Performance is in the noise, but we would need a really big speed up of jitted code for it to be more than noise overall.

The nbody benchmark, which spends a lot of time in the JIT shows a 13-18% speedup, except on Mac where it shows no speedup.
I don't know why that would be as I think we are using stock LLVM for Mac, not the Apple compiler.

The nbody benchmark, which spends a lot of time in the JIT shows a 13-18% speedup, except on Mac where it shows no speedup. I don't know why that would be as I think we are using stock LLVM for Mac, not the Apple compiler.

Nice. We use Apple's Compiler for the interpreter, though the JIT uses stock LLVm. Thomas previously showed that the version of the Apple compiler we use is subject to huge fluctuations in performance due to a PGO bug.

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

Latest bechmarking results: https://github.com/faster-cpython/benchmarking-public/tree/main/results/bm-20250813-3.15.0a0-6a85f95-JIT

2.6% faster on Windows. No change on Linux.

It looks like coverage is slower on linux, which is presumably some sort of artifact as the coverage benchmark does lots of instrumentation which prevents the JIT form running (Plus the coverage benchmark uses an old version of coverage, the latest version is much faster).

The tail calling CI seems to be failing because homebrew changed where they install clang (yet again). Will put up a separate PR to fix that.

Ok, I fixed the macOS CI on main. Please pull the changes in.

I thought that caching through side exits would speed things up, but it looks like it slows things down a bit if anything.
https://github.com/faster-cpython/benchmarking-public/tree/main/results/bm-20250822-3.15.0a0-efe4628-JIT

So, I've reverted that change.

Will rerun the benchmarks, to confirm...

I was hoping to get a clear cross-the-board speedup before merging this.
But as it also enables decref removal and fixes the problem of intermediate values on the stack during tracing (#140277) I think we should merge this soon and tweak it later.