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[UR][Offload] Add option to build offload adapter #19864

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Merged
merged 10 commits into from
Sep 2, 2025
Merged

[UR][Offload] Add option to build offload adapter #19864

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2f8de1a
[UR][Offload] Add option to build offload adapter
againull Aug 19, 2025
750d5aa
Format
againull Aug 22, 2025
13d5408
Fix typos
againull Aug 22, 2025
d31e63c
Typo
againull Aug 22, 2025
de08c3f
Merge remote-tracking branch 'origin/sycl' into pushed
againull Aug 26, 2025
b65d042
Create worktree from existing workspace
againull Aug 25, 2025
b9a0b9f
Remove unused var
againull Aug 26, 2025
41ec405
Merge remote-tracking branch 'origin/sycl' into pushed
againull Aug 26, 2025
0410a38
Merge remote-tracking branch 'origin/sycl' into ur_offload_build_option
againull Sep 2, 2025
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againull Sep 2, 2025
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15 changes: 15 additions & 0 deletions buildbot/configure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,10 @@ def do_configure(args, passthrough_args):
if libclc_enabled:
llvm_enable_projects += ";libclc"

# DeviceRTL uses -fuse-ld=lld, so enable lld.
if args.offload:
llvm_enable_projects += ";lld"

if args.cuda:
llvm_targets_to_build += ";NVPTX"
libclc_targets_to_build = libclc_nvidia_target_names
Expand Down Expand Up @@ -210,6 +214,12 @@ def do_configure(args, passthrough_args):
"-DSYCL_ENABLE_MAJOR_RELEASE_PREVIEW_LIB={}".format(sycl_preview_lib),
"-DBUG_REPORT_URL=https://github.com/intel/llvm/issues",
]
if args.offload:
cmake_cmd.extend(
[
"-DUR_BUILD_ADAPTER_OFFLOAD=ON",
]
)

if libclc_enabled:
cmake_cmd.extend(
Expand Down Expand Up @@ -340,6 +350,11 @@ def main():
default="AMD",
help="choose hardware platform for HIP backend",
)
parser.add_argument(
"--offload",
action="store_true",
help="Enable UR liboffload adapter (experimental)",
)
parser.add_argument(
"--level_zero_adapter_version",
type=str,
Expand Down
98 changes: 76 additions & 22 deletions unified-runtime/source/adapters/offload/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,14 +5,84 @@

set(TARGET_NAME ur_adapter_offload)

set(UR_OFFLOAD_INSTALL_DIR "" CACHE PATH "Path to the directory containing libomptarget.so etc")
if (UR_OFFLOAD_INSTALL_DIR STREQUAL "")
message(FATAL_ERROR "UR_OFFLOAD_INSTALL_DIR must be defined for the Offload adapter")
endif()
add_ur_adapter(${TARGET_NAME}
SHARED
${CMAKE_CURRENT_SOURCE_DIR}/adapter.cpp
${CMAKE_CURRENT_SOURCE_DIR}/context.cpp
${CMAKE_CURRENT_SOURCE_DIR}/device.cpp
${CMAKE_CURRENT_SOURCE_DIR}/enqueue.cpp
${CMAKE_CURRENT_SOURCE_DIR}/event.cpp
${CMAKE_CURRENT_SOURCE_DIR}/kernel.cpp
${CMAKE_CURRENT_SOURCE_DIR}/memory.cpp
${CMAKE_CURRENT_SOURCE_DIR}/platform.cpp
${CMAKE_CURRENT_SOURCE_DIR}/program.cpp
${CMAKE_CURRENT_SOURCE_DIR}/queue.cpp
${CMAKE_CURRENT_SOURCE_DIR}/ur2offload.hpp
${CMAKE_CURRENT_SOURCE_DIR}/ur_interface_loader.cpp
${CMAKE_CURRENT_SOURCE_DIR}/usm.cpp
)

