1632444 - Wrong version of shaders are being optimized for cross compiled builds

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Jamie Nicol [:jnicol]]

In bug 1631778, I attempted to mitigate bug 1604615's installer size regression by only optimizing GL or GLES shaders, depending on the target platform. The intention was for Windows and Android builds we'd optimize GLES shaders, and for other builds we'd optimize GL shaders.

However, I used cfg!(target_os = "android") || cfg!(target_os = "windows") to detect the platform. But since this is being ran in a build script, and we are cross compiling these builds, it actually detects the host OS rather than the target OS. This resulted in us optimizing GL shaders for these builds, then at runtime we would be unable to find the optimized GLES shaders, and fall back to unoptimized shaders.

This unfortunately undid the nice win we got from bug 1604615 in the first place: https://treeherder.mozilla.org/perf.html#/graphs?highlightAlerts=1&series=autoland,2134897,1,10&timerange=1209600&zoom=1587394468959,1587644111241,1138.3322095195642,1741.5375737033658

It looks like I should be using env::var("CARGO_CFG_TARGET_OS") instead.

Comment 1

[Jamie Nicol [:jnicol]]

Attachment: Bug 1632444 - Correctly detect target OS when deciding what shaders to optimize. r?jrmuizel

A previous patch attempted to optimize only GL or GLES shaders,
depending on the target platform. However, it was trying to detect the
platform by using cfg!(target_os = {}), but as this is in a
build script that actually detects the host platform instead. This
resulted in the wrong version of shaders being optimized, and
therefore falling back to unoptimized shaders at runtime.

This fix uses env::var("CARGO_CFG_TARGET_OS") instead, which works
correctly in build scripts.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/17a4926b6c65
Correctly detect target OS when deciding what shaders to optimize. r=jrmuizel

Comment 3

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/17a4926b6c65