Resurrect HelloBaremetal

.github/workflows/testing-linux.yml

@@ -209,3 +209,69 @@ jobs:
           script: |
             apps/support/android_smoke_test.sh apps/HelloAndroid/app/build/outputs/apk/debug/app-debug.apk com.example.hellohalide .CameraActivity android.permission.CAMERA "requires a buffer of exactly"
             apps/support/android_smoke_test.sh apps/HelloAndroidCamera2/app/build/outputs/apk/debug/app-debug.apk com.example.helloandroidcamera2 .CameraActivity android.permission.CAMERA
+
+  baremetal-apps:
+    # Deliberately its own job: needs an arm-none-eabi cross toolchain and
+    # QEMU's Arm system emulator, neither of which any other job installs.
+    # Actually cross-compiles and runs all three documented build methods
+    # (see apps/HelloBaremetal/README.md) under QEMU with semihosting, rather
+    # than only checking that they build for host.
+    if: "!contains(github.event.pull_request.labels.*.name, 'skip_buildbots')"
+    name: HelloBaremetal apps
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: astral-sh/setup-uv@v7
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libpng-dev libjpeg-dev gcc-arm-none-eabi qemu-system-arm
+
+      - name: Sync CI environment
+        run: |
+          uv sync --group ci-llvm-main --no-install-project
+          echo "${GITHUB_WORKSPACE}/.venv/bin" >> "$GITHUB_PATH"
+          echo "VIRTUAL_ENV=${GITHUB_WORKSPACE}/.venv" >> "$GITHUB_ENV"
+
+      - name: Configure LLVM
+        run: echo "Halide_LLVM_ROOT=$(halide-llvm --prefix)" >> "$GITHUB_ENV"
+
+      - name: Configure CMake
+        run: >-
+          cmake --preset ci-linux-x86-64
+          -DCMAKE_INSTALL_PREFIX="${{ github.workspace }}/install"
+
+      - name: Build and install Halide
+        run: cmake --build build --target install
+
+      - name: Build HelloBaremetal (host target)
+        working-directory: apps/HelloBaremetal
+        env:
+          CMAKE_PREFIX_PATH: ${{ github.workspace }}/install
+        run: |
+          for method in cmake-twice cmake-super_build cmake-external_project; do
+            cmake -S "$method" -B "$method/build"
+            cmake --build "$method/build"
+          done
+
+      # The actual point of this job: build.sh cross-compiles each method for
+      # the bare-metal Arm target, then ctest runs the result under QEMU with
+      # semihosting, actually exercising the cross-compiled binary rather than
+      # only checking that it builds for host.
+      - name: Build and run HelloBaremetal (bare-metal cross-compile under QEMU)
+        working-directory: apps/HelloBaremetal
+        env:
+          CMAKE_PREFIX_PATH: ${{ github.workspace }}/install
+        run: |
+          declare -A test_dir=(
+            [cmake-twice]=build-target
+            [cmake-super_build]=build/app
+            [cmake-external_project]=build
+          )
+          for method in cmake-twice cmake-super_build cmake-external_project; do
+            ( cd "$method" && ./build.sh )
+            ctest --test-dir "$method/${test_dir[$method]}" --output-on-failure
+          done

apps/CMakeLists.txt

@@ -57,7 +57,7 @@ add_app(hannk)
 add_app(harris)
 # add_app(HelloAndroid)  # don't build HelloAndroid here because it is driven by gradle
 # add_app(HelloAndroidCamera2)  # don't build HelloAndroidCamera2 here because it is driven by gradle
-add_app(HelloBaremetal)
+# add_app(HelloBaremetal)  # cross-compiles for a bare-metal ARM target; see apps/HelloBaremetal/README.md
 # add_app(HelloiOS)  # don't build HelloiOS here because it isn't universal.
 add_app(HelloPyTorch)
 # add_app(HelloWasm)  # driven by its own super-build; see apps/HelloWasm/README.md

apps/HelloBaremetal/README.md

@@ -26,29 +26,34 @@ modify some parts if you target for different setup.
 
