[GPU] Get unclipped draw height by running VS on the CPU

src/xenia/gpu/draw_extent_estimator.h

@@ -0,0 +1,76 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2022 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_GPU_DRAW_EXTENT_ESTIMATOR_H_
+#define XENIA_GPU_DRAW_EXTENT_ESTIMATOR_H_
+
+#include <cstdint>
+#include <optional>
+
+#include "xenia/gpu/register_file.h"
+#include "xenia/gpu/shader.h"
+#include "xenia/gpu/shader_interpreter.h"
+#include "xenia/gpu/trace_writer.h"
+#include "xenia/memory.h"
+
+namespace xe {
+namespace gpu {
+
+class DrawExtentEstimator {
+ public:
+  DrawExtentEstimator(const RegisterFile& register_file, const Memory& memory,
+                      TraceWriter* trace_writer)
+      : register_file_(register_file),
+        memory_(memory),
+        trace_writer_(trace_writer),
+        shader_interpreter_(register_file, memory) {
+    shader_interpreter_.SetTraceWriter(trace_writer);
+  }
+
+  // The shader must have its ucode analyzed.
+  uint32_t EstimateVertexMaxY(const Shader& vertex_shader);
+  uint32_t EstimateMaxY(bool try_to_estimate_vertex_max_y,
+                        const Shader& vertex_shader);
+
+ private:
+  class PositionYExportSink : public ShaderInterpreter::ExportSink {
+   public:
+    void Export(ucode::ExportRegister export_register, const float* value,
+                uint32_t value_mask) override;
+
+    void Reset() {
+      position_y_.reset();
+      position_w_.reset();
+      point_size_.reset();
+      vertex_kill_.reset();
+    }
+
+    const std::optional<float>& position_y() const { return position_y_; }
+    const std::optional<float>& position_w() const { return position_w_; }
+    const std::optional<float>& point_size() const { return point_size_; }
+    const std::optional<uint32_t>& vertex_kill() const { return vertex_kill_; }
+
+   private:
+    std::optional<float> position_y_;
+    std::optional<float> position_w_;
+    std::optional<float> point_size_;
+    std::optional<uint32_t> vertex_kill_;
+  };
+
+  const RegisterFile& register_file_;
+  const Memory& memory_;
+  TraceWriter* trace_writer_;
+
+  ShaderInterpreter shader_interpreter_;
+};
+
+}  // namespace gpu
+}  // namespace xe
+
+#endif  // XENIA_GPU_DRAW_EXTENT_ESTIMATOR_H_