Added helper functions in LoopInfo: isLoopExit and numBackEdges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4112 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopInfo.h

@@ -44,7 +44,10 @@ public:
 
   /// isLoopExit - True if terminator in the block can branch to another block
   /// that is outside of the current loop.
-  bool isLoopExit(BasicBlock *BB) const;
+  bool isLoopExit(const BasicBlock *BB) const;
+
+  /// Find number of back edges
+  unsigned getNumBackEdges() const;
 
   /// getLoopPreheader - If there is a preheader for this loop, return it.  A
   /// loop has a preheader if there is only one edge to the header of the loop

lib/Analysis/LoopInfo.cpp

@@ -24,6 +24,30 @@ bool Loop::contains(const BasicBlock *BB) const {
   return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
 }
 
+bool Loop::isLoopExit(const BasicBlock *BB) const {
+  for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
+       SI != SE; ++SI) {
+    if (! contains(*SI))
+      return true;
+  }
+  return false;
+}
+
+unsigned Loop::getNumBackEdges() const {
+  unsigned numBackEdges = 0;
+  BasicBlock *header = Blocks.front();
+
+  for (std::vector<BasicBlock*>::const_iterator i = Blocks.begin(), e = Blocks.end();
+       i != e; ++i) {
+    for (BasicBlock::succ_iterator Successor = succ_begin(*i), SEnd = succ_end(*i);
+	 Successor != SEnd; ++Successor) {
+      if (header == *Successor)
+	++numBackEdges;
+    }
+  }
+  return numBackEdges;
+}
+
 void Loop::print(std::ostream &OS) const {
   OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: ";