How to set wasm-opt level to -O4 ?

[michalsustr]

Hello, I'm building a wasm application.

I noticed that wasm-opt is by default on level -O2. I'd like to change it to the highest level. How to do this?
I tried setting wasm-opt = ['-O4'] in Trunk.toml, or some magical incantations like

# Configure wasm-opt settings
[package.metadata.wasm-pack.profile.release]
wasm-opt = ['-O4']  # Most aggressive optimizations

in workspace Cargo.toml, and tried to delete target/ cache each time, but none of these helped.
What is the proper way to set this?

Here is my output:

$ trunk build --verbose --release
2025-02-19T08:44:27.017403Z  INFO 🚀 Starting trunk 0.21.7
2025-02-19T08:44:27.017448Z DEBUG update_check: Spawning update check skip=false
2025-02-19T08:44:27.017551Z DEBUG Enforce version - actual: 0.21.7, required: *
2025-02-19T08:44:27.017560Z  INFO 📦 starting build
2025-02-19T08:44:27.017760Z DEBUG spawning asset pipelines
2025-02-19T08:44:27.017871Z DEBUG Performing update check
2025-02-19T08:44:27.017934Z DEBUG Time since last check: 24m20s359ms504µs545ns
2025-02-19T08:44:27.017939Z DEBUG No refresh needed
2025-02-19T08:44:27.017941Z DEBUG Current: 0.21.7, Most recent: 0.21.7
2025-02-19T08:44:27.165198Z DEBUG copying file path="assets/sw.js"
2025-02-19T08:44:27.165198Z DEBUG copying file path="assets/maskable_icon_x512.png"
2025-02-19T08:44:27.165239Z DEBUG building minato_frontend
2025-02-19T08:44:27.165224Z DEBUG copying file path="assets/icon-256.png"
2025-02-19T08:44:27.165245Z DEBUG cargo args args=["build", "--target=wasm32-unknown-unknown", "--manifest-path", "/home/michal/Code/minato/minato_frontend/Cargo.toml", "--release"]
2025-02-19T08:44:27.165255Z DEBUG copying file path="assets/manifest.json"
2025-02-19T08:44:27.165262Z DEBUG copying file path="assets/icon-1024.png"
2025-02-19T08:44:27.165266Z DEBUG copying file path="assets/icon_ios_touch_192.png"
2025-02-19T08:44:27.165279Z DEBUG copying & hashing icon path="assets/favicon.ico"
2025-02-19T08:44:27.165434Z DEBUG finished copying file path="assets/sw.js"
2025-02-19T08:44:27.165460Z DEBUG finished copying file path="assets/manifest.json"
2025-02-19T08:44:27.165548Z DEBUG finished copying & hashing icon path="assets/favicon.ico"
2025-02-19T08:44:27.165553Z DEBUG finished copying file path="assets/icon-256.png"
2025-02-19T08:44:27.165568Z DEBUG finished copying file path="assets/icon_ios_touch_192.png"
2025-02-19T08:44:27.165742Z DEBUG finished copying file path="assets/maskable_icon_x512.png"
2025-02-19T08:44:27.166192Z DEBUG finished copying file path="assets/icon-1024.png"
    Finished `release` profile [optimized] target(s) in 0.07s
2025-02-19T08:44:27.277117Z DEBUG fetching cargo artifacts
2025-02-19T08:44:27.387115Z DEBUG get_info: Getting tool app=WasmBindgen version=Some("0.2.99") offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false }
2025-02-19T08:44:27.387226Z DEBUG get_info:find_system: failed to detect system tool: cannot find binary path app=WasmBindgen version=Some("0.2.99") offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false } app=WasmBindgen
2025-02-19T08:44:27.387307Z DEBUG get_info: Using wasm-bindgen (0.2.99) from: /home/michal/.cache/trunk/wasm-bindgen-0.2.99/wasm-bindgen app=WasmBindgen version=Some("0.2.99") offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false }
2025-02-19T08:44:27.387354Z DEBUG calling wasm-bindgen for minato_frontend
2025-02-19T08:44:27.387358Z DEBUG wasm-bindgen args args=["--target=web", "--out-dir=/home/michal/Code/minato/target/wasm-bindgen/release", "--out-name=minato_frontend", "/home/michal/Code/minato/target/wasm32-unknown-unknown/release/minato_frontend.wasm", "--no-typescript"]
2025-02-19T08:44:27.576644Z DEBUG copying generated wasm-bindgen artifacts
2025-02-19T08:44:27.576665Z DEBUG copying /home/michal/Code/minato/target/wasm-bindgen/release/minato_frontend.js to /home/michal/Code/minato/minato_frontend/dist/.stage/minato_frontend.js
2025-02-19T08:44:27.576866Z DEBUG copying /home/michal/Code/minato/target/wasm-bindgen/release/minato_frontend_bg.wasm to /home/michal/Code/minato/minato_frontend/dist/.stage/minato_frontend_bg.wasm
2025-02-19T08:44:27.578461Z DEBUG recording SRI record - type: Sha384. name: minato_frontend.js, value: OutputDigest { integrity: Sha384, hash: "9dUBDNOop3cK5FOUU2maN+ql7KyMEiUSYbHq8KPblj4LGbxZsBXi0v8yB0l/+m83" }
2025-02-19T08:44:27.578508Z DEBUG get:get_info: Getting tool app=WasmOpt version=None offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false } app=WasmOpt version=None offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false }
2025-02-19T08:44:27.580700Z DEBUG get:get_info:find_system: system version found for wasm-opt: version_116 app=WasmOpt version=None offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false } app=WasmOpt version=None offline=false client_options=HttpClientOptions { root_certificate: None, accept_invalid_certificates: false } app=WasmOpt
2025-02-19T08:44:27.580753Z DEBUG calling wasm-opt

