Bug 101984

Summary: [BSW BXT BYT] piglit.spec.arb_shader_ballot.execution.fs-readinvocation-uint broken
Product: Mesa Reporter: Mark Janes <mark.a.janes>
Component: Drivers/DRI/i965Assignee: Matt Turner <mattst88>
Status: RESOLVED FIXED QA Contact: Intel 3D Bugs Mailing List <intel-3d-bugs>
Severity: normal    
Priority: medium    
Version: 17.2   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Mark Janes 2017-07-31 15:51:18 UTC 
piglit.spec.arb_shader_ballot.execution.fs-readinvocation-uint
Standard Output

/tmp/build_root/m64/lib/piglit/bin/shader_runner /tmp/build_root/m64/lib/piglit/tests/spec/arb_shader_ballot/execution/fs-readInvocation-uint.shader_test -auto -fbo
piglit: debug: Requested an OpenGL 3.2 Core Context, and received a matching 4.5 context

Probe color at (4,244)
  Expected: 0 255 0 255
  Observed: 255 255 10 8
Test failure on line 37

This is a newly enabled feature that is broken on atom platforms.  It is not a regression, but the Intel Mesa engineers would like to fix it before the 17.2 release.
Comment 1 Matt Turner 2017-08-28 23:21:21 UTC 
I looked at this with Curro a few weeks ago, and we noticed that commenting out 

  if ((active_set & (1ul << i)) == 0ul)
     continue;

makes the test pass.

Poking a little at it, I think the cause is

shl(8)          g8<1>Q          g4<4,4,1>Q      g2<4,4,1>UD     { align1 1Q };

CHV/BXT require that the "Source and Destination horizontal stride must be aligned to the same qword." for 64-bit operations.

I'll see if fixing that sorts this out.
Comment 2 Matt Turner 2017-09-29 21:46:05 UTC 
The series I sent last night fixes this and adds EU validation code to that would catch the problem.
Comment 3 Matt Turner 2017-10-04 21:11:53 UTC 
Fixed by:

commit b541945c2027990ac571184bbf8e01285be0e33a
Author: Matt Turner <mattst88@gmail.com>
Date:   Thu Sep 21 16:42:02 2017 -0700

    i965/fs: Unpack count argument to 64-bit shift ops on Atom

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