## Summary
Backend loading is easier to maintain when native backend library
discovery, in-tree backend Python hook loading, and out-of-tree entry
point autoload are owned by the backend namespace. This PR consolidates
those paths under `tvm.backend._autoload_backends` while preserving
compatibility routes from the previous top-level helper and
`tvm.base.load_backend_libs`.
- Move backend runtime DSO loading into `tvm.backend._autoload_backends`
- Route `backend.load_all()` through the backend autoload helper
- Keep the previous top-level `_autoload_backends` module as a thin
compatibility import
This PR adds an autoload mechanism for out-of-tree backends, simplifies
TVM's Python library loading, and removes `TVMError` in favor of native
Python errors.
## Autoload out-of-tree backends
Out-of-tree packages can register an autoload callable under the
`tvm.backends` entry-point group (mirroring torch's device-backend
autoload). At `import tvm` startup each entry point is discovered and
its callable invoked once, after the core runtime and the `tvm`
namespace are fully initialized, so an extension can register
ops/targets/funcs or load extra libraries.
```toml
[project.entry-points."tvm.backends"]
tvm_foo = "tvm_foo:_autoload"
```
A failing extension is caught and surfaced via `warnings.warn` so it
cannot break `import tvm`. Autoload can be disabled with
`TVM_DEVICE_BACKEND_AUTOLOAD=0`.
## Simplify library loading
The library-loading path in `base.py` is consolidated around a single
`_LOADED_LIBS` dict (basename to ctypes handle) so downstream and
autoloaded extensions can skip already-loaded libraries; the per-backend
runtime DSO list is folded into `load_backend_libs`. Accumulated cruft
is removed: the Python-3.9 check, the readline shim, the `_FFI_MODE`
ctypes check, the `base.__version__` re-export, and `py_str` (call sites
inline `.decode("utf-8")`).
## Remove TVMError in favor of native Python errors
`TVMError` added a layer atop `RuntimeError` that downstream code had to
import and learn. It is removed; the registered FFI error kinds
(`InternalError`, `RPCError`, `OpError`, `DiagnosticError`,
`ScheduleError`) now subclass `RuntimeError` directly while staying
registered, so the FFI keeps throwing the right kinds. All `TVMError`
imports, `except`/`raise`/`isinstance` uses, and
`pytest.raises(tvm.TVMError)` sites move to the `RuntimeError` builtin.
This PR slims `tvm.libinfo` into a thin *info* layer that delegates path
discovery to the `tvm_ffi.libinfo` primitives and never loads libraries.
Loading responsibilities move to `tvm.base`, and the various ad-hoc
path-finding helpers are phased out in favor of the tvm-ffi resolvers.
## Changes
- **libinfo**: add `find_libtvm_runtime()` (resolves `libtvm_runtime`
via
`_find_library_by_basename` + `_resolve_and_validate`) and
`find_tvm_include_path()` (TVM's own `include/`). `find_include_path()`
now
returns `[find_tvm_include_path(), *tvm_ffi.libinfo.include_paths()]`,
folding
in the FFI + dlpack + python-helper include dirs. Remove
`find_lib_path`,
`get_dll_directories`, `use_runtime_lib`, `split_env_var`, and
`load_backend_libs`.
- **base**: receive `load_backend_libs` and the backend DSO list; the
runtime-only switch becomes a strict `TVM_USE_RUNTIME_LIB == "1"` check.
- **rpc**: `with_minrpc` uses `find_libtvm_runtime()` (the `runtime`
kwarg is
retained as an inert back-compat parameter); the rpc server
`load_library`
resolves the literal library name against the current working directory.
- **wasm**: move the `web/dist` asset search into `emcc.find_wasm_lib`,
used by
`emcc.create_tvmjs_wasm` and the tvmjs asset lookup.
- **hexagon**: fix a latent bug where `_get_hexagon_rpc_lib_dir` called
a
non-existent `tvm_ffi.libinfo.find_lib_path`; it now relies solely on
the
`HEXAGON_RPC_LIB_DIR` environment variable.
