powerpc: Improve memcmp performance for POWER8

Vectorization improves performance over the current implementation.
Tested on powerpc64 and powerpc64le.

ChangeLog

@@ -1,3 +1,14 @@
+2017-05-18  Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>
+
+	* sysdeps/powerpc/powerpc64/multiarch/Makefile
+	(sysdep_routines): Add memcmp-power8.
+	* sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
+	(memcmp): Add __memcmp_power8 to list of memcmp functions.
+	* sysdeps/powerpc/powerpc64/multiarch/memcmp.c
+	(memcmp): Add __memcmp_power8 to ifunc list.
+	* sysdeps/powerpc/powerpc64/multiarch/memcmp-power8.S: New file.
+	* sysdeps/powerpc/powerpc64/power8/memcmp.S: New file.
+
 2017-05-17  Gabriel F. T. Gomes  <gftg@linux.vnet.ibm.com>
 	    Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
 

sysdeps/powerpc/powerpc64/multiarch/Makefile

@@ -1,7 +1,8 @@
 ifeq ($(subdir),string)
 sysdep_routines += memcpy-power7 memcpy-a2 memcpy-power6 memcpy-cell \
-		   memcpy-power4 memcpy-ppc64 memcmp-power7 memcmp-power4 \
+		   memcpy-power4 memcpy-ppc64 \
-		   memcmp-ppc64 memset-power7 memset-power6 memset-power4 \
+		   memcmp-power8 memcmp-power7 memcmp-power4 memcmp-ppc64 \
+		   memset-power7 memset-power6 memset-power4 \
 		   memset-ppc64 memset-power8 \
 		   mempcpy-power7 mempcpy-ppc64 memchr-power7 memchr-ppc64 \
 		   memrchr-power7 memrchr-ppc64 rawmemchr-power7 \

sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c

@@ -146,6 +146,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/powerpc/powerpc64/multiarch/memcmp.c.  */
   IFUNC_IMPL (i, name, memcmp,
+	      IFUNC_IMPL_ADD (array, i, memcmp, hwcap2 & PPC_FEATURE2_ARCH_2_07,
+			      __memcmp_power8)
 	      IFUNC_IMPL_ADD (array, i, memcmp, hwcap & PPC_FEATURE_HAS_VSX,
 			      __memcmp_power7)
 	      IFUNC_IMPL_ADD (array, i, memcmp, hwcap & PPC_FEATURE_POWER4,

sysdeps/powerpc/powerpc64/multiarch/memcmp-power8.S

@@ -0,0 +1,28 @@
+/* Optimized memcmp implementation for PowerPC64/POWER8.
+   Copyright (C) 2017 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/>.  */
+
+#include <sysdep.h>
+
+#define MEMCMP __memcmp_power8
+
+#undef libc_hidden_builtin_def
+#define libc_hidden_builtin_def(name)
+#undef weak_alias
+#define weak_alias(name,alias)
+
+#include <sysdeps/powerpc/powerpc64/power8/memcmp.S>

sysdeps/powerpc/powerpc64/multiarch/memcmp.c

@@ -26,11 +26,14 @@
 extern __typeof (memcmp) __memcmp_ppc attribute_hidden;
 extern __typeof (memcmp) __memcmp_power4 attribute_hidden;
 extern __typeof (memcmp) __memcmp_power7 attribute_hidden;
+extern __typeof (memcmp) __memcmp_power8 attribute_hidden;
 # undef memcmp
 
 /* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
    ifunc symbol properly.  */
 libc_ifunc_redirected (__redirect_memcmp, memcmp,
+		       (hwcap2 & PPC_FEATURE2_ARCH_2_07)
+		       ? __memcmp_power8 :
 		       (hwcap & PPC_FEATURE_HAS_VSX)
 		       ? __memcmp_power7
 		       : (hwcap & PPC_FEATURE_POWER4)