S390: Refactor strncmp ifunc handling.

The ifunc handling for strncmp is adjusted in order to omit ifunc
variants if those will never be used as the minimum architecture level
already supports newer CPUs by default.
Glibc internal calls will then also use the "newer" ifunc variant.

ChangeLog:

	* sysdeps/s390/multiarch/Makefile
	(sysdep_routines): Remove strncmp variants.
	* sysdeps/s390/Makefile (sysdep_routines): Add strncmp variants.
	* sysdeps/s390/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Refactor ifunc handling for strncmp.
	* sysdeps/s390/multiarch/strncmp-c.c: Move to ...
	* sysdeps/s390/strncmp-c.c: ... here and adjust ifunc handling.
	* sysdeps/s390/multiarch/strncmp-vx.S: Move to ...
	* sysdeps/s390/strncmp-vx.S: ... here and adjust ifunc handling.
	* sysdeps/s390/multiarch/strncmp.c: Move to ...
	* sysdeps/s390/strncmp.c: ... here and adjust ifunc handling.
	* sysdeps/s390/ifunc-strncmp.h: New file.

7 files changed, 110 insertions, 20 deletions

diff --git a/sysdeps/s390/Makefile b/sysdeps/s390/Makefile
index 9e7d5625c9..3aaf5a0d40 100644
--- a/sysdeps/s390/Makefile
+++ b/sysdeps/s390/Makefile
@@ -68,5 +68,6 @@ sysdep_routines += bzero memset memset-z900 \
 		   stpncpy stpncpy-vx stpncpy-c \
 		   strcat strcat-vx strcat-c \
 		   strncat strncat-vx strncat-c \
-		   strcmp strcmp-vx strcmp-z900
+		   strcmp strcmp-vx strcmp-z900 \
+		   strncmp strncmp-vx strncmp-c
 endif
diff --git a/sysdeps/s390/ifunc-strncmp.h b/sysdeps/s390/ifunc-strncmp.h
new file mode 100644
index 0000000000..511b3e9720
--- /dev/null
+++ b/sysdeps/s390/ifunc-strncmp.h
@@ -0,0 +1,52 @@
+/* strncmp variant information on S/390 version.
+   Copyright (C) 2018 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 USE_MULTIARCH && IS_IN (libc)		\
+  && ! defined HAVE_S390_MIN_Z13_ZARCH_ASM_SUPPORT
+# define HAVE_STRNCMP_IFUNC	1
+#else
+# define HAVE_STRNCMP_IFUNC	0
+#endif
+
+#ifdef HAVE_S390_VX_ASM_SUPPORT
+# define HAVE_STRNCMP_IFUNC_AND_VX_SUPPORT HAVE_STRNCMP_IFUNC
+#else
+# define HAVE_STRNCMP_IFUNC_AND_VX_SUPPORT 0
+#endif
+
+#if defined HAVE_S390_MIN_Z13_ZARCH_ASM_SUPPORT
+# define STRNCMP_DEFAULT	STRNCMP_Z13
+# define HAVE_STRNCMP_C		0
+# define HAVE_STRNCMP_Z13	1
+#else
+# define STRNCMP_DEFAULT	STRNCMP_C
+# define HAVE_STRNCMP_C		1
+# define HAVE_STRNCMP_Z13	HAVE_STRNCMP_IFUNC_AND_VX_SUPPORT
+#endif
+
+#if HAVE_STRNCMP_C
+# define STRNCMP_C		__strncmp_c
+#else
+# define STRNCMP_C		NULL
+#endif
+
+#if HAVE_STRNCMP_Z13
+# define STRNCMP_Z13		__strncmp_vx
+#else
+# define STRNCMP_Z13		NULL
+#endif
diff --git a/sysdeps/s390/multiarch/Makefile b/sysdeps/s390/multiarch/Makefile
index 97421a4996..381376bf9f 100644
--- a/sysdeps/s390/multiarch/Makefile
+++ b/sysdeps/s390/multiarch/Makefile
@@ -1,6 +1,5 @@
 ifeq ($(subdir),string)
-sysdep_routines += strncmp strncmp-vx strncmp-c \
-		   strchr strchr-vx strchr-c \
+sysdep_routines += strchr strchr-vx strchr-c \
 		   strchrnul strchrnul-vx strchrnul-c \
 		   strrchr strrchr-vx strrchr-c \
 		   strspn strspn-vx strspn-c \
diff --git a/sysdeps/s390/multiarch/ifunc-impl-list.c b/sysdeps/s390/multiarch/ifunc-impl-list.c
index 44637c431b..d982de5788 100644
--- a/sysdeps/s390/multiarch/ifunc-impl-list.c
+++ b/sysdeps/s390/multiarch/ifunc-impl-list.c
@@ -35,6 +35,7 @@
 #include <ifunc-strcat.h>
 #include <ifunc-strncat.h>
 #include <ifunc-strcmp.h>
+#include <ifunc-strncmp.h>
 
