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/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->print(errs()));
  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 static RegisterPass<PostDominanceFrontier>
  58 H("postdomfrontier", "Post-Dominance Frontier Construction", true, true);
  59
  60 const DominanceFrontier::DomSetType &
  61 PostDominanceFrontier::calculate(const PostDominatorTree &DT,
  62                                  const DomTreeNode *Node) {
  63   // Loop over CFG successors to calculate DFlocal[Node]
  64   BasicBlock *BB = Node->getBlock();
  65   DomSetType &S = Frontiers[BB];       // The new set to fill in...
  66   if (getRoots().empty()) return S;
  67
  68   if (BB)
  69     for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
  70          SI != SE; ++SI) {
  71       // Does Node immediately dominate this predecessor?
  72       DomTreeNode *SINode = DT[*SI];
  73       if (SINode && SINode->getIDom() != Node)
  74         S.insert(*SI);
  75     }
  76
  77   // At this point, S is DFlocal.  Now we union in DFup's of our children...
  78   // Loop through and visit the nodes that Node immediately dominates (Node's
  79   // children in the IDomTree)
  80   //
  81   for (DomTreeNode::const_iterator
  82          NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
  83     DomTreeNode *IDominee = *NI;
  84     const DomSetType &ChildDF = calculate(DT, IDominee);
  85
  86     DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
  87     for (; CDFI != CDFE; ++CDFI) {
  88       if (!DT.properlyDominates(Node, DT[*CDFI]))
  89         S.insert(*CDFI);
  90     }
  91   }
  92
  93   return S;
  94 }
  95
  96 FunctionPass* llvm::createPostDomFrontier() {
  97   return new PostDominanceFrontier();
  98 }