x86-64: Optimize memchr/rawmemchr/wmemchr with SSE2/AVX2

SSE2 memchr is extended to support wmemchr.  AVX2 memchr/rawmemchr/wmemchr
are added to search 32 bytes with a single vector compare instruction.
AVX2 memchr/rawmemchr/wmemchr are as fast as SSE2 memchr/rawmemchr/wmemchr
for small sizes and up to 1.5X faster for larger sizes on Haswell and
Skylake.  Select AVX2 memchr/rawmemchr/wmemchr 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/memchr.S (MEMCHR): New.  Depending on if
	USE_AS_WMEMCHR is defined.
	(PCMPEQ): Likewise.
	(memchr): Renamed to ...
	(MEMCHR): This.  Support wmemchr if USE_AS_WMEMCHR is defined.
	Replace pcmpeqb with PCMPEQ.
	* sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
	memchr-sse2, rawmemchr-sse2, memchr-avx2, rawmemchr-avx2,
	wmemchr-sse4_1, wmemchr-avx2 and wmemchr-c.
	* sysdeps/x86_64/multiarch/ifunc-avx2.h: New file.
	* sysdeps/x86_64/multiarch/memchr-avx2.S: Likewise.
	* sysdeps/x86_64/multiarch/memchr-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/memchr.c: Likewise.
	* sysdeps/x86_64/multiarch/rawmemchr-avx2.S: Likewise.
	* sysdeps/x86_64/multiarch/rawmemchr-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/rawmemchr.c: Likewise.
	* sysdeps/x86_64/multiarch/wmemchr-avx2.S: Likewise.
	* sysdeps/x86_64/multiarch/wmemchr-sse2.S: Likewise.
	* sysdeps/x86_64/multiarch/wmemchr.c: Likewise.
	* sysdeps/x86_64/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Test __memchr_avx2, __memchr_sse2,
	__rawmemchr_avx2, __rawmemchr_sse2, __wmemchr_avx2 and
	__wmemchr_sse2.

1 files changed, 36 insertions, 0 deletions

diff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h
new file mode 100644
index 0000000000..25432b83f2
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h
@@ -0,0 +1,36 @@
+/* Common definition for ifunc selections optimized with SSE2 and AVX2.
+   All versions must be listed in ifunc-impl-list.c.
+   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 <init-arch.h>
+
+extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
+extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
+
+static inline void *
+IFUNC_SELECTOR (void)
+{
+  const struct cpu_features* cpu_features = __get_cpu_features ();
+
+  if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER)
+      && CPU_FEATURES_ARCH_P (cpu_features, AVX2_Usable)
+      && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
+    return OPTIMIZE (avx2);
+
+  return OPTIMIZE (sse2);
+}