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

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>.

llvm-svn: 115099