 ## How to build
 
+Unlike most other apps in this repo, there is no top-level `CMakeLists.txt` here
+-- each of the three `cmake-<xxx>` subdirectories below is an independent CMake
+project you build directly.
+
 ### Cross compilation
 
 Halide cross-compiling in CMake is tricky and there are a couple of ways to
 realize it. This application demonstrates 3 different ways with concrete code,
-located in `CMakeLists.txt` in the following sub directories.
+located in `CMakeLists.txt` in the following subdirectories.
 
 1. cmake-twice
 2. cmake-super_build
 3. cmake-external_project
 
 If you want to understand the detail of build steps, please read "Cross
-compiling" section of [README_cmake](../../README_cmake.md#cross-compiling), and
-then `build.sh` and `CMakeLists.txt` in each sub directories.
+compiling" section of
+[HalideCMakePackage](../../doc/HalideCMakePackage.md#cross-compiling), and then
+`build.sh` and `CMakeLists.txt` in each subdirectory.
 
 ### Build procedure
 
 #### Baremetal target
 
 As a prerequisite, toolchain described above needs to be installed in your host
-machine. The detail of the toolchanin configuration is set in
-[toolchain.arm-32-sample.cmake](cmake/toolchain.arm-32-sample.cmake), which you
-might need to modify depending on the target baremetal system. Then, just run
-the build script in one of the aforementioned sub directories.
+machine. The detail of the toolchain configuration is set in
+[toolchain.noos-arm32-sample.cmake](cmake/toolchain.noos-arm32-sample.cmake),
+which you might need to modify depending on the target baremetal system. Then,
+just run the build script in one of the aforementioned subdirectories.
 
 ```
 cd cmake-<xxx>/
@@ -68,5 +73,14 @@ cmake --build build/
 
 ## How to run
 
-`run.sh` in each sub directories is a sample script that shows how to run the
-executable on QEMU Arm System emulator with semihosting mode.
+After building for the bare-metal target, `ctest` runs the executable on QEMU
+Arm System emulator with semihosting mode:
+
+```
+ctest --test-dir build-target --output-on-failure  # cmake-twice
+ctest --test-dir build/app --output-on-failure      # cmake-super_build
+ctest --test-dir build --output-on-failure          # cmake-external_project
+```
+
+`run_baremetal.sh` (the script `ctest` invokes under the hood) can also be run
+directly against any executable built for this target.

apps/HelloBaremetal/cmake-external_project/CMakeLists.txt

@@ -1,7 +1,5 @@
 cmake_minimum_required(VERSION 3.28)
-
-# Enable assembly language (.s) support additionally
-project(HelloBaremetal LANGUAGES C CXX ASM)
+project(HelloBaremetal)
 
 # Set up C++ language settings
 set(CMAKE_CXX_STANDARD 17)
@@ -10,7 +8,6 @@ set(CMAKE_CXX_EXTENSIONS NO)
 
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 
-set(GEN_EXE "add.generator")
 set(GEN_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/generator)
 
 # Step 1
@@ -22,10 +19,10 @@ ExternalProject_Add(
     SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/generator
     BINARY_DIR ${GEN_BINARY_DIR}
     INSTALL_COMMAND ""
-    CMAKE_ARGS -DGEN_EXE=${GEN_EXE}
+    CMAKE_ARGS -DCMAKE_PREFIX_PATH=${CMAKE_PREFIX_PATH}
+    CONFIGURE_HANDLED_BY_BUILD TRUE
 )
 
-
