IR is thus the interface to the LLVM compiler framework. Frontend parses the source into LLVM IR, IR is fed through optimizer(s) which is then fed into code generator to generate target output. This way we end up with a really modular design which allows reusing different parts of the compiler for different programming languages without having to start from scratch for every new compiler. Similarly, backend can be designed to operate on IR as input and output code which is target specific. Optimizer can be designed in such a way that it optimizes only IR which is going to be the same for all the languages. For example, we can write different frontends for different programming languages which all output the same intermediate representation. This design has the advantage that each of these steps can be implemented independently of each other. It does it’s magic to optimize the code with techniques such as dead code elimination, branch elimination, loop unrolling, etc.īackend - This generates the final output depending on the compilation target (os, architecture, etc) Optimizer - This is also called “middle-end”. It can also translate from one high level language to another, those are sometimes called transpilers.įrontend - This tokenizes the code, parses, checks for errors, converts to AST (Abstract Syntax Tree) and optionally intermediate output called IR (intermediate representation) Compiler is a program that translates a program from one language to another, most commonly from a high level language to native machine language. Let’s try to understand what a compiler is before we go into any further topics.

By the way LLVM doesn’t stands for anything, it’s just LLVM. In fact, LLVM is not a “single” project but is composed of multiple subprojects under the same umbrella which includes LLVM Core, Clang, LLDB, libc++, etc.

So what even is LLVM? LLVM Project is a compiler framework and collection of tools which can be used to build programming languages. You can find the full source code in this repository What is LLVM? Goal of this post is to take a brief look into LLVM infrastructure and LLVM IR, then use that knowledge to build a toy brainfuck compiler that emits IR which can then further be compiled into native executable by LLVM tools.

Writing a compiler