diff --git a/Source/Core/InputCommon/CMakeLists.txt b/Source/Core/InputCommon/CMakeLists.txt
index df8fa6423c..b47503a9ae 100644
--- a/Source/Core/InputCommon/CMakeLists.txt
+++ b/Source/Core/InputCommon/CMakeLists.txt
@@ -45,6 +45,8 @@ add_library(inputcommon
   ControlReference/ControlReference.h
   ControlReference/ExpressionParser.cpp
   ControlReference/ExpressionParser.h
+  ControlReference/FunctionExpression.cpp
+  ControlReference/FunctionExpression.h
 )
 
 target_link_libraries(inputcommon PUBLIC
diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
index 1c9ea370ce..b0704d3d8d 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
@@ -2,29 +2,24 @@
 // Licensed under GPLv2+
 // Refer to the license.txt file included.
 
-#include <algorithm>
 #include <cassert>
-#include <chrono>
 #include <cmath>
 #include <iostream>
-#include <locale>
-#include <map>
 #include <memory>
 #include <regex>
 #include <string>
+#include <utility>
 #include <vector>
 
-#include "Common/MathUtil.h"
 #include "Common/StringUtil.h"
+
 #include "InputCommon/ControlReference/ExpressionParser.h"
+#include "InputCommon/ControlReference/FunctionExpression.h"
 
 namespace ciface::ExpressionParser
 {
 using namespace ciface::Core;
 
-constexpr int LOOP_MAX_REPS = 10000;
-constexpr ControlState CONDITION_THRESHOLD = 0.5;
-
 enum TokenType
 {
   TOK_DISCARD,
@@ -420,253 +415,6 @@ public:
   }
 };
 
