[Bug 96971] invariant qualifier is not valid for shader inputs

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96971

            Bug ID: 96971
           Summary: invariant qualifier is not valid for shader inputs
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: idr at freedesktop.org
          Reporter: qiankun.miao at intel.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

Currently, only glsl es in mesa follows this rule. But glsl compiler should
also follow this rule. The behavior is specified in GLSLangSpec.4.40, in
Section 4.8.1 The Invariant Qualifier: "Only variables output from a shader can
be candidates for invariance." and "As only outputs need be declared with
invariant, an output from one shader stage will still match an input of a
subsequent stage without the input being declared as invariant."

So, input without invariant declaration should be valid.
But following code snippet in mesa/src/compiler/glsl/link_varyings.cpp makes it
an error:


   if (!prog->IsES && input->data.invariant != output->data.invariant) {
      linker_error(prog,                                                        
                   "%s shader output `%s' %s invariant qualifier, "
                   "but %s shader input %s invariant qualifier\n",
                   _mesa_shader_stage_to_string(producer_stage),
                   output->name,
                   (output->data.invariant) ? "has" : "lacks",
                   _mesa_shader_stage_to_string(consumer_stage),
                   (input->data.invariant) ? "has" : "lacks");
      return;
   }

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