1696390 - Reduce default precision in fragment shaders to mediump

Status: RESOLVED DUPLICATE of bug 1823411

(Core :: Graphics: WebRender, task)

Description

[Jamie Nicol [:jnicol]]

In this bug we see that webrender is heavily GPU bound on many different websites on a Mali-T830 MP1 GPU. To help with this we should try to reduce the amount of work that our fragment shaders need to do. One such issue is that we use a default highp precision. Using the Mali offline compiler to statically analyze our shaders has shown that reducing this can help, although it won't be enough by itself.

Simply changing the default precision will result in many rendering issues, however. For example, mediump has 2^-10 floating point precision, therefore normalized UV coordinates must be highp if the texture can be greater than 1024 in size.

Comment 1

[Jamie Nicol [:jnicol]]

This is not quite a dup of 1823411 but it's effectively the same thing, we don't need this any more