4 ms·

Inversely with LLVM around (and the JVM, sort of), people now get to focus on building the frontend of the compiler and forget about all those optimisation pass

by pdpi 7y ago

Inversely with LLVM around (and the JVM, sort of), people now get to focus on building the frontend of the compiler and forget about all those optimisation passes.

ernst_klim 7y ago
>now get to focus on building the frontend of the compiler Although LLVM is cool, it's just a backend, so besides frontend you need some runtime, type checker, type inference, and, if your lang is sufficiently complex, you still need a huge middle end layer which knows something about semantics of your language and how to optimize it properly. So if your language is just a very simple featureless language with procedures and simple data types, like Pascal, you could just write a direct code generator. But when you have a language with GC, exceptions, modules and all that kind of stuff, you need a middle end, and a complex one.
pizlonator 7y ago
Only suckers forget about optimization passes. ;-) Don't forget that: - Optimization work on llvm and other compilers is still happening in anger. - Frontend is a relative term. For example, the "frontend" to LLVM when WebKit used LLVM as a "backend" was a full-blown compiler with >100KLoC of code. Since then that "frontend" grew its own backend and dropped LLVM, but point is, just because you're a frontend doesn't mean you don't have optimizations. Frontend doesn't just mean parser. - Rust's or Haskell's "frontends" to LLVM are seriously impressive compilers and the complexity is not to do with parsing AFAICT but all the other stuff (type checking comes to mind but there's also really impressive lowering and optimization). - Backends aren't just complex because of optimization passes. The register allocator and instruction selector aren't so much optimization passes as necessary transformations for turning a compiler's IR into machine code. Those things just grow and grow. - The whispers in the wind that I'm hearing from compiler folks looking to make bank is that there's shitloads of work to be done porting compilers to new targets. It's much more work to port a compiler to a new target than it is to write a parser. That said, writing a frontend for a language as complex as Rust/Haskell/etc is probably on the same order of complexity as parting a backend or maybe even more complex - but that's not because of parsing; it's usually either because of System F type shit (if you have a statically typed language) or dynamic type inference (if you have a dynamically typed language).

by pdpi 7y ago

Inversely with LLVM around (and the JVM, sort of), people now get to focus on building the frontend of the compiler and forget about all those optimisation passes.

ernst_klim 7y ago

>now get to focus on building the frontend of the compiler Although LLVM is cool, it's just a backend, so besides frontend you need some runtime, type checker, type inference, and, if your lang is sufficiently complex, you still need a huge middle end layer which knows something about semantics of your language and how to optimize it properly. So if your language is just a very simple featureless language with procedures and simple data types, like Pascal, you could just write a direct code generator. But when you have a language with GC, exceptions, modules and all that kind of stuff, you need a middle end, and a complex one.

pizlonator 7y ago

Only suckers forget about optimization passes. ;-) Don't forget that: - Optimization work on llvm and other compilers is still happening in anger. - Frontend is a relative term. For example, the "frontend" to LLVM when WebKit used LLVM as a "backend" was a full-blown compiler with >100KLoC of code. Since then that "frontend" grew its own backend and dropped LLVM, but point is, just because you're a frontend doesn't mean you don't have optimizations. Frontend doesn't just mean parser. - Rust's or Haskell's "frontends" to LLVM are seriously impressive compilers and the complexity is not to do with parsing AFAICT but all the other stuff (type checking comes to mind but there's also really impressive lowering and optimization). - Backends aren't just complex because of optimization passes. The register allocator and instruction selector aren't so much optimization passes as necessary transformations for turning a compiler's IR into machine code. Those things just grow and grow. - The whispers in the wind that I'm hearing from compiler folks looking to make bank is that there's shitloads of work to be done porting compilers to new targets. It's much more work to port a compiler to a new target than it is to write a parser. That said, writing a frontend for a language as complex as Rust/Haskell/etc is probably on the same order of complexity as parting a backend or maybe even more complex - but that's not because of parsing; it's usually either because of System F type shit (if you have a statically typed language) or dynamic type inference (if you have a dynamically typed language).