{
  "$type": "site.standard.document",
  "description": "CI green on four platforms, a migration from TinyScheme to s7, and a 9x compiler speedup from hash table caches and union-find type unification.",
  "path": "/blog/2026/02/26/extempore-is-alive-on-aarch64-part-deux",
  "publishedAt": "2026-02-26T00:00:00.000Z",
  "site": "at://did:plc:tevykrhi4kibtsipzci76d76/site.standard.publication/self",
  "tags": [
    "extempore"
  ],
  "textContent": "A quick update on Extempore on aarch64: CI is now green on macOS, Windows, and two Linux architectures (aarch64 and x64) OpenGL graphics stuff is (soft) deprecated because that's increasingly tricky to maintain and keep up-to-date, but there are a couple of new WebGPU examples; the shadertoy one is kind of fun (no full \"xtmrender\" pipeline yet, and no ETA on that unfortunately) along the way I wrote a tree-sitter grammar for extempore (Scheme + xtlang) and some very hacked-together support for evaling code in helix (which I'm using these days) there's now a repl, although only on macOS/Linux at the moment upgraded to LLVM 22 (from 21), which went surprisingly smoothly I'm part-way through updating the docs website (bringing it into the docs/ folder in the main extempore repo) Compiler guts NOTE: these compiler & Scheme changes are in a couple of standalone commits and could be reverted in future... experimental stuff. But fun! The biggest under-the-hood change is a refactor of the xtlang compiler and a migration from TinyScheme to s7 Scheme---Bill Schottstaedt's embeddable Scheme interpreter from CCRMA. s7 was originally forked from TinyScheme anyway, so the migration path was relatively straightforward, but it's a much more capable interpreter with proper hash tables, first-class environments, and better performance across the board. On the compiler side, the old xtlang type checker used assoc-list caches for everything---which was fine when type environments were small, but scaled poorly for libraries with heavy generic instantiation. The refactored compiler replaces those with hash table caches, adds union-find for type unification, and moves to constraint-based solving. Here are ahead-of-time compilation benchmarks for all the core and external audio libraries[^bench-setup]: | Library | Before | After | Speedup | | ----------------------------------- | ---------: | --------: | --------: | | libs/base/base.xtm | 5.59s | 3.24s | 1.7x | | libs/core/math.xtm | 16.57s | 4.04s | 4.1x | | libs/core/rational.xtm | 6.47s | 3.47s | 1.9x | | libs/core/audiobuffer.xtm | 7.45s | 3.49s | 2.1x | | libs/core/audiodsp.xtm | 32.14s | 5.71s | 5.6x | | libs/core/instruments.xtm | 109.83s | 8.38s | 13.1x | | libs/external/fft.xtm | 5.71s | 3.99s | 1.4x | | libs/external/sndfile.xtm | 9.17s | 3.64s | 2.5x | | libs/external/audiodspext.xtm | 5.51s | 4.28s | 1.3x | | libs/external/instrumentsext.xtm | 12.57s | 9.26s | 1.4x | | libs/external/portmidi.xtm | 4.86s | 3.35s | 1.5x | | Total | 215.9s | 52.9s | 4.1x | The headline number is a 4.1x wall-clock speedup, but each invocation includes ~3s of startup overhead (there's a hard-coded sleep for NSApp initialisation because reasons). Subtracting that out, the pure compile time went from ~183s to ~20s---a 9x speedup. The standout is instruments.xtm at 13.1x; it's a longer file and works the compiler more than some of the others, which is exactly where the new union-find and hash table caches pay off. Libraries showing more modest improvements (1.3--1.5x) are dominated by LLVM JIT time and startup overhead rather than Scheme-level type checking, so there's not much to squeeze out of those on the compiler side. [^bench-setup]: Benchmarked on Linux x8664 (AMD Zen 4) with LLVM 22.1.0 and ORC JIT. Each library compiled in a separate extempore --nobase --batch process. \"Before\" is commit 44b7b5c5 (TinyScheme, assoc-list caches); \"After\" is commit 93dacf79 (s7 Scheme, hash table caches + union-find + constraint solver). This is still all on the aarch64 branch; I'm not ready to merge to master just yet. If you're an extempore user willing to get your hands a little dirty, try building from source on the tip of that branch and running your extempore workloads---I'd appreciate that, including bug reports of things that don't work.",
  "title": "Extempore is alive on aarch64 (part deux)"
}