LLVM - What is it?

LLVM - What is it?

Posted on 7th March 2011

What is LLVM? It’s homepage is somewhat cryptic - spends the first paragraph telling people what it is NOT!


In POE - it is used to build compilers - that means you can invent your own language, and use LLVM build the compiler and intepreter for you - voila!

The abstract from the original paper by Chris is more enlightening:

This paper describes LLVM (Low Level Virtual Machine), a compiler framework designed to support transparent, lifelong program analysis and transformation for arbitrary programs, by providing high-level information to compiler transformations at compile-time, link-time, run-time, and in idle time between runs. LLVM defines a common, low-level code representation in Static Single Assignment (SSA) form, with several novel features: a simple, language-independent type-system that exposes the primitives commonly used to implement high-level language features; an instruction for typed address arithmetic; and a simple mechanism that can be used to implement the exception handling features of high-level languages (and setjmp/longjmp in C) uniformly and efficiently. The LLVM compiler framework and code representation together provide a combination of key capabilities that are important for practical, lifelong analysis and transformation of programs. To our knowledge, no existing compilation approach provides all these capabilities. We describe the design of the LLVM representation and compiler framework, and evaluate the design in three ways: (a) the size and effectiveness of the representation, including the type information it provides; (b) compiler performance for several interprocedural problems; and (c) illustrative examples of the benefits LLVM provides for several challenging compiler problems

…er. Ok for those who are still wondering what it is - check out Chris’ presentation at FOSDEM - (did I tell you I also presented at FOSDEM this year - my claim to fame! )

Even Google is using LLVM in Android - check out RenderScript (beautiful stuff!!).

I still love GCC, but I will not ignore it’s shortcomings. As an engineer, we should strive to understand our tools especially it’s limitation