[PATCH 16/27] S390: Optimize strncmp and wcsncmp.

[Stefan Liebler <stli at linux dot vnet dot ibm dot com>]

This patch provides optimized versions of strncmp and wcsncmp with the z13
vector instructions.

ChangeLog:

	* sysdeps/s390/multiarch/strncmp-c.c: New File.
	* sysdeps/s390/multiarch/strncmp-vx.S: Likewise.
	* sysdeps/s390/multiarch/strncmp.c: Likewise.
	* sysdeps/s390/multiarch/wcsncmp-c.c: Likewise.
	* sysdeps/s390/multiarch/wcsncmp-vx.S: Likewise.
	* sysdeps/s390/multiarch/wcsncmp.c: Likewise.
	* sysdeps/s390/multiarch/Makefile (sysdep_routines): Add strncmp and
	wcsncmp functions.
	* sysdeps/s390/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Add ifunc test for strncmp, wcsncmp.
	* wcsmbs/wcsncmp.c (WCSNCMP): Define and use macro.
	* benchtests/bench-strncmp.c: Add wcsncmp support.
	* benchtests/bench-wcsncmp.c: New File.
	* benchtests/Makefile (wcsmbs-bench): Add wcsncmp.
---
 benchtests/Makefile                      |   2 +-
 benchtests/bench-strncmp.c               | 110 ++++++++++++++-----
 benchtests/bench-wcsncmp.c               |  20 ++++
 sysdeps/s390/multiarch/Makefile          |   6 +-
 sysdeps/s390/multiarch/ifunc-impl-list.c |   3 +
 sysdeps/s390/multiarch/strncmp-c.c       |  28 +++++
 sysdeps/s390/multiarch/strncmp-vx.S      | 137 ++++++++++++++++++++++++
 sysdeps/s390/multiarch/strncmp.c         |  30 ++++++
 sysdeps/s390/multiarch/wcsncmp-c.c       |  25 +++++
 sysdeps/s390/multiarch/wcsncmp-vx.S      | 177 +++++++++++++++++++++++++++++++
 sysdeps/s390/multiarch/wcsncmp.c         |  27 +++++
 wcsmbs/wcsncmp.c                         |   5 +-
 12 files changed, 541 insertions(+), 29 deletions(-)
 create mode 100644 benchtests/bench-wcsncmp.c
 create mode 100644 sysdeps/s390/multiarch/strncmp-c.c
 create mode 100644 sysdeps/s390/multiarch/strncmp-vx.S
 create mode 100644 sysdeps/s390/multiarch/strncmp.c
 create mode 100644 sysdeps/s390/multiarch/wcsncmp-c.c
 create mode 100644 sysdeps/s390/multiarch/wcsncmp-vx.S
 create mode 100644 sysdeps/s390/multiarch/wcsncmp.c

diff --git a/benchtests/Makefile b/benchtests/Makefile
index b47d5c1..0a85797 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -37,7 +37,7 @@ string-bench := bcopy bzero memccpy memchr memcmp memcpy memmem memmove \
 		strspn strstr strcpy_chk stpcpy_chk memrchr strsep strtok \
 		strcoll
 wcsmbs-bench := wcslen wcsnlen wcscpy wcpcpy wcsncpy wcpncpy wcscat wcsncat \
-		wcscmp
+		wcscmp wcsncmp
 string-bench-all := $(string-bench) ${wcsmbs-bench}
 
 # We have to generate locales
diff --git a/benchtests/bench-strncmp.c b/benchtests/bench-strncmp.c
index 1d06e5b..3b26414 100644
--- a/benchtests/bench-strncmp.c
+++ b/benchtests/bench-strncmp.c
@@ -17,17 +17,68 @@
    <http://www.gnu.org/licenses/>.  */
 
 #define TEST_MAIN
-#define TEST_NAME "strncmp"
+#ifdef WIDE
+# define TEST_NAME "wcsncmp"
+#else
+# define TEST_NAME "strncmp"
+#endif /* !WIDE */
 #include "bench-string.h"
 
