I find this :
https://dev.arma3.com/post/oprep-64-bit-executables
To make the transition as transparent for you as possible, we at least
made it so that no changes to scripts will be required. All you need to
do is build a 64-bit version of your extension and name it
<yourExtension>_x64.dll on Windows (or
<yourExtension>_x64.so on Linux). In other words, you add the
"_x64" suffix to the name.