Grab the TargetRegisterInfo off of the subtarget from the
MachineFunction rather than a lookup on the TargetMachine
to avoid unnecessary lookups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219291 91177308-0d34-0410-b5e6-96231b3b80d8
Use the TargetLowering information we already have on the
SelectionDAG in SelectionDAGBuilder rather than going through
the TargetMachine for lookup.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219292 91177308-0d34-0410-b5e6-96231b3b80d8