[SystemZ] Avoid generating 2 XOR instructions for (and (xor x, -1), y)

Summary:
Created a pattern to match 64-bit mode (and (xor x, -1), y)
to a shorter sequence of instructions.

Before the change, the canonical form is translated to:
        xihf    %r3, 4294967295
        xilf    %r3, 4294967295
        ngr     %r2, %r3

After the change, the canonical form is translated to:
        ngr     %r3, %r2
        xgr     %r2, %r3

Reviewers: zhanjunl, uweigand

Subscribers: llvm-commits

Author: assem

Committing on behalf of Assem.

Differential Revision: http://reviews.llvm.org/D21693

llvm-svn: 273887