[Openmp-commits] [clang] [flang] [llvm] [openmp] [OpenMP] Remove LLVM_ENABLE_PROJECTS=openmp build mode (PR #176950)
Michael Kruse via Openmp-commits
openmp-commits at lists.llvm.org
Tue Jan 20 08:04:14 PST 2026
https://github.com/Meinersbur created https://github.com/llvm/llvm-project/pull/176950
Reapply #152189 and #174963 which were reverted because it broke publish-sphinx-docs and publish-doxygen-docs.
The build mode has been deprecated in #136314 and was supposed to be removed in the LLVM 21 release (#136314).
OpenMP currently supports 4 build modes:
* `cmake <llvm-project>/llvm -DLLVM_ENABLE_PROJECTS=openmp` (#152189)
* `cmake <llvm-project>/llvm -DLLVM_ENABLE_RUNTIMES=openmp` (bootstrapping build)
* `cmake <llvm-project>/openmp` (standalone build)
* `cmake <llvm-project>/runtimes -DLLVM_ENABLE_RUNTIMES=openmp` (runtimes default[^1]/standalone[^2] build)
Each build mode increased the maintanance overhead since all build modes must continue working and user confusion when there do not (see #151117, #174126, #154117, ...). Let's finally remove it.
[^1]: According to https://libcxx.llvm.org/VendorDocumentation.html#the-default-build
[^2]: According to https://github.com/llvm/llvm-project/blob/main/runtimes/CMakeLists.txt#L14
>From 097a30022211124c9025e5bc491cac0c65e8a97b Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Tue, 20 Jan 2026 16:44:44 +0100
Subject: [PATCH] Reapply "[OpenMP] Remove LLVM_ENABLE_PROJECTS=openmp build
mode (#174963)"
This reverts commit 8acf454ed1b297b239c0fa5901d09597bbbe6da5.
---
.github/workflows/docs.yml | 4 ++--
clang/utils/analyzer/entrypoint.py | 4 ++--
flang-rt/README.md | 4 ++--
flang/tools/f18/CMakeLists.txt | 19 ++-----------------
llvm/CMakeLists.txt | 23 ++++++++++-------------
llvm/runtimes/CMakeLists.txt | 7 -------
openmp/docs/ReleaseNotes.rst | 1 +
openmp/docs/SupportAndFAQ.rst | 4 +---
8 files changed, 20 insertions(+), 46 deletions(-)
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 1b1f027be1a7e..11a453b84418e 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -186,10 +186,10 @@ jobs:
steps.docs-changed-subprojects.outputs.openmp_any_changed == 'true' ||
steps.docs-changed-subprojects.outputs.workflow_any_changed == 'true'
run: |
- cmake -B openmp-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;openmp" -DLLVM_ENABLE_SPHINX=ON ./llvm
+ cmake -B openmp-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_RUNTIMES="openmp" -DLLVM_ENABLE_SPHINX=ON -DLLVM_INCLUDE_TESTS=OFF ./runtimes
TZ=UTC ninja -C openmp-build docs-openmp-html
mkdir built-docs/openmp
- cp -r openmp-build/docs/* built-docs/openmp/
+ cp -r openmp-build/openmp/docs/* built-docs/openmp/
- name: Build Polly docs
if: |
steps.docs-changed-subprojects.outputs.polly_any_changed == 'true' ||
diff --git a/clang/utils/analyzer/entrypoint.py b/clang/utils/analyzer/entrypoint.py
index c8dfc1a9f2ed8..20390d62374b8 100644
--- a/clang/utils/analyzer/entrypoint.py
+++ b/clang/utils/analyzer/entrypoint.py
@@ -53,8 +53,8 @@ def is_cmake_needed():
CMAKE_COMMAND = (
"cmake -G Ninja -DCMAKE_BUILD_TYPE=Release "
"-DCMAKE_INSTALL_PREFIX=/analyzer -DLLVM_TARGETS_TO_BUILD=X86 "
- '-DLLVM_ENABLE_PROJECTS="clang;openmp" -DLLVM_BUILD_RUNTIME=OFF '
- "-DCLANG_ENABLE_STATIC_ANALYZER=ON"
+ '-DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="openmp" '
+ "-DLLVM_BUILD_RUNTIME=OFF -DCLANG_ENABLE_STATIC_ANALYZER=ON"
)
diff --git a/flang-rt/README.md b/flang-rt/README.md
index 4fe66a85a269c..eecb7b8cbfdfd 100644
--- a/flang-rt/README.md
+++ b/flang-rt/README.md
@@ -58,8 +58,8 @@ not provide all C-ABI functionality (such as Windows).
