++CDFI) {
84      if (!DT.properlyDominates(Node, DT[*CDFI]))
85        S.insert(*CDFI);
86    }
87  }
88
89  return S;
90}
91
92FunctionPass* llvm::createPostDomFrontier() {
93  return new PostDominanceFrontier();
94}
95