Add PredicateSimplifier pass. Collapses equal variables into one form

and simplifies expressions. This implements the optimization described
in PR807.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29947 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Scalar.h

@@ -308,6 +308,11 @@ FunctionPass *createBlockPlacementPass();
 FunctionPass *createLCSSAPass();
 extern const PassInfo *LCSSAID;
 
+//===----------------------------------------------------------------------===//
+// This pass collapses duplicate variables into one canonical form,
+// and tries to simplify expressions along the way.
+FunctionPass *createPredicateSimplifierPass();
+
 } // End llvm namespace
 
 #endif