Attributes: Avoid unnecessarily initializing new attributes

The "write_only" (i.e. no reading) API function expects the caller to
set values for all new attribute elements, so using calloc or setting
 the default value first is redundant. In theory this can improve
performance by avoiding an extra pass over the array. I observed a
6% improvement in a basic test with the mesh to points node:
from 47.9ms to 45ms on average.

See 25237d2625078c6d for more info.
Similar to cccc6d6905be7ac.

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/attribute_access.cc b/source/blender/blenkernel/intern/attribute_access.cc
index aed55c5db45..0187dbd6f78 100644
--- a/source/blender/blenkernel/intern/attribute_access.cc
+++ b/source/blender/blenkernel/intern/attribute_access.cc
@@ -966,7 +966,8 @@ GSpanAttributeWriter MutableAttributeAccessor::lookup_or_add_for_write_span(
 GSpanAttributeWriter MutableAttributeAccessor::lookup_or_add_for_write_only_span(
     const AttributeIDRef &attribute_id, const eAttrDomain domain, const eCustomDataType data_type)
 {
-  GAttributeWriter attribute = this->lookup_or_add_for_write(attribute_id, domain, data_type);
+  GAttributeWriter attribute = this->lookup_or_add_for_write(
+      attribute_id, domain, data_type, AttributeInitConstruct());
   if (attribute) {
     return GSpanAttributeWriter{std::move(attribute), false};
   }