From: Alejandro Colomar <alx.manpages@gmail.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>,
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v5 03/17] Add string-maskoff.h generic header
Date: Fri, 6 Jan 2023 00:26:04 +0100 [thread overview]
Message-ID: <8c026b5b-9f65-dda4-83a8-daf2ec9b3355@gmail.com> (raw)
In-Reply-To: <CAFUsyfJXz7JbB8_Mc7n98e++piy5Th48-BVv8uJjpF-FL7uMHw@mail.gmail.com>
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On 1/5/23 23:49, Noah Goldstein via Libc-alpha wrote:
> On Mon, Sep 19, 2022 at 12:59 PM Adhemerval Zanella via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>> Macros to operate on unaligned access for string operations:
>>
>> - create_mask: create a mask based on pointer alignment to sets up
>> non-zero bytes before the beginning of the word so a following
>> operation (such as find zero) might ignore these bytes.
>>
>> - highbit_mask: create a mask with high bit of each byte being 1,
>> and the low 7 bits being all the opposite of the input.
>>
>> These macros are meant to be used on optimized vectorized string
>> implementations.
>> ---
>> sysdeps/generic/string-maskoff.h | 73 ++++++++++++++++++++++++++++++++
>> 1 file changed, 73 insertions(+)
>> create mode 100644 sysdeps/generic/string-maskoff.h
>>
>> diff --git a/sysdeps/generic/string-maskoff.h b/sysdeps/generic/string-maskoff.h
>> new file mode 100644
>> index 0000000000..831647bda6
>> --- /dev/null
>> +++ b/sysdeps/generic/string-maskoff.h
>> @@ -0,0 +1,73 @@
>> +/* Mask off bits. Generic C 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
>> + <http://www.gnu.org/licenses/>. */
>> +
>> +#ifndef _STRING_MASKOFF_H
>> +#define _STRING_MASKOFF_H 1
>> +
>> +#include <endian.h>
>> +#include <limits.h>
>> +#include <stdint.h>
>> +#include <string-optype.h>
>> +
>> +/* Provide a mask based on the pointer alignment that sets up non-zero
>> + bytes before the beginning of the word. It is used to mask off
>> + undesirable bits from an aligned read from an unaligned pointer.
>> + For instance, on a 64 bits machine with a pointer alignment of
>> + 3 the function returns 0x0000000000ffffff for LE and 0xffffff0000000000
>> + (meaning to mask off the initial 3 bytes). */
>> +static inline op_t
>> +create_mask (uintptr_t i)
>> +{
>> + i = i % sizeof (op_t);
>> + if (__BYTE_ORDER == __LITTLE_ENDIAN)
>> + return ~(((op_t)-1) << (i * CHAR_BIT));
>> + else
>> + return ~(((op_t)-1) >> (i * CHAR_BIT));
>> +}
>> +
>> +/* Setup an word with each byte being c_in. For instance, on a 64 bits
>> + machine with input as 0xce the functions returns 0xcececececececece. */
>> +static inline op_t
Hi Adhemerval and Noah,
I don't know what is the minimum C version for compiling glibc, but if you can
ignore C89, I would propose something:
'static inline' should be restricted to .c files, since if the compiler decides
to not inline and you have it in a header, you end up with multiple static
definitions for the same code.
In headers, I use C99 inline, which doesn't emit any object code when the
compiler decides to not inline. Then in a .c file, you add a prototype using
'extern inline', and the compiler will emit code there, exactly once.
Even if you have to support C89, I'd use [[gnu::always_inline]] together with
'static inline', to make sure that the compiler doesn't do nefarious stuff.
Cheers,
Alex
--
<http://www.alejandro-colomar.es/>
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next prev parent reply other threads:[~2023-01-05 23:26 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-19 19:59 [PATCH v5 00/17] Improve generic string routines Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 02/17] Parameterize OP_T_THRES " Adhemerval Zanella
2022-09-20 10:49 ` Carlos O'Donell
2022-09-19 19:59 ` [PATCH v5 03/17] Add string-maskoff.h generic header Adhemerval Zanella
2022-09-20 11:43 ` Carlos O'Donell
2022-09-22 17:31 ` Adhemerval Zanella Netto
2023-01-05 22:49 ` Noah Goldstein
2023-01-05 23:26 ` Alejandro Colomar [this message]
2023-01-09 18:19 ` Adhemerval Zanella Netto
2023-01-09 18:02 ` Adhemerval Zanella Netto
2022-09-19 19:59 ` [PATCH v5 04/17] Add string vectorized find and detection functions Adhemerval Zanella
2023-01-05 22:53 ` Noah Goldstein
2023-01-09 18:51 ` Adhemerval Zanella Netto
2023-01-05 23:04 ` Noah Goldstein
2023-01-09 19:34 ` Adhemerval Zanella Netto
2022-09-19 19:59 ` [PATCH v5 05/17] string: Improve generic strlen Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 06/17] string: Improve generic strnlen Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 07/17] string: Improve generic strchr Adhemerval Zanella
2023-01-05 23:09 ` Noah Goldstein
2023-01-05 23:19 ` Noah Goldstein
2023-01-09 19:39 ` Adhemerval Zanella Netto
2022-09-19 19:59 ` [PATCH v5 08/17] string: Improve generic strchrnul Adhemerval Zanella
2023-01-05 23:17 ` Noah Goldstein
2023-01-09 20:35 ` Adhemerval Zanella Netto
2023-01-09 20:49 ` Richard Henderson
2023-01-09 20:59 ` Noah Goldstein
2023-01-09 21:01 ` Noah Goldstein
2023-01-09 23:33 ` Richard Henderson
2023-01-10 14:18 ` Adhemerval Zanella Netto
2023-01-10 16:24 ` Richard Henderson
2023-01-10 17:16 ` Noah Goldstein
2023-01-10 18:19 ` Adhemerval Zanella Netto
2023-01-10 17:17 ` Noah Goldstein
2023-01-10 18:16 ` Adhemerval Zanella Netto
2022-09-19 19:59 ` [PATCH v5 09/17] string: Improve generic strcmp Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 10/17] string: Improve generic memchr Adhemerval Zanella
2023-01-05 23:47 ` Noah Goldstein
2023-01-09 20:50 ` Adhemerval Zanella Netto
2023-01-05 23:49 ` Noah Goldstein
2023-01-09 20:51 ` Adhemerval Zanella Netto
2023-01-09 21:26 ` Noah Goldstein
2023-01-10 14:33 ` Adhemerval Zanella Netto
2022-09-19 19:59 ` [PATCH v5 11/17] string: Improve generic memrchr Adhemerval Zanella
2023-01-05 23:51 ` Noah Goldstein
2022-09-19 19:59 ` [PATCH v5 12/17] hppa: Add memcopy.h Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 13/17] hppa: Add string-fzb.h and string-fzi.h Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 14/17] alpha: " Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 15/17] arm: Add string-fza.h Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 16/17] powerpc: " Adhemerval Zanella
2022-09-19 19:59 ` [PATCH v5 17/17] sh: Add string-fzb.h Adhemerval Zanella
2022-12-05 17:07 ` [PATCH v5 00/17] Improve generic string routines Xi Ruoyao
2023-01-05 21:56 ` Adhemerval Zanella Netto
2023-01-05 23:52 ` Noah Goldstein
2023-01-06 13:43 ` Adhemerval Zanella Netto
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