[Mesa-dev] [PATCH 6/7] mesa/util: add allow_glsl_relaxed_es driconfig override

Timothy Arceri tarceri at itsqueeze.com
Fri Jun 8 14:14:24 UTC 2018

On 09/06/18 00:07, Eero Tamminen wrote:
> Hi,
> On 08.06.2018 15:19, Timothy Arceri wrote:
>> This relaxes a number of ES shader restrictions allowing shaders
>> to follow more desktop GLSL like rules.
>> This initial implementation relaxes the following:
>>   - allows linking ES shaders with desktop shaders
>>   - allows mismatching precision qualifiers
>>   - always enables standard derivative builtins
>> These relaxations allow Google Earth VR shaders to compile.
> The fixes should rather go to apps, than bug workarounds to Mesa.

Agreed but sometimes the real world means we require work arounds. 
Especially in corner cases like these were the CTS provides no cover and 
all other vendors do a sloppy job following the spec.

> Is bug reported to Google Earth VR maintainers and have they stated that 
> they aren't going to fix the issues?

Its been reported and they have stated that there are no plans to update 
this app for the foreseeable future.

> If different shader stages have different precision in a variable that's 
> actually being used, that's a real bug in the application.

The app is mixing desktop shaders with ES shaders. It really seems they 
expect desktop behavior rather than ES, in which case precision 
qualifiers are ignored.

> (There are lot of apps on Android that have mismatches on unused/dead 
> variables, but for those the mismatches don't matter in practice.)

They seem to be used as the shaders fail to compile.

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