-typedef int (*proto_t) (const char *, const char *, size_t);
-int simple_strncmp (const char *, const char *, size_t);
-int stupid_strncmp (const char *, const char *, size_t);
+#ifdef WIDE
+# include <wchar.h>
 
-IMPL (stupid_strncmp, 0)
-IMPL (simple_strncmp, 0)
-IMPL (strncmp, 1)
+# define L(str) L##str
+# define STRNCMP wcsncmp
+# define SIMPLE_STRNCMP simple_wcsncmp
+# define STUPID_STRNCMP stupid_wcsncmp
+# define CHAR wchar_t
+# define CHARBYTES 4
 
+/* Wcsncmp uses signed semantics for comparison, not unsigned.
+   Avoid using substraction since possible overflow.  */
+int
+simple_wcsncmp (const CHAR *s1, const CHAR *s2, size_t n)
+{
+  wchar_t c1, c2;
+
+  while (n--)
+    {
+      c1 = *s1++;
+      c2 = *s2++;
+      if (c1 == L ('\0') || c1 != c2)
+	return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
+    }
+  return 0;
+}
+
+int
+stupid_wcsncmp (const CHAR *s1, const CHAR *s2, size_t n)
+{
+  wchar_t c1, c2;
+  size_t ns1 = wcsnlen (s1, n) + 1, ns2 = wcsnlen (s2, n) + 1;
+
+  n = ns1 < n ? ns1 : n;
+  n = ns2 < n ? ns2 : n;
+
+  while (n--)
+    {
+      c1 = *s1++;
+      c2 = *s2++;
+      if (c1 != c2)
+	return c1 > c2 ? 1 : -1;
+    }
+  return 0;
+}
+
+#else
+# define L(str) str
+# define STRNCMP strncmp
+# define SIMPLE_STRNCMP simple_strncmp
+# define STUPID_STRNCMP stupid_strncmp
+# define CHAR char
+# define CHARBYTES 1
+
+/* Strncmp uses unsigned semantics for comparison.  */
 int
 simple_strncmp (const char *s1, const char *s2, size_t n)
 {
@@ -46,12 +97,21 @@ stupid_strncmp (const char *s1, const char *s2, size_t n)
 
   n = ns1 < n ? ns1 : n;
   n = ns2 < n ? ns2 : n;
-  while (n-- && (ret = *(unsigned char *) s1++ - * (unsigned char *) s2++) == 0);
+  while (n-- && (ret = *(unsigned char *) s1++ - *(unsigned char *) s2++) == 0);
   return ret;
 }
 
+#endif /* !WIDE */
+
+typedef int (*proto_t) (const CHAR *, const CHAR *, size_t);
+
+IMPL (STUPID_STRNCMP, 0)
+IMPL (SIMPLE_STRNCMP, 0)
+IMPL (STRNCMP, 1)
+
+
 static void
-do_one_test (impl_t *impl, const char *s1, const char *s2, size_t n,
+do_one_test (impl_t *impl, const CHAR *s1, const CHAR *s2, size_t n,
 	     int exp_result)
 {
   size_t i, iters = INNER_LOOP_ITERS;
@@ -74,12 +134,12 @@ do_test_limit (size_t align1, size_t align2, size_t len, size_t n, int max_char,
 	 int exp_result)
 {
   size_t i, align_n;
-  char *s1, *s2;
+  CHAR *s1, *s2;
 
   if (n == 0)
     {
-      s1 = (char*)(buf1 + page_size);
-      s2 = (char*)(buf2 + page_size);
+      s1 = (CHAR *) (buf1 + page_size);
+      s2 = (CHAR *) (buf2 + page_size);
       printf ("Length %4zd/%4zd:", len, n);
 
       FOR_EACH_IMPL (impl, 0)
@@ -92,16 +152,16 @@ do_test_limit (size_t align1, size_t align2, size_t len, size_t n, int max_char,
 
   align1 &= 15;
   align2 &= 15;
-  align_n = (page_size - n) & 15;
+  align_n = (page_size - n * CHARBYTES) & 15;
 
