Fix xnnpack pybind (#2802)

Summary:
Fixing XNNPACK Pybind.

Currently pybindings for xnnpack fail due to uninitialized error. We notice the following:
```
(gdb) info symbol xnn_initialize
xnn_initialize in section .text of /home/maxren/.conda/envs/executorch/lib/python3.10/site-packages/torch/lib/libtorch_cpu.so
(gdb) info symbol xnn_create_subgraph
xnn_create_subgraph in section .text of /home/maxren/.conda/envs/executorch/lib/python3.10/site-packages/executorch/extension/pybindings/portable_lib.cpython-310-x86_64-linux-gnu.so
```

That is xnn_initialize symbole comes from libtorch_cpu, but when we call xnn_create_subgraph we call it from another library. It seems like explicitly adding XNNPACK to the portable_libs pybind fixes this problem.

Additionaly, we fix some fPIC issues when building XNNPACK.

Pull Request resolved: #2802

Reviewed By: larryliu0820

Differential Revision: D55646601

Pulled By: mcr229

fbshipit-source-id: cf18de3246c9fdde4c08326c400d19cd407720e1

.github/workflows/_unittest.yml

@@ -37,6 +37,7 @@ jobs:
         # Setup MacOS dependencies as there is no Docker support on MacOS atm
         PYTHON_EXECUTABLE=python \
         EXECUTORCH_BUILD_PYBIND=ON \
+        EXECUTORCH_BUILD_XNNPACK=ON \
         .ci/scripts/setup-linux.sh "${BUILD_TOOL}"
 
         # Run pytest with coverage

.github/workflows/pull.yml

@@ -232,6 +232,7 @@ jobs:
         # build module for executorch.extension.pybindings.portable_lib
         BUILD_TOOL=${{ matrix.build-tool }}
         PYTHON_EXECUTABLE=python \
+        EXECUTORCH_BUILD_XNNPACK=ON \
         EXECUTORCH_BUILD_PYBIND=ON \
         bash .ci/scripts/setup-linux.sh "${BUILD_TOOL}"
 

CMakeLists.txt

@@ -508,7 +508,9 @@ if(EXECUTORCH_BUILD_PYBIND)
   endif()
 
   if(EXECUTORCH_BUILD_XNNPACK)
-    set(PYBIND_LINK_XNNPACK "xnnpack_backend")
+    # need to explicitly specify XNNPACK here
+    # otherwise uses XNNPACK symbols from libtorch_cpu
+    set(PYBIND_LINK_XNNPACK xnnpack_backend XNNPACK)
   endif()
 
   # find pytorch lib, to allow pybind to take at::Tensor as input/output

backends/xnnpack/CMakeLists.txt

@@ -33,7 +33,7 @@ if(NOT PYTHON_EXECUTABLE)
 endif()
 
 set(_common_include_directories ${EXECUTORCH_ROOT}/..)
-set(_common_compile_options -Wno-deprecated-declarations)
+set(_common_compile_options -Wno-deprecated-declarations -fPIC)
 
 set(_xnnpack_schema__include_dir "${CMAKE_BINARY_DIR}/schema/include")
 # Paths to headers generated from the .fbs files.
@@ -72,7 +72,7 @@ target_include_directories(
   xnnpack_schema INTERFACE ${_xnnpack_schema__include_dir}
                            ${EXECUTORCH_ROOT}/third-party/flatbuffers/include)
 
-set(xnnpack_third_party)
+set(xnnpack_third_party pthreadpool cpuinfo)
 
 include(cmake/Dependencies.cmake)
 
@@ -105,8 +105,7 @@ if(NOT CMAKE_TOOLCHAIN_FILE MATCHES ".*iOS\.cmake$")
   list(TRANSFORM _xnn_executor_runner__srcs PREPEND "${EXECUTORCH_ROOT}/")
   add_executable(xnn_executor_runner ${_xnn_executor_runner__srcs})
   target_link_libraries(xnn_executor_runner
-                        xnnpack_backend gflags portable_ops_lib
-                        pthreadpool cpuinfo)
+                        xnnpack_backend gflags portable_ops_lib)
   target_compile_options(xnn_executor_runner PUBLIC ${_common_compile_options})
 endif()
 

backends/xnnpack/cmake/Dependencies.cmake

@@ -9,6 +9,13 @@
 set(THIRD_PARTY_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/third-party")
 
 # --- XNNPACK
+
+# Setting this global PIC flag for all XNNPACK targets.
+# This is needed for Object libraries within XNNPACK which must
+# be PIC to successfully link this static libXNNPACK
+set(ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG ${CMAKE_POSITION_INDEPENDENT_CODE})
+set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+
 set(XNNPACK_SOURCE_DIR "${THIRD_PARTY_ROOT}/XNNPACK")
 set(XNNPACK_INCLUDE_DIR "${XNNPACK_SOURCE_DIR}/include")
 set(XNNPACK_LIBRARY_TYPE "static" CACHE STRING "")
@@ -18,3 +25,6 @@ set(XNNPACK_ENABLE_AVXVNNI OFF CACHE BOOL "")
 add_subdirectory("${XNNPACK_SOURCE_DIR}")
 include_directories(SYSTEM ${XNNPACK_INCLUDE_DIR})
 list(APPEND xnnpack_third_party XNNPACK)
+
+# Revert PIC Flag to what it originally was
+set(CMAKE_POSITION_INDEPENDENT_CODE ${ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG})

pytest.ini

@@ -36,6 +36,8 @@ addopts =
     kernels/test/test_case_gen.py
     # backends/arm
     backends/arm/test
+    # backends/xnnpack
+    backends/xnnpack/test/models
     # test
     test/end2end/test_end2end.py