$ firefox --new-instance --profile $(mktemp -d) about:support
...
Features
Compositing: OpenGL
...
GPU #1
Active: Yes
Description: Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)
Vendor ID: mesa/i965
Device ID: 0x1912
Driver Version: 19.0.2.0
RAM: 3072MB
...
Decision Log
WEBRENDER: opt-in by default: WebRender is an opt-in feature
WEBRENDER_QUALIFIED: blocked by env: Screen size too large

Why XP_LINUX was used instead of MOZ_WIDGET_GTK for what overrides gfxPlatformGtk::AccelerateLayersByDefault()? Sorry, I can't submit a fix due to bug 1536716.
https://searchfox.org/mozilla-central/rev/6dab6dad9cc8/gfx/thebes/gfxPlatform.cpp#2765-2774

In addition to fixing this we should add more columns (for FreeBSD, for example) to https://wiki.mozilla.org/Platform/Platform-specific_build_defines

https://treeherder.mozilla.org/#/jobs?repo=try&revision=53cc18f2f3ba6eec3970f6077a6ae681ec4ba03d

The patch is in the public domain. Feel free to reset git author.

As release channels are affected if none helps this will haunt Tier3 throughout ESR68 lifetime, so applying the patch downstream will be required. Otherwise, besides performance cost there's also risk of crashes due to unstable gfx drivers.

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #2)

In addition to fixing this we should add more columns (for FreeBSD, for example) to
https://wiki.mozilla.org/Platform/Platform-specific_build_defines

Maybe but I disagree with XP_* (Netscape/XPCOM cruft) usage:

• Don't use XP_FREEBSD where FreeBSD works fine
• FreeBSD conditionals should be avoided in favor more generic
  conditionals or detecting features via moz.configure

I can land the patch, thanks for writing it.

Re the wiki page, I mostly want a quick reference to know that e.g. XP_LINUX is actually true on FreeBSD, which is not at all obvious from the name. Knowing which defines are true on which platforms will make it easier to avoid this sort of problem in the future, which is why I created that page to begin with.

Err whoops, I misread the patch. It's MOZ_WIDGET_GTK that's true on FreeBSD, not XP_LINUX. Still good to document.

https://hg.mozilla.org/mozilla-central/rev/139558138e3e

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #2)

In addition to fixing this we should add more columns (for FreeBSD, for example) to https://wiki.mozilla.org/Platform/Platform-specific_build_defines

Too much trouble to edit a single page: (my account wasn't approved)

• reCAPTCHA is hosted by Google which is notorious for being unfriendly to Tor users
• "Your biography must be at least 15 words long." but "I'm not a product..." didn't pass
• "Name of mentor or guide at Mozilla:" assumes every contributor had one or only single one
• "Where can we learn more about you?" wants a social media account, not a bugzilla profile

OS                 | DragonFly | FreeBSD | NetBSD  | OpenBSD | Solaris |
----------------------------------------------------------------------
Product            |  Desktop  | Desktop | Desktop | Desktop | Desktop |
XP_WIN             |           |         |         |         |         |
XP_DARWIN          |           |         |         |         |         |
XP_MACOSX          |           |         |         |         |         |
XP_IOS             |           |         |         |         |         |
XP_UNIX            |     V     |   V     |   V     |   V     |   V     |
XP_LINUX           |           |         |         |         |         |
ANDROID            |           |         |         |         |         |
MOZ_WIDGET_GTK     |     V     |   V     |   V     |   V     |   V     |
MOZ_WIDGET_ANDROID |           |         |         |         |         |
MOZ_WIDGET_UIKIT   |           |         |         |         |         |

Tier3 platforms don't run tests as many are broken. Some os == "linux" should be toolkit == "gtk3" but others fail for unrelated reasons which requires too much time to investigate unless manifested as real issues.

Thanks, I added it to the table.