[llvm-branch-commits] [llvm] [openmp] [openmp] Add support for Arm64X to libomp (PR #176157)
David Truby via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Mar 12 09:09:21 PDT 2026
https://github.com/DavidTruby updated https://github.com/llvm/llvm-project/pull/176157
>From a0258878453f27b3abfb7e5f3f78145c7f437b63 Mon Sep 17 00:00:00 2001
From: David Truby <david.truby at arm.com>
Date: Thu, 15 Jan 2026 12:53:09 +0000
Subject: [PATCH 1/2] [openmp] Add support for Arm64X to libomp
This patch allows building libomp.dll and libomp.lib as Arm64X binaries
containing both arm64 and arm64ec code and useable from applications
compiled for both architectures.
---
llvm/CMakeLists.txt | 16 +++++
llvm/runtimes/CMakeLists.txt | 6 ++
openmp/runtime/CMakeLists.txt | 11 ++++
openmp/runtime/cmake/arm64x.cmake | 97 +++++++++++++++++++++++++++++++
4 files changed, 130 insertions(+)
create mode 100644 openmp/runtime/cmake/arm64x.cmake
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 420774b629b8b..90390e1b2962e 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -223,6 +223,22 @@ if(LIBC_GPU_BUILD)
list(APPEND RUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES "libc")
endif()
+# Set up Arm64X build of the OpenMP runtime
+option(LIBOMP_ENABLE_ARM64X "Build the OpenMP library as Arm64X for compatibility with both Arm64 and Arm64EC" OFF)
+if(LIBOMP_ENABLE_ARM64X)
+ if(NOT LLVM_HOST_TRIPLE STREQUAL "aarch64-pc-windows-msvc")
+ messsage(FATAL_ERROR "Arm64X builds are only supported on Windows on Arm hosts.")
+ endif()
+ if(NOT LLVM_RUNTIME_TARGETS)
+ set(LLVM_RUNTIME_TARGETS "default")
+ endif()
+
+ if(NOT "arm64ec-pc-windows-msvc" IN_LIST LLVM_RUNTIME_TARGETS)
+ list(APPEND LLVM_RUNTIME_TARGETS "arm64ec-pc-windows-msvc")
+ endif()
+ set(RUNTIMES_arm64ec-pc-windows-msvc_LIBOMP_ENABLE_ARM64X ON)
+endif()
+
foreach(_name ${LLVM_RUNTIME_TARGETS})
if("libc" IN_LIST RUNTIMES_${_name}_LLVM_ENABLE_RUNTIMES)
if("${_name}" STREQUAL "amdgcn-amd-amdhsa" OR "${_name}" STREQUAL "nvptx64-nvidia-cuda" OR "${_name}" STREQUAL "spirv64-intel-unknown")
diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index fba0c7a01f972..56f0bd7891039 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -716,3 +716,9 @@ if(build_runtimes)
set_property(GLOBAL APPEND PROPERTY LLVM_ALL_ADDITIONAL_TEST_TARGETS runtimes ${extra_deps})
endif()
endif()
+
+if(LIBOMP_ENABLE_ARM64X)
+ # TODO: This only needs to depend on openmp-arm64ec-pc-windows-msvc, but the
+ # openmp targets set up for cross build runtimes don't currently work correctly.
+ add_dependencies(runtimes-configure runtimes-arm64ec-pc-windows-msvc-build)
+endif()
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 680e845ffdc95..06d015be85d0f 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -81,6 +81,11 @@ if(LIBOMP_ARCH STREQUAL "aarch64")
endif()
endif()
+# Include support file for arm64x builds
+if(LIBOMP_ENABLE_ARM64X)
+ include(arm64x)
+endif()
+
libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc ppc64 ppc64le aarch64 aarch64_32 aarch64_a64fx arm64ec mic mips mips64 riscv64 loongarch64 ve s390x sparc sparcv9 wasm32)
set(LIBOMP_LIB_TYPE normal CACHE STRING
@@ -432,3 +437,9 @@ set(LIBOMP_OMP_TOOLS_INCLUDE_DIR ${LIBOMP_OMP_TOOLS_INCLUDE_DIR} PARENT_SCOPE)
# make these variables available for tools/libompd:
set(LIBOMP_SRC_DIR ${LIBOMP_SRC_DIR} PARENT_SCOPE)
set(LIBOMP_OMPD_SUPPORT ${LIBOMP_OMPD_SUPPORT} PARENT_SCOPE)
+
+# Set up the targets we want to build arm64x libs for
+if(LIBOMP_ENABLE_ARM64X)
+ set(ARM64X_TARGETS omp ompimp)
+ handle_arm64x()
+endif()
diff --git a/openmp/runtime/cmake/arm64x.cmake b/openmp/runtime/cmake/arm64x.cmake
new file mode 100644
index 0000000000000..a32485fda1a17
--- /dev/null
+++ b/openmp/runtime/cmake/arm64x.cmake
@@ -0,0 +1,97 @@
+# check if we have the right linker flags to enable Arm64X
+include(CheckLinkerFlag)
+check_linker_flag(CXX "LINKER:/linkreprofullpathrsp:test_rsp" LIBOMP_HAVE_LINKREPROFULLPATHRSP_FLAG)
+if(NOT LIBOMP_HAVE_LINKREPROFULLPATHRSP_FLAG)
+ message(FATAL_ERROR "Arm64X builds are enabled but the linker does not support the required flag. "
+ "Either update Visual Studio if using link.exe or add lld to LLVM_ENABLE_PROJECTS to use a newer lld.")
