AST to AST JIT Backend

[Francesco Mecca]

On Tuesday, 1 September 2020 at 00:15:24 UTC, James Lu wrote:
> I have an idea, one way we can get faster compiles for Dlang is 
> by compiling to an existing JITted language, which could be 
> easier to build a proof of concept for than a full optimizing 
> JIT compiler.
>
> Perhaps we could compile Dlang to Lua, targeting LuaJIT or 
> JavaScript, targeting V8.
>
> I personally know to write highly performant JavaScript very 
> well. Combined with Dlang's natural type information, it could 
> result in fast machine code, fast. Backends for the Nim 
> language tend to output poor (slow) JavaScript code.
>
> In an earlier thread, I showed that the V8 JavaScript engine 
> could generate decent quality machine code much faster than 
> LLVM D Compiler.

Over the years I have made some experiments in ast-to-ast 
conversions for luajit, there is even a nice tool to do that 
easily here:
https://github.com/franko/luajit-lang-toolkit

The results weren't always satisfying because most of the time 
the luajit optimizer expects idiomatic lua code.
To be more precise, luajit is so powerful because it is optimized 
for the kind of ast that is emitted from idiomatic lua code when 
compiled.
It is very difficult to reproduce that for non trivial snippets 
of code.

I suggest you to try that yourself.