implement a new optimization to sink pattern predicates (like isSSE1)

implement a new optimization to sink pattern predicates (like isSSE1)
as deeply into the pattern as we can get away with.  In pratice, this
means "all the way to to the emitter code, but not across
ComplexPatterns".  This substantially increases the amount of factoring
we get.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97305 91177308-0d34-0410-b5e6-96231b3b80d8