Addition of IntervalIterator. Preparing for rename of Intervals.h to

Interval.h, IntervalPartition.h, and IntervalIterator.h


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/Interval.h

@@ -7,19 +7,21 @@
 // In this way, the interval partition may be used to reduce a flow graph down
 // to its degenerate single node interval partition (unless it is irreducible).
 //
-// TODO: Provide an interval iterator that codifies the internals of 
-// IntervalPartition.  Inside, it would have a stack of Interval*'s, and would
-// walk the interval partition in depth first order.  IntervalPartition would
-// then be a client of this iterator.  The iterator should work on Method*,
-// const Method*, IntervalPartition*, and const IntervalPartition*.
+// TODO: The IntervalPartition class should take a bool parameter that tells
+// whether it should add the "tails" of an interval to an interval itself or if
+// they should be represented as distinct intervals.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_INTERVALS_H
 #define LLVM_INTERVALS_H
 
+#include "llvm/Method.h"
+#include "llvm/CFG.h"
 #include <vector>
 #include <map>
+#include <stack>
+#include <set>
 #include <algorithm>
 
 class Method;
@@ -77,7 +79,7 @@ public:
   // isLoop - Find out if there is a back edge in this interval...
   bool isLoop() const;
 
-private:           // Only accessable by IntervalPartition class
+  //private:           // Only accessable by IntervalPartition class
   inline Interval(BasicBlock *Header) : HeaderNode(Header) {
     Nodes.push_back(Header);
   }
@@ -105,6 +107,141 @@ inline Interval::pred_iterator pred_end(Interval *I) {
 }
 
 
+//===----------------------------------------------------------------------===//
+//                             IntervalIterator
+//
+// TODO: Provide an interval iterator that codifies the internals of 
+// IntervalPartition.  Inside, it would have a stack of Interval*'s, and would
+// walk the interval partition in depth first order.  IntervalPartition would
+// then be a client of this iterator.  The iterator should work on Method*,
+// const Method*, IntervalPartition*, and const IntervalPartition*.
+//
+
+template<class NodeTy, class OrigContainer_t>
+class IntervalIterator {
+  stack<pair<Interval, typename Interval::succ_iterator> > IntStack;
+  set<BasicBlock*> Visited;
+  OrigContainer_t *OrigContainer;
+public:
+  typedef BasicBlock* _BB;
+
+  typedef IntervalIterator<NodeTy, OrigContainer_t> _Self;
+  typedef forward_iterator_tag iterator_category;
+ 
+  IntervalIterator() {} // End iterator, empty stack
+  IntervalIterator(Method *M) {
+    OrigContainer = M;
+    if (!ProcessInterval(M->getBasicBlocks().front())) {
+      assert(0 && "ProcessInterval should never fail for first interval!");
+    }
+  }
+
+  inline bool operator==(const _Self& x) const { return IntStack == x.IntStack; }
+  inline bool operator!=(const _Self& x) const { return !operator==(x); }
+
+  inline Interval &operator*() const { return IntStack.top(); }
+  inline Interval *operator->() const { return &(operator*()); }
+
+  inline _Self& operator++() {  // Preincrement
+    do {
+      // All of the intervals on the stack have been visited.  Try visiting their
+      // successors now.
+      Interval           &CurInt = IntStack.top().first;
+      Interval::iterator &SuccIt = IntStack.top().second,End = succ_end(&CurInt);
+
+      for (; SuccIt != End; ++SuccIt)    // Loop over all interval successors
+	if (ProcessInterval(*SuccIt))    // Found a new interval!
+	  return *this;                  // Use it!
+
+      // We ran out of successors for this interval... pop off the stack
+      IntStack.pop();
+    } while (!IntStack.empty());
+
+    return *this; 
+  }
+  inline _Self operator++(int) { // Postincrement
+    _Self tmp = *this; ++*this; return tmp; 
+  }
+
+private:
+  // ProcessInterval - This method is used during the construction of the 
+  // interval graph.  It walks through the source graph, recursively creating
+  // an interval per invokation until the entire graph is covered.  This uses
+  // the ProcessNode method to add all of the nodes to the interval.
+  //
+  // This method is templated because it may operate on two different source
+  // graphs: a basic block graph, or a preexisting interval graph.
+  //
+  bool ProcessInterval(NodeTy *Node) {
+    BasicBlock *Header = getNodeHeader(Node);
+    if (Visited.count(Header)) return false;
+
+    Interval Int(Header);
+    Visited.insert(Header);   // The header has now been visited!
+
+    // Check all of our successors to see if they are in the interval...
+    for (typename NodeTy::succ_iterator I = succ_begin(Node), E = succ_end(Node);
+	 I != E; ++I)
+      ProcessNode(&Int, getSourceGraphNode(OrigContainer, *I));
+
+    IntStack.push(make_pair(Int, succ_begin(&Int)));
+    return true;
+  }
+  
+  // ProcessNode - This method is called by ProcessInterval to add nodes to the
+  // interval being constructed, and it is also called recursively as it walks
+  // the source graph.  A node is added to the current interval only if all of
+  // its predecessors are already in the graph.  This also takes care of keeping
+  // the successor set of an interval up to date.
+  //
+  // This method is templated because it may operate on two different source
+  // graphs: a basic block graph, or a preexisting interval graph.
+  //
+  void ProcessNode(Interval *Int, NodeTy *Node) {
+    assert(Int && "Null interval == bad!");
+    assert(Node && "Null Node == bad!");
+  
+    BasicBlock *NodeHeader = getNodeHeader(Node);
+
+    if (Visited.count(NodeHeader)) {     // Node already been visited?
+      if (Int->contains(NodeHeader)) {   // Already in this interval...
+	return;
+      } else {                           // In another interval, add as successor
+	if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
+	  Int->Successors.push_back(NodeHeader);
+      }
+    } else {                             // Otherwise, not in interval yet
+      for (typename NodeTy::pred_iterator I = pred_begin(Node), 
+	                                  E = pred_end(Node); I != E; ++I) {
+	if (!Int->contains(*I)) {        // If pred not in interval, we can't be
+	  if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
+	    Int->Successors.push_back(NodeHeader);
+	  return;                        // See you later
+	}
+      }
+
+      // If we get here, then all of the predecessors of BB are in the interval
+      // already.  In this case, we must add BB to the interval!
+      addNodeToInterval(Int, Node);
+      Visited.insert(NodeHeader);     // The node has now been visited!
+    
+      if (Int->isSuccessor(NodeHeader)) {
+	// If we were in the successor list from before... remove from succ list
+	Int->Successors.erase(remove(Int->Successors.begin(),
+				     Int->Successors.end(), NodeHeader), 
+			      Int->Successors.end());
+      }
+    
+      // Now that we have discovered that Node is in the interval, perhaps some
+      // of its successors are as well?
+      for (typename NodeTy::succ_iterator It = succ_begin(Node), 
+	     End = succ_end(Node); It != End; ++It)
+	ProcessNode(Int, getSourceGraphNode(OrigContainer, *It));
+    }
+  }
+};
+
+
 //===----------------------------------------------------------------------===//
 //
 // IntervalPartition - This class builds and holds an "interval partition" for
@@ -200,6 +337,60 @@ private:
   void updatePredecessors(Interval *Int);
 };
 
