x86-64: Optimize strchr/strchrnul/wcschr with AVX2

Optimize strchr/strchrnul/wcschr with AVX2 to search 32 bytes with vector
instructions.  It is as fast as SSE2 versions for size <= 16 bytes and up
to 1X faster for or size > 16 bytes on Haswell.  Select AVX2 version on
AVX2 machines where vzeroupper is preferred and AVX unaligned load is fast.

NB: It uses TZCNT instead of BSF since TZCNT produces the same result
as BSF for non-zero input.  TZCNT is faster than BSF and is executed
as BSF if machine doesn't support TZCNT.

	* sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
	strchr-sse2, strchrnul-sse2, strchr-avx2, strchrnul-avx2,
	wcschr-sse2 and wcschr-avx2.
	* sysdeps/x86_64/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Add tests for __strchr_avx2,
	__strchrnul_avx2, __strchrnul_sse2, __wcschr_avx2 and
	__wcschr_sse2.
	* sysdeps/x86_64/multiarch/strchr-avx2.S: New file.
	* sysdeps/x86_64/multiarch/strchr-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/strchr.c: Likewise.
	* sysdeps/x86_64/multiarch/strchrnul-avx2.S: Likewise.
	* sysdeps/x86_64/multiarch/strchrnul-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/strchrnul.c: Likewise.
	* sysdeps/x86_64/multiarch/wcschr-avx2.S: Likewise.
	* sysdeps/x86_64/multiarch/wcschr-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/wcschr.c: Likewise.
	* sysdeps/x86_64/multiarch/strchr.S: Removed.

1 files changed, 28 insertions, 0 deletions

diff --git a/sysdeps/x86_64/multiarch/strchr-sse2.S b/sysdeps/x86_64/multiarch/strchr-sse2.S
new file mode 100644
index 0000000000..c4d1c0c773
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/strchr-sse2.S
@@ -0,0 +1,28 @@
+/* strchr optimized with SSE2.
+   Copyright (C) 2009-2017 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/>.  */
+
+#if IS_IN (libc)
+# define strchr __strchr_sse2
+
+# undef weak_alias
+# define weak_alias(strchr, index)
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(strchr)
+#endif
+
+#include "../strchr.S"