Fix multiple MKL targets

Author: huydhn

CMakeLists.txt

@@ -602,6 +602,13 @@ target_compile_definitions(executorch PUBLIC C10_USING_CUSTOM_GENERATED_MACROS)
 target_compile_options(executorch PUBLIC ${_common_compile_options})
 target_link_options_shared_lib(executorch)
 
+#
+# find pytorch lib here to make it available to all sub-directories, trying to
+# call find_package(Torch) multiple times doesn't work because it brings in MKL
+# which is defined once globally
+#
+find_package(Torch CONFIG REQUIRED)
+
 #
 # portable_ops_lib: A library to register core ATen ops using portable kernels,
 # see kernels/portable/CMakeLists.txt.
@@ -749,8 +756,7 @@ if(EXECUTORCH_BUILD_PYBIND)
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/devtools)
   endif()
 
-  # find pytorch lib, to allow pybind to take at::Tensor as input/output
-  find_package(Torch CONFIG REQUIRED)
+  # to allow pybind to take at::Tensor as input/output
   find_library(
     TORCH_PYTHON_LIBRARY torch_python PATHS "${TORCH_INSTALL_PREFIX}/lib"
   )

build/Codegen.cmake

@@ -146,7 +146,9 @@ function(gen_custom_ops_aot_lib)
     ${_out_dir}/CustomOpsNativeFunctions.h "${GEN_KERNEL_SOURCES}"
   )
   # Find `Torch`.
-  find_package(Torch REQUIRED)
+  if(NOT TARGET torch)
+    find_package(Torch REQUIRED)
+  endif()
   # This lib uses ATen lib, so we explicitly enable rtti and exceptions.
   target_compile_options(${GEN_LIB_NAME} PRIVATE -frtti -fexceptions)
   target_compile_definitions(${GEN_LIB_NAME} PRIVATE USE_ATEN_LIB=1)

extension/llm/custom_ops/CMakeLists.txt

@@ -69,7 +69,9 @@ install(TARGETS custom_ops DESTINATION lib)
 
 if(EXECUTORCH_BUILD_KERNELS_CUSTOM_AOT)
   # Add a AOT library
-  find_package(Torch CONFIG REQUIRED)
+  if(NOT TARGET torch)
+    find_package(Torch CONFIG REQUIRED)
+  endif()
   add_library(
     custom_ops_aot_lib SHARED
     ${_custom_ops__srcs}