-  s1 = (char*)(buf1 + page_size - n);
-  s2 = (char*)(buf2 + page_size - n);
+  s1 = (CHAR *) (buf1 + page_size - n * CHARBYTES);
+  s2 = (CHAR *) (buf2 + page_size - n * CHARBYTES);
 
   if (align1 < align_n)
-    s1 -= (align_n - align1);
+    s1 = (CHAR *) ((char *) s1 - (align_n - align1));
 
   if (align2 < align_n)
-    s2 -= (align_n - align2);
+    s2 = (CHAR *) ((char *) s2 - (align_n - align2));
 
   for (i = 0; i < n; i++)
     s1[i] = s2[i] = 1 + 23 * i % max_char;
@@ -129,24 +189,24 @@ do_test (size_t align1, size_t align2, size_t len, size_t n, int max_char,
 	 int exp_result)
 {
   size_t i;
-  char *s1, *s2;
+  CHAR *s1, *s2;
 
   if (n == 0)
     return;
 
-  align1 &= 7;
-  if (align1 + n + 1 >= page_size)
+  align1 &= 63;
+  if (align1 + (n + 1) * CHARBYTES >= page_size)
     return;
 
   align2 &= 7;
-  if (align2 + n + 1 >= page_size)
+  if (align2 + (n + 1) * CHARBYTES >= page_size)
     return;
 
-  s1 = (char*)(buf1 + align1);
-  s2 = (char*)(buf2 + align2);
+  s1 = (CHAR *) (buf1 + align1);
+  s2 = (CHAR *) (buf2 + align2);
 
   for (i = 0; i < n; i++)
-    s1[i] = s2[i] = 1 + 23 * i % max_char;
+    s1[i] = s2[i] = 1 + (23 << ((CHARBYTES - 1) * 8)) * i % max_char;
 
   s1[n] = 24 + exp_result;
   s2[n] = 23;
@@ -162,7 +222,7 @@ do_test (size_t align1, size_t align2, size_t len, size_t n, int max_char,
   printf ("Length %4zd/%4zd, alignment %2zd/%2zd:", len, n, align1, align2);
 
   FOR_EACH_IMPL (impl, 0)
-    do_one_test (impl, (char*)s1, (char*)s2, n, exp_result);
+    do_one_test (impl, s1, s2, n, exp_result);
 
   putchar ('\n');
 }
diff --git a/benchtests/bench-wcsncmp.c b/benchtests/bench-wcsncmp.c
new file mode 100644
index 0000000..8720060
--- /dev/null
+++ b/benchtests/bench-wcsncmp.c
@@ -0,0 +1,20 @@
+/* Measure wcsncmp functions.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#define WIDE 1
+#include "bench-strncmp.c"
diff --git a/sysdeps/s390/multiarch/Makefile b/sysdeps/s390/multiarch/Makefile
index d8fbd55..d77bee5 100644
--- a/sysdeps/s390/multiarch/Makefile
+++ b/sysdeps/s390/multiarch/Makefile
@@ -7,7 +7,8 @@ sysdep_routines += strlen strlen-vx strlen-c \
 		   stpncpy stpncpy-vx stpncpy-c \
 		   strcat strcat-vx strcat-c \
 		   strncat strncat-vx strncat-c \
-		   strcmp strcmp-vx
+		   strcmp strcmp-vx \
+		   strncmp strncmp-vx strncmp-c
 endif
 
 ifeq ($(subdir),wcsmbs)
@@ -19,5 +20,6 @@ sysdep_routines += wcslen wcslen-vx wcslen-c \
 		   wcpncpy wcpncpy-vx wcpncpy-c \
 		   wcscat wcscat-vx wcscat-c \
 		   wcsncat wcsncat-vx wcsncat-c \
-		   wcscmp wcscmp-vx wcscmp-c
+		   wcscmp wcscmp-vx wcscmp-c \
+		   wcsncmp wcsncmp-vx wcsncmp-c
 endif
diff --git a/sysdeps/s390/multiarch/ifunc-impl-list.c b/sysdeps/s390/multiarch/ifunc-impl-list.c
index 196d3ec..5bfc493 100644
--- a/sysdeps/s390/multiarch/ifunc-impl-list.c
+++ b/sysdeps/s390/multiarch/ifunc-impl-list.c
@@ -106,6 +106,9 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_VX_IMPL (strcmp);
   IFUNC_VX_IMPL (wcscmp);
 
