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specmicp/cmake/lto.cmake
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lto.cmake
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# Link time optimisation
# =======================
# Ref : https://lists.launchpad.net/kicad-developers/msg17900.html
# The script need to find the GCC/llvm version of ar / nm / ranlib to access
# the LTO plugin.
# If they are not in PATH, their location can be given by the variable BINUTILS_DIR
# They also set the flags to use.
if( SPECMICP_LTO AND USE_LD_GOLD)
check_cxx_compiler_flag( "-flto -fuse-ld=gold" HAVE_LTO_FLAG )
check_cxx_compiler_flag( "-flto -ffat-lto-objects -fuse-ld=gold" HAVE_FAT_LTO_OBJECT )
if (HAVE_LTO_FLAG)
# It's necessary to find the gcc/llvm ar/nm/ranlib because we need the lto plugin
if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
find_program( LTO_AR NAMES gcc-ar HINTS ${BINUTILS_DIR} )
find_program( LTO_NM NAMES gcc-nm HINTS ${BINUTILS_DIR} )
find_program( LTO_RANLIB NAMES gcc-ranlib HINTS ${BINUTILS_DIR} )
if ( HAVE_FLAT_LTO_OBJECT )
if( SPECMICP_FAT_LTO )
set ( LTO_FLAGS "-flto -ffat-lto-objects" )
else()
set ( LTO_FLAGS "-flto -fno-fat-lto-objects" )
endif( SPECMICP_FAT_LTO )
else()
set( LTO_FLAGS "-flto" )
endif( HAVE_FLAT_LTO_OBJECT )
elseif ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
find_program( LTO_AR NAMES llvm-ar HINTS ${BINUTILS_DIR} )
find_program( LTO_NM NAMES llvm-nm HINTS ${BINUTILS_DIR} )
find_program( LTO_RANLIB NAMES llvm-ranlib HINTS ${BINUTILS_DIR} )
set ( LTO_FLAGS " -flto")
endif()
if( LTO_AR AND LTO_NM AND LTO_RANLIB )
set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${LTO_FLAGS}")
# use correct programs
set( CMAKE_AR "${LTO_AR}" )
set( CMAKE_NM "${LTO_NM}" )
set( CMAKE_RANLIB "${LTO_RANLIB}" )
else()
message( WARNING "Binutils wrappers with LTO plugin could not be found. Disabling LTO." )
endif()
mark_as_advanced(
LTO_AR
LTO_NM
LTO_RANLIB
LTO_FLAGS
)
endif(HAVE_LTO_FLAG)
endif()
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