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Using LLVM is not exactly an indelible architectural decision — switching to a bespoke JIT would be entirely possible, it’s just not worth it yet. Moreover, if

Using LLVM is not exactly an indelible architectural decision — switching to a bespoke JIT would be entirely possible, it’s just not worth it yet. Moreover, if you want to generate world-class high speed code, you really need something like LLVM. So yes, it’s a bit of a drag but it’s also a massive enabler of critical performance. That’s the real reason the project continues to use it. There are a number of approaches to reducing latency further, which are being pursued. The most promising current avenue is better tooling around system images (compiled executables with additional functionality beyond the core language pre-loaded): generating them faster, generating them incrementally (load one, add a few things and produce another), and generating them automatically for the set of packages in the current active project (not feasible until the first two are done). That will give an experience comparable to compiled languages.

neolog 5y ago
How much communication is there between the Julia compiler team and the LLVM team? I don't get the impression LLVM has been very sensitive to Julia's needs so far.
- stabbles 5y ago
  Not an answer to the question, but a fun fact: there is a julia source file in the llvm project [1] [1] https://github.com/llvm/llvm-project/blob/d480f968ad8b56d3ee4a6b6df5532d485b0ad01e/libc/AOR_v20.02/math/tools/remez.jl https://github.com/llvm/llvm-project/blob/d480f968ad8b56d3ee...
- StefanKarpinski 5y ago
  Quite a bit: several of the Julia compiler team are LLVM maintainers and contributors. LLVM has started to track compile time, so that's gotten a bit better with recent releases. Making noise about compile time was mainly to get the LLVM project to start paying attention to compile time, which they now have, so mission accomplished — as long as they stop completely allowing latency to degenerate, it's ok. LLVM is never going to be fast at compiling code (and if we used something else that was as good at producing fast code, it would almost certainly also be slow), so avoiding putting LLVM in the fast path is always going to be necessary to make more latency improvements.
  - neolog 5y ago
    That's great to hear. I found some info about it which looks promising. https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html
canadianfella 5y ago
Graal may be a good option for Julia. It would take a huge amount of work.

neolog 5y ago

How much communication is there between the Julia compiler team and the LLVM team? I don't get the impression LLVM has been very sensitive to Julia's needs so far.

stabbles 5y ago
Not an answer to the question, but a fun fact: there is a julia source file in the llvm project [1] [1] https://github.com/llvm/llvm-project/blob/d480f968ad8b56d3ee4a6b6df5532d485b0ad01e/libc/AOR_v20.02/math/tools/remez.jl https://github.com/llvm/llvm-project/blob/d480f968ad8b56d3ee...
StefanKarpinski 5y ago
Quite a bit: several of the Julia compiler team are LLVM maintainers and contributors. LLVM has started to track compile time, so that's gotten a bit better with recent releases. Making noise about compile time was mainly to get the LLVM project to start paying attention to compile time, which they now have, so mission accomplished — as long as they stop completely allowing latency to degenerate, it's ok. LLVM is never going to be fast at compiling code (and if we used something else that was as good at producing fast code, it would almost certainly also be slow), so avoiding putting LLVM in the fast path is always going to be necessary to make more latency improvements.
- neolog 5y ago
  That's great to hear. I found some info about it which looks promising. https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html

canadianfella 5y ago

Graal may be a good option for Julia. It would take a huge amount of work.