 # Step 2
 # Build application with cross compiler,
 # where the generator executable built in Step 1 is imported and called
@@ -36,16 +33,15 @@ set(SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR}/..)
 
 # NOTE : find_package(HelloBaremetal-add_generator REQUIRED) is not ready at configuration time.
 # Instead, declare the generator executable as imported, which is built in external project
-add_executable(${GEN_EXE} IMPORTED)
-# Specify the location of exe file to import
-set_property(TARGET ${GEN_EXE} PROPERTY IMPORTED_LOCATION ${GEN_BINARY_DIR}/${GEN_EXE})
+add_executable(add.generator IMPORTED)
+set_property(TARGET add.generator PROPERTY IMPORTED_LOCATION ${GEN_BINARY_DIR}/add.generator)
 # Associate with external project so that it invokes build process
-add_dependencies(${GEN_EXE} gen_project)
+add_dependencies(add.generator gen_project)
 
 # Generate filter function
 add_halide_library(
     add
-    FROM ${GEN_EXE}
+    FROM add.generator
     GENERATOR add
     # You may set Target feature in addition to what is set in the toolchain file
     FEATURES debug
@@ -58,8 +54,17 @@ add_halide_library(
 add_executable(add_filter ${SRC_DIR}/filter.cpp)
 target_link_libraries(add_filter PRIVATE Halide::ImageIO add)
 
-# Depending on the target CPU, we need to enable Arm NEON manually
-# if the executable contains any SIMD instructions.
-target_sources(add_filter PRIVATE "$<$<BOOL:${BAREMETAL}>:${SRC_DIR}/enable_neon.s>")
-# It is safe to do it in boot up process before main function (or C runtime) starts.
-target_link_options(add_filter PRIVATE "$<$<BOOL:${BAREMETAL}>:--entry=_enable_neon>")
+# Test that the app actually works, under QEMU with semihosting. Only
+# meaningful for the actual bare-metal cross-compile; in the host-target
+# build mode there's no toolchain to run it through.
+if (CMAKE_CROSSCOMPILING)
+    enable_testing()
+    set(IMAGE ${SRC_DIR}/../images/gray_small.pgm)
+    if (EXISTS ${IMAGE})
+        add_test(
+            NAME add_filter
+            COMMAND ${SRC_DIR}/run_baremetal.sh $<TARGET_FILE:add_filter> ${IMAGE} 16 out.pgm
+        )
+        set_tests_properties(add_filter PROPERTIES PASS_REGULAR_EXPRESSION "Success!")
+    endif ()
+endif ()

apps/HelloBaremetal/cmake-external_project/build.sh

@@ -7,9 +7,5 @@ set -eo pipefail
 cd "$(dirname "${BASH_SOURCE[0]}")"
 readonly TOOLCHAIN_FILE="${PWD}/../cmake/toolchain.noos-arm32-sample.cmake"
 
-rm -rf build
-
-cmake -S . -B build \
-    -DCMAKE_TOOLCHAIN_FILE="${TOOLCHAIN_FILE}"
-
-cmake --build build/
+cmake -S . -B build --toolchain "${TOOLCHAIN_FILE}" --fresh
+cmake --build build

apps/HelloBaremetal/cmake-external_project/generator/CMakeLists.txt

@@ -1,11 +1,6 @@
 cmake_minimum_required(VERSION 3.28)
-
 project(HelloBaremetal-gen)
 
-if (NOT DEFINED GEN_EXE)
-    message(FATAL_ERROR "CMakeVariable GEN_EXE is not set")
-endif ()
-
 # Set up C++ language settings
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
@@ -16,4 +11,4 @@ set(SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../..)
 find_package(Halide REQUIRED)
 
 # Build generator
-add_halide_generator(${GEN_EXE} SOURCES ${SRC_DIR}/add_generator.cpp)
+add_halide_generator(add.generator SOURCES ${SRC_DIR}/add_generator.cpp)

