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/Assembly/Writer.h"
23 #include "llvm/Analysis/DominatorInternals.h"
24 using namespace llvm;
25 
26 //===----------------------------------------------------------------------===//
27 //  PostDominatorTree Implementation
28 //===----------------------------------------------------------------------===//
29 
30 char PostDominatorTree::ID = 0;
31 char PostDominanceFrontier::ID = 0;
32 INITIALIZE_PASS(PostDominatorTree, "postdomtree",
33                 "Post-Dominator Tree Construction", true, true)
34 
35 bool PostDominatorTree::runOnFunction(Function &F) {
36   DT->recalculate(F);
37   return false;
38 }
39 
40 PostDominatorTree::~PostDominatorTree() {
41   delete DT;
42 }
43 
44 void PostDominatorTree::print(raw_ostream &OS, const Module *) const {
45   DT->print(OS);
46 }
47 
48 
49 FunctionPass* llvm::createPostDomTree() {
50   return new PostDominatorTree();
51 }
52 
53 //===----------------------------------------------------------------------===//
54 //  PostDominanceFrontier Implementation
55 //===----------------------------------------------------------------------===//
56 
57 INITIALIZE_PASS_BEGIN(PostDominanceFrontier, "postdomfrontier",
58                 "Post-Dominance Frontier Construction", true, true)
59 INITIALIZE_PASS_DEPENDENCY(PostDominatorTree)
60 INITIALIZE_PASS_END(PostDominanceFrontier, "postdomfrontier",
61                 "Post-Dominance Frontier Construction", true, true)
62 
63 const DominanceFrontier::DomSetType &
64 PostDominanceFrontier::calculate(const PostDominatorTree &DT,
65                                  const DomTreeNode *Node) {
66   // Loop over CFG successors to calculate DFlocal[Node]
67   BasicBlock *BB = Node->getBlock();
68   DomSetType &S = Frontiers[BB];       // The new set to fill in...
69   if (getRoots().empty()) return S;
70 
71   if (BB)
72     for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
73          SI != SE; ++SI) {
74       BasicBlock *P = *SI;
75       // Does Node immediately dominate this predecessor?
76       DomTreeNode *SINode = DT[P];
77       if (SINode && SINode->getIDom() != Node)
78         S.insert(P);
79     }
80 
81   // At this point, S is DFlocal.  Now we union in DFup's of our children...
82   // Loop through and visit the nodes that Node immediately dominates (Node's
83   // children in the IDomTree)
84   //
85   for (DomTreeNode::const_iterator
86          NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
87     DomTreeNode *IDominee = *NI;
88     const DomSetType &ChildDF = calculate(DT, IDominee);
89 
90     DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
91     for (; CDFI != CDFE; ++CDFI) {
92       if (!DT.properlyDominates(Node, DT[*CDFI]))
93         S.insert(*CDFI);
94     }
95   }
96 
97   return S;
98 }
99 
100 FunctionPass* llvm::createPostDomFrontier() {
101   return new PostDominanceFrontier();
102 }
103