[PATCH] [llvm] [Hexagon] Adding tests, TableGen entries, and code for emitting add opcode.

[Rafael Espíndola]

> That is right.  The hexagon assembly language syntax is somewhat C-like and violates some of the assumptions the MC assembler makes.
>
> We want to get the TD files updated with encoding bits and update the rest of MCTargetDesc so that object files can be directly emitted.  Using this test framework allows us to add the encoding bits and have a directed test for each instruction.

Can you test the encoding with disassembler tests? Even if is printing
in a sudo-hexagon syntax for now that should be sufficient for
testing. I am afraid that using gtest for instruction encoding might
get even messier then the clang-format tests.

Cheers,
Rafael