[mlir][python][cmake] Allows for specifying NB_DOMAIN in add_mlir_python_extension

[erwei-xilinx]

This PR allows the users to specify the NB_DOMAIN for add_mlir_python_extension. This allows users to avoid nanobind domain conflicts, when python bindings from multiple mlir projects were imported. (https://nanobind.readthedocs.io/en/latest/faq.html#how-can-i-avoid-conflicts-with-other-projects-using-nanobind)

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[llvmbot]

@llvm/pr-subscribers-mlir

Author: None (erwei-xilinx)

Changes

This PR allows the users to specify the NB_DOMAIN for add_mlir_python_extension. This allows users to avoid nanobind domain conflicts, when python bindings from multiple mlir projects were imported. (https://nanobind.readthedocs.io/en/latest/faq.html#how-can-i-avoid-conflicts-with-other-projects-using-nanobind)

---

Full diff: https://github.com/llvm/llvm-project/pull/122865.diff

1 Files Affected:

• (modified) mlir/cmake/modules/AddMLIRPython.cmake (+8-1)

diff --git a/mlir/cmake/modules/AddMLIRPython.cmake b/mlir/cmake/modules/AddMLIRPython.cmake
index 0679db9cf93e19..82a93c1a3c78c9 100644
--- a/mlir/cmake/modules/AddMLIRPython.cmake
+++ b/mlir/cmake/modules/AddMLIRPython.cmake
@@ -658,6 +658,13 @@ function(add_mlir_python_extension libname extname)
     set(eh_rtti_enable -frtti -fexceptions)
   endif ()
 
+  # Avoids domain conflict with nanobind by specifying NB_DOMAIN.
+  if(NB_DOMAIN)
+    set(_nb_domain ${NB_DOMAIN})
+  else()
+    set(_nb_domain "mlir")
+  endif ()
+
   # The actual extension library produces a shared-object or DLL and has
   # sources that must be compiled in accordance with pybind11 needs (RTTI and
   # exceptions).
@@ -667,7 +674,7 @@ function(add_mlir_python_extension libname extname)
     )
   elseif(ARG_PYTHON_BINDINGS_LIBRARY STREQUAL "nanobind")
     nanobind_add_module(${libname}
-      NB_DOMAIN mlir
+      NB_DOMAIN ${_nb_domain}
       FREE_THREADED
       ${ARG_SOURCES}
     )

[erwei-xilinx]

@makslevental

[makslevental]

I prefer if this were an argument to add_mlir_python_extension rather than a global but maybe a global is fine? @jpienaar @hawkinsp what do you guys think?

Edit: hmm I guess (duh) you need to expose this to downstream people that are just building the upstream extension without using add_mlir_python_extension explicitly. So on second thought @erwei-xilinx can you please promote this to a full global called MLIR_BINDINGS_PYTHON_NB_DOMAIN with something like

set(MLIR_BINDINGS_PYTHON_NB_DOMAIN "mlir" 
  CACHE STRING "nanobind domain for MLIR python bindings")

You can put it right by MLIR_BINDINGS_PYTHON here https://github.com/llvm/llvm-project/blob/main/mlir/CMakeLists.txt#L177

[erwei-xilinx]

I prefer if this were an argument to add_mlir_python_extension rather than a global but maybe a global is fine? @jpienaar @hawkinsp what do you guys think?

Edit: hmm I guess (duh) you need to expose this to downstream people that are just building the upstream extension without using add_mlir_python_extension explicitly. So on second thought @erwei-xilinx can you please promote this to a full global called MLIR_BINDINGS_PYTHON_NB_DOMAIN with something like

Sure, makes sense. PR updated. Thanks for the comment.

[makslevental]

This isn't really needed anymore right? Can just move ${MLIR_BINDINGS_PYTHON_NB_DOMAIN} down to the nanobind_add_module call site.

[erwei-xilinx]

I think it is still needed. In our project when we directly call the add_mlir_python_module method, it didn't inherit the cache default in the MLIR build's CMakeCache. Instead the MLIR_BINDINGS_PYTHON_NB_DOMAIN global variable was left undefined.

I see your point. If called from outside then it's the caller's responsibility to supply reasonable variables.

[makslevental]

LGTM thanks

[makslevental]

@erwei-xilinx let me know if you need me to merge

[erwei-xilinx]

@erwei-xilinx let me know if you need me to merge

Yeah that would be great as I do not have permission to start the check nor merge the PR. Thanks!

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