The jenkins regression system began reproducing IVB failures for this piglit test somewhere after 10.5. On the CI system it reproduces fairly regularly (10% of the time?). The test passes all other platforms, and does not reproduce (yet) in the 10.5 branch. Test Output: /tmp/build_root/m64/lib/piglit/bin/shader_runner /tmp/build_root/m64/lib/piglit/tests/spec/glsl-1.10/execution/fs-dfdy-accuracy.shader_test -auto Probe color at (36,164) Expected: 0.000000 1.000000 0.000000 1.000000 Observed: 1.000000 0.000000 0.000000 1.000000
This happens quite reliably when running a while loop in bash, I've bisected this to following commit: --- 8< ----------------------------------- dd5c8250537640f92dbc1ee63d516c6e3e2aaf77 is the first bad commit commit dd5c8250537640f92dbc1ee63d516c6e3e2aaf77 Author: Matt Turner <mattst88@gmail.com> Date: Tue Apr 14 12:40:34 2015 -0700 i965: Replace guess_execution_size with something simpler. guess_execution_size() does two things: 1. Cope with small destination registers. 2. Cope with SIMD8 vs SIMD16 mode. This patch replaces the first with a simple if block in brw_set_dest: if the destination register width is less than 8, you probably want the execution size to match. (I didn't put this in the 3src block because it doesn't seem to matter.) Since only the FS compiler cares about SIMD16 mode, it's easy to just set the default execution size there. This pattern was already been proven in the Gen8+ generator, but we didn't port it back to the existing generator when we combined the two. This is based on a patch from Ken from about a year ago. I've rebased it and and fixed a few bugs. Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Between passing and a failing run there is no difference in the generated assembly, I checked this by comparing INTEL_DEBUG=vs,fs outputs.
However with patch and before it there are changes in assembly: before: add(8) g7<1>F g5<4,4,1>.xyxyF -g5<4,4,1>.zwzwF { align16 1Q }; add(8) g8<1>F g6<4,4,1>.xyxyF -g6<4,4,1>.zwzwF { align16 2Q }; after: add(16) g7<1>F g5<4,4,1>.xyxyF -g5<4,4,1>.zwzwF { align16 1H }; add(16) g8<1>F g6<4,4,1>.xyxyF -g6<4,4,1>.zwzwF { align16 1H }; with help from Curro I think I can tackle this one!
Created attachment 115712 [details] [review] patch to fix the issue will test
pushed to master (sorry Mark, I forgot to add tested-by tag, many thanks for testing!)
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