[RISCV 4/10] Add basic RISCV{InstrFormats,InstrInfo,RegisterInfo,}.td

For now, only add instruction definitions for basic ALU operations. Our 
initial target is a working MC layer rather than codegen, so appropriate 
SelectionDAG patterns will come later.

Differential Revision: https://reviews.llvm.org/D23561


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285769 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed