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Reapply "Skipping host target exports during cross-compilation" (#210… (#210496)

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This reverts commit 42eb7db188. This
reland 3fbb037d03 (#209922).

Under CMake 4+, calling add_library(... SHARED IMPORTED) on a target
platform that lacks dynamic linking support triggers a fatal error. This
becomes an issue when building LLVM and runtimes for baremetal targets
like armv6m-none-eabi. This patch adds the option
"LLVM_OMIT_EXPORTS_FROM_CONFIG" in LLVM. When used in sub builds like
LLVM runtimes, it makes CMake to skip including the LLVM and Clang
exports. This mitigates the CMake 4 errors on baremetal runtimes.

42eb7db188 originally
apply this flag on all runtimes build and causing issues on runtimes
like intel-sycl-gpu, amdgpu-offload-ubuntu-22-cmake-build-only.
This PR only set this flag when the target platform lacks shared library
support.
This commit is contained in:
Haowei 2026-07-20 10:47:59 -07:00 committed by GitHub
parent a6b49df445
commit a04f87fdd9
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GPG key ID: B5690EEEBB952194
4 changed files with 27 additions and 3 deletions
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7
clang/cmake/modules/ClangConfig.cmake.in
View file

@ -12,8 +12,11 @@ set(CLANG_INCLUDE_DIRS "@CLANG_CONFIG_INCLUDE_DIRS@")
set(CLANG_LINK_CLANG_DYLIB "@CLANG_LINK_CLANG_DYLIB@")
set(CLANG_DEFAULT_LINKER "@CLANG_DEFAULT_LINKER@")
# Provide all our library targets to users.
@CLANG_CONFIG_INCLUDE_EXPORTS@
# Provide all our library targets to users. Skip when
# LLVM_OMIT_EXPORTS_FROM_CONFIG flag is set.
if(NOT LLVM_OMIT_EXPORTS_FROM_CONFIG)
@CLANG_CONFIG_INCLUDE_EXPORTS@
endif()
# By creating clang-tablegen-targets here, subprojects that depend on Clang's
# tablegen-generated headers can always depend on this target whether building

10
compiler-rt/cmake/Modules/CompilerRTUtils.cmake
View file

@ -313,6 +313,16 @@ macro(load_llvm_config)
"You are not using the monorepo layout. This configuration is DEPRECATED.")
endif()
# Exports from LLVM and Clang may contain shared libraries. When targeting
# platforms that lack shared library support, importing such
# exports unrestrictedly will trigger an error. Set
# LLVM_OMIT_EXPORTS_FROM_CONFIG flag to skip importing these exports
# when the target platform does not support shared libraries.
get_property(HAS_SHARED_SUPPORT GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS)
message(NOTICE "HAS_SHARED_SUPPORT is ${HAS_SHARED_SUPPORT}")
if (NOT HAS_SHARED_SUPPORT)
set(LLVM_OMIT_EXPORTS_FROM_CONFIG ON)
endif()
find_package(LLVM HINTS "${LLVM_CMAKE_DIR}")
if (NOT LLVM_FOUND)
message(WARNING "UNSUPPORTED COMPILER-RT CONFIGURATION DETECTED: "

2
llvm/cmake/modules/LLVMConfig.cmake.in
View file

@ -152,7 +152,7 @@ set(LLVM_ENABLE_SHARED_LIBS @BUILD_SHARED_LIBS@)
set(LLVM_DEFAULT_EXTERNAL_LIT "@LLVM_CONFIG_DEFAULT_EXTERNAL_LIT@")
set(LLVM_LIT_ARGS "@LLVM_LIT_ARGS@")
if(NOT TARGET LLVMSupport)
if(NOT TARGET LLVMSupport AND NOT LLVM_OMIT_EXPORTS_FROM_CONFIG)
@LLVM_CONFIG_INCLUDE_EXPORTS@
@llvm_config_include_buildtree_only_exports@
endif()

11
runtimes/CMakeLists.txt
View file

@ -76,6 +76,17 @@ if(LLVM_BINARY_DIR)
list(APPEND llvm_search_paths "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
list(APPEND clang_search_paths "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
endif()
# Exports from LLVM and Clang may contain shared libraries. When targeting
# platforms that lack shared library support, importing such
# exports unrestrictedly will trigger an error. Set
# LLVM_OMIT_EXPORTS_FROM_CONFIG flag to skip importing these exports
# when the target platform does not support shared libraries.
get_property(HAS_SHARED_SUPPORT GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS)
message(NOTICE "HAS_SHARED_SUPPORT is ${HAS_SHARED_SUPPORT}")
if (NOT HAS_SHARED_SUPPORT)
set(LLVM_OMIT_EXPORTS_FROM_CONFIG ON)
endif()
find_package(LLVM PATHS ${llvm_search_paths} NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH)
find_package(Clang PATHS ${clang_search_paths} NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH)