Samsung AI LiteCore - buildsystem: separate backend and example builds. (pytorch#22582)

### Summary
To keep backend and example artifacts distinct.

AS-IS:
- The backend library and 'enn_executor_runner' were built together.
- The example artifact 'enn_executor_runner' was placed under
'backend/samsung', it is not proper location for example artifacts.
TO-BE:
- Build the backend library first, then let the example projects refer
to already-built backend library.
- Adjust CMakeLists so that 'enn_executor_runner' is compiled in the
'examples/samsung/' directory and its output is placed in there.


### Test plan
${EXECUTORCH_ROOT}/backends/samsung/build.sh -b all

cc @SS-JIA @digantdesai @kimishpatel

---------

Signed-off-by: Jiseong.oh <jiseong.oh@samsung.coms>
Signed-off-by: jiseong.oh <jiseong.oh@samsung.com>

Author: Jiseong-oh

.ci/scripts/setup-samsung-linux-deps.sh

@@ -165,6 +165,7 @@ install_enn_backend() {
   echo "NDK will be installed/used at: ${ANDROID_NDK_ROOT}"
 
   bash backends/samsung/build.sh --build all
+  bash examples/samsung/build.sh
 
   export EXECUTORCH_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
   export PYTHONPATH="${PYTHONPATH:-}:${EXECUTORCH_ROOT}/.."

backends/samsung/CMakeLists.txt

@@ -146,24 +146,6 @@ if(${ANDROID})
   executorch_target_link_options_shared_lib(enn_backend)
   target_compile_options(enn_backend PRIVATE -Wno-deprecated-declarations)
 
-  set(__enn_executor_runner_srcs
-      ${EXECUTORCH_SOURCE_DIR}/examples/samsung/executor_runner/enn_executor_runner.cpp
-  )
-  add_executable(enn_executor_runner ${__enn_executor_runner_srcs})
-  add_dependencies(enn_executor_runner enn_backend)
-  target_link_libraries(
-    enn_executor_runner
-    PRIVATE enn_logging
-            enn_backend
-            gflags
-            executorch
-            extension_data_loader
-            portable_ops_lib
-            android
-  )
-  set_target_properties(
-    enn_executor_runner PROPERTIES CXX_VISIBILITY_PRESET hidden
-  )
   install(
     TARGETS enn_backend enn_logging
     EXPORT ExecuTorchTargets

backends/samsung/README.md

@@ -49,13 +49,16 @@ Generates python artifacts that allow user call `Compile` interface to lower a m
 ./backends/samsung/build.sh -b x86_64
 ```
 
-### Build ENN Executor Runner
+### Build Backend Delegate
 ```bash
 ./backends/samsung/build.sh -b android --ndk ${ANDROID_NDK}
 ```
-ANDROID_ABI=arm64-v8a is default, necessary runtime executable generated in `build_exynos_android` directory.
+ANDROID_ABI=arm64-v8a is default, necessary runtime backend library generated in `build_samsung_android` directory.
 
-### Build Anroid Extension
+### Build Executable
+Please see the [README.md](../../examples/samsung/README.md).
+
+### Build Android Extension
 This is later exposed Java app. Please turn on CMake option `EXECUTORCH_BUILD_ENN`, and ENN runtime will be added.
 ```bash
 cmake extension/android \

backends/samsung/build.sh

@@ -66,7 +66,17 @@ function build_android() {
   ANDROID_ABI=arm64-v8a
   ANDROID_PLATFORM=android-28 # Trace requires over android-23
 
+  local host_flatcc=${X86_64_BUILD_DIR}/third-party/flatcc_ep/bin/flatcc
+  local flatcc_args=()
+  if [[ -x ${host_flatcc} ]]; then
+    flatcc_args=(-DFLATCC_EXECUTABLE=${host_flatcc})
+  else
+    echo "Warning: ${host_flatcc} not found. Build the x86_64 target first" \
+         "('-b x86_64' or '-b all') if executor_runner fails to link libflatccrt.a."
+  fi
+
   cmake \
+        "${flatcc_args[@]}" \
         -DCMAKE_INSTALL_PREFIX=${ANDROID_BUILD_DIR} \
         -DCMAKE_TOOLCHAIN_FILE="${ANDROID_NDK_ROOT}/build/cmake/android.toolchain.cmake" \
         -DANDROID_NDK=${ANDROID_NDK} \

backends/samsung/test/utils/runtime_executor.py

@@ -26,7 +26,7 @@ def get_runner_path() -> Path:
         cwd=os.path.dirname(os.path.realpath(__file__)),
         text=True,
     ).strip()
-    return Path(git_root) / "build_samsung_android/backends/samsung/enn_executor_runner"
+    return Path(git_root) / "build_samsung_android/examples/samsung/enn_executor_runner"
 
 
 class EDBTestManager:

