[Mesa-dev] [Bug 100061] LODQ instruction generated with invalid dst mask

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100061

            Bug ID: 100061
           Summary: LODQ instruction generated with invalid dst mask
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Mesa core
          Assignee: mesa-dev at lists.freedesktop.org
          Reporter: imirkin at alum.mit.edu
        QA Contact: mesa-dev at lists.freedesktop.org

Created attachment 130064
  --> https://bugs.freedesktop.org/attachment.cgi?id=130064&action=edit
shader_test demonstrating the issue

The attached shader_test produces an instruction like this:

  2: LODQ TEMP[1], TEMP[1], SAMP[0], 2D

Which is clearly bogus (and hits an assert in nouveau code making sure that the
destmask is a subset of .xy). I tried to get this to happen with a much simpler
shader, but was unsuccessful. Haven't tried whittling this one down yet. It
comes from some radeonsi bug with a trace from Hitman.

My guess is that it's an issue in the st_glsl_to_tgsi register renumbering or
copy-prop passes... somehow. (Mostly because I hate them, and hope that this
hatred is vindicated by them having bugs.)

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