[ARM] Avoid creating duplicate ANDs in SelectionDAG

When expanding a BRCOND into a BR_CC, do not create an AND 1
if one already exists.

Review: D36705

Patch by Joel Galenson <jgalenson@google.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311447 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed