Support GL_EXT_fragment_shader_barycentric (#2704)

* Support GL_EXT_fragment_shader_barycentric

* Support pervertex  with GL_EXT_fragment_shader_barycentric

7 files changed, 101 insertions, 32 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 633c3d87e..d417e3b7c 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -2274,9 +2274,9 @@ matrix<T, N, M> fwidth(matrix<T, N, M> x)
 __generic<T : __BuiltinType>
 [__readNone]
 __target_intrinsic(hlsl)
-__target_intrinsic(glsl, "$0[$1]")
+__target_intrinsic(GL_NV_fragment_shader_barycentric, "$0[$1]")
+__target_intrinsic(GL_EXT_fragment_shader_barycentric, "$0[$1]")
 __glsl_version(450)
-__glsl_extension(GL_NV_fragment_shader_barycentric)
 T GetAttributeAtVertex(T attribute, uint vertexIndex);
 
 /// Get the value of a vertex attribute at a specific vertex.
@@ -2296,9 +2296,9 @@ T GetAttributeAtVertex(T attribute, uint vertexIndex);
 __generic<T : __BuiltinType, let N : int>
 [__readNone]
 __target_intrinsic(hlsl)
-__target_intrinsic(glsl, "$0[$1]")
+__target_intrinsic(GL_NV_fragment_shader_barycentric, "$0[$1]")
+__target_intrinsic(GL_EXT_fragment_shader_barycentric, "$0[$1]")
 __glsl_version(450)
-__glsl_extension(GL_NV_fragment_shader_barycentric)
 vector<T,N> GetAttributeAtVertex(vector<T,N> attribute, uint vertexIndex);
 
 /// Get the value of a vertex attribute at a specific vertex.
@@ -2318,9 +2318,9 @@ vector<T,N> GetAttributeAtVertex(vector<T,N> attribute, uint vertexIndex);
 __generic<T : __BuiltinType, let N : int, let M : int>
 [__readNone]
 __target_intrinsic(hlsl)
-__target_intrinsic(glsl, "$0[$1]")
+__target_intrinsic(GL_NV_fragment_shader_barycentric, "$0[$1]")
+__target_intrinsic(GL_EXT_fragment_shader_barycentric, "$0[$1]")
 __glsl_version(450)
-__glsl_extension(GL_NV_fragment_shader_barycentric)
 matrix<T,N,M> GetAttributeAtVertex(matrix<T,N,M> attribute, uint vertexIndex);
 
 
diff --git a/source/slang/slang-capability-defs.h b/source/slang/slang-capability-defs.h
index fc60f4dfa..14173b6bc 100644
--- a/source/slang/slang-capability-defs.h
+++ b/source/slang/slang-capability-defs.h
@@ -87,6 +87,11 @@ SLANG_CAPABILITY_ATOM1(GLSLRayTracing,      __glslRayTracing,   Abstract,None,0,
 SLANG_CAPABILITY_ATOM1(GL_NV_ray_tracing,   GL_NV_ray_tracing,  Concrete,RayTracingExtension,0,   GLSLRayTracing)
 SLANG_CAPABILITY_ATOM2(GL_EXT_ray_tracing,  GL_EXT_ray_tracing, Concrete,RayTracingExtension,1,   GLSLRayTracing, SPIRV_1_4)
 
+SLANG_CAPABILITY_ATOM1(GLSLFragmentShaderBarycentric,           __glslFragmentShaderBarycentric,         Abstract, None,                               0, GLSL)
+SLANG_CAPABILITY_ATOM1(GL_NV_fragment_shader_barycentric,       GL_NV_fragment_shader_barycentric,       Concrete, FragmentShaderBarycentricExtension, 0, GLSLFragmentShaderBarycentric)
+SLANG_CAPABILITY_ATOM1(GL_EXT_fragment_shader_barycentric,      GL_EXT_fragment_shader_barycentric,      Concrete, FragmentShaderBarycentricExtension, 1, GLSLFragmentShaderBarycentric)
+
+
 #undef SLANG_CAPABILITY_ATOM0
 #undef SLANG_CAPABILITY_ATOM1
 #undef SLANG_CAPABILITY_ATOM2
diff --git a/source/slang/slang-capability.cpp b/source/slang/slang-capability.cpp
index 0b82cb92c..235e211e5 100644
--- a/source/slang/slang-capability.cpp
+++ b/source/slang/slang-capability.cpp
@@ -67,6 +67,10 @@ enum class CapabilityAtomConflictMask : uint32_t
     // Capability atoms that represent GLSL ray tracing extensions conflict with
     // one another (we only want to use one such extension at a time).
     RayTracingExtension = 1 << 1,
+
+    // Capability atoms that represent GLSL fragment shader barycentric extensions conflict with
+    // one another (we only want to use one such extension at a time).
+    FragmentShaderBarycentricExtension = 1 << 2,
 };
 