+endif()
+
+# directory where the link.rsp file generated during arm64 build will be stored
+set(arm64ReproDir "${LLVM_BINARY_DIR}/runtimes/repros-arm64ec")
+
+# Don't install the runtime if we are doing an arm64ec build for arm64x.
+# The hybrid arm64x runtime will get installed by the host (default) runtime build
+if (LIBOMP_ARCH STREQUAL "arm64ec")
+ set(CMAKE_SKIP_INSTALL_RULES On)
+endif()
+
+# This function reads in the content of the rsp file outputted from the arm64ec build for a target,
+# then passes the arm64ec libs and objs to the linker using /machine:arm64x to combine them with the
+# arm64 counterparts and create an arm64x binary.
+function(set_arm64ec_dll_dependencies target)
+ set(REPRO_FILE "${arm64ReproDir}/${target}.rsp")
+ file(STRINGS "${REPRO_FILE}" ARM64_OBJS REGEX obj\"$)
+ file(STRINGS "${REPRO_FILE}" ARM64_LIBS REGEX lib\"$)
+ string(REPLACE "\"" ";" ARM64_OBJS "${ARM64_OBJS}")
+ string(REPLACE "\"" ";" ARM64_LIBS "${ARM64_LIBS}")
+
+ get_target_property(libs "${target}" LINK_FLAGS)
+ set(non_def "")
+
+ # Separate out the /def flag from the other link flags, so we can replcae it with /defArm64Native.
+ foreach(lib ${libs})
+ if(lib MATCHES ".*\.def")
+ string(REPLACE "/DEF:" "" def ${lib})
+ else()
+ list(APPEND non_def "${lib}")
+ endif()
+ endforeach()
+ # Remove the /def link flag
+ set_target_properties("${target}" PROPERTIES LINK_FLAGS "${non_def}")
+
+ target_sources("${target}" PRIVATE ${ARM64_OBJS})
+ target_link_options("${target}" PRIVATE /machine:arm64x "/def:${arm64ReproDir}/${target}.def" "/defArm64Native:${def}")
+endfunction()
+
+# Replace the /def flag with /defArm64Native and add the arm64ec /def file.
+function(set_arm64ec_lib_dependencies target)
+ get_target_property(opts ${target} STATIC_LIBRARY_OPTIONS)
+ string(REPLACE "/DEF:" "/defArm64Native:" opts "${opts}")
+ set_target_properties(${target} PROPERTIES STATIC_LIBRARY_OPTIONS "/machine:arm64x;${opts};/def:${arm64ReproDir}/${target}.def")
+endfunction()
+
+# Copy the def file for arm64ec to the repros directory so we can use it in the arm64x builds and add the linkreprofullpathrsp flag.
+function(handle_arm64ec_target target)
+ get_target_property(type "${target}" TYPE)
+ if(type STREQUAL "SHARED_LIBRARY")
+ get_target_property(libs "${target}" LINK_FLAGS)
+ elseif(type STREQUAL "STATIC_LIBRARY")
+ get_target_property(libs "${target}" STATIC_LIBRARY_OPTIONS)
+ endif()
+ list(FILTER libs INCLUDE REGEX ".*\.def")
+ string(REPLACE "/DEF:" "" def "${libs}")
+
+ add_custom_target("${target}.def"
+ BYPRODUCTS "${arm64ReproDir}/${target}.def"
+ COMMAND ${CMAKE_COMMAND} -E copy
+ "${def}"
+ "${arm64ReproDir}/${target}.def"
+ DEPENDS "${def}")
+ add_dependencies(${target} "${target}.def")
+ # tell the linker to produce this special rsp file that has absolute paths to its inputs
+ if(type STREQUAL "SHARED_LIBRARY")
+ target_link_options(${target} PRIVATE "/LINKREPROFULLPATHRSP:${arm64ReproDir}/${target}.rsp")
+ endif()
+endfunction()
+
+# Handle the targets we have requested arm64x builds for.
+function(handle_arm64x)
+ # During the arm64ec build, create rsp files that containes the absolute path to the inputs passed to the linker (objs, libs).
