From Assembler to C-Compiler

Question

i designed a small RISC in verilog. Which steps do I have to take to create ac compiler which uses my assembler-language? Or is it possible to modify a conventional compiler like gcc, cause I don't want to make things like linker, ...

Thanks

Answer 1

You need to use an unmodified C lexer+parser (often called the front end), and a modified code generation component (the back end) to do that.

Eli Bendersky's pycparser can be used as the front end, and Atul's mini C compiler can be used as inspiration for the code generating back end: http://people.cs.uchicago.edu/~varmaa/mini_c/

With Eli Bendersky's pycparser, all you need to do is convert the AST to a Control Flow Graph (CFG) and generate code from there. It is easier to start with supporting a subset of C than the full shebang.

The two tools are written in Python, but you didn't mention any implementation language preferences :)

I have found most open sourcen compilers (except clang it seems) too tightly coupled to easily modify the back end. Clang and especially GCC are not easy to dive into, nowhere NEAR as easy as the two above. And since Eli's parser does full C99 (it parses everything I've thrown at it) it seem like a nice front end to use for further development. The examples on the Github project demonstrates most of the features of the project and it's easy to get started. The example that parses C to literal English is worth taking a look at, but may take a while to fully grok. It basically handles any C expression, so it is a good reference for how to handle the different nodes of the AST.

I also recommended the tools above, in my answer to this question: Build AST from C code