From 071926e94edabd47fed6639a1100a8e65de996a8 Mon Sep 17 00:00:00 2001
From: Siarhei Fedartsou <siarhei.fedartsou@gmail.com>
Date: Sat, 29 Jun 2024 22:07:18 +0200
Subject: [PATCH] Enable LTO by default

---
 .github/workflows/osrm-backend.yml | 6 +-----
 CHANGELOG.md                       | 1 +
 CMakeLists.txt                     | 2 +-
 scripts/ci/windows-build.bat       | 2 +-
 4 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/osrm-backend.yml b/.github/workflows/osrm-backend.yml
index 613c29a56..762e5dc0c 100644
--- a/.github/workflows/osrm-backend.yml
+++ b/.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
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b0eb65a8..23170c79d 100644
--- a/CHANGELOG.md
+++ b/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)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f114ee8d5..046d8877f 100644
--- a/CMakeLists.txt
+++ b/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)
diff --git a/scripts/ci/windows-build.bat b/scripts/ci/windows-build.bat
index 7b3f86146..2102c9340 100644
--- a/scripts/ci/windows-build.bat
+++ b/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 ^