+  IFUNC_VX_IMPL (strncmp);
+  IFUNC_VX_IMPL (wcsncmp);
+
 #endif /* HAVE_S390_VX_ASM_SUPPORT */
 
   return i;
diff --git a/sysdeps/s390/multiarch/strncmp-c.c b/sysdeps/s390/multiarch/strncmp-c.c
new file mode 100644
index 0000000..b32a994
--- /dev/null
+++ b/sysdeps/s390/multiarch/strncmp-c.c
@@ -0,0 +1,28 @@
+/* Default strncmp implementation for S/390.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+# define STRNCMP  __strncmp_c
+# ifdef SHARED
+#  undef libc_hidden_builtin_def
+#  define libc_hidden_builtin_def(name)			\
+  __hidden_ver1 (__strncmp_c, __GI_strncmp, __strncmp_c);
+# endif /* SHARED */
+
+# include <string/strncmp.c>
+#endif /* HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) */
diff --git a/sysdeps/s390/multiarch/strncmp-vx.S b/sysdeps/s390/multiarch/strncmp-vx.S
new file mode 100644
index 0000000..ad01079
--- /dev/null
+++ b/sysdeps/s390/multiarch/strncmp-vx.S
@@ -0,0 +1,137 @@
+/* Vector optimized 32/64 bit S/390 version of strncmp.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+
+# include "sysdep.h"
+# include "asm-syntax.h"
+
+	.text
+
+/* int strncmp (const char *s1, const char *s2, size_t n)
+   Compare at most n characters of two strings.
+
+   Register usage:
+   -r0=tmp
+   -r1=tmp
+   -r2=s1
+   -r3=s2
+   -r4=n
+   -r5=current_len
+   -v16=part of s1
+   -v17=part of s2
+   -v18=index of unequal
+*/
+ENTRY(__strncmp_vx)
+	.machine "z13"
+	.machinemode "zarch_nohighgprs"
+
+# if !defined __s390x__
+	llgfr	%r4,%r4
+# endif /* !defined __s390x__ */
+
+	clgije	%r4,0,.Lend_equal /* Nothing to do if n == 0,  */
+	lghi	%r5,0		/* current_len = 0.  */
+
+.Lloop:
+	vlbb	%v16,0(%r5,%r2),6 /* Load s1 to block boundary.  */
+	vlbb	%v17,0(%r5,%r3),6 /* Load s2 to block boundary.  */
+	lcbb	%r0,0(%r5,%r2),6 /* Get loaded byte count of s1.  */
+	jo	.Llt16_1	/* Jump away if vr is not fully loaded.  */
+	lcbb	%r1,0(%r5,%r3),6 /* Get loaded byte count of s2.  */
+	jo	.Llt16_2	/* Jump away if vr is not fully loaded.  */
+	aghi	%r5,16		/* Both vrs are fully loaded.  */
+	clgrjhe	%r5,%r4,.Llastcmp /* If current_len >= n ->last compare.  */
+	vfenezbs %v18,%v16,%v17	/* Compare not equal with zero search.  */
+	jno	.Lfound
+
+	vlbb	%v16,0(%r5,%r2),6
+	vlbb	%v17,0(%r5,%r3),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	clgrjhe	%r5,%r4,.Llastcmp
+	vfenezbs %v18,%v16,%v17
+	jno	.Lfound
+
+	vlbb	%v16,0(%r5,%r2),6
+	vlbb	%v17,0(%r5,%r3),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	clgrjhe	%r5,%r4,.Llastcmp
+	vfenezbs %v18,%v16,%v17
+	jno	.Lfound
+
+	vlbb	%v16,0(%r5,%r2),6
+	vlbb	%v17,0(%r5,%r3),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	clgrjhe	%r5,%r4,.Llastcmp
+	vfenezbs %v18,%v16,%v17
+	jno	.Lfound
+	j	.Lloop
+
+.Llt16_1:
+	lcbb	%r1,0(%r5,%r3),6 /* Get loaded byte count ofs2.  */
+.Llt16_2:
