fix rdar://7653908, a crash on a case where we would fold a load

fix rdar://7653908, a crash on a case where we would fold a load
into a roundss intrinsic, producing a cyclic dag.  The root cause
of this is badness handling ComplexPattern nodes in the old dagisel
that I noticed through inspection.  Eliminate a copy of the of the
code that handled ComplexPatterns by making EmitChildMatchCode call
into EmitMatchCode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96408 91177308-0d34-0410-b5e6-96231b3b80d8