LoongArch: Add ifunc support for strncmp{aligned, lsx}

Based on the glibc microbenchmark, only a few short inputs with this
strncmp-aligned and strncmp-lsx implementation experience performance
degradation, overall, strncmp-aligned could reduce the runtime 0%-10%
for aligned comparision, 10%-25% for unaligend comparision, strncmp-lsx
could reduce the runtime about 0%-60%.

1 files changed, 35 insertions, 0 deletions

diff --git a/sysdeps/loongarch/lp64/multiarch/strncmp.c b/sysdeps/loongarch/lp64/multiarch/strncmp.c
new file mode 100644
index 0000000000..af6d0bc4a7
--- /dev/null
+++ b/sysdeps/loongarch/lp64/multiarch/strncmp.c
@@ -0,0 +1,35 @@
+/* Multiple versions of strncmp.
+   All versions must be listed in ifunc-impl-list.c.
+   Copyright (C) 2023 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 multiple versions only for the definition in libc.  */
+#if IS_IN (libc)
+# define strncmp __redirect_strncmp
+# include <string.h>
+# undef strncmp
+
+# define SYMBOL_NAME strncmp
+# include "ifunc-strncmp.h"
+
+libc_ifunc_redirected (__redirect_strncmp, strncmp, IFUNC_SELECTOR ());
+
+# ifdef SHARED
+__hidden_ver1 (strncmp, __GI_strncmp, __redirect_strncmp)
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strncmp);
+# endif
+#endif