ShaderGen: Implement pixel ubershaders

Source/Core/VideoCommon/UberShaderCommon.h

@@ -0,0 +1,24 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "VideoCommon/ShaderGenCommon.h"
+#include "VideoCommon/VideoCommon.h"
+
+namespace UberShader
+{
+// Common functions across all ubershaders
+void WriteUberShaderCommonHeader(ShaderCode& out, APIType api_type,
+                                 const ShaderHostConfig& host_config);
+
+// bitfieldExtract generator for BitField types
+template <typename T>
+std::string BitfieldExtract(const std::string& source, T type)
+{
+  return StringFromFormat("bitfieldExtract(%s, %u, %u)", source.c_str(),
+                          static_cast<u32>(type.StartBit()), static_cast<u32>(type.NumBits()));
+}
+
+}  // namespace UberShader