## Motivation
Historically TVM ships a single monolithic `libtvm.so` that bundles both
the
runtime and the compiler/LLVM-heavy code paths. Deployment scenarios
that only
need the runtime end up paying the full compiler footprint (LLVM-static
dominates
the binary size), and the layout makes it awkward to install the project
under a
single Python package directory the way
`tvm_ffi`/`libinfo.load_lib_ctypes`
expects.
This PR splits the single shared library into two:
- `libtvm_runtime.so` — runtime-only symbols (loaded `RTLD_GLOBAL`).
- `libtvm_compiler.so` — compiler / LLVM / codegen, links
`libtvm_runtime.so`
publicly (loaded `RTLD_LOCAL`).
## Target restructure
- New CMake target `tvm_compiler` replaces the old `tvm` SHARED target.
- `tvm_compiler` depends on `tvm_runtime` via `target_link_libraries(...
PUBLIC tvm_runtime)`,
so anything that linked the old `tvm` now picks up the runtime
transitively.
- `tvm_libinfo_objs` (build-info TU) moved from `tvm_runtime` into
`tvm_compiler`
— it is compiler-side metadata and the runtime no longer needs it.
- All `target_link_libraries` / `target_compile_*` /
`set_target_properties` /
`tvm_ffi_add_apple_dsymutil` callsites have been rewired.
- The separate `libtvm_allvisible.so` target is **removed** (was only
consumed
by cpptests). Cpptests with private-symbol deps are deleted; remaining
cpptests now link directly against `libtvm_compiler.so` /
`libtvm_runtime.so`. `src/support/hexdump.cc` is folded into the header.
- `BUILD_DUMMY_LIBTVM` and the `BUILD_FOR_HEXAGON + USE_HEXAGON_GTEST`
cpp-test wiring are removed.
## Output and install layout
- All artifacts now go to `build/lib/` (was `build/`):
- `build/lib/libtvm_runtime.so`
- `build/lib/libtvm_compiler.so`
- Install layout is now `<package>/lib/` so
`tvm_ffi.libinfo.load_lib_ctypes`
with `package="tvm"` finds the libs in the wheel.
- CI Jenkins stash paths and `apps/hexagon_*` paths updated to the new
`build/lib/...` location.
## Python loader change
`python/tvm/base.py` now resolves the libs directly via a small
`package_lib_paths()` helper in `python/tvm/libinfo.py` (anchored on
`python/tvm/__file__`, returning the wheel `lib/`,
`<worktree>/build/lib`, and
`<worktree>/lib` candidates). Module-level `_LIB_RUNTIME`, `_LIB`, and
`_RUNTIME_ONLY` are set inline at import time:
- `libtvm_runtime.{so,dylib,dll}` loaded `RTLD_GLOBAL`.
- `libtvm_compiler.{so,dylib,dll}` loaded `RTLD_LOCAL`.
- `TVM_USE_RUNTIME_LIB` (parsed strictly: `1`/`true`/`yes`) selects
runtime-only at the loader level.
- When the compiler lib is absent, `_RUNTIME_ONLY` is set to True
automatically and `_LIB is _LIB_RUNTIME`.
## Non-obvious build-integration fixes
Three issues surfaced once both libs are loaded into the same process
and are
worth calling out:
1. **`fpA_intB_gemm` double-registration.** `fpA_intB_gemm_tvm` is an
OBJECT
library that registers a global `fastertransformer.gemm_fp16_int` at
static
init. Linking it into both `tvm_runtime` and `tvm_compiler` made the
registration run twice and trip the duplicate-registration check. Fix:
link
it (and the other runtime-only externals — `flash_attn`, NCCL, NVSHMEM,
RCCL) only into `tvm_runtime`. `tvm_compiler` picks them up via the
PUBLIC
`tvm_runtime` link.
2. **`-Wl,--no-as-needed` for minrpc.** `python/tvm/rpc/minrpc.py`
defaults
to `runtime="libtvm_runtime"` and passes `-Wl,--no-as-needed` so the
runtime static initializers actually run in the spawned minrpc binary
(without it, the linker drops the lib because no symbol is referenced
directly from the minrpc TU). minrpc does **not** link
`libtvm_compiler.so`.