cmake -S <path-to-llvm-project-source>/llvm \
-GNinja \
-DCMAKE_BUILD_TYPE=Release \
- -DLLVM_ENABLE_PROJECTS="clang;flang;openmp" \
- -DLLVM_ENABLE_RUNTIMES="compiler-rt;flang-rt" \
+ -DLLVM_ENABLE_PROJECTS="clang;flang" \
+ -DLLVM_ENABLE_RUNTIMES="compiler-rt;flang-rt;openmp" \
...
```
diff --git a/flang/tools/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
index 58ea782ce213e..ffd92f033840b 100644
--- a/flang/tools/f18/CMakeLists.txt
+++ b/flang/tools/f18/CMakeLists.txt
@@ -135,18 +135,7 @@ if (NOT CMAKE_CROSSCOMPILING)
# Special case for omp_lib.mod, because its source comes from openmp/runtime/src/include.
# It also produces two module files: omp_lib.mod and omp_lib_kinds.mod. Compile these
# files only if OpenMP support has been configured.
- if (LLVM_TOOL_OPENMP_BUILD)
- message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_PROJECTS, building omp_lib.mod")
- set(base ${FLANG_INTRINSIC_MODULES_DIR}/omp_lib)
- add_custom_command(OUTPUT ${base}.mod ${base}_kinds.mod
- COMMAND ${CMAKE_COMMAND} -E make_directory ${FLANG_INTRINSIC_MODULES_DIR}
- COMMAND flang -cpp -fsyntax-only ${opts} -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
- ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.F90
- DEPENDS flang ${FLANG_INTRINSIC_MODULES_DIR}/iso_c_binding.mod ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.F90 ${depends}
- )
- list(APPEND MODULE_FILES ${base}.mod ${base}_kinds.mod)
- install(FILES ${base}.mod ${base}_kinds.mod DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang" COMPONENT flang-module-interfaces)
- elseif ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
+ if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_RUNTIMES, assuming omp_lib.mod is built there")
else()
message(WARNING "Not building omp_lib.mod, no OpenMP runtime in either LLVM_ENABLE_PROJECTS or LLVM_ENABLE_RUNTIMES")
@@ -160,11 +149,7 @@ set_target_properties(module_files PROPERTIES FOLDER "Flang/Resources")
# TODO Move this to a more suitable location
# Copy the generated omp_lib.h header file, if OpenMP support has been configured.
-if (LLVM_TOOL_OPENMP_BUILD)
- message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_PROJECTS, building omp_lib.h")
- file(COPY ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.h DESTINATION "${CMAKE_BINARY_DIR}/include/flang/OpenMP/" FILE_PERMISSIONS OWNER_READ OWNER_WRITE)
- install(FILES ${CMAKE_BINARY_DIR}/include/flang/OpenMP/omp_lib.h DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang/OpenMP")
-elseif ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
+if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_RUNTIMES, assuming omp_lib.h is built there")
else()
message(STATUS "Not copying omp_lib.h, no OpenMP runtime in either LLVM_ENABLE_PROJECTS or LLVM_ENABLE_RUNTIMES")
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 9954053591d30..a85f0b0ede1d3 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -104,12 +104,7 @@ endif()
# This allows an easy way of setting up a build directory for llvm and another
# one for llvm+clang+... using the same sources.
# These projects will be included when "all" is included in LLVM_ENABLE_PROJECTS.
-set(LLVM_ALL_PROJECTS "bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libclc;lld;lldb;mlir;openmp;polly")
-if ("${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
- # Disallow 'openmp' as a LLVM PROJECT on AIX as the supported way is to use
- # LLVM_ENABLE_RUNTIMES.
