From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
Richard Henderson <rth@twiddle.net>,
Joseph Myers <joseph@codesourcery.com>,
caiyinyu <caiyinyu@loongson.cn>
Subject: Re: [PATCH 10/17] string: Improve generic memchr
Date: Mon, 19 Sep 2022 16:17:00 -0300 [thread overview]
Message-ID: <0358c009-eda0-ae01-5d63-69003e3fe375@linaro.org> (raw)
In-Reply-To: <CAFUsyfJnneN8wJE4Rbi7qyrAPBXaoU5P536j_2hHJxk8UPys3g@mail.gmail.com>
On 03/09/22 00:47, Noah Goldstein wrote:
>>
>> - longword_ptr = (const longword *) char_ptr;
>> + /* Compute the address of the word containing the last byte. */
>> + const op_t *lword = word_containing (lbyte);
>>
>> - /* All these elucidatory comments refer to 4-byte longwords,
>> - but the theory applies equally well to any size longwords. */
>> + /* Read the first word, but munge it so that bytes before the array
>> + will not match goal. */
>> + const op_t * word_ptr = word_containing (s);
>> + op_t word = (*word_ptr | before_mask) ^ (repeated_c & before_mask);
>
> Why do you xor with repeated_c & before_mask here?
>
> Doesn't the has_eq(word, repeated_c) do that?
For the case of c_in being 0xff, since for this case or with before_mask
will make has_eq to return early. The test-memchr does not trigger it,
but test-memccpy does fail without the XOR.
next prev parent reply other threads:[~2022-09-19 19:17 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-02 20:39 [PATCH 00/17] Improve generic string routines Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 02/17] Parameterize OP_T_THRES " Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 03/17] Add string-maskoff.h generic header Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 04/17] Add string vectorized find and detection functions Adhemerval Zanella
2022-09-03 3:20 ` Noah Goldstein
2022-09-19 14:00 ` Adhemerval Zanella Netto
2022-09-02 20:39 ` [PATCH 05/17] string: Improve generic strlen Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 06/17] string: Improve generic strnlen Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 07/17] string: Improve generic strchr Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 08/17] string: Improve generic strchrnul Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 09/17] string: Improve generic strcmp Adhemerval Zanella
2022-09-03 3:31 ` Noah Goldstein
2022-09-19 14:04 ` Adhemerval Zanella Netto
2022-09-03 8:54 ` Richard Henderson
2022-09-02 20:39 ` [PATCH 10/17] string: Improve generic memchr Adhemerval Zanella
2022-09-03 3:47 ` Noah Goldstein
2022-09-19 19:17 ` Adhemerval Zanella Netto [this message]
2022-09-19 21:59 ` Noah Goldstein
2022-09-22 17:51 ` Adhemerval Zanella Netto
2022-09-02 20:39 ` [PATCH 11/17] string: Improve generic memrchr Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 12/17] hppa: Add memcopy.h Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 13/17] hppa: Add string-fzb.h and string-fzi.h Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 14/17] alpha: " Adhemerval Zanella
2022-09-02 20:39 ` [PATCH 15/17] arm: Add string-fza.h Adhemerval Zanella
2022-09-05 15:40 ` Richard Earnshaw
2022-09-05 15:50 ` Richard Earnshaw
2022-09-02 20:39 ` [PATCH 16/17] powerpc: " Adhemerval Zanella
2022-09-06 14:48 ` Paul E Murphy
2022-09-19 19:55 ` Adhemerval Zanella Netto
2022-09-02 20:39 ` [PATCH 17/17] sh: Add string-fzb.h Adhemerval Zanella
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