 // For simplicity in building up our data structure representing
diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index 13eb6e2f6..d0154ab91 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -80,6 +80,27 @@ void GLSLSourceEmitter::_requireRayTracing()
     m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_460);
 }
 
+void GLSLSourceEmitter::_requireFragmentShaderBarycentric()
+{
+    // There is more than one extension that provides barycentric coords in fragment shaders,
+    // and we need to pick which one to enable.
+    //
+    // By default, we will use the `GL_EXT_fragment_shader_barycentric` extension, but if
+    // the user has explicitly opted in to the `GL_NV_fragment_shader_barycentric` extension 
+    // we will use that one instead.
+    
+    if( getTargetCaps().implies(CapabilityAtom::GL_NV_fragment_shader_barycentric) )
+    {
+        m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_NV_fragment_shader_barycentric"));
+    }
+    else
+    {
+        m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_fragment_shader_barycentric"));
+    }
+    m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_450);
+}
+
+
 void GLSLSourceEmitter::_requireGLSLExtension(const UnownedStringSlice& name)
 {
     m_glslExtensionTracker->requireExtension(name);
@@ -2250,27 +2271,40 @@ void GLSLSourceEmitter::emitRateQualifiersImpl(IRRate* rate)
     }
 }
 
-static UnownedStringSlice _getInterpolationModifierText(IRInterpolationMode mode, Stage stage, bool isInput)
+bool GLSLSourceEmitter::_maybeEmitInterpolationModifierText(IRInterpolationMode mode, Stage stage, bool isInput)
 {
     switch (mode)
     {
-        case IRInterpolationMode::NoInterpolation:      return UnownedStringSlice::fromLiteral("flat");
-        case IRInterpolationMode::NoPerspective:        return UnownedStringSlice::fromLiteral("noperspective");
-        case IRInterpolationMode::Linear:               return UnownedStringSlice::fromLiteral("smooth");
-        case IRInterpolationMode::Sample:               return UnownedStringSlice::fromLiteral("sample");
-        case IRInterpolationMode::Centroid:             return UnownedStringSlice::fromLiteral("centroid");
-
+        case IRInterpolationMode::NoInterpolation:      
+            m_writer->emit("flat "); return true;
+        case IRInterpolationMode::NoPerspective:        
+            m_writer->emit("noperspective "); return true;
+        case IRInterpolationMode::Linear:               
+            m_writer->emit("smooth "); return true;
+        case IRInterpolationMode::Sample:              
+            m_writer->emit("sample "); return true;
+        case IRInterpolationMode::Centroid:             
+            m_writer->emit("centroid "); return true;
         case IRInterpolationMode::PerVertex:
-            if( stage == Stage::Fragment )
+            if( stage == Stage::Fragment && isInput)
             {
-                if( isInput )
+                _requireFragmentShaderBarycentric();
+                if (getTargetCaps().implies(CapabilityAtom::GL_NV_fragment_shader_barycentric))
                 {
-                    return UnownedStringSlice::fromLiteral("pervertexNV");
+                    m_writer->emit("pervertexNV ");    
+                }
+                else 
+                {
+                    m_writer->emit("pervertexEXT ");
                 }
             }
-            return UnownedStringSlice::fromLiteral("flat");
-
-        default:                                        return UnownedStringSlice();
+            else 
+            {
+                m_writer->emit("flat ");
+            }
+            return true;
+        default:
+            return false;
     }
 }
 
@@ -2293,14 +2327,8 @@ void GLSLSourceEmitter::emitInterpolationModifiersImpl(IRInst* varInst, IRType*
             continue;
 
         auto decoration = (IRInterpolationModeDecoration*)dd;
-        const UnownedStringSlice slice = _getInterpolationModifierText(decoration->getMode(), stage, isInput);
 
-        if (slice.getLength())
-        {
-            m_writer->emit(slice);
-            m_writer->emitChar(' ');
-            anyModifiers = true;
-        }
+        anyModifiers |= _maybeEmitInterpolationModifierText(decoration->getMode(), stage, isInput);
 
         switch( decoration->getMode() )
         {
@@ -2312,8 +2340,7 @@ void GLSLSourceEmitter::emitInterpolationModifiersImpl(IRInst* varInst, IRType*
             {
                 if( isInput )
                 {
-                    _requireGLSLVersion(ProfileVersion::GLSL_450);
-                    _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_NV_fragment_shader_barycentric"));
+                    _requireFragmentShaderBarycentric();
                 }
             }
             break;
diff --git a/source/slang/slang-emit-glsl.h b/source/slang/slang-emit-glsl.h
index 6a18fe035..99259463b 100644
--- a/source/slang/slang-emit-glsl.h
+++ b/source/slang/slang-emit-glsl.h
@@ -67,6 +67,8 @@ protected:
 
     void _maybeEmitGLSLBuiltin(IRGlobalParam* var, UnownedStringSlice name);
 
