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->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 }