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if(NOT CCACHE_DEV_MODE)
# For ccache, using a faster linker is in practice only relevant to reduce the
# compile-link-test cycle for developers, so use the standard linker for
# non-developer builds.
return()
endif()
if(DISABLE_FASTEST_LINKER)
message(STATUS "Not probing for fastest linker")
return()
endif()
if(MSVC)
message(STATUS "Using standard linker for MSVC")
return()
endif()
if(ENABLE_IPO)
message(STATUS "Using standard linker for IPO")
return()
endif()
if(NOT CMAKE_SYSTEM_PROCESSOR STREQUAL x86_64)
# Be conservative and only probe for a faster linker on platforms that likely
# don't have toolchain bugs. See for example
# <https://www.sourceware.org/bugzilla/show_bug.cgi?id=22838>.
message(STATUS "Not probing for faster linker on ${CMAKE_SYSTEM_PROCESSOR}")
return()
endif()
function(check_linker linker)
string(TOUPPER ${linker} upper_linker)
file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/CMakefiles/CMakeTmp/main.c" "int main() { return 0; }")
try_compile(
HAVE_LD_${upper_linker}
${CMAKE_CURRENT_BINARY_DIR}
"${CMAKE_CURRENT_BINARY_DIR}/CMakefiles/CMakeTmp/main.c"
LINK_LIBRARIES "-fuse-ld=${linker}"
)
endfunction()
function(use_fastest_linker)
if(NOT CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
message(WARNING "use_fastest_linker() disabled, as it is not called at the project top level")
return()
endif()
# prefer an lld that matches the clang version
if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION MATCHES "^([0-9]*)\\.")
check_linker(lld-${CMAKE_MATCH_1})
if(HAVE_LD_LLD-${CMAKE_MATCH_1})
link_libraries("-fuse-ld=lld-${CMAKE_MATCH_1}")
message(STATUS "Using lld-${CMAKE_MATCH_1} linker")
return()
endif()
endif()
check_linker(lld)
if(HAVE_LD_LLD)
link_libraries("-fuse-ld=lld")
message(STATUS "Using lld linker")
return()
endif()
check_linker(gold)
if(HAVE_LD_GOLD)
link_libraries("-fuse-ld=gold")
message(STATUS "Using gold linker")
return()
endif()
message(STATUS "Using default linker")
endfunction()
option(USE_FASTER_LINKER "Use the lld or gold linker instead of the default for faster linking" TRUE)
if(USE_FASTER_LINKER)
use_fastest_linker()
endif()
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