Add GLSL translations for many `SV_*` semantics

I haven't tried to be 100% exhaustie, but this should cover the main cases we are likely to encounter in library code.

1 files changed, 123 insertions, 3 deletions

diff --git a/source/slang/lower.cpp b/source/slang/lower.cpp
index fa38264d4..d77e573d4 100644
--- a/source/slang/lower.cpp
+++ b/source/slang/lower.cpp
@@ -1531,6 +1531,14 @@ struct LoweringVisitor
         VaryingParameterArraySpec*  arraySpecs = nullptr;
     };
 
+    RefPtr<ExpressionSyntaxNode> createGLSLBuiltinRef(
+        char const* name)
+    {
+        RefPtr<VarExpressionSyntaxNode> globalVarRef = new VarExpressionSyntaxNode();
+        globalVarRef->name = name;
+        return globalVarRef;
+    }
+
 
     void lowerSimpleShaderParameterToGLSLGlobal(
         VaryingParameterInfo const&     info,
@@ -1570,9 +1578,121 @@ struct LoweringVisitor
             }
             else if (ns == "sv_position")
             {
-                RefPtr<VarExpressionSyntaxNode> globalVarRef = new VarExpressionSyntaxNode();
-                globalVarRef->name = "gl_Position";
-                globalVarExpr = globalVarRef;
+                if (info.direction == VaryingParameterDirection::Input)
+                {
+                    globalVarExpr = createGLSLBuiltinRef("gl_FragCoord");
+                }
+                else
+                {
+                    globalVarExpr = createGLSLBuiltinRef("gl_Position");
+                }
+            }
+            else if (ns == "sv_clipdistance")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_ClipDistance");
+            }
+            else if (ns == "sv_culldistance")
+            {
+                // TODO: ARB_cull_distance
+                globalVarExpr = createGLSLBuiltinRef("gl_CullDistance");
+            }
+            else if (ns == "sv_coverage")
+            {
+                if (info.direction == VaryingParameterDirection::Input)
+                {
+                    globalVarExpr = createGLSLBuiltinRef("gl_SampleMaskIn");
+                }
+                else
+                {
+                    globalVarExpr = createGLSLBuiltinRef("gl_SampleMask");
+                }
+            }
+            else if (ns == "sv_depth")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_FragDepth");
+            }
+            else if (ns == "sv_depthgreaterequal")
+            {
+                // TODO: layout(depth_greater) out float gl_FragDepth;
+                globalVarExpr = createGLSLBuiltinRef("gl_FragDepth");
+            }
+            else if (ns == "sv_depthlessequal")
+            {
+                // TODO: layout(depth_less) out float gl_FragDepth;
+                globalVarExpr = createGLSLBuiltinRef("gl_FragDepth");
+            }
+            else if (ns == "sv_dispatchthreadid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_GlobalInvocationID");
+            }
+            else if (ns == "sv_domainlocation")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_TessCoord");
+            }
+            else if (ns == "sv_groupid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_WorkGroupID");
+            }
+            else if (ns == "sv_groupindex")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_LocationInvocationIndex");
+            }
+            else if (ns == "sv_groupthreadid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_LocalInvocationID");
+            }
+            else if (ns == "sv_gsinstanceid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_InvocationID");
+            }
+            else if (ns == "sv_insidetessfactor")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_TessLevelInner");
+            }
+            else if (ns == "sv_instanceid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_InstanceIndex");
+            }
+            else if (ns == "sv_isfrontface")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_FrontFacing");
+            }
+            else if (ns == "sv_outputcontrolpointid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_InvocationID");
+            }
+            else if (ns == "sv_outputcontrolpointid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_InvocationID");
+            }
+            else if (ns == "sv_primitiveid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_PrimitiveID");
+            }
+            else if (ns == "sv_rendertargetarrayindex")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_Layer");
+            }
+            else if (ns == "sv_sampleindex")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_SampleID");
+            }
+            else if (ns == "sv_stencilref")
+            {
+                // TODO: ARB_shader_stencil_export
+                globalVarExpr = createGLSLBuiltinRef("gl_SampleID");
+            }
+            else if (ns == "sv_tessfactor")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_TessLevelOuter");
+            }
+            else if (ns == "sv_vertexid")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_VertexIndex");
+            }
+            else if (ns == "sv_viewportarrayindex")
+            {
+                globalVarExpr = createGLSLBuiltinRef("gl_ViewportIndex");
             }
             else
             {