# This line: I'd like to use -O4
2025-02-19T08:44:27.580756Z DEBUG wasm-opt args args=["--output=/home/michal/Code/minato/target/wasm-opt/release/minato_frontend_bg.wasm", "-O2", "/home/michal/Code/minato/minato_frontend/dist/.stage/minato_frontend_bg.wasm"]

2025-02-19T08:44:29.581035Z DEBUG copying generated wasm-opt artifact from '/home/michal/Code/minato/target/wasm-opt/release/minato_frontend_bg.wasm' to '/home/michal/Code/minato/minato_frontend/dist/.stage/minato_frontend_bg.wasm'
2025-02-19T08:44:29.589198Z DEBUG recording SRI record - type: Sha384. name: minato_frontend_bg.wasm, value: OutputDigest { integrity: Sha384, hash: "83i61br9aAxlTr3bGrmy4xqgFFLmIwzyHmj1tNz5E5NmYeedxZibN9XyeARLMnqr" }
2025-02-19T08:44:29.589210Z DEBUG rust build complete
2025-02-19T08:44:29.590696Z  INFO applying new distribution
2025-02-19T08:44:29.591490Z  INFO ✅ success

I

[airblast-dev]

You can set the wasm-opt level in the rust asset element. This is done by setting the data-wasm-opt to "4".
You can check out the docs for other accepted values: https://trunkrs.dev/assets/#rust

Here is the modified rust asset from the yew example that sets the wasm-opt level to 4.

<link data-trunk rel="rust" href="Cargo.toml" data-wasm-opt="4" data-bin="yew-example" data-cargo-features="demo-abc,demo-xyz"/>

[michalsustr]

Great, this helped, thank you!

And as a follow-up, how to configure this to be O4 in release, and Os in debug?

[airblast-dev]

I am not fully sure. A while back I remember using hooks and scripts for different optimization levels.
Though there is an issue that might be relevant to your question: #933

I haven't used trunk in a while so its perhaps better if someone else answers this instead.

[michalsustr]

Thanks for the pointer.

Do you prefer something else than trunk? Maybe a more explicit manual workflow?
I'm new to Rust ecosystem, so I just went with what I found in the first egui tutorial, and maybe there are better options out there I don't know about.

[airblast-dev]

Do you prefer something else than trunk? Maybe a more explicit manual workflow?

No, trunk is able to lift a lot of the manual work regardless of what you are trying to do. Even if doing things manually you are probably better off writing a script that calls trunk or add a few hooks (for example I added in compression related stuff via hooks).

A more manual workflow would always be better as it would be tailored for your needs specifically. The problem is it takes time to develop and maintain such a build system where as solutions such as trunk will get you all if not most of the way there. Anything else you need either be it a niche functionality or something that trunk doesn't have yet can generally be added via hooks.

TLDR; Just use trunk, add hooks if you need something more than what trunk already offers

I'm new to Rust ecosystem, so I just went with what I found in the first egui tutorial, and maybe there are better options out there I don't know about.

I just checked the docs and examples for trunk whilst learning and back then there wasn't that many resources so its hard for me to say which is good or not. IMO trunks docs are pretty solid and reading the docs and examples is probably more than enough for starters but I would assume egui's guide is fine as well.