+    bool _maybeEmitInterpolationModifierText(IRInterpolationMode mode, Stage stage, bool isInput);
+
     void _requireGLSLExtension(const UnownedStringSlice& name);
 
     void _requireGLSLVersion(ProfileVersion version);
@@ -108,6 +110,8 @@ protected:
 
     void _requireRayTracing();
 
+    void _requireFragmentShaderBarycentric();
+
     void _emitSpecialFloatImpl(IRType* type, const char* valueExpr);
 
     RefPtr<GLSLExtensionTracker> m_glslExtensionTracker;
diff --git a/source/slang/slang-ir-glsl-legalize.cpp b/source/slang/slang-ir-glsl-legalize.cpp
index 9c16f40ac..986f98c84 100644
--- a/source/slang/slang-ir-glsl-legalize.cpp
+++ b/source/slang/slang-ir-glsl-legalize.cpp
@@ -448,6 +448,7 @@ GLSLSystemValueInfo* getMeshOutputIndicesSystemValueInfo(
 
 GLSLSystemValueInfo* getGLSLSystemValueInfo(
     GLSLLegalizationContext*    context,
+    CodeGenContext*             codeGenContext,
     IRVarLayout*                varLayout,
     LayoutResourceKind          kind,
     Stage                       stage,
@@ -843,9 +844,16 @@ GLSLSystemValueInfo* getGLSLSystemValueInfo(
     else if (semanticName == "sv_barycentrics")
     {
         context->requireGLSLVersion(ProfileVersion::GLSL_450);
-        context->requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_NV_fragment_shader_barycentric"));
-
-        name = "gl_BaryCoordNV";
+        if (codeGenContext->getTargetCaps().implies(CapabilityAtom::GL_NV_fragment_shader_barycentric))
+        {
+            context->requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_NV_fragment_shader_barycentric"));
+            name = "gl_BaryCoordNV";
+        }
+        else
+        {
+            context->requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_fragment_shader_barycentric"));
+            name = "gl_BaryCoordEXT";
+        }
 
         // TODO: There is also the `gl_BaryCoordNoPerspNV` builtin, which
         // we ought to use if the `noperspective` modifier has been
@@ -874,6 +882,7 @@ GLSLSystemValueInfo* getGLSLSystemValueInfo(
 
 ScalarizedVal createSimpleGLSLGlobalVarying(
     GLSLLegalizationContext*    context,
+    CodeGenContext*             codeGenContext,
     IRBuilder*                  builder,
     IRType*                     inType,
     IRVarLayout*                inVarLayout,
@@ -889,6 +898,7 @@ ScalarizedVal createSimpleGLSLGlobalVarying(
     GLSLSystemValueInfo systemValueInfoStorage;
     auto systemValueInfo = getGLSLSystemValueInfo(
         context,
+        codeGenContext,
         inVarLayout,
         kind,
         stage,
@@ -1040,6 +1050,7 @@ ScalarizedVal createSimpleGLSLGlobalVarying(
 
 ScalarizedVal createGLSLGlobalVaryingsImpl(
     GLSLLegalizationContext*    context,
+    CodeGenContext*             codeGenContext,
     IRBuilder*                  builder,
     IRType*                     type,
     IRVarLayout*                varLayout,
@@ -1059,12 +1070,14 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
     {
         return createSimpleGLSLGlobalVarying(
             context,
+            codeGenContext,
             builder, type, varLayout, typeLayout, kind, stage, bindingIndex, bindingSpace, declarator, leafVar);
     }
     else if( as<IRVectorType>(type) )
     {
         return createSimpleGLSLGlobalVarying(
             context,
+            codeGenContext,
             builder, type, varLayout, typeLayout, kind, stage, bindingIndex, bindingSpace, declarator, leafVar);
     }
     else if( as<IRMatrixType>(type) )
@@ -1072,6 +1085,7 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
         // TODO: a matrix-type varying should probably be handled like an array of rows
         return createSimpleGLSLGlobalVarying(
             context,
+            codeGenContext,
             builder, type, varLayout, typeLayout, kind, stage, bindingIndex, bindingSpace, declarator, leafVar);
     }
     else if( auto arrayType = as<IRArrayType>(type) )
@@ -1091,6 +1105,7 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
 
