TableGen subtarget emitter, nearly first class support for SchedAlias.

A processor can now arbitrarily alias one SchedWrite onto
another. Only the SchedAlias definition need be within the processor
model. The aliased SchedWrite may be a SchedVariant, WriteSequence, or
transitively refer to another alias.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165179 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed