When --enable-cet is used to configure GCC, enable Intel CET in libphobos.
	* Makefile.am (AM_MAKEFLAGS): Add $(CET_FLAGS) to GCC FLAGS.
	* configure.ac (CET_FLAGS): Add GCC_CET_FLAGS and AC_SUBST.
	* Makefile.in: Regenerated.
	* aclocal.m4: Likewise.
	* configure.ac: Likewise.
+2020-05-08  H.J. Lu  <hongjiu.lu@intel.com>
+
+       * Makefile.am (AM_MAKEFLAGS): Add $(CET_FLAGS) to GCC FLAGS.
+       * configure.ac (CET_FLAGS): Add GCC_CET_FLAGS and AC_SUBST.
+       * Makefile.in: Regenerated.
+       * aclocal.m4: Likewise.
+       * configure.ac: Likewise.
+
 2020-04-30  Iain Buclaw  <ibuclaw@gdcproject.org>
 
        * libdruntime/Makefile.am (DRUNTIME_SOURCES_CONFIGURED): Remove
 
        "AR_FLAGS=$(AR_FLAGS)" \
        "CC_FOR_BUILD=$(CC_FOR_BUILD)" \
        "CC_FOR_TARGET=$(CC_FOR_TARGET)" \
-       "CCASFLAGS=$(CCASFLAGS)" \
-       "CFLAGS=$(CFLAGS)" \
-       "CXXFLAGS=$(CXXFLAGS)" \
+       "CCASFLAGS=$(CCASFLAGS) $(CET_FLAGS)" \
+       "CFLAGS=$(CFLAGS) $(CET_FLAGS)" \
+       "CXXFLAGS=$(CXXFLAGS) $(CET_FLAGS)" \
        "CFLAGS_FOR_BUILD=$(CFLAGS_FOR_BUILD)" \
-       "CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET)" \
+       "CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET) $(CET_FLAGS)" \
        "GDC_FOR_TARGET=$(GDC_FOR_TARGET)" \
        "GDC=$(GDC)" \
-       "GDCFLAGS=$(GDCFLAGS)" \
+       "GDCFLAGS=$(GDCFLAGS) $(CET_FLAGS)" \
        "INSTALL=$(INSTALL)" \
        "INSTALL_DATA=$(INSTALL_DATA)" \
        "INSTALL_PROGRAM=$(INSTALL_PROGRAM)" \
 
 CCAS = @CCAS@
 CCASFLAGS = @CCASFLAGS@
 CC_FOR_BUILD = @CC_FOR_BUILD@
+CET_FLAGS = @CET_FLAGS@
 CFLAGS = @CFLAGS@
 CFLAGS_FOR_BUILD = @CFLAGS_FOR_BUILD@
 CHECKING_DFLAGS = @CHECKING_DFLAGS@
        "AR_FLAGS=$(AR_FLAGS)" \
        "CC_FOR_BUILD=$(CC_FOR_BUILD)" \
        "CC_FOR_TARGET=$(CC_FOR_TARGET)" \
-       "CCASFLAGS=$(CCASFLAGS)" \
-       "CFLAGS=$(CFLAGS)" \
-       "CXXFLAGS=$(CXXFLAGS)" \
+       "CCASFLAGS=$(CCASFLAGS) $(CET_FLAGS)" \
+       "CFLAGS=$(CFLAGS) $(CET_FLAGS)" \
+       "CXXFLAGS=$(CXXFLAGS) $(CET_FLAGS)" \
        "CFLAGS_FOR_BUILD=$(CFLAGS_FOR_BUILD)" \
-       "CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET)" \
+       "CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET) $(CET_FLAGS)" \
        "GDC_FOR_TARGET=$(GDC_FOR_TARGET)" \
        "GDC=$(GDC)" \
-       "GDCFLAGS=$(GDCFLAGS)" \
+       "GDCFLAGS=$(GDCFLAGS) $(CET_FLAGS)" \
        "INSTALL=$(INSTALL)" \
        "INSTALL_DATA=$(INSTALL_DATA)" \
        "INSTALL_PROGRAM=$(INSTALL_PROGRAM)" \
 
 ]) # _AM_PROG_TAR
 
 m4_include([../config/acx.m4])
+m4_include([../config/cet.m4])
+m4_include([../config/enable.m4])
 m4_include([../config/lead-dot.m4])
 m4_include([../config/multi.m4])
 m4_include([../config/override.m4])
 
 CFLAGS_FOR_BUILD
 CC_FOR_BUILD
 AR
+CET_FLAGS
 RANLIB
 MAINT
 MAINTAINER_MODE_FALSE
 enable_multilib
 enable_silent_rules
 enable_maintainer_mode
+enable_cet
 enable_shared
 enable_static
 with_pic
   --enable-maintainer-mode
                           enable make rules and dependencies not useful (and
                           sometimes confusing) to the casual installer
+  --enable-cet            enable Intel CET in target libraries [default=no]
   --enable-shared[=PKGS]  build shared libraries [default=yes]
   --enable-static[=PKGS]  build static libraries [default=yes]
   --enable-fast-install[=PKGS]
 fi
 
 
+# Add CET specific flags if CET is enabled
+ # Check whether --enable-cet was given.
+if test "${enable_cet+set}" = set; then :
+  enableval=$enable_cet;
+      case "$enableval" in
+       yes|no|auto) ;;
+       *) as_fn_error $? "Unknown argument to enable/disable cet" "$LINENO" 5 ;;
+                          esac
+
+else
+  enable_cet=no
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for CET support" >&5
+$as_echo_n "checking for CET support... " >&6; }
+
+case "$host" in
+  i[34567]86-*-linux* | x86_64-*-linux*)
+    case "$enable_cet" in
+      auto)
+       # Check if target supports multi-byte NOPs
+       # and if assembler supports CET insn.
+       cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+#if !defined(__SSE2__)
+#error target does not support multi-byte NOPs
+#else
+asm ("setssbsy");
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  enable_cet=yes
+else
+  enable_cet=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+       ;;
+      yes)
+       # Check if assembler supports CET.
+       cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+asm ("setssbsy");
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+else
+  as_fn_error $? "assembler with CET support is required for --enable-cet" "$LINENO" 5
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+       ;;
+    esac
+    ;;
+  *)
+    enable_cet=no
+    ;;
+esac
+if test x$enable_cet = xyes; then
+  CET_FLAGS="-fcf-protection -mshstk"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+
 # This should be inherited in the recursive make, but ensure it is defined.
 test "$AR" || AR=ar
 
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11650 "configure"
+#line 11737 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11756 "configure"
+#line 11843 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
 
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET
 
+# Add CET specific flags if CET is enabled
+GCC_CET_FLAGS(CET_FLAGS)
+AC_SUBST(CET_FLAGS)
+
 # This should be inherited in the recursive make, but ensure it is defined.
 test "$AR" || AR=ar
 AC_SUBST(AR)