Intent to ship: Branch hinting

114 views

Skip to first unread message

Julien Pages

unread,

Dec 12, 2025, 2:37:13 PMDec 12

to dev-pl...@mozilla.org

As of Firefox 148, I intend to enable the WebAssembly Branch Hinting proposal by default on all platforms. It is currently enabled by default in Nightly builds and can be controlled by the `javascript.options.wasm_branch_hinting` preference. The motivation for this proposal is to improve the performance of the compiled wasm code, by informing the engine that a particular branch instruction is very likely to take a specific path.

The proposal is designed to provide optimization opportunities for engines without modifying any existing wasm code. Our implementation improves code layout by moving unlikely branches out of line.

The branch hinting proposal has reached stage 5 in July 2024, which means it is now part of the wasm standard. Branch hinting was shipped in Chrome 137, and in Safari 16.

Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1950729

Standard: https://github.com/WebAssembly/branch-hinting

Reply all

Reply to author

Forward

0 new messages