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Re: [PATCH][AArch64] Add rawmemchr
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Thu, 2 Jun 2016 08:57:10 -0300
- Subject: Re: [PATCH][AArch64] Add rawmemchr
- Authentication-results: sourceware.org; auth=none
- References: <AM3PR08MB00888F05E81BE0117C6876AB83420 at AM3PR08MB0088 dot eurprd08 dot prod dot outlook dot com>
LGTM with a small nit.
On 27/05/2016 10:29, Wilco Dijkstra wrote:
> Add a simple rawmemchr implementation. Use strlen for rawmemchr(s, '\0') as
> it is the fastest way to search for '\0'. Otherwise use memchr with an infinite size.
> This is 3x faster on benchtests for large sizes.
>
> Passes GLIBC tests, OK for commit?
>
> ChangeLog:
> 2016-05-27 Wilco Dijkstra <wdijkstr@arm.com>
>
> * sysdeps/aarch64/rawmemchr.S (__rawmemchr): New file.
> * sysdeps/aarch64/strlen.S (__strlen): Change to __strlen to avoid PLT.
>
> ---
> sysdeps/aarch64/rawmemchr.S | 42 ++++++++++++++++++++++++++++++++++++++++++
> sysdeps/aarch64/strlen.S | 5 +++--
> 2 files changed, 45 insertions(+), 2 deletions(-)
> create mode 100644 sysdeps/aarch64/rawmemchr.S
>
> diff --git a/sysdeps/aarch64/rawmemchr.S b/sysdeps/aarch64/rawmemchr.S
> new file mode 100644
> index 0000000..ec958e8
> --- /dev/null
> +++ b/sysdeps/aarch64/rawmemchr.S
> @@ -0,0 +1,42 @@
> +/* rawmemchr - find a character in a memory zone
> +
> + Copyright (C) 2015-2016 Free Software Foundation, Inc.
I think it should be just 2016.
> +
> + 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 <sysdep.h>
> +
> +/* Special case rawmemchr (s, 0) as strlen, otherwise tailcall memchr.
> + Call strlen without setting up a full frame - it preserves x14/x15.
> +*/
> +
> +ENTRY (__rawmemchr)
> + cbz w1, L(do_strlen)
> + mov x2, -1
> + b __memchr
> +
> +L(do_strlen):
> + mov x15, x30
> + cfi_return_column (x15)
> + mov x14, x0
> + bl __strlen
> + add x0, x14, x0
> + ret x15
> +
> +END (__rawmemchr)
> +weak_alias (__rawmemchr, rawmemchr)
> +libc_hidden_builtin_def (__rawmemchr)
> diff --git a/sysdeps/aarch64/strlen.S b/sysdeps/aarch64/strlen.S
> index feb9e48..e2a4363 100644
> --- a/sysdeps/aarch64/strlen.S
> +++ b/sysdeps/aarch64/strlen.S
> @@ -84,7 +84,7 @@
> whether the first fetch, which may be misaligned, crosses a page
> boundary. */
>
> -ENTRY_ALIGN (strlen, 6)
> +ENTRY_ALIGN (__strlen, 6)
> and tmp1, srcin, MIN_PAGE_SIZE - 1
> mov zeroones, REP8_01
> cmp tmp1, MIN_PAGE_SIZE - 16
> @@ -213,5 +213,6 @@ L(page_cross):
> csel data1, data1, tmp4, eq
> csel data2, data2, tmp2, eq
> b L(page_cross_entry)
> -END (strlen)
> +END (__strlen)
> +weak_alias (__strlen, strlen)
> libc_hidden_builtin_def (strlen)
>