+ if("${LIBOMP_ARCH}" STREQUAL "arm64ec")
+ file(MAKE_DIRECTORY ${arm64ReproDir})
+ foreach (target ${ARM64X_TARGETS})
+ handle_arm64ec_target("${target}")
+ endforeach()
+
+ # During the ARM64 build, modify the link step appropriately to produce an arm64x binary
+ elseif("${LIBOMP_ARCH}" STREQUAL "aarch64")
+ foreach (target ${ARM64X_TARGETS})
+ get_target_property(type ${target} TYPE)
+ if(type STREQUAL "SHARED_LIBRARY")
+ set_arm64ec_dll_dependencies("${target}")
+ elseif(type STREQUAL "STATIC_LIBRARY")
+ set_arm64ec_lib_dependencies("${target}")
+ endif()
+ endforeach()
+ endif()
+endfunction()
>From 17db346dbcd55c452c03312a81d6a831dd67cf24 Mon Sep 17 00:00:00 2001
From: David Truby <david.truby at arm.com>
Date: Tue, 3 Mar 2026 15:37:50 +0000
Subject: [PATCH 2/2] CMake fixes
---
llvm/CMakeLists.txt | 4 ++--
openmp/runtime/CMakeLists.txt | 3 +--
openmp/runtime/cmake/arm64x.cmake | 16 ++++++++--------
3 files changed, 11 insertions(+), 12 deletions(-)
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 90390e1b2962e..f8108e31edd81 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -226,8 +226,8 @@ endif()
# Set up Arm64X build of the OpenMP runtime
option(LIBOMP_ENABLE_ARM64X "Build the OpenMP library as Arm64X for compatibility with both Arm64 and Arm64EC" OFF)
if(LIBOMP_ENABLE_ARM64X)
- if(NOT LLVM_HOST_TRIPLE STREQUAL "aarch64-pc-windows-msvc")
- messsage(FATAL_ERROR "Arm64X builds are only supported on Windows on Arm hosts.")
+ if(NOT CMAKE_HOST_WIN32 AND NOT CMAKE_HOST_SYSTEM_PROCESSOR STREQUAL "ARM64")
+ message(FATAL_ERROR "Arm64X builds are only supported on Windows hosts.")
endif()
if(NOT LLVM_RUNTIME_TARGETS)
set(LLVM_RUNTIME_TARGETS "default")
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 06d015be85d0f..3ccfa8463810f 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -440,6 +440,5 @@ set(LIBOMP_OMPD_SUPPORT ${LIBOMP_OMPD_SUPPORT} PARENT_SCOPE)
# Set up the targets we want to build arm64x libs for
if(LIBOMP_ENABLE_ARM64X)
- set(ARM64X_TARGETS omp ompimp)
- handle_arm64x()
+ handle_arm64x(omp ompimp)
endif()
diff --git a/openmp/runtime/cmake/arm64x.cmake b/openmp/runtime/cmake/arm64x.cmake
index a32485fda1a17..37682131b7c4c 100644
--- a/openmp/runtime/cmake/arm64x.cmake
+++ b/openmp/runtime/cmake/arm64x.cmake
@@ -28,10 +28,10 @@ function(set_arm64ec_dll_dependencies target)
get_target_property(libs "${target}" LINK_FLAGS)
set(non_def "")
- # Separate out the /def flag from the other link flags, so we can replcae it with /defArm64Native.
- foreach(lib ${libs})
+ # Separate out the /def flag from the other link flags, so we can replace it with /defArm64Native.
+ foreach(lib IN LISTS libs)
if(lib MATCHES ".*\.def")
- string(REPLACE "/DEF:" "" def ${lib})
+ string(REPLACE "/DEF:" "" "def" "${lib}")
else()
list(APPEND non_def "${lib}")
endif()
@@ -75,17 +75,17 @@ function(handle_arm64ec_target target)
endfunction()
# Handle the targets we have requested arm64x builds for.
-function(handle_arm64x)
+function(handle_arm64x targets)
# During the arm64ec build, create rsp files that containes the absolute path to the inputs passed to the linker (objs, libs).
- if("${LIBOMP_ARCH}" STREQUAL "arm64ec")
+ if(LIBOMP_ARCH STREQUAL "arm64ec")
file(MAKE_DIRECTORY ${arm64ReproDir})
- foreach (target ${ARM64X_TARGETS})
+ foreach (target IN LISTS targets)
handle_arm64ec_target("${target}")
endforeach()
# During the ARM64 build, modify the link step appropriately to produce an arm64x binary
- elseif("${LIBOMP_ARCH}" STREQUAL "aarch64")
- foreach (target ${ARM64X_TARGETS})
+ elseif(LIBOMP_ARCH STREQUAL "aarch64")
+ foreach (target IN LISTS targets)
get_target_property(type ${target} TYPE)
if(type STREQUAL "SHARED_LIBRARY")
set_arm64ec_dll_dependencies("${target}")
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