build: Enable LTO (Link Time Optimization) #8654

CMakeLists.txt

@@ -85,6 +85,14 @@ endif()
 
 option(ENABLE_LIBINTL "enable libintl" ON)
 option(ENABLE_LIBICONV "enable libiconv" ON)
+if (MINGW)
+  # Disable LTO by default as it may not compile
+  # See https://github.com/Alexpux/MINGW-packages/issues/3516
+  # and https://github.com/neovim/neovim/pull/8654#issuecomment-402316672
+  option(ENABLE_LTO "enable link time optimization" OFF)
+else()
+  option(ENABLE_LTO "enable link time optimization" ON)
+endif()
 
 # Set default build type.
 if(NOT CMAKE_BUILD_TYPE)

src/nvim/CMakeLists.txt

@@ -399,6 +399,10 @@ if(JEMALLOC_FOUND)
   list(APPEND NVIM_EXEC_LINK_LIBRARIES ${JEMALLOC_LIBRARIES})
 endif()
 
+if(POLICY CMP0069)
+  cmake_policy(SET CMP0069 NEW)
+endif()
+
 add_executable(nvim ${NVIM_GENERATED_FOR_SOURCES} ${NVIM_GENERATED_FOR_HEADERS}
   ${NVIM_GENERATED_SOURCES} ${NVIM_SOURCES} ${NVIM_HEADERS})
 target_link_libraries(nvim ${NVIM_EXEC_LINK_LIBRARIES})
@@ -407,6 +411,14 @@ install_helper(TARGETS nvim)
 set_property(TARGET nvim APPEND PROPERTY
              INCLUDE_DIRECTORIES ${LUA_PREFERRED_INCLUDE_DIRS})
 
+if(ENABLE_LTO AND (POLICY CMP0069))
+  include(CheckIPOSupported)
+  check_ipo_supported(RESULT IPO_SUPPORTED)
+  if(IPO_SUPPORTED AND (NOT CMAKE_BUILD_TYPE MATCHES Debug))
+    set_property(TARGET nvim PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+  endif()
+endif()
+
 if(WIN32)
   # Copy DLLs and third-party tools to bin/ and install them along with nvim
   add_custom_target(nvim_runtime_deps ALL