Functions: use static names for multi-functions

Previously, the function names were stored in `std::string` and were often
created dynamically (especially when the function just output a constant).
This resulted in a lot of overhead.

Now the function name is just a `const char *` that should be statically
allocated. This is good enough for the majority of cases. If a multi-function
needs a more dynamic name, it can override the `MultiFunction::debug_name`
method.

In my test file with >400,000 simple math nodes, the execution time improves from
3s to 1s.

2 files changed, 16 insertions, 13 deletions

diff --git a/source/blender/nodes/shader/nodes/node_shader_math.cc b/source/blender/nodes/shader/nodes/node_shader_math.cc
index 284a5f1189f..1e94148c5c7 100644
--- a/source/blender/nodes/shader/nodes/node_shader_math.cc
+++ b/source/blender/nodes/shader/nodes/node_shader_math.cc
@@ -88,7 +88,8 @@ static const blender::fn::MultiFunction *get_base_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl_to_fl(
       mode, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SO<float, float> fn{info.title_case_name, function};
+        static blender::fn::CustomMF_SI_SO<float, float> fn{info.title_case_name.c_str(),
+                                                            function};
         base_fn = &fn;
       });
   if (base_fn != nullptr) {
@@ -97,7 +98,7 @@ static const blender::fn::MultiFunction *get_base_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl_fl_to_fl(
       mode, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SI_SO<float, float, float> fn{info.title_case_name,
+        static blender::fn::CustomMF_SI_SI_SO<float, float, float> fn{info.title_case_name.c_str(),
                                                                       function};
         base_fn = &fn;
       });
@@ -108,7 +109,7 @@ static const blender::fn::MultiFunction *get_base_multi_function(bNode &node)
   blender::nodes::try_dispatch_float_math_fl_fl_fl_to_fl(
       mode, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
         static blender::fn::CustomMF_SI_SI_SI_SO<float, float, float, float> fn{
-            info.title_case_name, function};
+            info.title_case_name.c_str(), function};
         base_fn = &fn;
       });
   if (base_fn != nullptr) {
diff --git a/source/blender/nodes/shader/nodes/node_shader_vector_math.cc b/source/blender/nodes/shader/nodes/node_shader_vector_math.cc
index fad93962708..9b1b2467230 100644
--- a/source/blender/nodes/shader/nodes/node_shader_vector_math.cc
+++ b/source/blender/nodes/shader/nodes/node_shader_vector_math.cc
@@ -201,8 +201,8 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl3_fl3_to_fl3(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SI_SO<float3, float3, float3> fn{info.title_case_name,
-                                                                         function};
+        static blender::fn::CustomMF_SI_SI_SO<float3, float3, float3> fn{
+            info.title_case_name.c_str(), function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -212,7 +212,7 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
   blender::nodes::try_dispatch_float_math_fl3_fl3_fl3_to_fl3(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
         static blender::fn::CustomMF_SI_SI_SI_SO<float3, float3, float3, float3> fn{
-            info.title_case_name, function};
+            info.title_case_name.c_str(), function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -222,7 +222,7 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
   blender::nodes::try_dispatch_float_math_fl3_fl3_fl_to_fl3(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
         static blender::fn::CustomMF_SI_SI_SI_SO<float3, float3, float, float3> fn{
-            info.title_case_name, function};
+            info.title_case_name.c_str(), function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -231,8 +231,8 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl3_fl3_to_fl(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SI_SO<float3, float3, float> fn{info.title_case_name,
-                                                                        function};
+        static blender::fn::CustomMF_SI_SI_SO<float3, float3, float> fn{
+            info.title_case_name.c_str(), function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -241,8 +241,8 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl3_fl_to_fl3(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SI_SO<float3, float, float3> fn{info.title_case_name,
-                                                                        function};
+        static blender::fn::CustomMF_SI_SI_SO<float3, float, float3> fn{
+            info.title_case_name.c_str(), function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -251,7 +251,8 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl3_to_fl3(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SO<float3, float3> fn{info.title_case_name, function};
+        static blender::fn::CustomMF_SI_SO<float3, float3> fn{info.title_case_name.c_str(),
+                                                              function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {
@@ -260,7 +261,8 @@ static const blender::fn::MultiFunction *get_multi_function(bNode &node)
 
   blender::nodes::try_dispatch_float_math_fl3_to_fl(
       operation, [&](auto function, const blender::nodes::FloatMathOperationInfo &info) {
-        static blender::fn::CustomMF_SI_SO<float3, float> fn{info.title_case_name, function};
+        static blender::fn::CustomMF_SI_SO<float3, float> fn{info.title_case_name.c_str(),
+                                                             function};
         multi_fn = &fn;
       });
   if (multi_fn != nullptr) {