         return createGLSLGlobalVaryingsImpl(
             context,
+            codeGenContext,
             builder,
             elementType,
             varLayout,
@@ -1133,6 +1148,7 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
 
         return createGLSLGlobalVaryingsImpl(
             context,
+            codeGenContext,
             builder,
             elementType,
             varLayout,
@@ -1153,6 +1169,7 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
 
         return createGLSLGlobalVaryingsImpl(
             context,
+            codeGenContext,
             builder,
             elementType,
             varLayout,
@@ -1214,6 +1231,7 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
 
             auto fieldVal = createGLSLGlobalVaryingsImpl(
                 context,
+                codeGenContext,
                 builder,
                 field->getFieldType(),
                 fieldLayout,
@@ -1240,11 +1258,13 @@ ScalarizedVal createGLSLGlobalVaryingsImpl(
     // Default case is to fall back on the simple behavior
     return createSimpleGLSLGlobalVarying(
         context,
+        codeGenContext,
         builder, type, varLayout, typeLayout, kind, stage, bindingIndex, bindingSpace, declarator, leafVar);
 }
 
 ScalarizedVal createGLSLGlobalVaryings(
     GLSLLegalizationContext*    context,
+    CodeGenContext*             codeGenContext,
     IRBuilder*                  builder,
     IRType*                     type,
     IRVarLayout*                layout,
@@ -1261,6 +1281,7 @@ ScalarizedVal createGLSLGlobalVaryings(
     }
     return createGLSLGlobalVaryingsImpl(
         context,
+        codeGenContext,
         builder, type, layout, layout->getTypeLayout(), kind, stage, bindingIndex, bindingSpace, nullptr, leafVar);
 }
 
@@ -1722,6 +1743,7 @@ void legalizeMeshOutputParam(
 
     auto globalOutputVal = createGLSLGlobalVaryings(
         context,
+        codeGenContext,
         builder,
         meshOutputType,
         paramLayout,
@@ -2140,6 +2162,7 @@ void legalizeEntryPointParameterForGLSL(
 
             auto globalOutputVal = createGLSLGlobalVaryings(
                 context,
+                codeGenContext,
                 builder,
                 valueType,
                 paramLayout,
@@ -2305,6 +2328,7 @@ void legalizeEntryPointParameterForGLSL(
             // side and one for the `out` side.
             auto globalInputVal = createGLSLGlobalVaryings(
                 context,
+                codeGenContext,
                 builder, valueType, paramLayout, LayoutResourceKind::VaryingInput, stage, pp);
 
             assign(builder, localVal, globalInputVal);
@@ -2320,6 +2344,7 @@ void legalizeEntryPointParameterForGLSL(
         // when the function is done. We create them here.
         auto globalOutputVal = createGLSLGlobalVaryings(
                 context,
+                codeGenContext,
                 builder, valueType, paramLayout, LayoutResourceKind::VaryingOutput, stage, pp);
 
         // Now we need to iterate over all the blocks in the function looking
@@ -2361,6 +2386,7 @@ void legalizeEntryPointParameterForGLSL(
 
         auto globalValue = createGLSLGlobalVaryings(
             context,
+            codeGenContext,
             builder, paramType, paramLayout, LayoutResourceKind::VaryingInput, stage, pp);
 
         // Next we need to replace uses of the parameter with
@@ -2455,6 +2481,7 @@ void legalizeEntryPointForGLSL(
 
         auto resultGlobal = createGLSLGlobalVaryings(
             &context,
+            codeGenContext,
             &builder,
             resultType,
             entryPointLayout->getResultLayout(),
diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index 60bc087de..fea9a1c71 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -712,9 +712,11 @@ struct OptionsParser
             "  code accordingly.\n"
             "  Currently defined capabilities are:\n"
             "\n"
-            "    spriv_1_{0,1,2,3,4,5}   - minimum supported SPIR-V version\n"
+            "    spirv_1_{0,1,2,3,4,5}   - minimum supported SPIR-V version\n"
             "    GL_NV_ray_tracing       - enables the GL_NV_ray_tracing extension\n"
             "    GL_EXT_ray_tracing      - enables the GL_EXT_ray_tracing extension\n"
+            "    GL_NV_fragment_shader_barycentric  - enables the GL_NV_fragment_shader_barycentric extension\n"
+            "    GL_EXT_fragment_shader_barycentric - enables the GL_EXT_fragment_shader_barycentric extension\n"
             "\n";
 
 #undef EXECUTABLE_EXTENSION