Bug 92793

Summary:	Precision qualifier information gets lost
Product:	Mesa	Reporter:	Tapani Pälli <lemody>
Component:	glsl-compiler	Assignee:	Tapani Pälli <lemody>
Status:	RESOLVED FIXED	QA Contact:	Intel 3D Bugs Mailing List <intel-3d-bugs>
Severity:	normal
Priority:	medium
Version:	git
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Bug Depends on:
Bug Blocks:	92778

Description Tapani Pälli 2015-11-03 11:54:47 UTC

GLSL IR does not preserve precision information for variables. This is required to make precision validation checks when linking separate shader objects on OpenGL ES 3.1.

Iago's precision qualifier patches should be enough to tackle this:

https://patchwork.freedesktop.org/patch/43442/

Comment 1 Tapani Pälli 2015-11-03 12:59:22 UTC

I'll rebase Iago's patches and work on the linker checks

Comment 2 Tapani Pälli 2015-11-05 11:45:46 UTC

I've done this. Did not rebase linker checks just yet as ES 3.1 is failing for runtime validation of pipeline (not during linking). Will rebase linking part later if these changes get accepted.

Comment 3 Tapani Pälli 2015-11-13 18:34:37 UTC

precision information is now in IR level and required linker checks and runtime validation can be done

Comment 4 Kenneth Graunke 2015-11-15 13:27:08 UTC

FWIW, these changes broke tessellation shaders...I had to revert

    commit 5bd122cad9d16596f89260f3b115cd0fb72cb886
    glsl: do not lose precision information when packing varyings

    commit f84bc57d7dc02fceb805803131426c791eadeff9
    glsl: Add precision information to ir_variable

to prevent the linker from saying that gl_PerVertex blocks don't match up.

Ilia confirmed that this broke tessellation for Nouveau.

If you want to try it on Intel (Broadwell only), you can grab my 'tess' branch and run:
$ shader_runner tests/spec/arb_tessellation_shader/execution/nop.shader_test

(you'll need to rebase -i out my reverts of those patches to trigger the bug)

Comment 5 Tapani Pälli 2015-11-16 05:36:45 UTC

(In reply to Kenneth Graunke from comment #4)
> FWIW, these changes broke tessellation shaders...I had to revert
> 
>     commit 5bd122cad9d16596f89260f3b115cd0fb72cb886
>     glsl: do not lose precision information when packing varyings
> 
>     commit f84bc57d7dc02fceb805803131426c791eadeff9
>     glsl: Add precision information to ir_variable
> 
> to prevent the linker from saying that gl_PerVertex blocks don't match up.
> 
> Ilia confirmed that this broke tessellation for Nouveau.
> 
> If you want to try it on Intel (Broadwell only), you can grab my 'tess'
> branch and run:
> $ shader_runner tests/spec/arb_tessellation_shader/execution/nop.shader_test
> 
> (you'll need to rebase -i out my reverts of those patches to trigger the bug)

sorry about this, I'll take a look at what is wrong, precision should be ignored on desktop

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