+	clr	%r0,%r1		/* Compare logical.  */
+	locrh	%r0,%r1		/* Compute minimum of bytes loaded.  */
+	algfr	%r5,%r0		/* Add smallest loaded bytes to current_len.  */
+	clgrj	%r5,%r4,10,.Llastcmp /* If current_len >= n ->last compare.  */
+	vfenezbs %v18,%v16,%v17	/* Compare not equal with zero search.  */
+	vlgvb	%r1,%v18,7	/* Get not equal index or 16 if all equal.  */
+	clrjl	%r1,%r0,.Lfound /* Jump away if miscompare is within
+				    loaded bytes (index < loaded-bytes) */
+	j	.Lloop
+
+.Llastcmp:
+	/* Use comparision result only if located within first n characters.
+	   %r0: loaded byte count in vreg;
+	   %r5: current_len;
+	   %r4: n;
+	   (current_len - n): [0...16[
+	   First ignored match index: loaded bytes - (current_len-n): ]0...16]
+	*/
+	slgr	%r5,%r4		/* %r5 = current_len - n.  */
+	slr	%r0,%r5		/* %r0 = first ignored match index.  */
+	vfenezbs %v18,%v16,%v17	/* Compare not equal with zero search.  */
+	vlgvb	%r1,%v18,7	/* Get not equal index or 16 if all equal.  */
+	clrjl	%r1,%r0,.Lfound /* Jump away if miscompare is within
+				    loaded bytes and below n bytes.  */
+	j	.Lend_equal	/* Miscompare after n-bytes -> end equal.  */
+
+.Lfound:
+	/* Difference or end of string.  */
+	je	.Lend_equal
+	lghi	%r2,1
+	lghi	%r1,-1
+	locgrl	%r2,%r1
+	br	%r14
+.Lend_equal:
+	lghi	%r2,0
+	br	%r14
+END(__strncmp_vx)
+#endif /* HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) */
diff --git a/sysdeps/s390/multiarch/strncmp.c b/sysdeps/s390/multiarch/strncmp.c
new file mode 100644
index 0000000..9accafc
--- /dev/null
+++ b/sysdeps/s390/multiarch/strncmp.c
@@ -0,0 +1,30 @@
+/* Multiple versions of strncmp.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+# include <string.h>
+# include <ifunc-resolve.h>
+
+
+# undef strcmp
+extern __typeof (strncmp) __strncmp;
+s390_vx_libc_ifunc2 (__strncmp, strncmp)
+
+#else
+# include <string/strncmp.c>
+#endif /* !(defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)) */
diff --git a/sysdeps/s390/multiarch/wcsncmp-c.c b/sysdeps/s390/multiarch/wcsncmp-c.c
new file mode 100644
index 0000000..3d796ca
--- /dev/null
+++ b/sysdeps/s390/multiarch/wcsncmp-c.c
@@ -0,0 +1,25 @@
+/* Default wcsncmp implementation for S/390.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+# define WCSNCMP  __wcsncmp_c
+
+# include <wchar.h>
+extern __typeof (wcsncmp) __wcsncmp_c;
+# include <wcsmbs/wcsncmp.c>
+#endif
diff --git a/sysdeps/s390/multiarch/wcsncmp-vx.S b/sysdeps/s390/multiarch/wcsncmp-vx.S
new file mode 100644
index 0000000..e13727b
--- /dev/null
+++ b/sysdeps/s390/multiarch/wcsncmp-vx.S
@@ -0,0 +1,177 @@
+/* Vector optimized 32/64 bit S/390 version of wcsncmp.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+
+# include "sysdep.h"
+# include "asm-syntax.h"
+
+	.text
+
+/* int wcsncmp (const wchar_t *s1, const wchar_t *s2, size_t n)
