diff --git a/string/Makefile b/string/Makefile
index f0fce2a0b8..40d6fac133 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -48,8 +48,8 @@ routines	:= strcat strchr strcmp strcoll strcpy strcspn		\
 		   sigdescr_np sigabbrev_np strerrorname_np		\
 		   strerrordesc_np
 
-strop-tests	:= memchr memcmp memcpy memmove mempcpy memset memccpy	\
-		   stpcpy stpncpy strcat strchr strcmp strcpy strcspn	\
+strop-tests	:= memchr memcmp memcpy memcmpeq memmove mempcpy memset	\
+		   memccpy stpcpy stpncpy strcat strchr strcmp strcpy strcspn	\
 		   strlen strncmp strncpy strpbrk strrchr strspn memmem	\
 		   strstr strcasestr strnlen strcasecmp strncasecmp	\
 		   strncat rawmemchr strchrnul bcopy bzero memrchr	\
diff --git a/string/test-memcmp.c b/string/test-memcmp.c
index 6ddbc05d2f..e1f07cab58 100644
--- a/string/test-memcmp.c
+++ b/string/test-memcmp.c
@@ -17,11 +17,14 @@
    <https://www.gnu.org/licenses/>.  */
 
 #define TEST_MAIN
-#ifdef WIDE
+#ifdef TEST_MEMCMPEQ
+# define TEST_NAME "__memcmpeq"
+#elif defined WIDE
 # define TEST_NAME "wmemcmp"
 #else
 # define TEST_NAME "memcmp"
 #endif
+
 #include "test-string.h"
 #ifdef WIDE
 # include <inttypes.h>
@@ -35,6 +38,7 @@
 # define CHARBYTES 4
 # define CHAR__MIN WCHAR_MIN
 # define CHAR__MAX WCHAR_MAX
+
 int
 simple_wmemcmp (const wchar_t *s1, const wchar_t *s2, size_t n)
 {
@@ -48,8 +52,11 @@ simple_wmemcmp (const wchar_t *s1, const wchar_t *s2, size_t n)
 }
 #else
 # include <limits.h>
-
-# define MEMCMP memcmp
+# ifdef TEST_MEMCMPEQ
+#  define MEMCMP __memcmpeq
+# else
+#  define MEMCMP memcmp
+# endif
 # define MEMCPY memcpy
 # define SIMPLE_MEMCMP simple_memcmp
 # define CHAR char
@@ -69,6 +76,12 @@ simple_memcmp (const char *s1, const char *s2, size_t n)
 }
 #endif
 
+#ifndef BAD_RESULT
+# define BAD_RESULT(result, expec)                                      \
+    (((result) == 0 && (expec)) || ((result) < 0 && (expec) >= 0) ||    \
+     ((result) > 0 && (expec) <= 0))
+# endif
+
 typedef int (*proto_t) (const CHAR *, const CHAR *, size_t);
 
 IMPL (SIMPLE_MEMCMP, 0)
@@ -79,9 +92,7 @@ check_result (impl_t *impl, const CHAR *s1, const CHAR *s2, size_t len,
 	      int exp_result)
 {
   int result = CALL (impl, s1, s2, len);
-  if ((exp_result == 0 && result != 0)
-      || (exp_result < 0 && result >= 0)
-      || (exp_result > 0 && result <= 0))
+  if (BAD_RESULT(result, exp_result))
     {
       error (0, 0, "Wrong result in function %s %d %d", impl->name,
 	     result, exp_result);
@@ -186,9 +197,7 @@ do_random_tests (void)
 	{
 	  r = CALL (impl, (CHAR *) p1 + align1, (const CHAR *) p2 + align2,
 		    len);
-	  if ((r == 0 && result)
-	      || (r < 0 && result >= 0)
-	      || (r > 0 && result <= 0))
+	  if (BAD_RESULT(r, result))
 	    {
 	      error (0, 0, "Iteration %zd - wrong result in function %s (%zd, %zd, %zd, %zd) %ld != %d, p1 %p p2 %p",
 		     n, impl->name, align1 * CHARBYTES & 63,  align2 * CHARBYTES & 63, len, pos, r, result, p1, p2);
diff --git a/string/test-memcmpeq.c b/string/test-memcmpeq.c
new file mode 100644
index 0000000000..8889117868
--- /dev/null
+++ b/string/test-memcmpeq.c
@@ -0,0 +1,21 @@
+/* Test and measure __memcmpeq functions.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define BAD_RESULT(result, expec) ((!(result)) != (!(expec)))
+#define TEST_MEMCMPEQ 1
+#include "test-memcmp.c"
