diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9f7e5931217..fcabe2595f3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-27  Joseph Myers  <joseph@codesourcery.com>
+
+	* genmultilib (combination_space): Remove variable.
+	Validate reuse rules against regular expression for any sequence
+	of multilib options in any order.
+
 2017-06-27  Michael Collison  <michael.collison@arm.com>
 
 	* config/aarch64/aarch64-simd.md (aarch64_combine<mode>): Directly
diff --git a/gcc/genmultilib b/gcc/genmultilib
index c8bcdf3935d..0767e68719e 100644
--- a/gcc/genmultilib
+++ b/gcc/genmultilib
@@ -186,8 +186,7 @@ fi
 EOF
 chmod +x tmpmultilib
 
-combination_space=`initial=/ ./tmpmultilib ${options}`
-combinations="$combination_space"
+combinations=`initial=/ ./tmpmultilib ${options}`
 
 # If there exceptions, weed them out now
 if [ -n "${exceptions}" ]; then
@@ -460,6 +459,15 @@ done
 echo "NULL"
 echo "};"
 
+# Generate a regular expression to validate option combinations.
+options_re=
+for set in ${options}; do
+  for opt in `echo ${set} | sed -e 's_[/|]_ _g'`; do
+    options_re="${options_re}${options_re:+|}${opt}"
+  done
+done
+options_re="^/((${options_re})/)*\$"
+
 # Output rules used for multilib reuse.
 echo ""
 echo "static const char *const multilib_reuse_raw[] = {"
@@ -473,7 +481,7 @@ for rrule in ${multilib_reuse}; do
   # in this variable, it means no multilib will be built for current reuse
   # rule.  Thus the reuse purpose specified by current rule is meaningless.
   if expr "${combinations} " : ".*/${combo}/.*" > /dev/null; then
-    if expr "${combination_space} " : ".*/${copts}/.*" > /dev/null; then
+    if echo "/${copts}/" | grep -E "${options_re}" > /dev/null; then
       combo="/${combo}/"
       dirout=`./tmpmultilib3 "${combo}" "${todirnames}" "${toosdirnames}" "${enable_multilib}"`
       copts="/${copts}/"