+   Compare at most n characters of two strings.
+
+   Register usage:
+   -r0=tmp
+   -r1=tmp
+   -r2=s1
+   -r3=s2
+   -r4=n
+   -r5=current_len
+   -v16=part of s1
+   -v17=part of s2
+   -v18=index of unequal
+*/
+ENTRY(__wcsncmp_vx)
+	.machine "z13"
+	.machinemode "zarch_nohighgprs"
+
+# if !defined __s390x__
+	llgfr	%r4,%r4
+# endif /* !defined __s390x__ */
+
+	clgije	%r4,0,.Lend_equal /* Nothing to do if n == 0.  */
+
+	/* Check range of n and convert to byte-count.  */
+# ifdef __s390x__
+	tmhh	%r4,49152	/* Test bit 0 or 1 of maxlen.  */
+	lghi	%r1,-4		/* Max byte-count is 18446744073709551612.  */
+# else
+	tmlh	%r4,49152	/* Test bit 0 or 1 of maxlen.  */
+	llilf	%r1,4294967292	/* Max byte-count is 4294967292.  */
+# endif /* !__s390x__ */
+	sllg	%r4,%r4,2	/* Convert character-count to byte-count.  */
+	locgrne	%r4,%r1		/* Use max byte-count, if bit 0/1 was one.  */
+
+	/* Check first character without vector load.  */
+	lghi	%r5,4		/* current_len = 4 bytes.  */
+	/* Check s1/2[0].  */
+	lt	%r0,0(%r2)
+	l	%r1,0(%r3)
+	je	.Lend_cmp_one_char
+	crjne	%r0,%r1,.Lend_cmp_one_char
+
+.Lloop:
+	vlbb	%v17,0(%r5,%r3),6 /* Load s2 to block boundary.  */
+	vlbb	%v16,0(%r5,%r2),6 /* Load s1 to block boundary.  */
+	lcbb	%r0,0(%r5,%r2),6 /* Get loaded byte count of s1.  */
+	jo	.Llt16_1	/* Jump away if vector not fully loaded.  */
+	lcbb	%r1,0(%r5,%r3),6 /* Get loaded byte count of s2.  */
+	jo	.Llt16_2	/* Jump away if vector not fully loaded.  */
+	aghi	%r5,16		/* Both vectors are fully loaded.  */
+	vfenezfs %v18,%v16,%v17	/* Compare not equal with zero search.  */
+	clgrjhe	%r5,%r4,.Llastcmp /* If current_len >= n ->last compare.  */
+	jno	.Lfound
+
+	vlbb	%v17,0(%r5,%r3),6
+	vlbb	%v16,0(%r5,%r2),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	vfenezfs %v18,%v16,%v17
+	clgrjhe	%r5,%r4,.Llastcmp
+	jno	.Lfound
+
+	vlbb	%v17,0(%r5,%r3),6
+	vlbb	%v16,0(%r5,%r2),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	vfenezfs %v18,%v16,%v17
+	clgrjhe	%r5,%r4,.Llastcmp
+	jno	.Lfound
+
+	vlbb	%v17,0(%r5,%r3),6
+	vlbb	%v16,0(%r5,%r2),6
+	lcbb	%r0,0(%r5,%r2),6
+	jo	.Llt16_1
+	lcbb	%r1,0(%r5,%r3),6
+	jo	.Llt16_2
+	aghi	%r5,16
+	vfenezfs %v18,%v16,%v17
+	clgrjhe	%r5,%r4,.Llastcmp
+	jno	.Lfound
+
+	j	.Lloop
+
+.Llt16_1:
+	lcbb	%r1,0(%r5,%r3),6 /* Get loaded byte count of s2.  */
+.Llt16_2:
+	clr	%r0,%r1		/* Compare logical.  */
+	locrh	%r0,%r1		/* Compute minimum of bytes loaded.  */
+	nill	%r0,65532	/* Align bytes loaded to full characters.  */
+	jz	.Lcmp_one_char	/* Jump away if no full char is available.  */
+.Llt_cmp:
+	algfr	%r5,%r0		/* Add smallest loaded bytes to current_len.  */
+	vfenezfs %v18,%v16,%v17	/* Compare not equal with zero search.  */
+	clgrj	%r5,%r4,10,.Llastcmp /* If current_len >= n -> last compare  */