-class FunctionExpression : public Expression
-{
-public:
-  int CountNumControls() const override
-  {
-    int result = 0;
-
-    for (auto& arg : m_args)
-      result += arg->CountNumControls();
-
-    return result;
-  }
-
-  void UpdateReferences(ControlEnvironment& env) override
-  {
-    for (auto& arg : m_args)
-      arg->UpdateReferences(env);
-  }
-
-  operator std::string() const override
-  {
-    std::string result = '!' + GetFuncName();
-
-    for (auto& arg : m_args)
-      result += ' ' + static_cast<std::string>(*arg);
-
-    return result;
-  }
-
-  bool SetArguments(std::vector<std::unique_ptr<Expression>>&& args)
-  {
-    m_args = std::move(args);
-
-    return ValidateArguments(m_args);
-  }
-
-protected:
-  virtual std::string GetFuncName() const = 0;
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) = 0;
-
-  Expression& GetArg(u32 number) { return *m_args[number]; }
-  const Expression& GetArg(u32 number) const { return *m_args[number]; }
-
-private:
-  std::vector<std::unique_ptr<Expression>> m_args;
-};
-
-// TODO: Return an oscillating value to make it apparent something was spelled wrong?
-class UnknownFunctionExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return false;
-  }
-  ControlState GetValue() const override { return 0.0; }
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "unknown"; }
-};
-
-class ToggleExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 1 == args.size();
-  }
-
-  ControlState GetValue() const override
-  {
-    const ControlState inner_value = GetArg(0).GetValue();
-
-    if (inner_value < CONDITION_THRESHOLD)
-    {
-      m_released = true;
-    }
-    else if (m_released && inner_value > CONDITION_THRESHOLD)
-    {
-      m_released = false;
-      m_state ^= true;
-    }
-
-    return m_state;
-  }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "toggle"; }
-
-  mutable bool m_released{};
-  mutable bool m_state{};
-};
-
-class NotExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 1 == args.size();
-  }
-
-  ControlState GetValue() const override { return 1.0 - GetArg(0).GetValue(); }
-  void SetValue(ControlState value) override { GetArg(0).SetValue(1.0 - value); }
-  std::string GetFuncName() const override { return ""; }
-};
-
-class SinExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 1 == args.size();
-  }
-
-  ControlState GetValue() const override { return std::sin(GetArg(0).GetValue()); }
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "sin"; }
-};
-
-class TimerExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 1 == args.size();
-  }
-
-  ControlState GetValue() const override
-  {
-    const auto now = Clock::now();
-    const auto elapsed = now - m_start_time;
-
-    using FSec = std::chrono::duration<ControlState>;
-
-    const ControlState val = GetArg(0).GetValue();
-
-    ControlState progress = std::chrono::duration_cast<FSec>(elapsed).count() / val;
-
-    if (std::isinf(progress))
-    {
-      // User configured a 0.0 length timer. Reset the timer and return 0.0.
-      progress = 0.0;
-      m_start_time = now;
-    }
-    else if (progress >= 1.0)
-    {
-      const ControlState reset_count = std::floor(progress);
-
-      m_start_time += std::chrono::duration_cast<Clock::duration>(FSec(val * reset_count));
-      progress -= reset_count;
-    }
-
-    return progress;
-  }
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "timer"; }
-
-private:
-  using Clock = std::chrono::steady_clock;
-  mutable Clock::time_point m_start_time = Clock::now();
-};
-
-class IfExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 3 == args.size();
-  }
-
-  ControlState GetValue() const override
-  {
-    return (GetArg(0).GetValue() > CONDITION_THRESHOLD) ? GetArg(1).GetValue() :
-                                                          GetArg(2).GetValue();
-  }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "if"; }
-};
-
-class UnaryMinusExpression : public FunctionExpression
-{
-private:
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 1 == args.size();
-  }
-
-  ControlState GetValue() const override
-  {
-    // Subtraction for clarity:
-    return 0.0 - GetArg(0).GetValue();
-  }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "minus"; }
-};
-
-class WhileExpression : public FunctionExpression
-{
-  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
-  {
-    return 2 == args.size();
-  }
-
-  ControlState GetValue() const override
-  {
-    // Returns 1.0 on successful loop, 0.0 on reps exceeded. Sensible?
-
-    for (int i = 0; i != LOOP_MAX_REPS; ++i)
-    {
-      // Check condition of 1st argument:
-      const ControlState val = GetArg(0).GetValue();
-      if (val < CONDITION_THRESHOLD)
-        return 1.0;
-
-      // Evaluate 2nd argument:
-      GetArg(1).GetValue();
-    }
-
-    // Exceeded max reps:
-    return 0.0;
-  }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "while"; }
-};
-
-std::unique_ptr<FunctionExpression> MakeFunctionExpression(std::string name)
-{
-  if (name.empty())
-    return std::make_unique<NotExpression>();
-  else if ("if" == name)
-    return std::make_unique<IfExpression>();
-  else if ("sin" == name)
-    return std::make_unique<SinExpression>();
-  else if ("timer" == name)
-    return std::make_unique<TimerExpression>();
-  else if ("toggle" == name)
-    return std::make_unique<ToggleExpression>();
-  else if ("while" == name)
-    return std::make_unique<WhileExpression>();
-  else if ("minus" == name)
-    return std::make_unique<UnaryMinusExpression>();
-  else
-    return std::make_unique<UnknownFunctionExpression>();
-}
-
 class LiteralExpression : public Expression
 {
 public:
diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.h b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
index d9f7a5eb2b..0cb84af5cd 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.h
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
@@ -7,7 +7,7 @@
 #include <map>
 #include <memory>
 #include <string>
-#include <utility>
+
 #include "InputCommon/ControllerInterface/Device.h"
 
