From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org,
Richard Henderson <richard.henderson@linaro.org>,
Jeff Law <jeffreyalaw@gmail.com>, Xi Ruoyao <xry111@xry111.site>
Subject: Re: [PATCH v12 09/31] string: Improve generic stpcpy
Date: Fri, 3 Feb 2023 17:26:07 -0600 [thread overview]
Message-ID: <CAFUsyfLX=H1t2ungP744mCkMDNdhKRcA72E4uex+P1OAqL04HQ@mail.gmail.com> (raw)
In-Reply-To: <20230202181149.2181553-10-adhemerval.zanella@linaro.org>
On Thu, Feb 2, 2023 at 12:12 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> It follows the strategy:
>
> - Align the destination on word boundary using byte operations.
>
> - If source is also word aligned, read a word per time, check for
> null (using has_zero from string-fzb.h), and write the remaining
> bytes.
>
> - If source is not word aligned, loop by aligning the source, and
> merging the result of two reads. Similar to aligned case,
> check for null with has_zero, and write the remaining bytes if
> null is found.
>
> Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64-linux-gnu,
> and powerpc-linux-gnu by removing the arch-specific assembly
> implementation and disabling multi-arch (it covers both LE and BE
> for 64 and 32 bits).
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> string/stpcpy.c | 92 +++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 86 insertions(+), 6 deletions(-)
>
> diff --git a/string/stpcpy.c b/string/stpcpy.c
> index 8df5065cfe..dd0fef12ef 100644
> --- a/string/stpcpy.c
> +++ b/string/stpcpy.c
> @@ -15,12 +15,12 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> -#ifdef HAVE_CONFIG_H
> -# include <config.h>
> -#endif
> -
> #define NO_MEMPCPY_STPCPY_REDIRECT
> #include <string.h>
> +#include <stdint.h>
> +#include <memcopy.h>
> +#include <string-fzb.h>
> +#include <string-misc.h>
>
> #undef __stpcpy
> #undef stpcpy
> @@ -29,12 +29,92 @@
> # define STPCPY __stpcpy
> #endif
>
> +static __always_inline char *
> +write_byte_from_word (op_t *dest, op_t word)
> +{
> + char *d = (char *) dest;
> + for (size_t i = 0; i < OPSIZ; i++, ++d)
> + {
> + char c = extractbyte (word, i);
> + *d = c;
> + if (c == '\0')
> + break;
> + }
> + return d;
> +}
> +
> +static __always_inline char *
> +stpcpy_aligned_loop (op_t *restrict dst, const op_t *restrict src)
> +{
> + op_t word;
> + while (1)
> + {
> + word = *src++;
> + if (has_zero (word))
> + break;
> + *dst++ = word;
> + }
> +
> + return write_byte_from_word (dst, word);
> +}
> +
> +static __always_inline char *
> +stpcpy_unaligned_loop (op_t *restrict dst, const op_t *restrict src,
> + uintptr_t ofs)
> +{
> + op_t w2a = *src++;
> + uintptr_t sh_1 = ofs * CHAR_BIT;
> + uintptr_t sh_2 = OPSIZ * CHAR_BIT - sh_1;
> +
> + op_t w2 = MERGE (w2a, sh_1, (op_t)-1, sh_2);
> + if (!has_zero (w2))
> + {
> + op_t w2b;
> +
> + /* Unaligned loop. The invariant is that W2B, which is "ahead" of W1,
> + does not contain end-of-string. Therefore it is safe (and necessary)
> + to read another word from each while we do not have a difference. */
> + while (1)
> + {
> + w2b = *src++;
> + w2 = MERGE (w2a, sh_1, w2b, sh_2);
> + /* Check if there is zero on w2a. */
> + if (has_zero (w2))
> + goto out;
> + *dst++ = w2;
> + if (has_zero (w2b))
> + break;
> + w2a = w2b;
> + }
> +
> + /* Align the final partial of P2. */
> + w2 = MERGE (w2b, sh_1, 0, sh_2);
> + }
> +
> +out:
> + return write_byte_from_word (dst, w2);
> +}
> +
> +
> /* Copy SRC to DEST, returning the address of the terminating '\0' in DEST. */
> char *
> STPCPY (char *dest, const char *src)
> {
> - size_t len = strlen (src);
> - return memcpy (dest, src, len + 1) + len;
> + /* Copy just a few bytes to make DEST aligned. */
> + size_t len = (-(uintptr_t) dest) % OPSIZ;
> + for (; len != 0; len--, ++dest)
> + {
> + char c = *src++;
> + *dest = c;
> + if (c == '\0')
> + return dest;
> + }
> +
> + /* DEST is now aligned to op_t, SRC may or may not be. */
> + uintptr_t ofs = (uintptr_t) src % OPSIZ;
> + return ofs == 0 ? stpcpy_aligned_loop ((op_t*) dest, (const op_t *) src)
> + : stpcpy_unaligned_loop ((op_t*) dest,
> + (const op_t *) (src - ofs) , ofs);
> }
> weak_alias (__stpcpy, stpcpy)
> libc_hidden_def (__stpcpy)
> --
> 2.34.1
>
LGTM.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
