From af7892c08b2d4984f4c93bb8c7cc07aec36b5055 Mon Sep 17 00:00:00 2001
From: Damjan Marion <damarion@cisco.com>
Date: Thu, 22 Oct 2020 14:23:47 +0200
Subject: build: link time optimization for release builds

Type: improvement
Change-Id: I0e24f1d2ad5c7a11a8bd40125428f86aca867bec
Signed-off-by: Damjan Marion <damarion@cisco.com>
---
 src/CMakeLists.txt          | 13 ++++++++++++-
 src/cmake/library.cmake     |  9 ++++++++-
 src/vppinfra/CMakeLists.txt |  1 +
 3 files changed, 21 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0d971fd8ebc..6fc243ca4d2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -11,13 +11,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.10)
 
 set(CMAKE_C_COMPILER_NAMES clang-11 clang-10 clang-9 gcc-10 gcc-9 cc)
 
 project(vpp C)
 
 include(CheckCCompilerFlag)
+include(CheckIPOSupported)
 include(cmake/misc.cmake)
 include(cmake/cpu.cmake)
 include(cmake/ccache.cmake)
@@ -105,6 +106,16 @@ string(REPLACE ";" " " BUILD_TYPES "${BUILD_TYPES}")
 set_property(CACHE CMAKE_BUILD_TYPE PROPERTY
 	     HELPSTRING "Build type - valid options are: ${BUILD_TYPES}")
 
+##############################################################################
+# link time optimizations
+##############################################################################
+if (CMAKE_BUILD_TYPE_UC STREQUAL "RELEASE")
+  check_ipo_supported(RESULT _result)
+  if (_result)
+    option(VPP_USE_LTO "Link time optimization of release binaries" ON)
+  endif()
+endif()
+
 ##############################################################################
 # sanitizers
 ##############################################################################
diff --git a/src/cmake/library.cmake b/src/cmake/library.cmake
index 06248a57aa3..a5b6c76d2d1 100644
--- a/src/cmake/library.cmake
+++ b/src/cmake/library.cmake
@@ -13,7 +13,7 @@
 
 macro(add_vpp_library lib)
   cmake_parse_arguments(ARG
-    ""
+    "LTO"
     "COMPONENT"
     "SOURCES;MULTIARCH_SOURCES;API_FILES;LINK_LIBRARIES;INSTALL_HEADERS;DEPENDS"
     ${ARGN}
@@ -38,6 +38,13 @@ macro(add_vpp_library lib)
     COMPONENT ${ARG_COMPONENT}
   )
 
+  if (ARG_LTO AND VPP_USE_LTO)
+     set_property(TARGET ${lib} PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+     target_compile_options (${lib} PRIVATE "-ffunction-sections")
+     target_compile_options (${lib} PRIVATE "-fdata-sections")
+     target_link_libraries (${lib} "-Wl,--gc-sections")
+  endif()
+
   if(ARG_MULTIARCH_SOURCES)
     vpp_library_set_multiarch_sources(${lib} "${ARG_DEPENDS}" ${ARG_MULTIARCH_SOURCES})
   endif()
diff --git a/src/vppinfra/CMakeLists.txt b/src/vppinfra/CMakeLists.txt
index e0ae662e4ba..a670181732e 100644
--- a/src/vppinfra/CMakeLists.txt
+++ b/src/vppinfra/CMakeLists.txt
@@ -198,6 +198,7 @@ add_vpp_library(vppinfra
   LINK_LIBRARIES m
   INSTALL_HEADERS ${VPPINFRA_HEADERS}
   COMPONENT libvppinfra
+  LTO
 )
 
 ##############################################################################
-- 
cgit 1.2.3-korg