 namespace ciface::ExpressionParser
diff --git a/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp b/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp
new file mode 100644
index 0000000000..15a66ec9d1
--- /dev/null
+++ b/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp
@@ -0,0 +1,261 @@
+// Copyright 2019 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <chrono>
+#include <cmath>
+
+#include "InputCommon/ControlReference/FunctionExpression.h"
+
+namespace ciface
+{
+namespace ExpressionParser
+{
+constexpr int LOOP_MAX_REPS = 10000;
+constexpr ControlState CONDITION_THRESHOLD = 0.5;
+
+// TODO: Return an oscillating value to make it apparent something was spelled wrong?
+class UnknownFunctionExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return false;
+  }
+  ControlState GetValue() const override { return 0.0; }
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "unknown"; }
+};
+
+class ToggleExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 1 == args.size();
+  }
+
+  ControlState GetValue() const override
+  {
+    const ControlState inner_value = GetArg(0).GetValue();
+
+    if (inner_value < CONDITION_THRESHOLD)
+    {
+      m_released = true;
+    }
+    else if (m_released && inner_value > CONDITION_THRESHOLD)
+    {
+      m_released = false;
+      m_state ^= true;
+    }
+
+    return m_state;
+  }
+
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "toggle"; }
+
+  mutable bool m_released{};
+  mutable bool m_state{};
+};
+
+class NotExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 1 == args.size();
+  }
+
+  ControlState GetValue() const override { return 1.0 - GetArg(0).GetValue(); }
+  void SetValue(ControlState value) override { GetArg(0).SetValue(1.0 - value); }
+  std::string GetFuncName() const override { return ""; }
+};
+
+class SinExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 1 == args.size();
+  }
+
+  ControlState GetValue() const override { return std::sin(GetArg(0).GetValue()); }
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "sin"; }
+};
+
+class TimerExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 1 == args.size();
+  }
+
+  ControlState GetValue() const override
+  {
+    const auto now = Clock::now();
+    const auto elapsed = now - m_start_time;
+
+    using FSec = std::chrono::duration<ControlState>;
+
+    const ControlState val = GetArg(0).GetValue();
+
+    ControlState progress = std::chrono::duration_cast<FSec>(elapsed).count() / val;
+
+    if (std::isinf(progress))
+    {
+      // User configured a 0.0 length timer. Reset the timer and return 0.0.
+      progress = 0.0;
+      m_start_time = now;
+    }
+    else if (progress >= 1.0)
+    {
+      const ControlState reset_count = std::floor(progress);
+
+      m_start_time += std::chrono::duration_cast<Clock::duration>(FSec(val * reset_count));
+      progress -= reset_count;
+    }
+
+    return progress;
+  }
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "timer"; }
+
+private:
+  using Clock = std::chrono::steady_clock;
+  mutable Clock::time_point m_start_time = Clock::now();
+};
+
+class IfExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 3 == args.size();
+  }
+
+  ControlState GetValue() const override
+  {
+    return (GetArg(0).GetValue() > CONDITION_THRESHOLD) ? GetArg(1).GetValue() :
+                                                          GetArg(2).GetValue();
+  }
+
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "if"; }
+};
+
+class UnaryMinusExpression : public FunctionExpression
+{
+private:
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 1 == args.size();
+  }
+
+  ControlState GetValue() const override
+  {
+    // Subtraction for clarity:
+    return 0.0 - GetArg(0).GetValue();
+  }
+
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "minus"; }
+};
+
+class WhileExpression : public FunctionExpression
+{
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
+  {
+    return 2 == args.size();
+  }
+
+  ControlState GetValue() const override
+  {
+    // Returns 1.0 on successful loop, 0.0 on reps exceeded. Sensible?
+
+    for (int i = 0; i != LOOP_MAX_REPS; ++i)
+    {
+      // Check condition of 1st argument:
+      const ControlState val = GetArg(0).GetValue();
+      if (val < CONDITION_THRESHOLD)
+        return 1.0;
+
+      // Evaluate 2nd argument:
+      GetArg(1).GetValue();
+    }
+
+    // Exceeded max reps:
+    return 0.0;
+  }
+
+  void SetValue(ControlState value) override {}
+  std::string GetFuncName() const override { return "while"; }
+};
+
+std::unique_ptr<FunctionExpression> MakeFunctionExpression(std::string name)
+{
+  if (name.empty())
+    return std::make_unique<NotExpression>();
+  else if ("if" == name)
+    return std::make_unique<IfExpression>();
+  else if ("sin" == name)
+    return std::make_unique<SinExpression>();