set(UR_OFFLOAD_INSTALL_DIR "" CACHE PATH "Path to the directory containing libomptarget.so etc")
set(UR_OFFLOAD_INCLUDE_DIR "" CACHE PATH "Path to the directory containing LLVM headers")
if (UR_OFFLOAD_INCLUDE_DIR STREQUAL "")
message(FATAL_ERROR "UR_OFFLOAD_INCLUDE_DIR must be defined for the Offload adapter")
if (UR_OFFLOAD_INSTALL_DIR STREQUAL "" OR UR_OFFLOAD_INCLUDE_DIR STREQUAL "")
include(ExternalProject)

set(LLVM_PROJECT_GIT https://github.com/llvm/llvm-project.git)
set(LLVM_PROJECT_TAG ffddf33beb8097e760fafcbdd28d56c1d055e820)
message(STATUS "UR_OFFLOAD_INSTALL_DIR and/or UR_OFFLOAD_INCLUDE_DIR not set, building liboffload runtime from source using llvm-project tag: ${LLVM_PROJECT_TAG}")
set(LLVM_PROJECT_SOURCE_DIR ${CMAKE_BINARY_DIR}/llvm-project-src)
set(OPENMP_INSTALL_DIR ${CMAKE_BINARY_DIR}/openmp-install)
# Install to the same directory as main build
set(UR_OFFLOAD_INSTALL_DIR ${CMAKE_INSTALL_PREFIX})
set(UR_OFFLOAD_INCLUDE_DIR ${CMAKE_INSTALL_PREFIX}/include)
# Clone llvm-project only once
ExternalProject_Add(llvm_project_src
GIT_REPOSITORY ${LLVM_PROJECT_GIT}
GIT_TAG ${LLVM_PROJECT_TAG}
SOURCE_DIR ${LLVM_PROJECT_SOURCE_DIR}
CONFIGURE_COMMAND ""
BUILD_COMMAND ""
INSTALL_COMMAND ""
UPDATE_COMMAND ""
)
# Build OpenMP runtime (required dependency for offload's libomptarget) from the cloned source
ExternalProject_Add(openmp_ext
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Why are we not just using LLVM_ENABLE_RUNTIMES="offload;openmp" here?

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We’re not using LLVM_ENABLE_RUNTIMES="offload;openmp" here because that mode requires configuring from the top-level llvm directory. In that flow, clang/llvm would be built as part of the runtimes build, which means clang/llvm ends up being built twice.
Instead, I build OpenMP and offload in standalone mode, reusing the existing clang/llvm build from intel/llvm.

Also, in the latest commit I improved this further: rather than cloning llvm-project again, I now create a git worktree from the already cloned intel/llvm repository, pulling in only the directories needed for the runtime build.

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I looked into this a while ago and figured out how to build openmp without a dependency on clang. It required a few patches, which I should really figure out who to harass about.

rather than cloning llvm-project again, I now create a git worktree from the already cloned intel/llvm repository

What if the runtimes are using a newer version of llvm-project that hasn't been pulled down into intel/llvm yet?

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@againull againull Aug 26, 2025 •
edited
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Sorry if the statement was confusing, worktree is created from fresh enough hash specified in LLVM_PROJECT_TAG, i.e. assumption is that llvm-project remote and its main branch is visible in the cloned intel/llvm repo, i.e. just trying to avoid re-cloning what's already available.

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The issue I'm thinking of is with, for example the commit ee5022d63549032235247269903f6ccf7e70bd02 (which doesn't affect liboffload, but pretend it does). That commit exists on llvm/llvm-project, but not on intel/llvm at the time of writing (at the time of writing).

Although, there's a commit from 13 minutes ago on the main branch, so it might get mirrored frequently enough that that's not an issue. How often does intel/llvm pull down new llvm/llvm-project changes?

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pulldowns approximately once per week/2weeks.
How dependent are openmp and offload from other components in llvm? I wonder why an option of standalone building mode even exists if those runtimes have to be built in-tree with entire llvm project of exact same version. If you believe openmp and offload are tightly coupled with the rest of llvm and has to be of exactly same version, then I can switch to what you propose - using LLVM_ENABLE_RUNTIMES="offload;openmp" i,e, re-building clang/llvm entirely from llvm-project.
Or we can try the current approach first for some time and switch to LLVM_ENABLE_RUNTIMES="offload;openmp" if there will be cases when build breaks because of such dependency.

