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vendor/ — local copies of the three external engines

riscv_simulator.html loads three things it does not carry inside itself. Each is fetched from a CDN first and falls back to the copy here, so the simulator keeps working when the CDN is blocked, throttled or down.

Folder What it is Used for Size
codemirror/ CodeMirror 6 bundle (cm6_bundle.min.js) the code editor 0.4 MB
verisim/ Icarus Verilog compiled to WebAssembly (ivlpp, ivl, vvp + their .wasm) HDL simulation mode 2.9 MB
yosys/ @yowasp/yosys 0.68.1207 post-synthesis functional simulation 75 MB

Total: 78 MB, nearly all of it yosys/yosys.core.wasm (67 MB).

The one thing to know

The fallbacks only work when the page is served over HTTP — python3 -m http.server in this folder, GitHub Pages, or any other server. Opened straight from disk as file://, the browser blocks the fetch() that Emscripten and the Yosys bundle use to pull in their own .wasm, and the CDN path is the only one that works. CodeMirror is the exception: it loads through a <script> tag, which file:// allows, so the editor comes up either way.

Where the loader looks

Each engine tries its sources in order and takes the first that answers:

  • CodeMirror — CDN_SRC (jsDelivr) → vendor/codemirror/ → riscv_simulator_tests/
  • Icarus — jsDelivr → senolgulgonul.github.io/verisim/ → vendor/verisim/ → verisim/
  • Yosys — jsDelivr → vendor/yosys/

Refreshing these copies

Pinned versions, so nothing changes underfoot. Re-run only when you mean to upgrade, and bump HDL_YOSYS_VERSION in riscv_simulator.html to match.

cd vendor

# Icarus Verilog (WASM)
for f in ivlpp.js ivlpp.wasm ivl.js ivl.wasm vvp.js vvp.wasm; do
  curl -fsSL -o "verisim/$f" "https://cdn.jsdelivr.net/gh/senolgulgonul/verisim@main/$f"
done

# Yosys — must match HDL_YOSYS_VERSION in riscv_simulator.html
V=0.68.1207
for f in bundle.js yosys.core.wasm yosys.core2.wasm yosys.core3.wasm \
         yosys.core4.wasm yosys-resources.0.tar; do
  curl -fsSL -o "yosys/$f" "https://cdn.jsdelivr.net/npm/@yowasp/yosys@$V/gen/$f"
done

# CodeMirror — built from riscv_simulator_tests/cm6_entry.js, see that folder's README
cp ../riscv_simulator_tests/cm6_bundle.min.js codemirror/

All six Yosys files are required: bundle.js resolves the .wasm cores and the resource tar relative to its own URL, so the folder has to stay intact.