From 5916700c768803546b6fe7d093dcba40d22fcf57 Mon Sep 17 00:00:00 2001 From: Ken Steele Date: Thu, 1 Aug 2013 15:55:07 -0400 Subject: tile: optimize strnlen using SIMD instructions Using strlen as a model, add length checking to create strnlen. Signed-off-by: Ken Steele Signed-off-by: Chris Metcalf --- arch/tile/lib/strnlen_64.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 arch/tile/lib/strnlen_64.c (limited to 'arch/tile/lib/strnlen_64.c') diff --git a/arch/tile/lib/strnlen_64.c b/arch/tile/lib/strnlen_64.c new file mode 100644 index 000000000000..2e8de6a5136f --- /dev/null +++ b/arch/tile/lib/strnlen_64.c @@ -0,0 +1,48 @@ +/* + * Copyright 2013 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program 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, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + */ + +#include +#include +#include +#include "string-endian.h" + +size_t strnlen(const char *s, size_t count) +{ + /* Get an aligned pointer. */ + const uintptr_t s_int = (uintptr_t) s; + const uint64_t *p = (const uint64_t *)(s_int & -8); + size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1)); + size_t len; + uint64_t v, bits; + + /* Avoid page fault risk by not reading any bytes when count is 0. */ + if (count == 0) + return 0; + + /* Read and MASK the first word. */ + v = *p | MASK(s_int); + + while ((bits = __insn_v1cmpeqi(v, 0)) == 0) { + if (bytes_read >= count) { + /* Read COUNT bytes and didn't find the terminator. */ + return count; + } + v = *++p; + bytes_read += sizeof(v); + } + + len = ((const char *) p) + (CFZ(bits) >> 3) - s; + return (len < count ? len : count); +} +EXPORT_SYMBOL(strnlen); -- cgit v1.2.3