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"
23 using namespace llvm;
24 
25 //===----------------------------------------------------------------------===//
26 //  PostDominatorTree Implementation
27 //===----------------------------------------------------------------------===//
28 
29 char PostDominatorTree::ID = 0;
30 char PostDominanceFrontier::ID = 0;
31 static RegisterPass<PostDominatorTree>
32 F("postdomtree", "Post-Dominator Tree Construction", true, true);
33 
34 bool PostDominatorTree::runOnFunction(Function &F) {
35   DT->recalculate(F);
36   DEBUG(DT->dump());
37   return false;
38 }
39 
40 PostDominatorTree::~PostDominatorTree()
41 {
42   delete DT;
43 }
44 
45 FunctionPass* llvm::createPostDomTree() {
46   return new PostDominatorTree();
47 }
48 
49 //===----------------------------------------------------------------------===//
50 //  PostDominanceFrontier Implementation
51 //===----------------------------------------------------------------------===//
52 
53 static RegisterPass<PostDominanceFrontier>
54 H("postdomfrontier", "Post-Dominance Frontier Construction", true, true);
55 
56 const DominanceFrontier::DomSetType &
57 PostDominanceFrontier::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 
92 FunctionPass* llvm::createPostDomFrontier() {
93   return new PostDominanceFrontier();
94 }
95