 /* Maximum number of IFUNC implementations.  */
 #define MAX_IFUNC	3
@@ -281,6 +282,18 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 		)
 #endif /* HAVE_STRCMP_IFUNC  */
 
+#if HAVE_STRNCMP_IFUNC
+    IFUNC_IMPL (i, name, strncmp,
+# if HAVE_STRNCMP_Z13
+		IFUNC_IMPL_ADD (array, i, strncmp,
+				dl_hwcap & HWCAP_S390_VX, STRNCMP_Z13)
+# endif
+# if HAVE_STRNCMP_C
+		IFUNC_IMPL_ADD (array, i, strncmp, 1, STRNCMP_C)
+# endif
+		)
+#endif /* HAVE_STRNCMP_IFUNC  */
+
 #ifdef HAVE_S390_VX_ASM_SUPPORT
 
 # define IFUNC_VX_IMPL(FUNC)						\
@@ -307,7 +320,6 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   IFUNC_VX_IMPL (wcscmp);
 
-  IFUNC_VX_IMPL (strncmp);
   IFUNC_VX_IMPL (wcsncmp);
 
   IFUNC_VX_IMPL (strchr);
diff --git a/sysdeps/s390/multiarch/strncmp-c.c b/sysdeps/s390/strncmp-c.c
index e54277ec1b..c7ffdb03e3 100644
--- a/sysdeps/s390/multiarch/strncmp-c.c
+++ b/sysdeps/s390/strncmp-c.c
@@ -16,13 +16,17 @@
    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)			\
+#include <ifunc-strncmp.h>
+
+#if HAVE_STRNCMP_C
+# if HAVE_STRNCMP_IFUNC
+#  define STRNCMP STRNCMP_C
+#  if defined SHARED && IS_IN (libc)
+#   undef libc_hidden_builtin_def
+#   define libc_hidden_builtin_def(name)			\
   __hidden_ver1 (__strncmp_c, __GI_strncmp, __strncmp_c);
-# endif /* SHARED */
+#  endif
+# endif
 
 # include <string/strncmp.c>
-#endif /* HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) */
+#endif
diff --git a/sysdeps/s390/multiarch/strncmp-vx.S b/sysdeps/s390/strncmp-vx.S
index 168fd657da..f557afb336 100644
--- a/sysdeps/s390/multiarch/strncmp-vx.S
+++ b/sysdeps/s390/strncmp-vx.S
@@ -16,7 +16,9 @@
    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 <ifunc-strncmp.h>
+
+#if HAVE_STRNCMP_Z13
 
 # include "sysdep.h"
 # include "asm-syntax.h"
@@ -37,7 +39,7 @@
    -v17=part of s2
    -v18=index of unequal
 */
-ENTRY(__strncmp_vx)
+ENTRY(STRNCMP_Z13)
 	.machine "z13"
 	.machinemode "zarch_nohighgprs"
 
@@ -133,5 +135,14 @@ ENTRY(__strncmp_vx)
 .Lend_equal:
 	lghi	%r2,0
 	br	%r14
-END(__strncmp_vx)
-#endif /* HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) */
+END(STRNCMP_Z13)
+
+# if ! HAVE_STRNCMP_IFUNC
+strong_alias (STRNCMP_Z13, strncmp)
+# endif
+
+# if ! HAVE_STRNCMP_C && defined SHARED && IS_IN (libc)
+strong_alias (STRNCMP_Z13, __GI_strncmp)
+# endif
+
+#endif /* HAVE_STRNCMP_Z13  */
diff --git a/sysdeps/s390/multiarch/strncmp.c b/sysdeps/s390/strncmp.c
index 0ec472c3b0..71351273c4 100644
--- a/sysdeps/s390/multiarch/strncmp.c
+++ b/sysdeps/s390/strncmp.c
@@ -16,7 +16,9 @@
    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 <ifunc-strncmp.h>
+
+#if HAVE_STRNCMP_IFUNC
 # define strncmp __redirect_strncmp
 /* Omit the strncmp inline definitions because it would redefine strncmp.  */
 # define __NO_STRING_INLINES
@@ -24,8 +26,17 @@
 # undef strncmp
 # include <ifunc-resolve.h>
 
-s390_vx_libc_ifunc2_redirected (__redirect_strncmp, __strncmp, strncmp)
+# if HAVE_STRNCMP_C
+extern __typeof (__redirect_strncmp) STRNCMP_C attribute_hidden;
+# endif
+
+# if HAVE_STRNCMP_Z13
+extern __typeof (__redirect_strncmp) STRNCMP_Z13 attribute_hidden;
+# endif
 
-#else
-# include <string/strncmp.c>
-#endif /* !(defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc)) */
+s390_libc_ifunc_expr (__redirect_strncmp, strncmp,
+		      (HAVE_STRNCMP_Z13 && (hwcap & HWCAP_S390_VX))
+		      ? STRNCMP_Z13
+		      : STRNCMP_DEFAULT
+		      )
+#endif /* HAVE_STRNCMP_IFUNC  */