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Bug 1261988

Summary: fragment and vertex shaders can't decrement variables by 1
Product: Red Hat Enterprise Linux 7 Reporter: Oded Gabbay <ogabbay>
Component: mesaAssignee: Oded Gabbay <ogabbay>
Status: CLOSED ERRATA QA Contact: Desktop QE <desktop-qa-list>
Severity: medium Docs Contact:
Priority: unspecified    
Version: 7.2CC: bugproxy, hannsj_uhl, kem, tlavigne, tpelka
Target Milestone: rc   
Target Release: 7.2   
Hardware: ppc64le   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-11-19 09:08:02 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1118366, 1252514    

Description Oded Gabbay 2015-09-10 14:42:15 UTC
Description of problem:
On ppc64le and ppc64 machines that run with software rendering, the shader command to decrement a variable by 1 is never executed. This is because of a bug in the translation between tgsi and llvm ir for ppc64le and ppc64. 

Because this is such a basic command in shaders, it causes a lot of failures when running the piglit test suite

Version-Release number of selected component (if applicable):
mesa-10.6.5-1.20150824.el7

How reproducible:
By running various piglit tests. Around 350 tests fail because of this bug. It occurs 100% of the time

Steps to Reproduce:
1. Install piglit
2. Run bin/shader_runner tests/spec/glsl-1.30/execution/fs-decrement-int.shader_test -auto

Actual results:
The program returns "fail"

Expected results:
The program should return "success"

Comment 1 Oded Gabbay 2015-09-16 11:34:56 UTC
Fixed in mesa-10.6.5-2.20150824.el7

Comment 5 errata-xmlrpc 2015-11-19 09:08:02 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2250.html