examples/samsung/CMakeLists.txt

@@ -0,0 +1,61 @@
+# Copyright (c) 2025 Samsung Electronics Co. LTD
+# All rights reserved
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+cmake_minimum_required(VERSION 3.15)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+project(samsung_example)
+
+# Source root directory for executorch.
+if(NOT EXECUTORCH_ROOT)
+  set(EXECUTORCH_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../..)
+endif()
+
+include(${EXECUTORCH_ROOT}/tools/cmake/Utils.cmake)
+include(${EXECUTORCH_ROOT}/tools/cmake/Codegen.cmake)
+
+if(NOT PYTHON_EXECUTABLE)
+  resolve_python_executable()
+endif()
+
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE RelWithDebInfo)
+endif()
+
+if(CMAKE_TOOLCHAIN_FILE MATCHES ".*(iOS|ios\.toolchain)\.cmake$")
+  message(FATAL_ERROR "ios is not supported by Samsung AI system.")
+endif()
+
+# prebuilt libraries. executorch package should contain portable_ops_lib,
+# etdump, bundled_program.
+find_package(executorch CONFIG REQUIRED)
+target_compile_options(executorch INTERFACE -DET_EVENT_TRACER_ENABLED)
+find_package(gflags REQUIRED)
+
+set(_common_compile_options -Wno-deprecated-declarations -fPIC)
+
+add_compile_options(-Wall -Werror -fPIC)
+
+message("Build Samsung Android Examples")
+
+set(__enn_executor_runner__srcs
+    ${CMAKE_CURRENT_LIST_DIR}/executor_runner/enn_executor_runner.cpp
+)
+
+add_executable(enn_executor_runner ${__enn_executor_runner__srcs})
+
+target_include_directories(enn_executor_runner PRIVATE ${EXECUTORCH_ROOT}/..)
+
+target_compile_options(enn_executor_runner PRIVATE ${_common_compile_options})
+
+target_link_libraries(
+  enn_executor_runner PRIVATE enn_logging enn_backend gflags executorch
+                              extension_data_loader portable_ops_lib
+)
+
+set_target_properties(
+  enn_executor_runner PROPERTIES CXX_VISIBILITY_PRESET hidden
+)

examples/samsung/README.md

@@ -1,9 +1,9 @@
-# Exynos backend Examples
+# Exynos Backend examples
 
 This directory contains examples for some AI models.
 
-Please make sure you have built the library and executable before
-you start, if you have no idea how to build, please refer to [backend README](../../backends/samsung/README.md).
+Please make sure you have built the library before you start,
+if you have no idea how to build, please refer to [backend README](../../backends/samsung/README.md).
 
 ## Environment
 We set up `PYTHONPATH` because it's easier to develop and import executorch Python APIs.
@@ -42,15 +42,26 @@ Examples use "PerformanceMode.HIGH_PERFORMANCE" mode, this mode is experimental.
 If you want to use this mode on your model, verify your model on devicefarm which can use samsung developer society site
 firstly for checking stability. (https://soc-developer.semiconductor.samsung.com/)
 
+## Building Executable
+### Prerequisites
+Please set up the backend before building the executable, See the [backend README](../../backends/samsung/README.md) for details.
+### Building 'enn_executor_runner' for Android
+```bash
+export EXYNOS_AI_LITECORE_ROOT=/path/to/enn_sdk
+export ANDROID_NDK_ROOT=/path/to/android_ndk
+${EXECUTORCH_ROOT}/examples/samsung/build.sh
+```
+After the build completes, `enn_executor_runner` can be found at `${EXECUTORCH_ROOT}/build_samsung_android/examples/samsung/`
 ## Execution
 
+
 After lowering, we could get a pte model and then run it on mobile phone.
 
 #### Step 1: Push required ENN libraries and executor runner to device
 ```bash
 DEVICE_DIR=/data/local/tmp/executorch
 adb shell mkdir ${DEVICE_DIR}
-adb push ${EXECUTORCH_ROOT}/cmake-android-out/backends/samsung/enn_executor_runner ${DEVICE_DIR}
+adb push ${EXECUTORCH_ROOT}/build_samsung_android/examples/samsung/enn_executor_runner ${DEVICE_DIR}
 ```
 
 #### Step 2: Indicate dynamic linkers and execute model

examples/samsung/build.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+
+set -e
+
+BASE_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+PROJECT_DIR=$(realpath ${BASE_DIR}/../../)
+
+echo PROJECT_DIR=${PROJECT_DIR}
+
+if [[ -z ${ANDROID_NDK_ROOT} ]]; then
+  echo "Please export ANDROID_NDK_ROOT"
+  exit 1
+fi
+
+ANDROID_ABI=arm64-v8a
+ANDROID_PLATFORM=android-28 # Trace requires over android-23
+
+echo ANDROID_NDK_ROOT=${ANDROID_NDK_ROOT}
+echo ANDROID_ABI=${ANDROID_ABI}
+echo ANDROID_PLATFORM=${ANDROID_PLATFORM}
+
+main() {
+      cd "$PROJECT_DIR"
+      local build_dir_root="build_samsung_android"
+      local example_root="examples/samsung"
+      local build_dir_example="$PROJECT_DIR/${build_dir_root}/${example_root}"
+      local cmake_prefix_path="$PROJECT_DIR/${build_dir_root}/lib/cmake/ExecuTorch;$PROJECT_DIR/${build_dir_root}/third-party/gflags;$PROJECT_DIR/${build_dir_root}/lib/cmake/tokenizers;$PROJECT_DIR/${build_dir_root}/lib/cmake/re2;$PROJECT_DIR/${build_dir_root}/lib/cmake/absl;"
+
+      echo build_dir=${build_dir_root}
+      echo build_dir_example=${build_dir_example}
+      echo cmake_prefix_path=${cmake_prefix_path}
+
+      cmake -DCMAKE_PREFIX_PATH=${cmake_prefix_path} \
+            -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK_ROOT/build/cmake/android.toolchain.cmake" \
+            -DANDROID_NDK=$ANDROID_NDK \
+            -DANDROID_ABI="$ANDROID_ABI" \
+            -DANDROID_PLATFORM=$ANDROID_PLATFORM \
+            -DCMAKE_FIND_ROOT_PATH_MODE_PACKAGE=BOTH \
+            -DCMAKE_BUILD_TYPE=Release \
+            -B"${build_dir_example}" \
+            "$PROJECT_DIR/${example_root}"
+      cmake --build build_samsung_android/examples/samsung/ --config Release
+}
+
+main "$@"