Add the MLX backend to the mv3 Apple demo - #260
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Follow-up to removing the MPS backend. The mv3 image-classification demo now offers MLX, ExecuTorch's Apple GPU backend, as a third option next to Core ML and XNNPACK. Both demo Xcode projects are repinned from the old swiftpm-1.1.0 SwiftPM branch to the nightly swiftpm-1.5.0.20260827, which is the first published package that carries the new backend_mlx product. (This will be repinned to the 1.5 release branch once that is cut.) In the mv3 demo: - export.py lowers MobileNet v3 to MLX with MLXPartitioner and writes mv3_mlx.pte, the same shape as the existing Core ML and XNNPACK exports. MLX lowering is ahead-of-time and does not import the mlx runtime package, so it runs on the same Linux export runner as the others. - the model selector gains an MLX case that loads mv3_mlx.pte. - the Xcode project links executorch::backend_mlx from the package and bundles mv3_mlx.pte, mirroring exactly how backend_coreml and mv3_coreml_all.pte are wired. - the export workflow's artifact list includes mv3_mlx.pte. Test Plan: Verified the wheel side of MLX end to end on macOS arm64 in a fresh venv: exported MobileNet v3 with MLXPartitioner (all ops delegated), ran it through the pybindings runtime, and matched eager to 1.2e-07. Also built a C++ app with find_package(executorch) that links executorch::backend_mlx and ran the same delegated program, exit 0. export.py parses. The export workflow is valid YAML and lists all four mv3 outputs. ClassificationController.swift parses with swiftc and its Mode switch is exhaustive over the three cases. Both Xcode projects were checked with a real plist parser (plutil -convert json). The mv3 project has 116 objects with zero ids referenced-but-undefined and zero defined-but-unreferenced. backend_mlx is wired into all eight places backend_coreml is (build files, framework phase, product dependency, product block for both the app and test targets) and mv3_mlx.pte into all six places mv3_coreml_all.pte is. The etLLM project change is only the one-line branch repin. plutil -lint passes on both. Known dependency: build-demo-ios in executorch stages the demo's .pte files with its own export scripts (portable, Core ML, XNNPACK). That job needs an MLX export step added before mv3_mlx.pte is produced in CI; until then the MLX button has no model in that build. Filed separately.
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Add the MLX backend to the mv3 Apple demo
Follow-up to #259, which removed the deprecated MPS backend. This adds MLX,
ExecuTorch's Apple GPU backend, as a third option in the mv3 image-classification
demo, next to Core ML and XNNPACK.
What changed:
the nightly swiftpm-1.5.0.20260827, the first published package that carries the new
backend_mlx product. This will be repinned to the 1.5 release branch once it is cut.
mv3_mlx.pte, the same shape as the existing Core ML and XNNPACK exports. MLX
lowering is ahead-of-time and does not import the mlx runtime package, so it runs on
the same Linux export runner as the others.
mv3_mlx.pte, mirroring how backend_coreml and mv3_coreml_all.pte are already wired.
Dependency, important: the iOS build (build-demo-ios, run from ExecuTorch's
test_ios_ci.sh) stages the demo's model files with its own export scripts, currently
portable, Core ML and XNNPACK only. An MLX export step has to be added there before
mv3_mlx.pte is produced in that job. Until both that step lands and the pinned
nightly publishes backend_mlx, the iOS build of this demo will not be green. Merging
can wait on those, or this can land first so the app is ready.
Test Plan:
Verified the MLX path end to end on macOS arm64 in a fresh venv, using the macOS
wheel built at the tip of the merged runtime stack:
the resulting program carries the MLX delegate. Ran it through the pybindings
runtime and matched eager to a max error of 1.2e-07.
executorch::backend_mlx, and ran the same delegated program from C++, exit 0. otool
confirmed it links the shipped libexecutorch_backend_mlx.dylib and libexecutorch.dylib.
Static checks on this change:
over the three cases.
The mv3 project has 116 objects with zero ids referenced-but-undefined and zero
defined-but-unreferenced. backend_mlx is wired into all eight places backend_coreml
is, across the app and test targets, and mv3_mlx.pte into all six places
mv3_coreml_all.pte is. The etLLM project change is only the one-line branch repin.
plutil -lint passes on both.