From 306279901fccb634b7722de1b4cc17f70dd70f6b Mon Sep 17 00:00:00 2001
From: MajorP93 <majorp@mailbox.org>
Date: Fri, 13 Dec 2024 17:30:16 +0100
Subject: [PATCH]  ci: Use link-time optimization for building (#1636)

* ci: Use link-time optimization for building

* cmake: Set CMP0069 policy to new for external dependencies
* This enables LTO also when building external dependencies that do not
  handle CMP0069 in their CMake scripts.
---
 .github/workflows/build.yml | 12 ++++++------
 externals/CMakeLists.txt    |  3 +++
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 878c1086..bacfbea0 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -89,7 +89,7 @@ jobs:
         arch: amd64
 
     - name: Configure CMake
-      run: cmake --fresh -G Ninja -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+      run: cmake --fresh -G Ninja -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $env:NUMBER_OF_PROCESSORS
@@ -143,7 +143,7 @@ jobs:
         arch: amd64
 
     - name: Configure CMake
-      run: cmake --fresh -G Ninja -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+      run: cmake --fresh -G Ninja -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $env:NUMBER_OF_PROCESSORS
@@ -201,7 +201,7 @@ jobs:
         variant: sccache
 
     - name: Configure CMake
-      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_OSX_ARCHITECTURES=x86_64 -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache
+      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_OSX_ARCHITECTURES=x86_64 -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $(sysctl -n hw.ncpu)
@@ -265,7 +265,7 @@ jobs:
         variant: sccache
 
     - name: Configure CMake
-      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_OSX_ARCHITECTURES=x86_64 -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache
+      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_OSX_ARCHITECTURES=x86_64 -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $(sysctl -n hw.ncpu)
@@ -312,7 +312,7 @@ jobs:
         key: ${{ env.cache-name }}-${{ hashFiles('**/CMakeLists.txt', 'cmake/**') }}
 
     - name: Configure CMake
-      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $(nproc)
@@ -368,7 +368,7 @@ jobs:
         key: ${{ env.cache-name }}-${{ hashFiles('**/CMakeLists.txt', 'cmake/**') }}
 
     - name: Configure CMake
-      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+      run: cmake --fresh -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DENABLE_QT_GUI=ON -DENABLE_UPDATER=ON -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
 
     - name: Build
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} --parallel $(nproc)
diff --git a/externals/CMakeLists.txt b/externals/CMakeLists.txt
index 082be211..e1e67f23 100644
--- a/externals/CMakeLists.txt
+++ b/externals/CMakeLists.txt
@@ -8,6 +8,9 @@ set_directory_properties(PROPERTIES
     SYSTEM ON
 )
 
+# Set CMP0069 policy to "NEW" in order to ensure consistent behavior when building external targets with LTO enabled
+set(CMAKE_POLICY_DEFAULT_CMP0069 NEW)
+
 if (MSVC)
     # Silence "deprecation" warnings
     add_definitions(-D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS)