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