1675875 - Please document --enable-release and RUSTC_OPT_LEVEL

Status: RESOLVED FIXED

(Firefox Build System :: General, task, P3)

Description

[Markus Stange [:mstange]]

By default, rust code in local builds is not compiled with full optimizations. This can make local builds noticeably slower, and unfit for performance work.

The recommended workarounds, as far as I'm aware, are adding export RUSTC_OPT_LEVEL=2 or ac_add_options --enable-release to the mozconfig. The former closes most of the performance gap while making builds a little slower, and the latter makes linking a lot slower because it also turns on link time optimization. I use the former for my local builds.

However, I cannot find documentation for these flags on https://firefox-source-docs.mozilla.org/ . It would be nice to have them listed somewhere, maybe in this list of optimization build settings.

Comment 1

[Markus Stange [:mstange]]

See https://groups.google.com/g/mozilla.dev.platform/c/pN9O5EB_1q4/m/tbbzmWztAQAJ for context, and for a list of complaints.

Comment 2

[Ricky Stewart]

Attachment: Bug 1675875 - Document `--enable-release` and `RUSTC_OPT_LEVEL`

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bdc17cb7bac7
Document `--enable-release` and `RUSTC_OPT_LEVEL` r=sylvestre DONTBUILD

Comment 4

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/bdc17cb7bac7