Refactor Multiclass Def Processing

Move the code to instantiate a multiclass def, bind its arguments and
resolve its members into three helper functions.  These will be reused
to support a new kind of multiclass def: a multidef.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141229 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed