[Analysis/Interval] Remove isLoop (NFC)

The last use of isLoop was removed on Apr 29, 2002 in commit
09bbb5c as part of an effort to
remove "old induction varaible cannonicalization pass built on top of
interval analysis".

Author: kazutakahirata

llvm/include/llvm/Analysis/Interval.h

@@ -89,9 +89,6 @@ class Interval {
     return HeaderNode == I.HeaderNode;
   }
 
-  /// isLoop - Find out if there is a back edge in this interval...
-  bool isLoop() const;
-
   /// print - Show contents in human readable format...
   void print(raw_ostream &O) const;
 };

llvm/lib/Analysis/Interval.cpp

@@ -22,17 +22,6 @@ using namespace llvm;
 // Interval Implementation
 //===----------------------------------------------------------------------===//
 
-// isLoop - Find out if there is a back edge in this interval...
-bool Interval::isLoop() const {
-  // There is a loop in this interval iff one of the predecessors of the header
-  // node lives in the interval.
-  for (::pred_iterator I = ::pred_begin(HeaderNode), E = ::pred_end(HeaderNode);
-       I != E; ++I)
-    if (contains(*I))
-      return true;
-  return false;
-}
-
 void Interval::print(raw_ostream &OS) const {
   OS << "-------------------------------------------------------------\n"
        << "Interval Contents:\n";