我的Fortran编译器的中间代码生成：DAG或四倍

Question

I'm writing a mini Fortran compiler using Flex and Bison. Up to now I've finished the lexical and syntax analysis. I'm in the semantic analysis in type checking and I must now choose an IR. My target machine is MIPS. So I want final code generation based on MIPS IAS. So a good IR I believe are quadruples. But I want to introduce some optimizations. For that reason I've built a DAG structure (using a hash table). There are 2 paths for IR: quadruples or DAG and then quadruples.

If I go with DAG as my IR, how could I use the backpatching method for statements? With quadruples it'd be easy. The DAG on the other way is more abstract. I'll be forced to convert it to quadruples. I know that. My fear is backpatching.

Answer 1

I believe you are worrying about low-level details when you should concentrate on high-level design. Besides, current compilers don't use quadruples, but SSA (Static Single Asignment). For final code generation, perhaps take a look at the LCC compiler, they use a simple way to emit locally optimal code by tree matching.

A way to cheat is to just emit a high-level language (like C) and leave the heavy lifting to it's compiler (and you get portability for free ;-).

I don't know if the Usenet group comp.compilers lives on in some form, but it's FAQ would be my first stop. Possibly horribly dated, though.