What exactly is LLVM and how does it differ from a compiler?

LLVM is essentially an intermediate representation that different high-level programming languages compile into. Instead of building a whole compiler for each machine architecture with all the necessary optimizations, you can compile your code to LLVM, and it handles the rest—turning it into machine code for specific architectures while optimizing along the way.

Just to clarify, referencing LLVM as 'a llvm' is a bit off. It's actually an entire project that includes not just the intermediate language, but also powerful optimization tools and backends for different architectures. Think of it as a robust compiler infrastructure instead of just another programming language.

Think of LLVM as a toolkit for compiler developers. When you compile a high-level language into LLVM's intermediate representation, it makes optimizations easier because of how it's structured. Each variable in LLVM is assigned a single point of definition, which simplifies many optimizations. Plus, by targeting LLVM, you don’t have to worry about multiple hardware instructions; it takes care of converting to the appropriate machine code for you.

To break it down simply: LLVM allows a common middle ground for programming languages and computers. When you create a programming language, you don’t need to build a separate compiler for every computer out there. You just compile to LLVM, and then that LLVM code can be converted to whatever specific machine code is needed, making it super flexible.