- list(REMOVE_ITEM LLVM_ALL_PROJECTS openmp)
-endif()
+set(LLVM_ALL_PROJECTS "bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libclc;lld;lldb;mlir;polly")
# The "libc" project, which is not part of "all" projects, could be included in
# LLVM_ENABLE_PROJECTS. It is preferred to include "libc" in
@@ -126,6 +121,15 @@ if( LLVM_ENABLE_PROJECTS STREQUAL "all" )
set( LLVM_ENABLE_PROJECTS ${LLVM_ALL_PROJECTS})
endif()
+if ("openmp" IN_LIST LLVM_ENABLE_PROJECTS)
+ message(FATAL_ERROR "
+Support for the LLVM_ENABLE_PROJECTS=openmp build mode has been removed. Please switch to the bootstrapping build
+ cmake -S <llvm-project>/llvm -B build -DLLVM_ENABLE_PROJECTS=clang -DLLVM_ENABLE_RUNTIMES=openmp
+or to the runtimes default build
+ cmake -S <llvm-project>/runtimes -B build -DLLVM_ENABLE_RUNTIMES=openmp
+")
+endif()
+
foreach(proj ${LLVM_ENABLE_PROJECTS})
if (NOT proj STREQUAL "llvm" AND NOT "${proj}" IN_LIST LLVM_KNOWN_PROJECTS)
MESSAGE(FATAL_ERROR "${proj} isn't a known project: ${LLVM_KNOWN_PROJECTS}. Did you mean to enable it as a runtime in LLVM_ENABLE_RUNTIMES?")
@@ -195,13 +199,6 @@ if ("offload" IN_LIST LLVM_ENABLE_PROJECTS)
"https://openmp.llvm.org/ for building the runtimes.")
endif()
-if ("openmp" IN_LIST LLVM_ENABLE_PROJECTS)
- message(WARNING "Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will "
- "become a fatal error in a future release. Please use "
- "-DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at "
- "https://openmp.llvm.org/ for building the runtimes.")
-endif()
-
if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
if (NOT "flang" IN_LIST LLVM_ENABLE_PROJECTS)
message(FATAL_ERROR "Flang is not enabled, but is required for the Flang-RT runtime")
diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index 1302334777613..c5d1417ce583c 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -688,13 +688,6 @@ if(build_runtimes)
# We need to add the runtimes as a dependency because compiler-rt can be
# built as part of runtimes and we need the profile runtime for PGO
add_dependencies(clang-bootstrap-deps runtimes)
- # The bootstrap build will attempt to configure the offload runtime
- # before the openmp project which will error out due to failing to
- # find libomp.so. We must add omp as a dependency before runtimes
- # are configured.
- if("openmp" IN_LIST LLVM_ENABLE_PROJECTS AND "offload" IN_LIST LLVM_ENABLE_RUNTIMES)
- add_dependencies(clang-bootstrap-deps omp)
- endif()
endif()
if(LLVM_INCLUDE_TESTS)
diff --git a/openmp/docs/ReleaseNotes.rst b/openmp/docs/ReleaseNotes.rst
index 6c1a46caf1d81..b99947540acd7 100644
--- a/openmp/docs/ReleaseNotes.rst
+++ b/openmp/docs/ReleaseNotes.rst
@@ -27,3 +27,4 @@ Device Runtime
always build support for AMDGPU and NVPTX targets.
- Updated the offloading entry format but retained backwards compatibility with
the old format.
+- The LLVM_ENABLE_PROJECTS=openmp build mode has been removed.
\ No newline at end of file
diff --git a/openmp/docs/SupportAndFAQ.rst b/openmp/docs/SupportAndFAQ.rst
index f5a84784c8de8..4e2a6678e99dc 100644
--- a/openmp/docs/SupportAndFAQ.rst
+++ b/openmp/docs/SupportAndFAQ.rst
@@ -74,9 +74,7 @@ information about building LLVM is available `here
are targeted by OpenMP are enabled. That can be done by adjusting the CMake
option ``LLVM_TARGETS_TO_BUILD``. The corresponding targets for offloading to AMD
and Nvidia GPUs are ``"AMDGPU"`` and ``"NVPTX"``, respectively. By default,
-Clang will be built with all backends enabled. When building with
-``LLVM_ENABLE_RUNTIMES="openmp"`` OpenMP should not be enabled in
-``LLVM_ENABLE_PROJECTS`` because it is enabled by default.
+Clang will be built with all backends enabled.
Support for the device library comes from a separate build of the OpenMP library
that targets the GPU architecture. Building it requires enabling the runtime
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