Checkin of new dominator calculation routines. These will be improved in

the future to do post dominators and stuff


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 239 insertions, 0 deletions

diff --git a/lib/Analysis/PostDominators.cpp b/lib/Analysis/PostDominators.cpp
new file mode 100644
index 0000000000..d6483423eb
--- /dev/null
+++ b/lib/Analysis/PostDominators.cpp
@@ -0,0 +1,239 @@
+//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//
+// This file provides a simple class to calculate the dominator set of a method.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/CFG.h"
+#include "llvm/Tools/STLExtras.h"
+#include <algorithm>
+
+//===----------------------------------------------------------------------===//
+//  Helper Template
+//===----------------------------------------------------------------------===//
+
+// set_intersect - Identical to set_intersection, except that it works on 
+// set<>'s and is nicer to use.  Functionally, this iterates through S1, 
+// removing elements that are not contained in S2.
+//
+template <class Ty, class Ty2>
+void set_intersect(set<Ty> &S1, const set<Ty2> &S2) {
+  for (typename set<Ty>::iterator I = S1.begin(); I != S1.end();) {
+    const Ty &E = *I;
+    ++I;
+    if (!S2.count(E)) S1.erase(E);   // Erase element if not in S2
+  }
+}
+
+
+//===----------------------------------------------------------------------===//
+//  DominatorSet Implementation
+//===----------------------------------------------------------------------===//
+
+// DominatorSet ctor - Build either the dominator set or the post-dominator
+// set for a method...
+//
+cfg::DominatorSet::DominatorSet(const Method *M, bool PostDomSet)
+  : Root(M->front()) {
+  assert(Root && M && "Can't build dominator set of null method!");
+  bool Changed;
+  do {
+    Changed = false;
+
+    DomSetType WorkingSet;
+    df_const_iterator It = df_begin(M), End = df_end(M);
+    for ( ; It != End; ++It) {
+      const BasicBlock *BB = *It;
+      pred_const_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
+      if (PI != PEnd) {                // Is there SOME predecessor?
+	// Loop until we get to a predecessor that has had it's dom set filled
+	// in at least once.  We are guaranteed to have this because we are
+	// traversing the graph in DFO and have handled start nodes specially.
+	//
+	while (Doms[*PI].size() == 0) ++PI;
+	WorkingSet = Doms[*PI];
+
+	for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
+	  DomSetType &PredSet = Doms[*PI];
+	  if (PredSet.size())
+	    set_intersect(WorkingSet, PredSet);
+	}
+      }
+	
+      WorkingSet.insert(BB);           // A block always dominates itself
+      DomSetType &BBSet = Doms[BB];
+      if (BBSet != WorkingSet) {
+	BBSet.swap(WorkingSet);        // Constant time operation!
+	Changed = true;                // The sets changed.
+      }
+      WorkingSet.clear();              // Clear out the set for next iteration
+    }
+  } while (Changed);
+
+}
+
+
+//===----------------------------------------------------------------------===//
+//  ImmediateDominators Implementation
+//===----------------------------------------------------------------------===//
+
+// calcIDoms - Calculate the immediate dominator mapping, given a set of
+// dominators for every basic block.
+void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
+  // Loop over all of the nodes that have dominators... figuring out the IDOM
+  // for each node...
+  //
+  for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end(); 
+       DI != DEnd; ++DI) {
+    const BasicBlock *BB = DI->first;
+    const DominatorSet::DomSetType &Dominators = DI->second;
+    unsigned DomSetSize = Dominators.size();
+    if (DomSetSize == 1) continue;  // Root node... IDom = null
+
+    // Loop over all dominators of this node.  This corresponds to looping over
+    // nodes in the dominator chain, looking for a node whose dominator set is
+    // equal to the current nodes, except that the current node does not exist
+    // in it.  This means that it is one level higher in the dom chain than the
+    // current node, and it is our idom!
+    //
+    DominatorSet::DomSetType::const_iterator I = Dominators.begin();
+    DominatorSet::DomSetType::const_iterator End = Dominators.end();
+    for (; I != End; ++I) {   // Iterate over dominators...
+      // All of our dominators should form a chain, where the number of elements
+      // in the dominator set indicates what level the node is at in the chain.
+      // We want the node immediately above us, so it will have an identical 
+      // dominator set, except that BB will not dominate it... therefore it's
+      // dominator set size will be one less than BB's...
+      //
+      if (DS.getDominators(*I).size() == DomSetSize - 1) {
+	IDoms[BB] = *I;
+	break;
+      }
+    }
+  }
