In generic cpu model, there are only low 16 registers and little 32-bit instruction. CK801 is the cpu
family with least basic features like generic model.
Add test run and check for generic cpu model in original test case to cover basic LLVM IR functionality.
Complete basic arithmetic operations such as add/sub/mul/div, and it also includes converions
and some specific operations such as bswap.Add load/store patterns to generate different addressing mode instructions.
Also enable some infra such as copy physical register and eliminate frame index.
Add all CompressPat to map instructions between 16-bit and 32-bit with using the CompressInstEmitter infra.
Although it's only used in asm printer, also enable it in asm parser to debug mapping when -enable-csky-asm-compressed-inst is on.
Differential Revision: https://reviews.llvm.org/D115026
Ooops. It constructs codegen infra and provide only basic code to generate first add instruction successfully.
Differential Revision: https://reviews.llvm.org/D112206