+  else if ("timer" == name)
+    return std::make_unique<TimerExpression>();
+  else if ("toggle" == name)
+    return std::make_unique<ToggleExpression>();
+  else if ("while" == name)
+    return std::make_unique<WhileExpression>();
+  else if ("minus" == name)
+    return std::make_unique<UnaryMinusExpression>();
+  else
+    return std::make_unique<UnknownFunctionExpression>();
+}
+
+int FunctionExpression::CountNumControls() const
+{
+  int result = 0;
+
+  for (auto& arg : m_args)
+    result += arg->CountNumControls();
+
+  return result;
+}
+
+void FunctionExpression::UpdateReferences(ControlEnvironment& env)
+{
+  for (auto& arg : m_args)
+    arg->UpdateReferences(env);
+}
+
+FunctionExpression::operator std::string() const
+{
+  std::string result = '!' + GetFuncName();
+
+  for (auto& arg : m_args)
+    result += ' ' + static_cast<std::string>(*arg);
+
+  return result;
+}
+
+bool FunctionExpression::SetArguments(std::vector<std::unique_ptr<Expression>>&& args)
+{
+  m_args = std::move(args);
+
+  return ValidateArguments(m_args);
+}
+
+Expression& FunctionExpression::GetArg(u32 number)
+{
+  return *m_args[number];
+}
+
+const Expression& FunctionExpression::GetArg(u32 number) const
+{
+  return *m_args[number];
+}
+
+}  // namespace ExpressionParser
+}  // namespace ciface
diff --git a/Source/Core/InputCommon/ControlReference/FunctionExpression.h b/Source/Core/InputCommon/ControlReference/FunctionExpression.h
new file mode 100644
index 0000000000..8ac7e9800c
--- /dev/null
+++ b/Source/Core/InputCommon/ControlReference/FunctionExpression.h
@@ -0,0 +1,41 @@
+// Copyright 2019 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "InputCommon/ControlReference/ExpressionParser.h"
+#include "InputCommon/ControlReference/FunctionExpression.h"
+
+namespace ciface
+{
+namespace ExpressionParser
+{
+class FunctionExpression : public Expression
+{
+public:
+  int CountNumControls() const override;
+  void UpdateReferences(ControlEnvironment& env) override;
+  operator std::string() const override;
+
+  bool SetArguments(std::vector<std::unique_ptr<Expression>>&& args);
+
+protected:
+  virtual std::string GetFuncName() const = 0;
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) = 0;
+
+  Expression& GetArg(u32 number);
+  const Expression& GetArg(u32 number) const;
+
+private:
+  std::vector<std::unique_ptr<Expression>> m_args;
+};
+
+std::unique_ptr<FunctionExpression> MakeFunctionExpression(std::string name);
+
+}  // namespace ExpressionParser
+}  // namespace ciface
diff --git a/Source/Core/InputCommon/InputCommon.vcxproj b/Source/Core/InputCommon/InputCommon.vcxproj
index 8d0b0b3759..a22ad21394 100644
--- a/Source/Core/InputCommon/InputCommon.vcxproj
+++ b/Source/Core/InputCommon/InputCommon.vcxproj
@@ -64,6 +64,7 @@
     <ClCompile Include="ControllerInterface\ForceFeedback\ForceFeedbackDevice.cpp" />
     <ClCompile Include="ControllerInterface\Win32\Win32.cpp" />
     <ClCompile Include="ControllerInterface\XInput\XInput.cpp" />
+    <ClCompile Include="ControlReference\FunctionExpression.cpp" />
     <ClCompile Include="GCAdapter.cpp">
       <!--
       Disable "nonstandard extension used : zero-sized array in struct/union" warning,
@@ -100,6 +101,7 @@
     <ClInclude Include="ControllerInterface\DInput\DInputKeyboardMouse.h" />
     <ClInclude Include="ControllerInterface\DInput\XInputFilter.h" />
     <ClInclude Include="ControlReference\ControlReference.h" />
+    <ClInclude Include="ControlReference\FunctionExpression.h" />
     <ClInclude Include="ControlReference\ExpressionParser.h" />
     <ClInclude Include="ControllerInterface\ForceFeedback\ForceFeedbackDevice.h" />
     <ClInclude Include="ControllerInterface\Win32\Win32.h" />
diff --git a/Source/Core/InputCommon/InputCommon.vcxproj.filters b/Source/Core/InputCommon/InputCommon.vcxproj.filters
index 76195f5627..c1f26d6141 100644
--- a/Source/Core/InputCommon/InputCommon.vcxproj.filters
+++ b/Source/Core/InputCommon/InputCommon.vcxproj.filters
@@ -113,6 +113,9 @@
     <ClCompile Include="ControlReference\ControlReference.cpp">
       <Filter>ControllerInterface</Filter>
     </ClCompile>
+    <ClCompile Include="ControlReference\FunctionExpression.cpp">
+      <Filter>ControllerInterface</Filter>
+    </ClCompile>
     <ClCompile Include="InputProfile.cpp" />
     <ClCompile Include="ControllerEmu\ControlGroup\Attachments.cpp">
       <Filter>ControllerEmu\ControlGroup</Filter>
@@ -206,6 +209,9 @@
     <ClInclude Include="ControlReference\ControlReference.h">
       <Filter>ControllerInterface</Filter>
     </ClInclude>
+    <ClCompile Include="ControlReference\FunctionExpression.h">
+      <Filter>ControllerInterface</Filter>
+    </ClCompile>
     <ClInclude Include="InputProfile.h" />
     <ClInclude Include="ControllerEmu\ControlGroup\Attachments.h">
       <Filter>ControllerEmu\ControlGroup</Filter>