[RFC PATCH 17/19] riscv: Add ifunc support for strncmp

[Christoph Muellner <christoph.muellner@vrull.eu>]

From: Christoph Müllner <christoph.muellner@vrull.eu>

This patch adds ifunc support for calls to strncmp to the RISC-V code.
No optimized code is added as part of this patch.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
---
 sysdeps/riscv/multiarch/Makefile          |  3 +-
 sysdeps/riscv/multiarch/ifunc-impl-list.c |  2 ++
 sysdeps/riscv/multiarch/strncmp.c         | 40 +++++++++++++++++++++++
 sysdeps/riscv/multiarch/strncmp_generic.c | 32 ++++++++++++++++++
 4 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/riscv/multiarch/strncmp.c
 create mode 100644 sysdeps/riscv/multiarch/strncmp_generic.c

diff --git a/sysdeps/riscv/multiarch/Makefile b/sysdeps/riscv/multiarch/Makefile
index 73a62be85d..056ce2ffc0 100644
--- a/sysdeps/riscv/multiarch/Makefile
+++ b/sysdeps/riscv/multiarch/Makefile
@@ -13,5 +13,6 @@ sysdep_routines += \
 	\
 	strcmp_generic \
 	strcmp_zbb \
-	strcmp_zbb_unaligned
+	strcmp_zbb_unaligned \
+	strncmp_generic
 endif
diff --git a/sysdeps/riscv/multiarch/ifunc-impl-list.c b/sysdeps/riscv/multiarch/ifunc-impl-list.c
index d354aa1178..eb37ed6017 100644
--- a/sysdeps/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/riscv/multiarch/ifunc-impl-list.c
@@ -63,5 +63,7 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 	      IFUNC_IMPL_ADD (array, i, strcmp, 1, __strcmp_zbb)
 	      IFUNC_IMPL_ADD (array, i, strcmp, 1, __strcmp_generic))
 
+  IFUNC_IMPL (i, name, strncmp,
+	      IFUNC_IMPL_ADD (array, i, strncmp, 1, __strncmp_generic))
   return i;
 }
diff --git a/sysdeps/riscv/multiarch/strncmp.c b/sysdeps/riscv/multiarch/strncmp.c
new file mode 100644
index 0000000000..970aeb8b85
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strncmp.c
@@ -0,0 +1,40 @@
+/* Multiple versions of strncmp. RISC-V version.
+   Copyright (C) 2022 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 multiple versions only for the definition in libc.  */
+
+#if IS_IN (libc)
+/* Redefine strncmp so that the compiler won't complain about the type
+   mismatch with the IFUNC selector in strong_alias, below.  */
+# undef strncmp
+# define strncmp __redirect_strncmp
+# include <string.h>
+# include <ldsodefs.h>
+# include <sys/auxv.h>
+# include <init-arch.h>
+
+extern __typeof (__redirect_strncmp) __libc_strncmp;
+extern __typeof (__redirect_strncmp) __strncmp_generic attribute_hidden;
+
+libc_ifunc (__libc_strncmp, __strncmp_generic);
+
+# undef strncmp
+strong_alias (__libc_strncmp, strncmp);
+#else
+# include <string/strncmp.c>
+#endif
diff --git a/sysdeps/riscv/multiarch/strncmp_generic.c b/sysdeps/riscv/multiarch/strncmp_generic.c
new file mode 100644
index 0000000000..9d8cdf2f1a
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strncmp_generic.c
@@ -0,0 +1,32 @@
+/* strncmp for RISC-V, default version for internal use.
+   Copyright (C) 2022 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/>.  */
+
+#include <string.h>
+
+#define STRNCMP __strncmp_generic
+
+#ifdef SHARED
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name) \
+  __hidden_ver1(__strncmp_generic, __GI_strncmp, __strncmp_generic);
+#endif
+
+extern int __strncmp_generic(const char *s1, const char *s2, size_t n);
+
+#include <string/strncmp.c>
-- 
2.39.1