Metal: Vertex/Fragment builtin and layouts. (#4044)

* Metal: Vertex/Fragment builtin and layouts.

* Fix.

* Fix test.

* Emit user semantic on vertex/fragment attributes.

1 files changed, 126 insertions, 2 deletions

diff --git a/source/slang/slang-emit-metal.cpp b/source/slang/slang-emit-metal.cpp
index 3773b7c2a..7580ed74d 100644
--- a/source/slang/slang-emit-metal.cpp
+++ b/source/slang/slang-emit-metal.cpp
@@ -128,8 +128,13 @@ void MetalSourceEmitter::emitFuncParamLayoutImpl(IRInst* param)
             m_writer->emit(rr->getOffset());
             m_writer->emit(")]]");
             break;
+        case LayoutResourceKind::VaryingInput:
+            m_writer->emit(" [[stage_in]]");
+            break;
         }
     }
+    if (auto sysSemanticAttr = layout->findSystemValueSemanticAttr())
+       _emitSystemSemantic(sysSemanticAttr->getName(), sysSemanticAttr->getIndex());
 }
 
 void MetalSourceEmitter::emitParameterGroupImpl(IRGlobalParam* varDecl, IRUniformParameterGroupType* type)
@@ -610,11 +615,130 @@ void MetalSourceEmitter::emitRateQualifiersAndAddressSpaceImpl(IRRate* rate, [[m
     }
 }
 
+void MetalSourceEmitter::_emitSystemSemantic(UnownedStringSlice semanticName, IRIntegerValue semanticIndex)
+{
+    if (semanticName.caseInsensitiveEquals(toSlice("SV_POSITION")))
+    {
+        m_writer->emit(" [[position]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_VERTEXID")))
+    {
+        m_writer->emit(" [[vertex_id]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_INSTANCEID")))
+    {
+        m_writer->emit(" [[instance_id]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_Target")))
+    {
+        m_writer->emit(" [[color(");
+        m_writer->emit(semanticIndex);
+        m_writer->emit(")]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_PRIMITIVEID")))
+    {
+        m_writer->emit(" [[primitive_id]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_GROUPID")))
+    {
+        // TODO: not supported by metal.
+        // We need to implement the transformation logic in slang-ir-metal-legalize.cpp
+        // to convert SV_GroupID to something like METAL_threadgroup_position_in_grid.
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_GROUPINDEX")))
+    {
+        // TODO: not supported by metal.
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_DISPATCHTHREADID")))
+    {
+        m_writer->emit(" [[thread_position_in_grid]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_GROUPTHREADID")))
+    {
+        m_writer->emit(" [[thread_position_in_threadgroup]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_CLIPDISTANCE")))
+    {
+        m_writer->emit(" [[clip_distance]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_RENDERTARGETARRAYINDEX")))
+    {
+        m_writer->emit(" [[render_target_array_index]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_VIEWPORTARRAYINDEX")))
+    {
+        m_writer->emit(" [[viewport_array_index]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_Depth")))
+    {
+        m_writer->emit(" [[depth(any)]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_DepthGreaterEqual")))
+    {
+        m_writer->emit(" [[depth(greater)]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_DepthLessEqual")))
+    {
+        m_writer->emit(" [[depth(less)]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_Coverage")))
+    {
+        m_writer->emit(" [[sample_mask]]");
+    }
+    else if (semanticName.caseInsensitiveEquals(toSlice("SV_StencilRef")))
+    {
+        m_writer->emit(" [[stencil]]");
+    }
+    else
+    {
+        m_writer->emit(" [[user(");
+        m_writer->emit(semanticName);
+        if (semanticIndex != 0)
+        {
+            m_writer->emit("_");
+            m_writer->emit(semanticIndex);
+        }
+        m_writer->emit(")]]");
+    }
+}
+
 void MetalSourceEmitter::emitSemanticsImpl(IRInst* inst, bool allowOffsets)
 {
-    // Metal does not use semantics.
-    SLANG_UNUSED(inst);
     SLANG_UNUSED(allowOffsets);
+    if (inst->getOp() == kIROp_StructKey)
+    {
+        // Only emit [[attribute(n)]] on struct keys.
+        bool hasSemanticFromLayout = false;
+        if (auto varLayout = findVarLayout(inst))
+        {
+            for (auto attr : varLayout->getAllAttrs())
+            {
+                if (auto offsetAttr = as<IRVarOffsetAttr>(attr))
+                {
+                    if (offsetAttr->getResourceKind() == LayoutResourceKind::MetalAttribute)
+                    {
+                        m_writer->emit(" [[attribute(");
+                        m_writer->emit(offsetAttr->getOffset());
+                        m_writer->emit(")]]");
+                    }
+                }
+                else if (auto semanticAttr = as<IRSemanticAttr>(attr))
+                {
+                    auto semanticName = String(semanticAttr->getName()).toUpper();
+                    _emitSystemSemantic(semanticAttr->getName(), semanticAttr->getIndex());
+                    hasSemanticFromLayout = true;
+                }
+            }
+
+        }
+        if (!hasSemanticFromLayout)
+        {
+            if (auto semanticDecor = inst->findDecoration<IRSemanticDecoration>())
+            {
+                _emitSystemSemantic(semanticDecor->getSemanticName(), semanticDecor->getSemanticIndex());
+            }
+        }
+    }
 }
 
 void MetalSourceEmitter::_emitStageAccessSemantic(IRStageAccessDecoration* decoration, const char* name)