Merge DenseMapKeyInfo & DenseMapValueInfo into DenseMapInfo

Add a new DenseMapInfo::isEqual method to allow clients to redefine
the equality predicate used when probing the hash table.

llvm-svn: 42042
diff --git a/llvm/lib/Transforms/Scalar/GVNPRE.cpp b/llvm/lib/Transforms/Scalar/GVNPRE.cpp
index d362f54..b3d2fe2 100644
--- a/llvm/lib/Transforms/Scalar/GVNPRE.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNPRE.cpp
@@ -155,7 +155,7 @@
 }
 
 namespace llvm {
-template <> struct DenseMapKeyInfo<Expression> {
+template <> struct DenseMapInfo<Expression> {
   static inline Expression getEmptyKey() {
     return Expression(Expression::EMPTY);
   }
@@ -181,6 +181,9 @@
     
     return hash;
   }
+  static bool isEqual(const Expression &LHS, const Expression &RHS) {
+    return LHS == RHS;
+  }
   static bool isPod() { return true; }
 };
 }