Index: config/avr/driver-avr.c
===================================================================
--- config/avr/driver-avr.c	(revision 221321)
+++ config/avr/driver-avr.c	(working copy)
@@ -60,7 +60,10 @@ avr_device_to_as (int argc, const char *
 
   return concat ("-mmcu=", avr_current_arch->arch_name,
     avr_current_device->dev_attribute & AVR_ERRATA_SKIP ? "" : " -mno-skip-bug",
-    avr_current_device->dev_attribute & AVR_ISA_RMW ? " -mrmw" : "", NULL);
+#ifdef HAVE_AS_AVR_MRMW_OPTION
+    avr_current_device->dev_attribute & AVR_ISA_RMW ? " -mrmw" : "",
+#endif // have as -mrmw
+    NULL);
 }
 
 /* Returns command line parameters to pass to ld.  */
Index: configure
===================================================================
--- configure	(revision 221321)
+++ configure	(working copy)
@@ -24158,6 +24158,39 @@ $as_echo "#define HAVE_AS_NO_MUL_BUG_ABO
 fi
     ;;
 
+  avr-*-*)
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for -mrmw option" >&5
+$as_echo_n "checking assembler for -mrmw option... " >&6; }
+if test "${gcc_cv_as_avr_mrmw+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  gcc_cv_as_avr_mrmw=no
+  if test x$gcc_cv_as != x; then
+    $as_echo '.text' > conftest.s
+    if { ac_try='$gcc_cv_as $gcc_cv_as_flags -mrmw -o conftest.o conftest.s >&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+    then
+	gcc_cv_as_avr_mrmw=yes
+    else
+      echo "configure: failed program was" >&5
+      cat conftest.s >&5
+    fi
+    rm -f conftest.o conftest.s
+  fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_avr_mrmw" >&5
+$as_echo "$gcc_cv_as_avr_mrmw" >&6; }
+if test $gcc_cv_as_avr_mrmw = yes; then
+
+$as_echo "#define HAVE_AS_AVR_MRMW_OPTION 1" >>confdefs.h
+
+fi
+    ;;
+
   sparc*-*-*)
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for .register" >&5
 $as_echo_n "checking assembler for .register... " >&6; }
Index: config.in
===================================================================
--- config.in	(revision 221321)
+++ config.in	(working copy)
@@ -211,6 +211,12 @@ that are supported for each access macro
 #endif
 
 
+/* Define if your assembler supports -mrmw option. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_AS_AVR_MRMW_OPTION
+#endif
+
+
 /* Define if your assembler supports cmpb. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_AS_CMPB
@@ -235,6 +241,12 @@ that are supported for each access macro
 #endif
 
 
+/* Define if your assembler supports .module. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_AS_DOT_MODULE
+#endif
+
+
 /* Define if your assembler supports DSPR1 mult. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_AS_DSPR1_MULT
@@ -447,12 +459,6 @@ that are supported for each access macro
 #endif
 
 
-/* Define if the assembler understands .module. */
-#ifndef USED_FOR_TARGET
-#undef HAVE_AS_DOT_MODULE
-#endif
-
-
 /* Define if your assembler supports the -no-mul-bug-abort option. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_AS_NO_MUL_BUG_ABORT_OPTION
Index: configure.ac
===================================================================
--- configure.ac	(revision 221321)
+++ configure.ac	(working copy)
@@ -3603,6 +3603,13 @@ [	.set nomacro
 		[Define if your assembler supports the -no-mul-bug-abort option.])])
     ;;
 
+  avr-*-*)
+    gcc_GAS_CHECK_FEATURE([-mrmw option], gcc_cv_as_avr_mrmw,,
+      [-mrmw], [.text],,
+      [AC_DEFINE(HAVE_AS_AVR_MRMW_OPTION, 1,
+		[Define if your assembler supports -mrmw option.])])
+    ;;
+
   sparc*-*-*)
     gcc_GAS_CHECK_FEATURE([.register], gcc_cv_as_sparc_register_op,,,
       [.register %g2, #scratch],,