Enable LTO by default

.github/workflows/osrm-backend.yml

@@ -304,7 +304,6 @@ jobs:
             CXXCOMPILER: clang++-13
             ENABLE_CONAN: ON
             NODE_PACKAGE_TESTS_ONLY: ON
-            ENABLE_LTO: ON
 
           - name: conan-linux-debug-node
             build_node_package: true
@@ -316,7 +315,6 @@ jobs:
             CXXCOMPILER: clang++-13
             ENABLE_CONAN: ON
             NODE_PACKAGE_TESTS_ONLY: ON
-            ENABLE_LTO: ON
 
           - name: conan-macos-x64-release-node
             build_node_package: true
@@ -329,7 +327,6 @@ jobs:
             CUCUMBER_TIMEOUT: 60000
             ENABLE_ASSERTIONS: ON
             ENABLE_CONAN: ON
-            ENABLE_LTO: ON
 
           - name: conan-macos-arm64-release-node
             build_node_package: true
@@ -342,7 +339,6 @@ jobs:
             CUCUMBER_TIMEOUT: 60000
             ENABLE_ASSERTIONS: ON
             ENABLE_CONAN: ON
-            ENABLE_LTO: ON
 
     name: ${{ matrix.name}}
     continue-on-error: ${{ matrix.continue-on-error }}
@@ -527,7 +523,7 @@ jobs:
                  -DBUILD_TOOLS=${BUILD_TOOLS:-OFF} \
                  -DENABLE_CCACHE=ON \
                  -DCMAKE_INSTALL_PREFIX=${OSRM_INSTALL_DIR} \
-                 -DCMAKE_ENABLE_LTO=${ENABLE_LTO:-OFF}
+                 -DCMAKE_ENABLE_LTO=${ENABLE_LTO:-ON}
         make --jobs=${JOBS}
 
         if [[ "${NODE_PACKAGE_TESTS_ONLY}" != "ON" ]]; then

CHANGELOG.md

@@ -24,6 +24,7 @@
     - NodeJS:
       - CHANGED: Use node-api instead of NAN. [#6452](https://github.com/Project-OSRM/osrm-backend/pull/6452)
     - Misc:
+      - CHANGED: Use Link Time Optimisation whenever possible. [#6967](https://github.com/Project-OSRM/osrm-backend/pull/6967)
       - CHANGED: Use struct instead of tuple to define UnpackedPath. [#6974](https://github.com/Project-OSRM/osrm-backend/pull/6974)
       - CHANGED: Micro performance optimisation in map matching. [#6976](https://github.com/Project-OSRM/osrm-backend/pull/6976)
       - CHANGED: Re-use priority queue in StaticRTree. [#6952](https://github.com/Project-OSRM/osrm-backend/pull/6952)

CMakeLists.txt

@@ -31,7 +31,7 @@ option(ENABLE_ASSERTIONS "Use assertions in release mode" OFF)
 option(ENABLE_DEBUG_LOGGING "Use debug logging in release mode" OFF)
 option(ENABLE_COVERAGE "Build with coverage instrumentalisation" OFF)
 option(ENABLE_SANITIZER "Use memory sanitizer for Debug build" OFF)
-option(ENABLE_LTO "Use LTO if available" OFF)
+option(ENABLE_LTO "Use Link Time Optimisation" ON)
 option(ENABLE_FUZZING "Fuzz testing using LLVM's libFuzzer" OFF)
 option(ENABLE_NODE_BINDINGS "Build NodeJs bindings" OFF)
 option(ENABLE_CLANG_TIDY "Enables clang-tidy checks" OFF)

scripts/ci/windows-build.bat

@@ -11,7 +11,7 @@ mkdir build
 IF %ERRORLEVEL% NEQ 0 GOTO ERROR
 cd build
 IF %ERRORLEVEL% NEQ 0 GOTO ERROR
-cmake -DENABLE_CONAN=ON -DENABLE_NODE_BINDINGS=ON -DENABLE_LTO=ON -DCMAKE_BUILD_TYPE=%CONFIGURATION% -G "Visual Studio 17 2022" ..
+cmake -DENABLE_CONAN=ON -DENABLE_NODE_BINDINGS=ON -DCMAKE_BUILD_TYPE=%CONFIGURATION% -G "Visual Studio 17 2022" ..
 IF %ERRORLEVEL% NEQ 0 GOTO ERROR
 
 msbuild OSRM.sln ^