Enable Arm VGF delegate in pybind builds (#19290)

- Enable VGF in pybind build if directed by env var.
- Use VGF pybind in the wheel builds, based on package availability.


### Summary

This adds VGF runtime delegate to end pip installs, and gives the option
for ./install_executorch.sh to include it for developer side.

This tidies up vgf with runtime installation further to the following:

1. developer flows: ./examples/arm/setup.sh --enable-mlsdk-deps; export
EXECUTORCH_PYBIND_ENABLE_VGF=ON; ./install_executorch.sh --editable
--optional-dependency vgf

3. wheel builds: # will invoke .ci/scripts/wheel/pre_build_script.sh
which installs the build dependency # suitable platforms have
EXECUTORCH_PYBIND_ENABLE_VGF=ON set

4. end users: pip install executorch[vgf] # published wheels contain
runtime delegate on supported platforms

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils
@Sebastian-Larsson @rascani

---------

Signed-off-by: Rob Elliott <Robert.Elliott@arm.com>

Author: robell

.ci/scripts/wheel/pre_build_script.sh

@@ -2,6 +2,8 @@
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
 #
+# Copyright 2026 Arm Limited and/or its affiliates.
+#
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
@@ -57,6 +59,18 @@ fi
 
 "${GITHUB_WORKSPACE}/${REPOSITORY}/install_requirements.sh" --example
 
+# Enable VGF in pybind wheel builds when the platform-specific build input is
+# available from pip.
+if [[ "$UNAME_S" == "Linux" || "$UNAME_S" == "Darwin" ]]; then
+  if python3 -m pip install -r \
+    "${GITHUB_WORKSPACE}/${REPOSITORY}/backends/arm/requirements-arm-vgf-runtime.txt"; then
+    export EXECUTORCH_PYBIND_ENABLE_VGF=ON
+    echo "EXECUTORCH_PYBIND_ENABLE_VGF=ON" >> "${GITHUB_ENV}"
+  else
+    echo "VGF build dependency unavailable on this platform; building without VGF"
+  fi
+fi
+
 # Download Qualcomm QNN SDK on Linux x86_64 so the wheel build can include the
 # QNN backend.  The SDK is large, so we download it here (outside CMake) rather
 # than during cmake configure.

CMakeLists.txt

@@ -1040,6 +1040,10 @@ if(EXECUTORCH_BUILD_PYBIND)
     list(APPEND _dep_libs coremldelegate)
   endif()
 
+  if(EXECUTORCH_BUILD_VGF)
+    list(APPEND _dep_libs vgf_backend)
+  endif()
+
   if(EXECUTORCH_BUILD_MPS)
     list(APPEND _dep_libs mpsdelegate)
   endif()

backends/arm/CMakeLists.txt

@@ -197,6 +197,9 @@ if(EXECUTORCH_BUILD_VGF)
   set(_vgf_backend_sources backends/arm/runtime/VGFBackend.cpp
                            backends/arm/runtime/VGFSetup.cpp
   )
+  if(NOT EXECUTORCH_BUILD_VULKAN)
+    list(APPEND _vgf_backend_sources backends/vulkan/third-party/volk/volk.c)
+  endif()
 
   # vgf backend
   list(TRANSFORM _vgf_backend_sources PREPEND "${EXECUTORCH_ROOT}/")

backends/arm/requirements-arm-vgf-runtime.txt

@@ -0,0 +1,8 @@
+# Copyright 2026 Arm Limited and/or its affiliates.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# Runtime build dependencies for the Arm VGF backend.
+
+ai_ml_sdk_vgf_library == 0.9.0

backends/arm/requirements-arm-vgf.txt

@@ -7,4 +7,3 @@
 
 ai_ml_emulation_layer_for_vulkan == 0.9.0
 ai_ml_sdk_model_converter == 0.9.0
-ai_ml_sdk_vgf_library == 0.9.0

backends/arm/scripts/setup-mlsdk-from-source.sh

@@ -15,7 +15,7 @@ root_dir="${et_dir}/examples/arm/arm-scratch"
 setup_path_script=""
 mlsdk_manifest_dir="ml-sdk-for-vulkan-manifest"
 mlsdk_manifest_url="${MLSDK_MANIFEST_URL:-https://github.com/arm/ai-ml-sdk-manifest.git}"
-mlsdk_manifest_tag="${MLSDK_MANIFEST_TAG:-refs/tags/v2026.03.0}" # Keep this in sync with what is mentioned in requirements-arm-vgf.txt
+mlsdk_manifest_tag="${MLSDK_MANIFEST_TAG:-refs/tags/v2026.03.0}" # Keep this in sync with backends/arm/requirements-arm-vgf.txt and backends/arm/requirements-arm-vgf-runtime.txt
 
 enable_model_converter=0
 enable_vgf_lib=0

backends/arm/test/misc/test_vgf_check_env.py

@@ -223,6 +223,22 @@ def test_cmake_build_flags_pass(tmp_path):
     assert "EXECUTORCH_BUILD_VULKAN=TRUE" in result.detail
 
