From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Richard Henderson <richard.henderson@linaro.org>,
libc-alpha@sourceware.org
Cc: goldstein.w.n@gmail.com
Subject: Re: [PATCH v8 03/17] Add string-maskoff.h generic header
Date: Wed, 18 Jan 2023 09:45:24 -0300 [thread overview]
Message-ID: <01aff28e-5d12-6529-58a3-b287c695dee8@linaro.org> (raw)
In-Reply-To: <3426dd71-b114-5a2d-334d-5c7daf5938f2@linaro.org>
On 17/01/23 22:33, Richard Henderson wrote:
> On 1/17/23 08:49, Adhemerval Zanella Netto wrote:
>>
>>
>> On 16/01/23 17:58, Richard Henderson wrote:
>>> On 1/13/23 08:27, Richard Henderson wrote:
>>>> +/* 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 __always_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));
>>>> +}
>>>
>>> This has exactly one use, in strlen, which could now use shift_find, like strchrnul.
>>
>> Right, I remove the strlen usage then.
>
> The thing is... leaving things as they are is probably better for HPPA and SH, which get to use their boolean byte comparison instructions.
>
> The prior code in strchr(nul) was trying to prevent matches vs both 0 and C, consuming at least 4 extra insns (possibly more with the constant loads). The new code in strchrnul may be better (or at least close) everywhere.
>
> But perhaps simplicity demands removal in strlen as well?
I mimic the strchr code on strlen, so I hope it would produce better instruction
as well.
>
>> The word_containing can be removed as well in favor of PTR_ALIGN macros and
>
> Good idea.
>
>> I will rename the header to string-repeat_bytes.h.
>
> Or merge with string-extbyte.h and name string-misc.h?
I think it makes sense, I will update it.
next prev parent reply other threads:[~2023-01-18 12:45 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-13 18:27 [PATCH v8 00/17] Improve generic string routines Richard Henderson
2023-01-13 18:27 ` [PATCH v8 01/17] Parameterize op_t from memcopy.h Richard Henderson
2023-01-16 20:52 ` Richard Henderson
2023-01-13 18:27 ` [PATCH v8 02/17] Parameterize OP_T_THRES " Richard Henderson
2023-01-16 20:52 ` Richard Henderson
2023-01-13 18:27 ` [PATCH v8 03/17] Add string-maskoff.h generic header Richard Henderson
2023-01-16 20:58 ` Richard Henderson
2023-01-17 18:49 ` Adhemerval Zanella Netto
2023-01-18 1:33 ` Richard Henderson
2023-01-18 12:45 ` Adhemerval Zanella Netto [this message]
2023-01-13 18:27 ` [PATCH v8 04/17] Add string vectorized find and detection functions Richard Henderson
2023-01-16 21:04 ` Richard Henderson
2023-01-13 18:27 ` [PATCH v8 05/17] string: Improve generic strlen Richard Henderson
2023-01-13 18:27 ` [PATCH v8 06/17] string: Improve generic strnlen Richard Henderson
2023-01-13 18:27 ` [PATCH v8 07/17] string: Improve generic strchr Richard Henderson
2023-01-13 18:27 ` [PATCH v8 08/17] string: Improve generic strchrnul Richard Henderson
2023-01-13 18:27 ` [PATCH v8 09/17] string: Improve generic strcmp Richard Henderson
2023-01-13 18:27 ` [PATCH v8 10/17] string: Improve generic memchr Richard Henderson
2023-01-13 18:27 ` [PATCH v8 11/17] string: Improve generic memrchr Richard Henderson
2023-01-13 18:27 ` [PATCH v8 12/17] hppa: Add memcopy.h Richard Henderson
2023-01-13 18:27 ` [PATCH v8 13/17] hppa: Add string-fzb.h and string-fzi.h Richard Henderson
2023-01-13 18:27 ` [PATCH v8 14/17] alpha: " Richard Henderson
2023-01-13 18:27 ` [PATCH v8 15/17] arm: Add string-fza.h Richard Henderson
2023-01-13 18:27 ` [PATCH v8 16/17] powerpc: " Richard Henderson
2023-01-17 14:35 ` Adhemerval Zanella Netto
2023-01-13 18:27 ` [PATCH v8 17/17] sh: Add string-fzb.h Richard Henderson
2023-01-17 14:35 ` Adhemerval Zanella Netto
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