SPV: Don't add clip/cull distance capabilities unless used.

SPIRV/GlslangToSpv.cpp

@@ -109,7 +109,7 @@ public:
 
 protected:
     spv::Decoration TranslateInterpolationDecoration(const glslang::TQualifier& qualifier);
-    spv::BuiltIn TranslateBuiltInDecoration(glslang::TBuiltInVariable);
+    spv::BuiltIn TranslateBuiltInDecoration(glslang::TBuiltInVariable, bool member);
     spv::ImageFormat TranslateImageFormat(const glslang::TType& type);
     spv::Id createSpvVariable(const glslang::TIntermSymbol*);
     spv::Id getSampledType(const glslang::TSampler&);
@@ -122,6 +122,7 @@ protected:
     int getArrayStride(const glslang::TType& arrayType, glslang::TLayoutPacking, glslang::TLayoutMatrix);
     int getMatrixStride(const glslang::TType& matrixType, glslang::TLayoutPacking, glslang::TLayoutMatrix);
     void updateMemberOffset(const glslang::TType& structType, const glslang::TType& memberType, int& currentOffset, int& nextOffset, glslang::TLayoutPacking, glslang::TLayoutMatrix);
+    void declareClipCullCapability(const glslang::TTypeList& members, int member);
 
     bool isShaderEntrypoint(const glslang::TIntermAggregate* node);
     void makeFunctions(const glslang::TIntermSequence&);
@@ -393,7 +394,7 @@ spv::Decoration TranslateNoContractionDecoration(const glslang::TQualifier& qual
 }
 
 // Translate glslang built-in variable to SPIR-V built in decoration.
-spv::BuiltIn TGlslangToSpvTraverser::TranslateBuiltInDecoration(glslang::TBuiltInVariable builtIn)
+spv::BuiltIn TGlslangToSpvTraverser::TranslateBuiltInDecoration(glslang::TBuiltInVariable builtIn, bool member)
 {
     switch (builtIn) {
     case glslang::EbvPointSize:
@@ -410,11 +411,19 @@ spv::BuiltIn TGlslangToSpvTraverser::TranslateBuiltInDecoration(glslang::TBuiltI
         }
         return spv::BuiltInPointSize;
 
+    // These *Distance capabilities logically belong here, but if the member is declared and
+    // then never used, consumers of SPIR-V prefer the capability not be declared.
+    // They are now generated when used, rather than here when declared.
+    // Potentially, the specification should be more clear what the minimum
+    // use needed is to trigger the capability.
+    //
     case glslang::EbvClipDistance:
+        if (! member)
             builder.addCapability(spv::CapabilityClipDistance);
         return spv::BuiltInClipDistance;
 
     case glslang::EbvCullDistance:
+        if (! member)
             builder.addCapability(spv::CapabilityCullDistance);
         return spv::BuiltInCullDistance;
 
@@ -926,6 +935,10 @@ bool TGlslangToSpvTraverser::visitBinary(glslang::TVisit /* visit */, glslang::T
             } else {
                 // normal case for indexing array or structure or block
                 builder.accessChainPush(builder.makeIntConstant(index));
+
+                // Add capabilities here for accessing clip/cull distance
+                if (node->getLeft()->getType().isStruct() && ! node->getLeft()->getType().isArray())
+                    declareClipCullCapability(*node->getLeft()->getType().getStruct(), index);
             }
         }
         return false;
@@ -1919,7 +1932,7 @@ spv::Id TGlslangToSpvTraverser::convertGlslangToSpvType(const glslang::TType& ty
                         builder.addMemberDecoration(spvType, member, spv::DecorationMatrixStride, getMatrixStride(glslangType, explicitLayout, subQualifier.layoutMatrix));
 
                     // built-in variable decorations
-                    spv::BuiltIn builtIn = TranslateBuiltInDecoration(glslangType.getQualifier().builtIn);
+                    spv::BuiltIn builtIn = TranslateBuiltInDecoration(glslangType.getQualifier().builtIn, true);
                     if (builtIn != spv::BadValue)
                         addMemberDecoration(spvType, member, spv::DecorationBuiltIn, (int)builtIn);
                 }
@@ -2172,6 +2185,14 @@ void TGlslangToSpvTraverser::updateMemberOffset(const glslang::TType& /*structTy
     nextOffset = currentOffset + memberSize;
 }
 
+void TGlslangToSpvTraverser::declareClipCullCapability(const glslang::TTypeList& members, int member)
+{
+    if (members[member].type->getQualifier().builtIn == glslang::EbvClipDistance)
+        builder.addCapability(spv::CapabilityClipDistance);
+    if (members[member].type->getQualifier().builtIn == glslang::EbvCullDistance)
+        builder.addCapability(spv::CapabilityCullDistance);
+}
+
 bool TGlslangToSpvTraverser::isShaderEntrypoint(const glslang::TIntermAggregate* node)
 {
     // have to ignore mangling and just look at the base name
@@ -3936,7 +3957,7 @@ spv::Id TGlslangToSpvTraverser::getSymbolId(const glslang::TIntermSymbol* symbol
     }
 
     // built-in variable decorations
-    spv::BuiltIn builtIn = TranslateBuiltInDecoration(symbol->getQualifier().builtIn);
+    spv::BuiltIn builtIn = TranslateBuiltInDecoration(symbol->getQualifier().builtIn, false);
     if (builtIn != spv::BadValue)
         addDecoration(id, spv::DecorationBuiltIn, (int)builtIn);
 

Test/baseResults/spv.150.geom.out

@@ -9,7 +9,6 @@ Linked geometry stage:
 
                               Capability Geometry
                               Capability GeometryPointSize
-                              Capability ClipDistance
                               Capability GeometryStreams
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450

Test/baseResults/spv.430.vert.out

@@ -10,7 +10,6 @@ Linked vertex stage:
 // Id's are bound by 66
 
                               Capability Shader
-                              Capability ClipDistance
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
                               EntryPoint Vertex 4  "main" 12 23 34 38 41 42 62 65

Test/baseResults/spv.bool.vert.out

@@ -10,8 +10,6 @@ Linked vertex stage:
 // Id's are bound by 49
 
                               Capability Shader
-                              Capability ClipDistance
-                              Capability CullDistance
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
                               EntryPoint Vertex 4  "main" 24

Test/baseResults/spv.matFun.vert.out

@@ -10,7 +10,6 @@ Linked vertex stage:
 // Id's are bound by 103
 
                               Capability Shader
-                              Capability ClipDistance
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
                               EntryPoint Vertex 4  "main" 76 81