+}
+
+
+//===----------------------------------------------------------------------===//
+//  DominatorTree Implementation
+//===----------------------------------------------------------------------===//
+
+// DominatorTree dtor - Free all of the tree node memory.
+//
+cfg::DominatorTree::~DominatorTree() { 
+  for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
+    delete I->second;
+}
+
+
+cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms) 
+  : Root(IDoms.getRoot()) {
+  assert(Root && Root->getParent() && "No method for IDoms?");
+  const Method *M = Root->getParent();
+
+  Nodes[Root] = new Node(Root, 0);   // Add a node for the root...
+
+  // Iterate over all nodes in depth first order...
+  for (df_const_iterator I = df_begin(M), E = df_end(M); I != E; ++I) {
+    const BasicBlock *BB = *I, *IDom = IDoms[*I];
+
+    if (IDom != 0) {   // Ignore the root node and other nasty nodes
+      // We know that the immediate dominator should already have a node, 
+      // because we are traversing the CFG in depth first order!
+      //
+      assert(Nodes[IDom] && "No node for IDOM?");
+      Node *IDomNode = Nodes[IDom];
+
+      // Add a new tree node for this BasicBlock, and link it as a child of
+      // IDomNode
+      Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
+    }
+  }
+}
+
+void cfg::DominatorTree::calculate(const DominatorSet &DS) {
+  Root = DS.getRoot();
+  assert(Root && Root->getParent() && "No method for IDoms?");
+  const Method *M = Root->getParent();
+  Nodes[Root] = new Node(Root, 0);   // Add a node for the root...
+
+  // Iterate over all nodes in depth first order...
+  for (df_const_iterator I = df_begin(M), E = df_end(M); I != E; ++I) {
+    const BasicBlock *BB = *I;
+    const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
+    unsigned DomSetSize = Dominators.size();
+    if (DomSetSize == 1) continue;  // Root node... IDom = null
+
+    // Loop over all dominators of this node.  This corresponds to looping over
+    // nodes in the dominator chain, looking for a node whose dominator set is
+    // equal to the current nodes, except that the current node does not exist
+    // in it.  This means that it is one level higher in the dom chain than the
+    // current node, and it is our idom!  We know that we have already added
+    // a DominatorTree node for our idom, because the idom must be a
+    // predecessor in the depth first order that we are iterating through the
+    // method.
+    //
+    DominatorSet::DomSetType::const_iterator I = Dominators.begin();
+    DominatorSet::DomSetType::const_iterator End = Dominators.end();
+    for (; I != End; ++I) {   // Iterate over dominators...
+      // All of our dominators should form a chain, where the number of elements
+      // in the dominator set indicates what level the node is at in the chain.
+      // We want the node immediately above us, so it will have an identical 
+      // dominator set, except that BB will not dominate it... therefore it's
+      // dominator set size will be one less than BB's...
+      //
+      if (DS.getDominators(*I).size() == DomSetSize - 1) {
+	// We know that the immediate dominator should already have a node, 
+	// because we are traversing the CFG in depth first order!
+	//
+	Node *IDomNode = Nodes[*I];
+	assert(Nodes[*I] && "No node for IDOM?");
+	
+	// Add a new tree node for this BasicBlock, and link it as a child of
+	// IDomNode
+	Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
+	break;
+      }
+    }
+  }
+}
+
+
+
+//===----------------------------------------------------------------------===//
+//  DominanceFrontier Implementation
+//===----------------------------------------------------------------------===//
+
+const cfg::DominanceFrontier::DomSetType &
+cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT, 
+					const DominatorTree::Node *Node) {
+  // Loop over CFG successors to calculate DFlocal[Node]
+  const BasicBlock *BB = Node->getNode();
+  DomSetType &S = Frontiers[BB];       // The new set to fill in...
+
+  for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); 
+       SI != SE; ++SI) {
+    // Does Node immediately dominate this successor?
+    if (DT[*SI]->getIDom() != Node)
+      S.insert(*SI);
+  }
+
+  // At this point, S is DFlocal.  Now we union in DFup's of our children...
+  // Loop through and visit the nodes that Node immediately dominates (Node's
+  // children in the IDomTree)
+  //
+  for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
+       NI != NE; ++NI) {
+    DominatorTree::Node *IDominee = *NI;
+    const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
+
+    DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
+    for (; CDFI != CDFE; ++CDFI) {
+      if (!Node->dominates(DT[*CDFI]))
+	S.insert(*CDFI);
+    }
+  }
+
+  return S;
+}