1530058 - Disable macOS LTO for non-PGO (opt) builds

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[Chris Peterson [:cpeterson]]

Developers want fast local builds and try runs, so we should disable LTO in non-shipping builds (i.e. non-PGO opt and debug).

Once we have macOS PGO builds (bug 1395325), we can disable LTO for opt builds. PGO would then imply LTO, like clang-cl did on Windows in bug 1475660.

Would we want to disable LTO for opt builds in all branches (autoland, inbound, central, and try) or just on autoland, inbound, and try? Is there value in building and testing opt with LTO in central in addition to opt without LTO on autoland and inbound? Any bugs we find in one of those configurations but not the other is most likely a compiler bug, not a Firefox bug. Do we care?

Comment 1

[Eric Rahm [:erahm]]

I'm reasonably sure we only LTO shippable builds, is the right glandium?

Comment 2

[Mike Hommey [:glandium]]

We're still manually enabling LTO on opt mac builds on automation. See browser/config/mozconfigs/macosx64/nightly, browser/config/mozconfigs/macosx64/devedition, browser/config/mozconfigs/macosx64/beta and browser/config/mozconfigs/macosx64/release. Which means it's enabled on shippable builds and opt builds.

Comment 3

[Mike Hommey [:glandium]]

Attachment: Bug 1530058 - Disable LTO on non-PGO macOS builds.

Now that shippable macOS builds have PGO+LTO enabled, it is not
necessary to build the normal macOS builds with LTO enabled.

Comment 4

[Chris Manchester (limited bugmail, email directly)]

Thanks for taking this. Completely slipped my mind.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/12c9312e15bb
Disable LTO on non-PGO macOS builds. r=froydnj

Comment 6

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/12c9312e15bb