From 7bce3771135ec738cd9db28beaa060c62bb53f6d Mon Sep 17 00:00:00 2001
From: Changming Sun <chasun@microsoft.com>
Date: Thu, 16 May 2019 14:06:38 -0700
Subject: [PATCH] Fix LTO build failure on ubuntu (#1048)

* Fix LTO build failure on ubuntu
---
 cmake/CMakeLists.txt           | 23 +++++++++++------------
 cmake/onnxruntime.cmake        |  5 ++++-
 cmake/onnxruntime_python.cmake |  5 ++++-
 3 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 2e6337efc6..85af7df79a 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -68,7 +68,8 @@ option(onnxruntime_ENABLE_MICROSOFT_INTERNAL "Use this option to enable/disable
 option(onnxruntime_USE_NUPHAR "Build with Nupha" OFF)
 option(onnxruntime_USE_BRAINSLICE "Build with BrainSlice" OFF)
 option(onnxruntime_USE_TENSORRT "Build with TensorRT support" OFF)
-option(onnxruntime_ENABLE_LTO "Enable link time optimization, which is not stable on older GCCs" OFF)
+option(onnxruntime_ENABLE_LTO "Enable link time optimization" ON)
+
 option(onnxruntime_CROSS_COMPILING "Cross compiling onnx runtime" OFF)
 option(onnxruntime_BUILD_SERVER "Build ONNX Runtime Server" OFF)
 option(onnxruntime_USE_FULL_PROTOBUF "Use full protobuf" OFF)
@@ -82,18 +83,16 @@ set(NSYNC_ENABLE_TESTS OFF CACHE BOOL "Build protobuf tests" FORCE)
 set(ONNX_ML 1)
 
 if(onnxruntime_ENABLE_LTO)
-  #LTO(or LTCG) is great, in our case it can reduce binary size by 1/3.
-  #cmake can only help us check if the compiler support LTO or not, it can't tell us if the feature works well
-  #Don't enable this option in Ubuntu 16.04, protoc will crash
-  include(CheckIPOSupported)
-  check_ipo_supported(RESULT ipo_enabled OUTPUT ipo_output)
   #TODO: figure out why nsync doesn't work
-  if(NOT onnxruntime_USE_NSYNC)
-    if(ipo_enabled)
-      set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE ON)
-      set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO ON)
-    else()
-      message(WARNING "IPO is not supported: ${ipo_output}")
+  if(onnxruntime_USE_NSYNC)
+    message(WARNING "IPO is not supported when nsync is in use")
+    set(onnxruntime_ENABLE_LTO OFF)
+  else()
+    include(CheckIPOSupported)
+    check_ipo_supported(RESULT ipo_enabled OUTPUT ipo_output)
+    if(NOT ipo_enabled)
+      message(WARNING "IPO is not supported by this compiler")
+      set(onnxruntime_ENABLE_LTO OFF)
     endif()
   endif()
 endif()
diff --git a/cmake/onnxruntime.cmake b/cmake/onnxruntime.cmake
index 952732b99d..ecf833a546 100644
--- a/cmake/onnxruntime.cmake
+++ b/cmake/onnxruntime.cmake
@@ -74,7 +74,10 @@ target_link_libraries(onnxruntime PRIVATE
 
 set_property(TARGET onnxruntime APPEND_STRING PROPERTY LINK_FLAGS ${ONNXRUNTIME_SO_LINK_FLAG})
 set_target_properties(onnxruntime PROPERTIES LINK_DEPENDS ${SYMBOL_FILE})
-
+if(onnxruntime_ENABLE_LTO)
+  set_target_properties(onnxruntime PROPERTIES INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)
+  set_target_properties(onnxruntime PROPERTIES INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO TRUE)
+endif()
 install(TARGETS onnxruntime
         ARCHIVE  DESTINATION ${CMAKE_INSTALL_LIBDIR}
         LIBRARY  DESTINATION ${CMAKE_INSTALL_LIBDIR}
diff --git a/cmake/onnxruntime_python.cmake b/cmake/onnxruntime_python.cmake
index 6f2d325090..24a2e973bc 100644
--- a/cmake/onnxruntime_python.cmake
+++ b/cmake/onnxruntime_python.cmake
@@ -109,7 +109,10 @@ endif()
 
 set_target_properties(onnxruntime_pybind11_state PROPERTIES PREFIX "")
 set_target_properties(onnxruntime_pybind11_state PROPERTIES FOLDER "ONNXRuntime")
-
+if(onnxruntime_ENABLE_LTO)
+  set_target_properties(onnxruntime_pybind11_state PROPERTIES INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)
+  set_target_properties(onnxruntime_pybind11_state PROPERTIES INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO TRUE)
+endif()
 if (MSVC)
   set_target_properties(onnxruntime_pybind11_state PROPERTIES SUFFIX ".pyd")
 else()