apps/HelloBaremetal/cmake-super_build/CMakeLists.txt

@@ -20,9 +20,11 @@ ExternalProject_Add(
     BINARY_DIR ${GEN_BINARY_DIR}
     INSTALL_COMMAND ""
     CMAKE_ARGS
-    -DGEN_PACKAGE=${GEN_PACKAGE}
-    -DGEN_NAMESPACE=${GEN_NAMESPACE}
-    -DGEN_EXE=${GEN_EXE}
+        -DCMAKE_PREFIX_PATH=${CMAKE_PREFIX_PATH}
+        -DGEN_PACKAGE=${GEN_PACKAGE}
+        -DGEN_NAMESPACE=${GEN_NAMESPACE}
+        -DGEN_EXE=${GEN_EXE}
+    CONFIGURE_HANDLED_BY_BUILD TRUE
 )
 
 # Step 2
@@ -32,11 +34,14 @@ ExternalProject_Add(
 ExternalProject_Add(
     app_project
     SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/app
+    BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/app
     INSTALL_COMMAND ""
     DEPENDS gen_project  # To make sure generator is ready
     CMAKE_ARGS
-    -DCMAKE_TOOLCHAIN_FILE=${APP_TOOLCHAIN_FILE}
-    -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=${CMAKE_CURRENT_BINARY_DIR}/bin
-    -D${GEN_PACKAGE}_ROOT:FILEPATH=${GEN_BINARY_DIR}
-    -DGEN_TARGET=${GEN_NAMESPACE}${GEN_EXE}
+        -DCMAKE_PREFIX_PATH=${CMAKE_PREFIX_PATH}
+        -DCMAKE_TOOLCHAIN_FILE=${APP_TOOLCHAIN_FILE}
+        -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=${CMAKE_CURRENT_BINARY_DIR}/bin
+        -D${GEN_PACKAGE}_ROOT:FILEPATH=${GEN_BINARY_DIR}
+        -DGEN_TARGET=${GEN_NAMESPACE}${GEN_EXE}
+    CONFIGURE_HANDLED_BY_BUILD TRUE
 )

apps/HelloBaremetal/cmake-super_build/app/CMakeLists.txt

@@ -1,7 +1,5 @@
 cmake_minimum_required(VERSION 3.28)
-
-# Enable assembly language (.s) support additionally
-project(HelloBaremetal-app LANGUAGES C CXX ASM)
+project(HelloBaremetal-app)
 
 if (NOT DEFINED GEN_TARGET)
     message(FATAL_ERROR "CMakeVariable GEN_TARGET is not set")
@@ -35,8 +33,17 @@ add_halide_library(
 add_executable(add_filter ${SRC_DIR}/filter.cpp)
 target_link_libraries(add_filter PRIVATE Halide::ImageIO add)
 
-# Depending on the target CPU, we need to enable Arm NEON manually
-# if the executable contains any SIMD instructions.
-target_sources(add_filter PRIVATE "$<$<BOOL:${BAREMETAL}>:${SRC_DIR}/enable_neon.s>")
-# It is safe to do it in boot up process before main function (or C runtime) starts.
-target_link_options(add_filter PRIVATE "$<$<BOOL:${BAREMETAL}>:--entry=_enable_neon>")
+# Test that the app actually works, under QEMU with semihosting. Only
+# meaningful for the actual bare-metal cross-compile; in the host-target
+# build mode there's no toolchain to run it through.
+if (CMAKE_CROSSCOMPILING)
+    enable_testing()
+    set(IMAGE ${SRC_DIR}/../images/gray_small.pgm)
+    if (EXISTS ${IMAGE})
+        add_test(
+            NAME add_filter
+            COMMAND ${SRC_DIR}/run_baremetal.sh $<TARGET_FILE:add_filter> ${IMAGE} 16 out.pgm
+        )
+        set_tests_properties(add_filter PROPERTIES PASS_REGULAR_EXPRESSION "Success!")
+    endif ()
+endif ()

apps/HelloBaremetal/cmake-super_build/build.sh

@@ -7,9 +7,5 @@ set -eo pipefail
 cd "$(dirname "${BASH_SOURCE[0]}")"
 readonly TOOLCHAIN_FILE="${PWD}/../cmake/toolchain.noos-arm32-sample.cmake"
 
-rm -rf build
-
-cmake -S . -B build \
-    -DAPP_TOOLCHAIN_FILE="${TOOLCHAIN_FILE}"
-
-cmake --build build/
+cmake -S . -B build -DAPP_TOOLCHAIN_FILE="${TOOLCHAIN_FILE}" --fresh
+cmake --build build