3. **`testing.GetShape{Elem,Size}` moved to runtime.** Those two test
helpers
(the only `testing.*` symbols the minrpc test exercises) were registered
in
`src/support/ffi_testing.cc` (compiler-side). They are now registered in
`src/runtime/rpc/testing.cc` under `rpc.testing.GetShape{Elem,Size}` so
the minrpc server binary — runtime-only — can resolve them.
## Deprecations and breaking changes
- `BUILD_DUMMY_LIBTVM` is **removed** (option, libinfo entry, and CMake
wiring). Downstream consumers that built the dummy variant should link
`libtvm_runtime.so` directly.
- **Breaking change for downstream consumers** that read `libtvm.so` by
name:
there is no longer a `libtvm.so`. Replace with `libtvm_compiler.so`
(full)
or `libtvm_runtime.so` (runtime-only). The Vulkan device comment and a
few
test/CI comments have been updated accordingly.
- `libtvm_allvisible.so` is **removed**. Cpptests that depended on
private
out-of-line symbols have been deleted; the remaining cpp-test contract
is
documented as "public API or private header-only API only" (see
`tests/cpp/`).
- `tests/cpp-runtime/` (Hexagon + OpenCL backend tests) is **removed**
until
TVM moves to a plugin-mode backend architecture where each backend can
ship its own test harness with its own visibility scope.
## Tested
- `ninja` build: `build/lib/libtvm_runtime.so`,
`build/lib/libtvm_compiler.so`;
no `build/libtvm.so`, no `build/lib/libtvm_allvisible.so`.
`ldd build/lib/libtvm_compiler.so` links `libtvm_runtime.so`,
`libtvm_ffi.so`, `libfpA_intB_gemm.so`, `libflash_attn.so`.
- `ldd build/cpptest`: only `libtvm_compiler.so` + `libtvm_runtime.so` +
`libtvm_ffi.so` (no `libtvm_allvisible.so`).
- `./build/cpptest`: 144 / 144 tests pass across 29 suites.
- Smoke imports: full and `TVM_USE_RUNTIME_LIB=1` — both pass.
`TVM_USE_RUNTIME_LIB=0` correctly disables runtime-only mode (strict
parse).
- `tests/python/all-platform-minimal-test`: 75 passed, 77 skipped.
- `tests/python/runtime/`: 81 passed, 2 skipped (incl.
`test_rpc_return_remote_object` exercising the minrpc executable
end-to-end
via `rpc.testing.GetShape{Elem,Size}`).
- `tests/python/relax/test_vm_*.py`: 150 passed, 3 deselected
(`test_vm_multi_device.py` requires 3+ GPUs; host has 2 — env, not
regression),
2 xfailed.
- `tests/python/tirx-base/`: 273 passed, 2 skipped.
- `pre-commit` on edited files: green.
Closes#19443.
* [FFI][REFACTOR] Establish tvm_ffi as a standalone python module
This PR establishes tvm_ffi as a standalone python module.
The ffi is structured as a minimal pip module that can be
directly install by path or url.
examples/get_started provided a minimal example.
This is a major change as we are decoupling tvm_ffi as a
separate package, users need to install tvm_ffi separately.
Thanks to its minimal dependency, tvm_ffi can be easily installed
even just from the source by pip install ./ffi
This change would enable future improvement for library plugins
to have lightweight dependencies by just working on top of
the tvm_ffi, while the main compiler toolchain and runtime
can be layered on top.
* [FFI] Improve traceback setups
This PR improves traceback related setups
- Set Python minimal version to 3.9 as Python 3.8 has reached end of life
- Update AST handling to match Python 3.9+ API changes
- Fix deprecation warning: "Support for arbitrary keyword arguments is deprecated and will be removed in Python 3.15"
- Update TVMScript parser components to use modern AST interfaces
- Adjust linting and test infrastructure for Python 3.9+ compatibility
This PR phases out tvm._ffi redirections in favor of new FFI
new functions are now called via tvm.ffi.
We also enabled limited API support for python 3.12+
so the compiled binary can be forward compatible to future
python versions.
Tianqi Chen