Reminds me of the 2024 blog post Look ma, I wrote a new JIT compiler for PostgreSQL [0]. Both articles lament that Postgres's LLVM-based JIT [1] takes a while to generate code.
> The rarity of JIT compilers makes me believe that implementing a JIT compiler historically was too difficult for it to be worthwhile.
That's only true of writing a JIT from scratch. There's no rarity of JITs, it's just that LLVM (and other frameworks) are often used. Every major interpreter has a JIT compiler. PCRE2 has a JIT compiler. There are JIT frameworks out there with much faster code-generation than LLVM: Cranelift, GNU Lightning, Mir. I doubt they could do code-generation faster than a custom copy-and-patch JIT, but they'd be much faster than LLVM.
Uhm, Common Lisp, where JIT is not only available but is also manageable: the programmer can decide what deserves to be compiled and what does not.
Besides run time, JIT is available also when the code is compiled or loaded for execution (i.e., do you have a compilation or loading speed-up in mind? no problem, you can also compile that speed-up into native machine code, and so ad infinitum...).
pgrust sounds very interesting, but with the deep changes there’s no viable path to upstream it - is the end goal to be robust enough that it’ll get wide adoption?
You're entirely correct because JIT requires violating Write xor Execute security policy. This is the reason on iOS, it is limited to Apple shipped software.
> The rarity of JIT compilers makes me believe that implementing a JIT compiler historically was too difficult for it to be worthwhile.
That's only true of writing a JIT from scratch. There's no rarity of JITs, it's just that LLVM (and other frameworks) are often used. Every major interpreter has a JIT compiler. PCRE2 has a JIT compiler. There are JIT frameworks out there with much faster code-generation than LLVM: Cranelift, GNU Lightning, Mir. I doubt they could do code-generation faster than a custom copy-and-patch JIT, but they'd be much faster than LLVM.
[0] https://www.pinaraf.info/2024/03/look-ma-i-wrote-a-new-jit-c... , discussed: https://news.ycombinator.com/item?id=39742916
[1] https://www.postgresql.org/docs/current/jit-reason.html
Besides run time, JIT is available also when the code is compiled or loaded for execution (i.e., do you have a compilation or loading speed-up in mind? no problem, you can also compile that speed-up into native machine code, and so ad infinitum...).
https://en.wikipedia.org/wiki/W%5EX
https://en.wikipedia.org/wiki/W%5EX