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Find libdevice via pathfinder #798

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8b8b95c
find libdevice via pathfinder
brandon-b-miller Feb 17, 2026
23cf18e
Merge branch 'main' into libdevice-pathfinder
brandon-b-miller Feb 24, 2026
71b8e74
pathfinder minimum
brandon-b-miller Feb 24, 2026
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95 changes: 18 additions & 77 deletions numba_cuda/numba/cuda/cuda_paths.py
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Original file line number Diff line number Diff line change
Expand Up @@ -82,29 +82,27 @@ def _find_valid_path(options):
return "<unknown>", None


def _get_libdevice_path_decision():
options = _build_options(
[
("Conda environment", get_libdevice_conda_path),
("NVIDIA NVCC Wheel", get_libdevice_wheel_path),
(
"CUDA_HOME",
lambda: get_cuda_home("nvvm", "libdevice", "libdevice.10.bc"),
),
(
"System",
lambda: get_system_ctk("nvvm", "libdevice", "libdevice.10.bc"),
),
]
)
return _find_first_valid_lazy(options)
# Map cuda-pathfinder found_via to numba-cuda path source labels
_LIBDEVICE_FOUND_VIA_TO_LABEL = {
"site-packages": "NVIDIA NVCC Wheel",
"conda": "Conda environment",
"CUDA_HOME": "CUDA_HOME",
}


def _get_libdevice_path():
by, out = _get_libdevice_path_decision()
if not out:
return _env_path_tuple(by, None)
return _env_path_tuple(by, out)
"""Get libdevice path and source using cuda-pathfinder's locate_bitcode_lib."""
located = pathfinder.locate_bitcode_lib("device")
if located is not None:
by = _LIBDEVICE_FOUND_VIA_TO_LABEL.get(
located.found_via, located.found_via
)
return _env_path_tuple(by, located.abs_path)
# Fallback: system CTK (pathfinder does not search /usr/local/cuda)
system_path = get_system_ctk("nvvm", "libdevice", "libdevice.10.bc")
if system_path and os.path.isfile(system_path):
return _env_path_tuple("System", system_path)
return _env_path_tuple("<unknown>", None)


def _cuda_static_libdir():
Expand Down Expand Up @@ -239,26 +237,6 @@ def get_conda_ctk_libdir():
return os.path.dirname(max(paths))


def get_libdevice_conda_path():
"""Return path to directory containing the libdevice bitcode library."""
is_conda_env = os.path.isdir(os.path.join(sys.prefix, "conda-meta"))
if not is_conda_env:
return None

# Linux: nvvm/libdevice/libdevice.10.bc
# Windows: Library/nvvm/libdevice/libdevice.10.bc
libdevice_path = os.path.join(
sys.prefix,
"Library" if IS_WIN32 else "",
"nvvm",
"libdevice",
"libdevice.10.bc",
)
if os.path.isfile(libdevice_path):
return libdevice_path
return None


def get_wheel_static_libdir():
cuda_module_static_lib_dir = None
# CUDA 12
Expand Down Expand Up @@ -362,43 +340,6 @@ def get_cuda_paths():
return d


def get_libdevice_wheel_path():
libdevice_path = None
# CUDA 12
nvvm_distribution = _get_distribution("nvidia-cuda-nvcc-cu12")
if nvvm_distribution is not None:
site_packages_path = nvvm_distribution.locate_file("")
libdevice_path = os.path.join(
site_packages_path,
"nvidia",
"cuda_nvcc",
"nvvm",
"libdevice",
"libdevice.10.bc",
)

# CUDA 13
if libdevice_path is None:
nvvm_distribution = _get_distribution("nvidia-nvvm")
if (
nvvm_distribution is not None
and nvvm_distribution.version.startswith("13.")
):
site_packages_path = nvvm_distribution.locate_file("")
libdevice_path = os.path.join(
site_packages_path,
"nvidia",
"cu13",
"nvvm",
"libdevice",
"libdevice.10.bc",
)

if libdevice_path and os.path.isfile(libdevice_path):
return libdevice_path
return None


def get_current_cuda_target_name():
"""Determine conda's CTK target folder based on system and machine arch.

Expand Down
48 changes: 0 additions & 48 deletions numba_cuda/numba/cuda/tests/nocuda/test_library_lookup.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,9 +16,7 @@
skip_unless_conda_cudatoolkit,
)
from numba.cuda.cuda_paths import (
_get_libdevice_path_decision,
_get_cudalib_dir_path_decision,
get_system_ctk,
get_system_ctk_libdir,
_find_cuda_home_from_lib_path,
)
Expand Down Expand Up @@ -88,52 +86,6 @@ def check_lib_lookup(qout, qin):
status = False


@skip_on_cudasim("Library detection unsupported in the simulator")
@unittest.skipUnless(has_mp_get_context, "mp.get_context not available")
@skip_unless_conda_cudatoolkit("test assumes conda installed cudatoolkit")
class TestLibDeviceLookUp(LibraryLookupBase):
def test_libdevice_path_decision(self):
# Check that the default is using conda environment
by, info, warns = self.remote_do(self.do_clear_envs)
if has_cuda:
self.assertEqual(by, "Conda environment")
else:
self.assertEqual(by, "<unknown>")
self.assertIsNone(info)
self.assertFalse(warns)
# Check that CUDA_HOME works by removing conda-env
by, info, warns = self.remote_do(self.do_set_cuda_home)
self.assertEqual(by, "CUDA_HOME")
self.assertTrue(
info.startswith(os.path.join("mycudahome", "nvvm", "libdevice"))
)
self.assertFalse(warns)

if get_system_ctk("nvvm", "libdevice") is None:
# Fake remove conda environment so no cudatoolkit is available
by, info, warns = self.remote_do(self.do_clear_envs)
self.assertEqual(by, "<unknown>")
self.assertIsNone(info)
self.assertFalse(warns)
else:
# Use system available cudatoolkit
by, info, warns = self.remote_do(self.do_clear_envs)
self.assertEqual(by, "System")
self.assertFalse(warns)

@staticmethod
def do_clear_envs():
remove_env("CUDA_HOME")
remove_env("CUDA_PATH")
return True, _get_libdevice_path_decision()

@staticmethod
def do_set_cuda_home():
os.environ["CUDA_HOME"] = os.path.join("mycudahome")
_fake_non_conda_env()
return True, _get_libdevice_path_decision()


@skip_on_cudasim("Library detection unsupported in the simulator")
@unittest.skipUnless(has_mp_get_context, "mp.get_context not available")
@skip_unless_conda_cudatoolkit("test assumes conda installed cudatoolkit")
Expand Down