lib/Analysis/PostDominators.cpp

   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 }