next prev parent reply other threads:[~2023-02-03 23:26 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-02 18:11 [PATCH v12 00/31] Improve generic string routines Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 01/31] Parameterize op_t from memcopy.h Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 02/31] Parameterize OP_T_THRES " Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 03/31] Add string vectorized find and detection functions Adhemerval Zanella
2023-02-03 0:24 ` Richard Henderson
2023-02-03 12:39 ` Adhemerval Zanella Netto
2023-02-03 13:40 ` Adhemerval Zanella Netto
2023-02-04 2:54 ` Richard Henderson
2023-02-02 18:11 ` [PATCH v12 04/31] string: Improve generic strlen Adhemerval Zanella
2023-02-03 23:23 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 05/31] string: Improve generic strchrnul Adhemerval Zanella
2023-02-03 23:23 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 06/31] string: Improve generic strchr Adhemerval Zanella
2023-02-03 23:24 ` Noah Goldstein
2023-02-04 2:58 ` Richard Henderson
2023-02-06 13:07 ` Adhemerval Zanella Netto
2023-02-02 18:11 ` [PATCH v12 07/31] string: Improve generic strcmp Adhemerval Zanella
2023-02-03 23:25 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 08/31] string: Improve generic strncmp Adhemerval Zanella
2023-02-03 0:34 ` Richard Henderson
2023-02-21 9:28 ` Szabolcs Nagy
2023-02-21 12:24 ` Adhemerval Zanella Netto
2023-02-02 18:11 ` [PATCH v12 09/31] string: Improve generic stpcpy Adhemerval Zanella
2023-02-03 23:26 ` Noah Goldstein [this message]
2023-02-02 18:11 ` [PATCH v12 10/31] string: Improve generic strcpy Adhemerval Zanella
2023-02-03 23:26 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 11/31] string: Improve generic memchr Adhemerval Zanella
2023-02-03 23:26 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 12/31] string: Improve generic strnlen with memchr Adhemerval Zanella
2023-02-03 23:27 ` Noah Goldstein
2023-02-02 18:11 ` [PATCH v12 13/31] string: Improve generic memrchr Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 14/31] string: Improve generic strrchr with memrchr and strlen Adhemerval Zanella
2023-02-04 3:06 ` Richard Henderson
2023-02-06 14:01 ` Adhemerval Zanella Netto
2023-02-02 18:11 ` [PATCH v12 15/31] hppa: Add memcopy.h Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 16/31] hppa: Add string-fza.h, string-fzc.h, and string-fzi.h Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 17/31] alpha: Add string-fza, string-fzb.h, string-fzi.h, and string-shift.h Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 18/31] arm: Add string-fza.h Adhemerval Zanella
2023-02-20 13:24 ` Szabolcs Nagy
2023-02-20 13:45 ` Szabolcs Nagy
2023-02-20 14:01 ` Adhemerval Zanella Netto
2023-02-20 16:12 ` Szabolcs Nagy
2023-02-02 18:11 ` [PATCH v12 19/31] powerpc: " Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 20/31] sh: Add string-fzb.h Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 21/31] riscv: Add string-fza.h and string-fzi.h Adhemerval Zanella
2023-02-03 19:47 ` Noah Goldstein
2023-02-06 16:14 ` Adhemerval Zanella Netto
2023-02-02 18:11 ` [PATCH v12 22/31] string: Hook up the default implementation on test-strlen Adhemerval Zanella
2023-02-03 23:30 ` Noah Goldstein
2023-02-06 17:36 ` Adhemerval Zanella Netto
2023-02-02 18:11 ` [PATCH v12 23/31] string: Hook up the default implementation on test-strnlen Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 24/31] string: Hook up the default implementation on test-strchr Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 25/31] string: Hook up the default implementation on test-strcmp Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 26/31] string: Hook up the default implementation on test-strncmp Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 27/31] string: Hook up the default implementation on test-stpcpy Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 28/31] string: Hook up the default implementation on test-strcpy Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 29/31] string: Hook up the default implementation on test-memchr Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 30/31] string: Hook up the default implementation on test-memrchr Adhemerval Zanella
2023-02-02 18:11 ` [PATCH v12 31/31] string: Hook up the default implementation on test-strrchr Adhemerval Zanella
2023-02-03 1:55 ` Richard Henderson
2023-02-02 18:17 ` [PATCH v12 00/31] Improve generic string routines Adhemerval Zanella Netto
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