Language Frontend Integration

EVM target specific changes

The EVM architecture is the only 256-bit machine out there in the market, and so far it have not yet received support from LLVM community. We added 256-bit and 160-bit support in the LLVM IR level.

In order to utilize 256-bit and 160-bit operands, developers are expected to emit i256 and i160 data types in their IR code generation. Include the evm_llvm's header files so that these two pre-defined data types can be properly generated.

Notice that development of this backend is based on LLVM 10.0.dev, which is the master trunk. We could do back porting to lower versions such as LLVM 9 or LLVM 8 at the request of developers for better stability or compatibility.