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 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 }