+	vlgvb	%r1,%v18,7	/* Get not equal index or 16 if all equal.  */
+	clrjl	%r1,%r0,.Lfound /* Jump away if miscompare is within
+				   loaded bytes; (index < loaded-bytes) */
+	j	.Lloop
+
+.Lcmp_one_char:
+	/* At least one of both strings is not 4-byte aligned
+	   and there is no full character before next block-boundary.
+	   Compare one character to get over the boundary and
+	   proceed with normal loop!  */
+	vlef	%v16,0(%r5,%r2),0 /* Load one character.  */
+	lghi	%r0,4		/* Loaded byte count is 4.  */
+	vlef	%v17,0(%r5,%r3),0
+	j	.Llt_cmp	/* Proceed with comparision.  */
+
+.Llastcmp:
+	/* Use comparision result only if located within first n characters.
+	   %r0: loaded byte count in vreg;
+	   %r5: current_len;
+	   %r4: n;
+	   (current_len - n): [0...16[
+	   First ignored match index: loaded bytes - (current_len-n): ]0...16]
+	*/
+	slgr	%r5,%r4		/* %r5 = current_len - n.  */
+	slr	%r0,%r5		/* %r0 = first ignored match index.  */
+	vlgvb	%r4,%v18,7	/* Get not equal index or 16 if all equal.  */
+	clrjl	%r4,%r0,.Lfound2 /* Jump away if miscompare is within
+				     loaded bytes and below n bytes.  */
+.Lend_equal:
+	lghi	%r2,0
+	br	%r14
+
+.Lfound:
+	/* Difference or end of string.  */
+	/* vfenezf found an unequal element or zero.
+	   This instruction compares unsigned words, but wchar_t is signed.
+	   Thus we have to compare the found element again.  */
+	vlgvb	%r4,%v18,7	/* Extract not equal byte-index.  */
+.Lfound2:
+	srl	%r4,2		/* And convert it to character-index.  */
+	vlgvf	%r0,%v16,0(%r4)	/* Load character-values.  */
+	vlgvf	%r1,%v17,0(%r4)
+.Lend_cmp_one_char:
+	cr	%r0,%r1
+	je	.Lend_equal
+	lghi	%r2,1
+	lghi	%r1,-1
+	locgrl	%r2,%r1
+	br	%r14
+END(__wcsncmp_vx)
+#endif /* HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) */
diff --git a/sysdeps/s390/multiarch/wcsncmp.c b/sysdeps/s390/multiarch/wcsncmp.c
new file mode 100644
index 0000000..165c002
--- /dev/null
+++ b/sysdeps/s390/multiarch/wcsncmp.c
@@ -0,0 +1,27 @@
+/* Multiple versions of wcsncmp.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)
+# include <wchar.h>
+# include <ifunc-resolve.h>
+
+s390_vx_libc_ifunc2 (__wcsncmp, wcsncmp)
+
+#else
+# include <wcsmbs/wcsncmp.c>
+#endif /* !(defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)) */
diff --git a/wcsmbs/wcsncmp.c b/wcsmbs/wcsncmp.c
index e083ad8..4de2ca8 100644
--- a/wcsmbs/wcsncmp.c
+++ b/wcsmbs/wcsncmp.c
@@ -18,13 +18,16 @@
 
 #include <wchar.h>
 
+#ifndef WCSNCMP
+# define WCSNCMP wcsncmp
+#endif
 
 /* Compare no more than N characters of S1 and S2,
    returning less than, equal to or greater than zero
    if S1 is lexicographically less than, equal to or
    greater than S2.  */
 int
-wcsncmp (s1, s2, n)
+WCSNCMP (s1, s2, n)
      const wchar_t *s1;
      const wchar_t *s2;
      size_t n;
-- 
1.8.4.2