+
+
+// getNodeHeader - Given a source graph node and the source graph, return the 
+// BasicBlock that is the header node.  This is the opposite of
+// getSourceGraphNode.
+//
+inline BasicBlock *getNodeHeader(BasicBlock *BB) { return BB; }
+inline BasicBlock *getNodeHeader(Interval *I) { return I->getHeaderNode(); }
+
+// getSourceGraphNode - Given a BasicBlock and the source graph, return the 
+// source graph node that corresponds to the BasicBlock.  This is the opposite
+// of getNodeHeader.
+//
+inline BasicBlock *getSourceGraphNode(Method *, BasicBlock *BB) {
+  return BB; 
+}
+inline Interval *getSourceGraphNode(IntervalPartition *IP, BasicBlock *BB) { 
+  return IP->getBlockInterval(BB);
+}
+
+// addNodeToInterval - This method exists to assist the generic ProcessNode
+// with the task of adding a node to the new interval, depending on the 
+// type of the source node.  In the case of a CFG source graph (BasicBlock 
+// case), the BasicBlock itself is added to the interval.
+//
+inline void addNodeToInterval(Interval *Int, BasicBlock *BB){
+  Int->Nodes.push_back(BB);
+}
+
+// addNodeToInterval - This method exists to assist the generic ProcessNode
+// with the task of adding a node to the new interval, depending on the 
+// type of the source node.  In the case of a CFG source graph (BasicBlock 
+// case), the BasicBlock itself is added to the interval.  In the case of
+// an IntervalPartition source graph (Interval case), all of the member
+// BasicBlocks are added to the interval.
+//
+inline void addNodeToInterval(Interval *Int, Interval *I) {
+  // Add all of the nodes in I as new nodes in Int.
+  copy(I->Nodes.begin(), I->Nodes.end(), back_inserter(Int->Nodes));
+}
+
+
+
+
+typedef IntervalIterator<BasicBlock, Method> method_interval_iterator;
+
+
+method_interval_iterator intervals_begin(Method *M) {
+  return method_interval_iterator(M);
+}
+method_interval_iterator intervals_end(Method *M) {
+  return method_interval_iterator();
+}
+
 }    // End namespace cfg
 
 #endif