gl_shader_decompiler: Implement gl_ViewportIndex and gl_Layer in vertex shaders

This commit implements gl_ViewportIndex and gl_Layer in vertex and
geometry shaders. In the case it's used in a vertex shader, it requires
ARB_shader_viewport_layer_array. This extension is available on AMD and
Nvidia devices (mesa and proprietary drivers), but not available on
Intel on any platform. At the moment of writing this description I don't
know if this is a hardware limitation or a driver limitation.

In the case that ARB_shader_viewport_layer_array is not available,
writes to these registers on a vertex shader are ignored, with the
appropriate logging.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/video_core/renderer_opengl/gl_device.h b/src/video_core/renderer_opengl/gl_device.h
index 8c8c93760..7a3a0675b 100644
--- a/src/video_core/renderer_opengl/gl_device.h
+++ b/src/video_core/renderer_opengl/gl_device.h
@@ -26,6 +26,10 @@ public:
         return max_varyings;
     }
 
+    bool HasVertexViewportLayer() const {
+        return has_vertex_viewport_layer;
+    }
+
     bool HasVariableAoffi() const {
         return has_variable_aoffi;
     }
@@ -41,6 +45,7 @@ private:
     std::size_t uniform_buffer_alignment{};
     u32 max_vertex_attributes{};
     u32 max_varyings{};
+    bool has_vertex_viewport_layer{};
     bool has_variable_aoffi{};
     bool has_component_indexing_bug{};
 };