Early CFG simplification can fold conditionals down to selects, which is often a...

Early CFG simplification can fold conditionals down to selects, which is often a good thing, but it can also
hide jump threading opportunities by turning control flow into data flow.  Run an early JumpThreading pass
(adds approximately an additional 1% to optimization time on SPEC), allowing it to get a shot at these cases
first.  Fixes <rdar://problem/8447345>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115099 91177308-0d34-0410-b5e6-96231b3b80d8