[mlir][py] Fix python modules build with clang-cl due to requiring exceptions

[zero9178]

Summary

The generator expression previously used to enable exceptions would not work since the compiler id of clang-cl is Clang, even if used via clang-cl.

The patch fixes that by replacing the generator expression with simple logic, setting the right compiler flags for all MSVC like compilers (including clang-cl) and all GCC like compilers.

[stellaraccident]

mlir/cmake/modules/AddMLIRPython.cmake

613

I assume this variable is available when used out of tree but need to double check (and afk right now).

[zero9178]

mlir/cmake/modules/AddMLIRPython.cmake

613

Yes. MLIR does include(AddLLVM) in a standalone build which then has include(DetermineGCCComptaible) which sets this variable.
It is also used by other subprojects that that have working standalone builds.

[stellaraccident]

Perfect. Thanks for checking. Do you need help landing this patch?

[zero9178]

In D141155#4032488, @stellaraccident wrote:

Perfect. Thanks for checking. Do you need help landing this patch?

No, but thanks for asking!

[jpienaar]

Thanks!

mlir/cmake/modules/AddMLIRPython.cmake

function(add_mlir_python_extension libname extname)
   # sources that must be compiled in accordance with pybind11 needs (RTTI and
   # exceptions).
   pybind11_add_module(${libname}
     ${ARG_SOURCES}
   )
 
   # The extension itself must be compiled with RTTI and exceptions enabled.
   # Also, some warning classes triggered by pybind11 are disabled.
-  target_compile_options(${libname} PRIVATE
-    $<$<OR:$<CXX_COMPILER_ID:Clang>,$<CXX_COMPILER_ID:AppleClang>,$<CXX_COMPILER_ID:GNU>>:
-      # Enable RTTI and exceptions.
-      -frtti -fexceptions
-    >
-    $<$<CXX_COMPILER_ID:MSVC>:
-      # Enable RTTI and exceptions.
-      /EHsc /GR>
-  )
+  set(eh_rtti_enable)
+  if (MSVC)
+    set(eh_rtti_enable /EHsc /GR)
+  elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+    set(eh_rtti_enable -frtti -fexceptions)
+  endif ()
+  target_compile_options(${libname} PRIVATE ${eh_rtti_enable})
 
   # Configure the output to match python expectations.
   set_target_properties(
     ${libname} PROPERTIES
     LIBRARY_OUTPUT_DIRECTORY ${ARG_OUTPUT_DIRECTORY}
     OUTPUT_NAME "${extname}"
     NO_SONAME ON
   )