 
+def test_cmake_build_flags_pass_when_vulkan_disabled(tmp_path):
+    (tmp_path / "CMakeCache.txt").write_text(
+        "EXECUTORCH_BUILD_VGF:BOOL=ON\n" "EXECUTORCH_BUILD_VULKAN:BOOL=OFF\n",
+        encoding="utf-8",
+    )
+
+    result = check_env._check_cmake_build_flags(
+        build_dir=tmp_path,
+        require_runtime_build=True,
+    )
+
+    assert result.status == check_env.STATUS_OK
+    assert "EXECUTORCH_BUILD_VGF=ON" in result.detail
+    assert "EXECUTORCH_BUILD_VULKAN=OFF" in result.detail
+
+
 def test_cmake_build_flags_fail_when_vgf_disabled(tmp_path):
     (tmp_path / "CMakeCache.txt").write_text(
         "EXECUTORCH_BUILD_VGF:BOOL=OFF\n" "EXECUTORCH_BUILD_VULKAN:BOOL=ON\n",

backends/arm/vgf/check_env.py

@@ -704,8 +704,8 @@ def _check_cmake_build_flags(
                 "VGF source-build CMake flags",
                 STATUS_FAIL,
                 f"No CMakeCache.txt found for build_dir={build_dir!s}.",
-                "Configure the runtime build with -DEXECUTORCH_BUILD_VGF=ON "
-                "-DEXECUTORCH_BUILD_VULKAN=ON, then pass --build-dir <dir>.",
+                "Configure the runtime build with -DEXECUTORCH_BUILD_VGF=ON, "
+                "then pass --build-dir <dir>.",
             )
 
         status = STATUS_FAIL if require_runtime_build else STATUS_WARN
@@ -720,12 +720,15 @@ def _check_cmake_build_flags(
     values = _parse_cmake_cache(cache)
     required = {
         "EXECUTORCH_BUILD_VGF": values.get("EXECUTORCH_BUILD_VGF"),
+    }
+    observed = {
+        **required,
         "EXECUTORCH_BUILD_VULKAN": values.get("EXECUTORCH_BUILD_VULKAN"),
     }
     bad = [key for key, value in required.items() if not _is_cmake_truthy(value)]
     rendered = ", ".join(
         f"{key}={value if value is not None else '<missing>'}"
-        for key, value in required.items()
+        for key, value in observed.items()
     )
 
     if bad:
@@ -734,8 +737,7 @@ def _check_cmake_build_flags(
             STATUS_FAIL,
             f"{cache}: required runtime flag(s) are disabled or missing: "
             f"{', '.join(bad)}. Current values: {rendered}",
-            "Reconfigure CMake with -DEXECUTORCH_BUILD_VGF=ON "
-            "-DEXECUTORCH_BUILD_VULKAN=ON.",
+            "Reconfigure CMake with -DEXECUTORCH_BUILD_VGF=ON.",
         )
 
     return VgfEnvironmentCheck(

examples/arm/setup.sh

@@ -209,7 +209,7 @@ function setup_root_dir() {
 
 function setup_ethos_u_tools() {
     log_step "ethos-u-tools" "Installing Ethos-U Python tooling"
-    CMAKE_POLICY_VERSION_MINIMUM=3.5 BUILD_PYBIND=1 pip install --no-dependencies -r $et_dir/backends/arm/requirements-arm-ethos-u.txt
+    CMAKE_POLICY_VERSION_MINIMUM=3.5 BUILD_PYBIND=1 pip install --no-dependencies -r "$et_dir/backends/arm/requirements-arm-ethos-u.txt"
 }
 
 function setup_cortex_m_tools() {
@@ -219,7 +219,13 @@ function setup_cortex_m_tools() {
 
 function setup_mlsdk_dependencies() {
     log_step "mlsdk" "Installing MLSDK dependencies"
-    pip install -r $et_dir/backends/arm/requirements-arm-vgf.txt
+    if [[ "${enable_model_converter}" -eq 1 || "${enable_emulation_layer}" -eq 1 ]]; then
+        pip install -r "$et_dir/backends/arm/requirements-arm-vgf.txt"
+    fi
+
+    if [[ "${enable_vgf_lib}" -eq 1 ]]; then
+        pip install -r "$et_dir/backends/arm/requirements-arm-vgf-runtime.txt"
+    fi
 }
 
 function validate_mlsdk_pip_compatibility() {

tools/cmake/preset/pybind.cmake

@@ -1,5 +1,6 @@
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
+# Copyright 2026 Arm Limited and/or its affiliates.
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
@@ -25,9 +26,22 @@ set_overridable_option(EXECUTORCH_BUILD_EXTENSION_MODULE ON)
 set_overridable_option(EXECUTORCH_BUILD_EXTENSION_NAMED_DATA_MAP ON)
 set_overridable_option(EXECUTORCH_BUILD_WHEEL_DO_NOT_USE ON)
 
+# Optional VGF enable for the default pybind/install flow. This is intentionally
+# scoped to this preset rather than acting as a general environment-to-CMake
+# override mechanism.
+set(_executorch_pybind_enable_vgf OFF)
+if(DEFINED ENV{EXECUTORCH_PYBIND_ENABLE_VGF})
+  if("$ENV{EXECUTORCH_PYBIND_ENABLE_VGF}" STREQUAL "ON")
+    set(_executorch_pybind_enable_vgf ON)
+  else()
+    set(_executorch_pybind_enable_vgf OFF)
+  endif()
+endif()
+
 # TODO(larryliu0820): Temporarily disable building llm_runner for Windows wheel
 # due to the issue of tokenizer file path length limitation.
 if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+  set_overridable_option(EXECUTORCH_BUILD_VGF ${_executorch_pybind_enable_vgf})
   set_overridable_option(EXECUTORCH_BUILD_COREML ON)
   set_overridable_option(EXECUTORCH_BUILD_EXTENSION_TRAINING ON)
   set_overridable_option(EXECUTORCH_BUILD_EXTENSION_LLM_RUNNER ON)
@@ -51,6 +65,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
     endif()
   endif()
 elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  set_overridable_option(EXECUTORCH_BUILD_VGF ${_executorch_pybind_enable_vgf})
   set_overridable_option(EXECUTORCH_BUILD_COREML ON)
   set_overridable_option(EXECUTORCH_BUILD_EXTENSION_TRAINING ON)
   set_overridable_option(EXECUTORCH_BUILD_EXTENSION_LLM_RUNNER ON)