Functions: make multi functions smaller and cheaper to construct in many cases

Previously, the signature of a `MultiFunction` was always embedded into the function.
There are two issues with that. First, `MFSignature` is relatively large, because it contains
multiple strings and vectors. Secondly, constructing it can add overhead that should not
be necessary, because often the same signature can be reused.

The solution is to only keep a pointer to a signature in `MultiFunction` that is set during
construction. Child classes are responsible for making sure that the signature lives
long enough. In most cases, the signature is either embedded into the child class or
it is allocated statically (and is only created once).

1 files changed, 35 insertions, 7 deletions

diff --git a/source/blender/functions/FN_multi_function_builder.hh b/source/blender/functions/FN_multi_function_builder.hh
index b73c41d3f59..389d0b14bb5 100644
--- a/source/blender/functions/FN_multi_function_builder.hh
+++ b/source/blender/functions/FN_multi_function_builder.hh
@@ -40,13 +40,16 @@ template<typename In1, typename Out1> class CustomMF_SI_SO : public MultiFunctio
  private:
   using FunctionT = std::function<void(IndexMask, const VArray<In1> &, MutableSpan<Out1>)>;
   FunctionT function_;
+  MFSignature signature_;
 
  public:
   CustomMF_SI_SO(StringRef name, FunctionT function) : function_(std::move(function))
   {
-    MFSignatureBuilder signature = this->get_builder(name);
+    MFSignatureBuilder signature{name};
     signature.single_input<In1>("In1");
     signature.single_output<Out1>("Out1");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   template<typename ElementFuncT>
@@ -83,14 +86,17 @@ class CustomMF_SI_SI_SO : public MultiFunction {
   using FunctionT =
       std::function<void(IndexMask, const VArray<In1> &, const VArray<In2> &, MutableSpan<Out1>)>;
   FunctionT function_;
+  MFSignature signature_;
 
  public:
   CustomMF_SI_SI_SO(StringRef name, FunctionT function) : function_(std::move(function))
   {
-    MFSignatureBuilder signature = this->get_builder(name);
+    MFSignatureBuilder signature{name};
     signature.single_input<In1>("In1");
     signature.single_input<In2>("In2");
     signature.single_output<Out1>("Out1");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   template<typename ElementFuncT>
@@ -135,15 +141,18 @@ class CustomMF_SI_SI_SI_SO : public MultiFunction {
                                        const VArray<In3> &,
                                        MutableSpan<Out1>)>;
   FunctionT function_;
+  MFSignature signature_;
 
  public:
   CustomMF_SI_SI_SI_SO(StringRef name, FunctionT function) : function_(std::move(function))
   {
-    MFSignatureBuilder signature = this->get_builder(name);
+    MFSignatureBuilder signature{name};
     signature.single_input<In1>("In1");
     signature.single_input<In2>("In2");
     signature.single_input<In3>("In3");
     signature.single_output<Out1>("Out1");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   template<typename ElementFuncT>
@@ -193,16 +202,19 @@ class CustomMF_SI_SI_SI_SI_SO : public MultiFunction {
                                        const VArray<In4> &,
                                        MutableSpan<Out1>)>;
   FunctionT function_;
+  MFSignature signature_;
 
  public:
   CustomMF_SI_SI_SI_SI_SO(StringRef name, FunctionT function) : function_(std::move(function))
   {
-    MFSignatureBuilder signature = this->get_builder(name);
+    MFSignatureBuilder signature{name};
     signature.single_input<In1>("In1");
     signature.single_input<In2>("In2");
     signature.single_input<In3>("In3");
     signature.single_input<In4>("In4");
     signature.single_output<Out1>("Out1");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   template<typename ElementFuncT>
@@ -244,12 +256,15 @@ template<typename Mut1> class CustomMF_SM : public MultiFunction {
  private:
   using FunctionT = std::function<void(IndexMask, MutableSpan<Mut1>)>;
   FunctionT function_;
+  MFSignature signature_;
 
  public:
   CustomMF_SM(StringRef name, FunctionT function) : function_(std::move(function))
   {
-    MFSignatureBuilder signature = this->get_builder(name);
+    MFSignatureBuilder signature{name};
     signature.single_mutable<Mut1>("Mut1");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   template<typename ElementFuncT>
@@ -279,10 +294,17 @@ template<typename From, typename To> class CustomMF_Convert : public MultiFuncti
  public:
   CustomMF_Convert()
   {
+    static MFSignature signature = create_signature();
+    this->set_signature(&signature);
+  }
+
+  static MFSignature create_signature()
+  {
     std::string name = CPPType::get<From>().name() + " to " + CPPType::get<To>().name();
-    MFSignatureBuilder signature = this->get_builder(std::move(name));
+    MFSignatureBuilder signature{std::move(name)};
     signature.single_input<From>("Input");
     signature.single_output<To>("Output");
+    return signature.build();
   }
 
   void call(IndexMask mask, MFParams params, MFContext UNUSED(context)) const override
@@ -304,6 +326,7 @@ class CustomMF_GenericConstant : public MultiFunction {
  private:
   const CPPType &type_;
   const void *value_;
+  MFSignature signature_;
 
   template<typename T> friend class CustomMF_Constant;
 
@@ -321,6 +344,7 @@ class CustomMF_GenericConstant : public MultiFunction {
 class CustomMF_GenericConstantArray : public MultiFunction {
  private:
   GSpan array_;
+  MFSignature signature_;
 
  public:
   CustomMF_GenericConstantArray(GSpan array);
@@ -333,14 +357,17 @@ class CustomMF_GenericConstantArray : public MultiFunction {
 template<typename T> class CustomMF_Constant : public MultiFunction {
  private:
   T value_;
+  MFSignature signature_;
 
  public:
   template<typename U> CustomMF_Constant(U &&value) : value_(std::forward<U>(value))
   {
-    MFSignatureBuilder signature = this->get_builder("Constant");
+    MFSignatureBuilder signature{"Constant"};
     std::stringstream ss;
     ss << value_;
     signature.single_output<T>(ss.str());
+    signature_ = signature.build();
+    this->set_signature(&signature_);
   }
 
   void call(IndexMask mask, MFParams params, MFContext UNUSED(context)) const override
@@ -375,6 +402,7 @@ template<typename T> class CustomMF_Constant : public MultiFunction {
 class CustomMF_DefaultOutput : public MultiFunction {
  private:
   int output_amount_;
+  MFSignature signature_;
 
  public:
   CustomMF_DefaultOutput(StringRef name,