1277320 - Get GTests working on Windows PGO builds

Status: RESOLVED FIXED

(Testing :: GTest, defect)

Description

[Ryan VanderMeulen [:RyanVM]]

GTests on Windows PGO builds are currently broken and hidden on Treeherder. My understanding is that this was an intentional decision made to avoid lengthening the already-long PGO build times due to having to link everything twice.

The big trade-off to this decision is that it leaves us with effectively zero Windows opt GTest coverage on the release branches. On the builds that go out to 90+% of our users. Which seems like a Bad thing.

Now that we've clawed back a lot of PGO build time wins, I think we should revisit the earlier decision and consider re-enabling them.

Comment 1

[(not currently active) Ted Mielczarek]

I'm not entirely sure this will be useful, to be honest. The problem is that xul.dll and xul-gtest.dll *are not the same binary*. When we re-link xul.dll using the profiling info, we can't use that same profiling info to re-link xul-gtest.dll, it's just not valid for that binary. That means that we'd wind up re-linking xul-gtest.dll and generating different code than exists in xul.dll, so the tests wouldn't actually test anything meaningful anyway.

Unfortunately this is a hard problem and I don't know a way to solve it.

Comment 2

[Ryan VanderMeulen [:RyanVM]]

For perpetuity's sake, it may be worth trying to get MSVC to use the xul.pgd files for xul-gtest.dll.
https://msdn.microsoft.com/en-us/library/438sd1tf.aspx

Not sure if that'd actually work in practice, but in theory that would at least give us reasonably-comparable end results for both DLLs.

Comment 3

[Ryan VanderMeulen [:RyanVM]]

Shot in the dark, but does the move to clang-cl make this more doable?

Comment 4

[Mike Hommey [:glandium]]

More than clang-cl, the move to cross-compiles should make that more manageable. Try it?

Comment 5

[Ryan VanderMeulen [:RyanVM]]

It works!
https://treeherder.mozilla.org/jobs?repo=try&revision=62102dd3ecff31e1a22a5cb7da18e86c553fcaac

Comment 6

[Ryan VanderMeulen [:RyanVM]]

Attachment: Bug 1277320 - Run GTests on all Windows flavors as Tier 1.

Comment 7

[Ryan VanderMeulen [:RyanVM]]

As a ride-along to this patch, it turns out that the Tier3 Windows ASAN GTest job has been running reliably green for a long time now, so let's bump that up to Tier 1 alongside the others.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/83b3639f3423
Run GTests on all Windows flavors as Tier 1. r=glandium

Comment 9

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/83b3639f3423

Comment 10

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-esr91/rev/2eef0feffdac