From b7db4cbab037c8ff5a52206eb405d26720412275 Mon Sep 17 00:00:00 2001
From: Kittywhiskers Van Gogh <63189531+kwvg@users.noreply.github.com>
Date: Fri, 1 Oct 2021 12:37:03 +0800
Subject: [PATCH] merge bitcoin#23152: add `--enable-lto` configuration option

---
 configure.ac    | 17 +++++++++++++++--
 src/Makefile.am |  4 ++--
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 35eaffcfbf..50a484d1c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -334,6 +334,11 @@ AC_ARG_WITH([boost-process],
     [boost_process=$withval],
     [boost_process=no])
 
+AC_ARG_ENABLE([lto],
+    [AS_HELP_STRING([--enable-lto],[build using LTO (default is no)])],
+    [enable_lto=$enableval],
+    [enable_lto=no])
+
 AC_LANG_PUSH([C++])
 
 dnl Check for a flag to turn compiler warnings into errors. This is helpful for checks which may
@@ -392,6 +397,11 @@ else
     fi
 fi
 
+if test "x$enable_lto" = "xyes"; then
+  AX_CHECK_COMPILE_FLAG([-flto], [LTO_CXXFLAGS="$LTO_CXXFLAGS -flto"], [AC_MSG_ERROR([compile failed with -flto])], [$CXXFLAG_WERROR])
+  AX_CHECK_LINK_FLAG([-flto], [LTO_LDFLAGS="$LTO_LDFLAGS -flto"], [AC_MSG_ERROR([link failed with -flto])], [$CXXFLAG_WERROR])
+fi
+
 if test "x$enable_stacktraces" != xno; then
   AC_CHECK_HEADERS([execinfo.h], [], [enable_stacktraces=no])
 fi
@@ -1886,6 +1896,8 @@ AC_SUBST(GPROF_LDFLAGS)
 AC_SUBST(HARDENED_CXXFLAGS)
 AC_SUBST(HARDENED_CPPFLAGS)
 AC_SUBST(HARDENED_LDFLAGS)
+AC_SUBST(LTO_CXXFLAGS)
+AC_SUBST(LTO_LDFLAGS)
 AC_SUBST(PIC_FLAGS)
 AC_SUBST(PIE_FLAGS)
 AC_SUBST(SANITIZER_CXXFLAGS)
@@ -1985,6 +1997,7 @@ echo "  crash hooks enabled = $enable_crashhooks"
 echo "  miner enabled       = $enable_miner"
 echo "  gprof enabled       = $enable_gprof"
 echo "  werror              = $enable_werror"
+echo "  LTO                 = $enable_lto"
 echo
 echo "  target os           = $host_os"
 echo "  build os            = $build_os"
@@ -1993,7 +2006,7 @@ echo "  CC                  = $CC"
 echo "  CFLAGS              = $PTHREAD_CFLAGS $CFLAGS"
 echo "  CPPFLAGS            = $DEBUG_CPPFLAGS $HARDENED_CPPFLAGS $CPPFLAGS"
 echo "  CXX                 = $CXX"
-echo "  CXXFLAGS            = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
-echo "  LDFLAGS             = $PTHREAD_LIBS $HARDENED_LDFLAGS $GPROF_LDFLAGS $LDFLAGS"
+echo "  CXXFLAGS            = $LTO_CXXFLAGS $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
+echo "  LDFLAGS             = $LTO_LDFLAGS $PTHREAD_LIBS $HARDENED_LDFLAGS $GPROF_LDFLAGS $LDFLAGS"
 echo "  ARFLAGS             = $ARFLAGS"
 echo
diff --git a/src/Makefile.am b/src/Makefile.am
index e91973a67c..170c900961 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -9,8 +9,8 @@ print-%: FORCE
 
 DIST_SUBDIRS = secp256k1
 
-AM_LDFLAGS = $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS)
-AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(WARN_CXXFLAGS) $(NOWARN_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS)
+AM_LDFLAGS = $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS) $(LTO_LDFLAGS)
+AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(WARN_CXXFLAGS) $(NOWARN_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS) $(LTO_CXXFLAGS)
 AM_CPPFLAGS = $(DEBUG_CPPFLAGS) $(HARDENED_CPPFLAGS)
 AM_LIBTOOLFLAGS = --preserve-dup-deps
 PTHREAD_FLAGS = $(PTHREAD_CFLAGS) $(PTHREAD_LIBS)