2 files changed, 84 insertions, 0 deletions

diff --git a/src/video_core/shader/shader.cpp b/src/video_core/shader/shader.cpp
index 67ed19ba8..b12468d3a 100644
--- a/src/video_core/shader/shader.cpp
+++ b/src/video_core/shader/shader.cpp
@@ -82,6 +82,44 @@ void UnitState::WriteOutput(const ShaderRegs& config, AttributeBuffer& output) {
     }
 }
 
+UnitState::UnitState(GSEmitter* emitter) : emitter_ptr(emitter) {}
+
+GSEmitter::GSEmitter() {
+    handlers = new Handlers;
+}
+
+GSEmitter::~GSEmitter() {
+    delete handlers;
+}
+
+void GSEmitter::Emit(Math::Vec4<float24> (&vertex)[16]) {
+    ASSERT(vertex_id < 3);
+    std::copy(std::begin(vertex), std::end(vertex), buffer[vertex_id].begin());
+    if (prim_emit) {
+        if (winding)
+            handlers->winding_setter();
+        for (size_t i = 0; i < buffer.size(); ++i) {
+            AttributeBuffer output;
+            unsigned int output_i = 0;
+            for (unsigned int reg : Common::BitSet<u32>(output_mask)) {
+                output.attr[output_i++] = buffer[i][reg];
+            }
+            handlers->vertex_handler(output);
+        }
+    }
+}
+
+GSUnitState::GSUnitState() : UnitState(&emitter) {}
+
+void GSUnitState::SetVertexHandler(VertexHandler vertex_handler, WindingSetter winding_setter) {
+    emitter.handlers->vertex_handler = std::move(vertex_handler);
+    emitter.handlers->winding_setter = std::move(winding_setter);
+}
+
+void GSUnitState::ConfigOutput(const ShaderRegs& config) {
+    emitter.output_mask = config.output_mask;
+}
+
 MICROPROFILE_DEFINE(GPU_Shader, "GPU", "Shader", MP_RGB(50, 50, 240));
 
 #ifdef ARCHITECTURE_x86_64
diff --git a/src/video_core/shader/shader.h b/src/video_core/shader/shader.h
index e156f6aef..caec96043 100644
--- a/src/video_core/shader/shader.h
+++ b/src/video_core/shader/shader.h
@@ -6,6 +6,7 @@
 
 #include <array>
 #include <cstddef>
+#include <functional>
 #include <type_traits>
 #include <nihstro/shader_bytecode.h>
 #include "common/assert.h"
@@ -31,6 +32,12 @@ struct AttributeBuffer {
     alignas(16) Math::Vec4<float24> attr[16];
 };
 
+/// Handler type for receiving vertex outputs from vertex shader or geometry shader
+using VertexHandler = std::function<void(const AttributeBuffer&)>;
+
+/// Handler type for signaling to invert the vertex order of the next triangle
+using WindingSetter = std::function<void()>;
+
 struct OutputVertex {
     Math::Vec4<float24> pos;
     Math::Vec4<float24> quat;
@@ -61,12 +68,36 @@ static_assert(std::is_pod<OutputVertex>::value, "Structure is not POD");
 static_assert(sizeof(OutputVertex) == 24 * sizeof(float), "OutputVertex has invalid size");
 
 /**
+ * This structure contains state information for primitive emitting in geometry shader.
+ */
+struct GSEmitter {
+    std::array<std::array<Math::Vec4<float24>, 16>, 3> buffer;
+    u8 vertex_id;
+    bool prim_emit;
+    bool winding;
+    u32 output_mask;
+
+    // Function objects are hidden behind a raw pointer to make the structure standard layout type,
+    // for JIT to use offsetof to access other members.
+    struct Handlers {
+        VertexHandler vertex_handler;
+        WindingSetter winding_setter;
+    } * handlers;
+
+    GSEmitter();
+    ~GSEmitter();
+    void Emit(Math::Vec4<float24> (&vertex)[16]);
+};
+static_assert(std::is_standard_layout<GSEmitter>::value, "GSEmitter is not standard layout type");
+
+/**
  * This structure contains the state information that needs to be unique for a shader unit. The 3DS
  * has four shader units that process shaders in parallel. At the present, Citra only implements a
  * single shader unit that processes all shaders serially. Putting the state information in a struct
  * here will make it easier for us to parallelize the shader processing later.
  */
 struct UnitState {
+    explicit UnitState(GSEmitter* emitter = nullptr);
     struct Registers {
         // The registers are accessed by the shader JIT using SSE instructions, and are therefore
         // required to be 16-byte aligned.
@@ -82,6 +113,8 @@ struct UnitState {
     // TODO: How many bits do these actually have?
     s32 address_registers[3];
 
+    GSEmitter* emitter_ptr;
+
     static size_t InputOffset(const SourceRegister& reg) {
         switch (reg.GetRegisterType()) {
         case RegisterType::Input:
@@ -125,6 +158,19 @@ struct UnitState {
     void WriteOutput(const ShaderRegs& config, AttributeBuffer& output);
 };
 
+/**
+ * This is an extended shader unit state that represents the special unit that can run both vertex
+ * shader and geometry shader. It contains an additional primitive emitter and utilities for
+ * geometry shader.
+ */
+struct GSUnitState : public UnitState {
+    GSUnitState();
+    void SetVertexHandler(VertexHandler vertex_handler, WindingSetter winding_setter);
+    void ConfigOutput(const ShaderRegs& config);
+
+    GSEmitter emitter;
+};
+
 struct ShaderSetup {
     struct {
         // The float uniforms are accessed by the shader JIT using SSE instructions, and are