# DeviceRTL uses -fuse-ld=lld, so add lld to the dependencies.
DEPENDS llvm_project_src llvm-tblgen LLVMSupport clang lld
SOURCE_DIR ${LLVM_PROJECT_SOURCE_DIR}/openmp
CMAKE_ARGS
-DCMAKE_INSTALL_PREFIX=${OPENMP_INSTALL_DIR}
-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-DCMAKE_C_COMPILER=${CMAKE_BINARY_DIR}/bin/clang
-DCMAKE_CXX_COMPILER=${CMAKE_BINARY_DIR}/bin/clang++
-DLIBOMP_OMPD_GDB_SUPPORT=OFF
INSTALL_COMMAND ${CMAKE_COMMAND} --build . --target install
UPDATE_COMMAND ""
DOWNLOAD_COMMAND ""
)

# Build liboffload runtime from the same source tree
ExternalProject_Add(offload_ext
DEPENDS openmp_ext
SOURCE_DIR ${LLVM_PROJECT_SOURCE_DIR}/offload
LIST_SEPARATOR |
CMAKE_ARGS
-DCMAKE_INSTALL_PREFIX=${UR_OFFLOAD_INSTALL_DIR}
-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-DCMAKE_C_COMPILER=${CMAKE_BINARY_DIR}/bin/clang
-DCMAKE_CXX_COMPILER=${CMAKE_BINARY_DIR}/bin/clang++
-DLIBOMPTARGET_LLVM_INCLUDE_DIRS=${LLVM_PROJECT_SOURCE_DIR}/llvm/include;${CMAKE_BINARY_DIR}/include
-DLLVM_DIR=${CMAKE_BINARY_DIR}/lib/cmake/llvm
-DLIBOMPTARGET_PLUGINS_TO_BUILD=cuda|amdgpu
-DLIBOMP_INCLUDE_DIR=${OPENMP_INSTALL_DIR}/include
-DLLVM_TABLEGEN=${CMAKE_BINARY_DIR}/bin/llvm-tblgen
-DCMAKE_PREFIX_PATH=${OPENMP_INSTALL_DIR};${CMAKE_BINARY_DIR}/bin
INSTALL_COMMAND ${CMAKE_COMMAND} --build . --target install
UPDATE_COMMAND ""
DOWNLOAD_COMMAND ""
BUILD_BYPRODUCTS "${UR_OFFLOAD_INSTALL_DIR}/lib/libLLVMOffload.so"
)
add_dependencies(${TARGET_NAME} offload_ext)
endif()

# When targetting CUDA devices, we need a workaround to avoid sending PTX to
Expand All @@ -29,22 +99,6 @@ if (NOT TARGET cudadrv)
)
endif()

add_ur_adapter(${TARGET_NAME}
SHARED
${CMAKE_CURRENT_SOURCE_DIR}/adapter.cpp
${CMAKE_CURRENT_SOURCE_DIR}/context.cpp
${CMAKE_CURRENT_SOURCE_DIR}/device.cpp
${CMAKE_CURRENT_SOURCE_DIR}/enqueue.cpp
${CMAKE_CURRENT_SOURCE_DIR}/event.cpp
${CMAKE_CURRENT_SOURCE_DIR}/kernel.cpp
${CMAKE_CURRENT_SOURCE_DIR}/memory.cpp
${CMAKE_CURRENT_SOURCE_DIR}/platform.cpp
${CMAKE_CURRENT_SOURCE_DIR}/program.cpp
${CMAKE_CURRENT_SOURCE_DIR}/queue.cpp
${CMAKE_CURRENT_SOURCE_DIR}/ur2offload.hpp
${CMAKE_CURRENT_SOURCE_DIR}/ur_interface_loader.cpp
${CMAKE_CURRENT_SOURCE_DIR}/usm.cpp
)
install_ur_library(${TARGET_NAME})

set_target_properties(${TARGET_NAME} PROPERTIES
Expand Down
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