From: Augustin Degomme <adegomme@gmail.com>
Date: Mon, 24 Feb 2020 14:11:22 +0000 (+0100)
Subject: add an LTO_EXTRA_FLAG flag for cmake.
X-Git-Tag: v3.26~903
X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/d030a75b32b364f4fa464be3878256cf429f0cee?ds=sidebyside

add an LTO_EXTRA_FLAG flag for cmake.
This enables to give "auto", to use all cores, a number to use n cores and speedup linking phase.
flto=auto should be enabled by default in GCC 10, so this option can be used to give a lower value in case resources are scarce.
---

diff --git a/tools/cmake/Flags.cmake b/tools/cmake/Flags.cmake
index 740e7f5d8c..d44d17c10b 100644
--- a/tools/cmake/Flags.cmake
+++ b/tools/cmake/Flags.cmake
@@ -143,6 +143,10 @@ else()
 endif()
 if(enable_lto) # User wants LTO, and it seems usable. Go for it
   set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+  if(LTO_EXTRA_FLAG AND CMAKE_COMPILER_IS_GNUCC)
+    list(APPEND CMAKE_C_COMPILE_OPTIONS_IPO "-flto=${LTO_EXTRA_FLAG}")
+    list(APPEND CMAKE_CXX_COMPILE_OPTIONS_IPO "-flto=${LTO_EXTRA_FLAG}")
+  endif()
   # "Since version 4.9 gcc produces slim object files that only contain
   # the intermediate representation. In order to handle archives of
   # these objects you have to use the gcc wrappers: