build: add --enable-lto configuration option

Co-authored-by: Cory Fields <[email protected]>
Co-authored-by: Elichai Turkel <[email protected]>

Author: 3 people

configure.ac

@@ -323,6 +323,11 @@ AC_ARG_ENABLE([external-signer],
     [use_external_signer=$enableval],
     [use_external_signer=yes])
 
+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
@@ -370,6 +375,11 @@ if test "x$enable_debug" = xyes; then
   AX_CHECK_COMPILE_FLAG([-ftrapv], [DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -ftrapv"], [], [$CXXFLAG_WERROR])
 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])], [$CXXFLAG_WERROR])
+fi
+
 if test x$use_sanitizers != x; then
   dnl First check if the compiler accepts flags. If an incompatible pair like
   dnl -fsanitize=address,thread is used here, this check will fail. This will also
@@ -1826,6 +1836,8 @@ 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)
@@ -1941,6 +1953,7 @@ echo "  sanitizers      = $use_sanitizers"
 echo "  debug enabled   = $enable_debug"
 echo "  gprof enabled   = $enable_gprof"
 echo "  werror          = $enable_werror"
+echo "  LTO             = $enable_lto"
 echo
 echo "  target os       = $TARGET_OS"
 echo "  build os        = $build_os"
@@ -1949,7 +1962,7 @@ 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

src/Makefile.am

@@ -8,8 +8,8 @@ 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)