Add new cleanup pass:

//  1. PHI nodes with multiple entries for the same predecessor.  GCC sometimes
//     generates code that looks like this:
//
//  bb7:  br bool %cond1004, label %bb8, label %bb8
//  bb8: %reg119 = phi uint [ 0, %bb7 ], [ 1, %bb7 ]
//
//     which is completely illegal LLVM code.  To compensate for this, we insert
//     an extra basic block, and convert the code to look like this:
//
//  bb7: br bool %cond1004, label %bbX, label %bb8
//  bbX: br label bb8
//  bb8: %reg119 = phi uint [ 0, %bbX ], [ 1, %bb7 ]
//

llvm-svn: 1114