Add CMake flag USE_LTO

CMakeLists.txt

@@ -17,16 +17,28 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-stack-protector")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-stack-protector")
 set(CMAKE_C_FLAGS_FASTBUILD "${CMAKE_C_FLAGS_RELEASE}")
 set(CMAKE_C_FLAGS_GCSTATS "${CMAKE_C_FLAGS_DEBUG}")
+if (USE_LTO)
 set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -flto")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -flto -fno-omit-frame-pointer")
+endif()
+set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -fno-omit-frame-pointer")
+if (USE_LTO)
+set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -flto")
+endif()
 set(CMAKE_CXX_FLAGS_FASTBUILD "${CMAKE_CXX_FLAGS_RELEASE}")
 set(CMAKE_CXX_FLAGS_GCSTATS "${CMAKE_CXX_FLAGS_DEBUG}")
+if (USE_LTO)
 set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -flto")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -flto -fno-omit-frame-pointer")
+endif()
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -fno-omit-frame-pointer")
+if (USE_LTO)
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -flto")
+endif()
 set(CMAKE_EXE_LINKER_FLAGS_FASTBUILD "${CMAKE_EXE_LINKER_FLAGS_RELEASE}")
 set(CMAKE_EXE_LINKER_FLAGS_GCSTATS "${CMAKE_EXE_LINKER_FLAGS_DEBUG}")
+if (USE_LTO)
 set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto")
 set(CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto")
+endif()
 
 if(APPLE)
 set(BACKEND_TARGET_TRIPLE "x86_64-apple-darwin")
@@ -39,7 +51,7 @@ pkg_check_modules(FFI REQUIRED libffi)
 include_directories(AFTER ${FFI_INCLUDE_DIRS})
 link_directories(AFTER ${FFI_LIBRARY_DIRS})
 
-if (CMAKE_BUILD_TYPE STREQUAL "Release" OR CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
+if (USE_LTO AND (CMAKE_BUILD_TYPE STREQUAL "Release" OR CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo"))
 set(LLVM_KOMPILE_LTO "lto")
 else()
 set(LLVM_KOMPILE_LTO "nolto")

nix/llvm-backend.nix

@@ -36,11 +36,13 @@ stdenv.mkDerivation {
   buildInputs = [ boost gmp libffi libyaml jemalloc mpfr ];
 
   enableParallelBuilding = false;
-  cmakeFlags = [
-    ''-DCMAKE_C_COMPILER=${lib.getBin stdenv.cc}/bin/cc''
-    ''-DCMAKE_CXX_COMPILER=${lib.getBin stdenv.cc}/bin/c++''
-    ''-DCMAKE_VERBOSE_MAKEFILE=ON''
-  ];
+  cmakeFlags =
+    [
+      ''-DCMAKE_C_COMPILER=${lib.getBin stdenv.cc}/bin/cc''
+      ''-DCMAKE_CXX_COMPILER=${lib.getBin stdenv.cc}/bin/c++''
+      ''-DCMAKE_VERBOSE_MAKEFILE=ON''
+      ''-DUSE_LTO=${if stdenv.isDarwin then "FALSE" else "TRUE"}''
+    ];
   NIX_CFLAGS_COMPILE = [ "-Wno-error" ];
 
   doCheck = true;