Geometry Nodes: refactor array devirtualization

Goals:
* Better high level control over where devirtualization occurs. There is always
  a trade-off between performance and compile-time/binary-size.
* Simplify using array devirtualization.
* Better performance for cases where devirtualization wasn't used before.

Many geometry nodes accept fields as inputs. Internally, that means that the
execution functions have to accept so called "virtual arrays" as inputs. Those
 can be e.g. actual arrays, just single values, or lazily computed arrays.
Due to these different possible virtual arrays implementations, access to
individual elements is slower than it would be if everything was just a normal
array (access does through a virtual function call). For more complex execution
functions, this overhead does not matter, but for small functions (like a simple
addition) it very much does. The virtual function call also prevents the compiler
from doing some optimizations (e.g. loop unrolling and inserting simd instructions).

The solution is to "devirtualize" the virtual arrays for small functions where the
overhead is measurable. Essentially, the function is generated many times with
different array types as input. Then there is a run-time dispatch that calls the
best implementation. We have been doing devirtualization in e.g. math nodes
for a long time already. This patch just generalizes the concept and makes it
easier to control. It also makes it easier to investigate the different trade-offs
when it comes to devirtualization.

Nodes that we've optimized using devirtualization before didn't get a speedup.
However, a couple of nodes are using devirtualization now, that didn't before.
Those got a 2-4x speedup in common cases.
* Map Range
* Random Value
* Switch
* Combine XYZ

Differential Revision: https://developer.blender.org/D14628

3 files changed, 13 insertions, 13 deletions

diff --git a/source/blender/functions/intern/multi_function.cc b/source/blender/functions/intern/multi_function.cc
index 6a9cb9c424c..c05087a4c2d 100644
--- a/source/blender/functions/intern/multi_function.cc
+++ b/source/blender/functions/intern/multi_function.cc
@@ -96,18 +96,18 @@ void MultiFunction::call_auto(IndexMask mask, MFParams params, MFContext context
     for (const int param_index : this->param_indices()) {
       const MFParamType param_type = this->param_type(param_index);
       switch (param_type.category()) {
-        case MFParamType::SingleInput: {
+        case MFParamCategory::SingleInput: {
           const GVArray &varray = params.readonly_single_input(param_index);
           offset_params.add_readonly_single_input(varray.slice(input_slice_range));
           break;
         }
-        case MFParamType::SingleMutable: {
+        case MFParamCategory::SingleMutable: {
           const GMutableSpan span = params.single_mutable(param_index);
           const GMutableSpan sliced_span = span.slice(input_slice_range);
           offset_params.add_single_mutable(sliced_span);
           break;
         }
-        case MFParamType::SingleOutput: {
+        case MFParamCategory::SingleOutput: {
           const GMutableSpan span = params.uninitialized_single_output_if_required(param_index);
           if (span.is_empty()) {
             offset_params.add_ignored_single_output();
@@ -118,9 +118,9 @@ void MultiFunction::call_auto(IndexMask mask, MFParams params, MFContext context
           }
           break;
         }
-        case MFParamType::VectorInput:
-        case MFParamType::VectorMutable:
-        case MFParamType::VectorOutput: {
+        case MFParamCategory::VectorInput:
+        case MFParamCategory::VectorMutable:
+        case MFParamCategory::VectorOutput: {
           BLI_assert_unreachable();
           break;
         }
diff --git a/source/blender/functions/intern/multi_function_procedure.cc b/source/blender/functions/intern/multi_function_procedure.cc
index 6655e051723..bc045bfd44b 100644
--- a/source/blender/functions/intern/multi_function_procedure.cc
+++ b/source/blender/functions/intern/multi_function_procedure.cc
@@ -314,7 +314,7 @@ bool MFProcedure::validate_all_params_provided() const
     const MultiFunction &fn = instruction->fn();
     for (const int param_index : fn.param_indices()) {
       const MFParamType param_type = fn.param_type(param_index);
-      if (param_type.category() == MFParamType::SingleOutput) {
+      if (param_type.category() == MFParamCategory::SingleOutput) {
         /* Single outputs are optional. */
         continue;
       }
diff --git a/source/blender/functions/intern/multi_function_procedure_executor.cc b/source/blender/functions/intern/multi_function_procedure_executor.cc
index c58ca0bb8fd..d852fe19924 100644
--- a/source/blender/functions/intern/multi_function_procedure_executor.cc
+++ b/source/blender/functions/intern/multi_function_procedure_executor.cc
@@ -854,32 +854,32 @@ class VariableStates {
       };
 
       switch (param_type.category()) {
-        case MFParamType::SingleInput: {
+        case MFParamCategory::SingleInput: {
           const GVArray &data = params.readonly_single_input(param_index);
           add_state(value_allocator_.obtain_GVArray(data), true);
           break;
         }
-        case MFParamType::VectorInput: {
+        case MFParamCategory::VectorInput: {
           const GVVectorArray &data = params.readonly_vector_input(param_index);
           add_state(value_allocator_.obtain_GVVectorArray(data), true);
           break;
         }
-        case MFParamType::SingleOutput: {
+        case MFParamCategory::SingleOutput: {
           GMutableSpan data = params.uninitialized_single_output(param_index);
           add_state(value_allocator_.obtain_Span_not_owned(data.data()), false, data.data());
           break;
         }
-        case MFParamType::VectorOutput: {
+        case MFParamCategory::VectorOutput: {
           GVectorArray &data = params.vector_output(param_index);
           add_state(value_allocator_.obtain_GVectorArray_not_owned(data), false, &data);
           break;
         }
-        case MFParamType::SingleMutable: {
+        case MFParamCategory::SingleMutable: {
           GMutableSpan data = params.single_mutable(param_index);
           add_state(value_allocator_.obtain_Span_not_owned(data.data()), true, data.data());
           break;
         }
-        case MFParamType::VectorMutable: {
+        case MFParamCategory::VectorMutable: {
           GVectorArray &data = params.vector_mutable(param_index);
           add_state(value_allocator_.obtain_GVectorArray_not_owned(data), true, &data);
           break;