[v2,2/2] aarch64: Optimized memcpy and memmove for Kunpeng processor

This is an optimized implementation of the memcpy and memmove on the
Huawei Kunpeng processor.

Based on the prefetch mechanism on Kunpeng arch, branch to handle 96
to 2K bytes in memcpy is written without prfm instruction. Hence,
memcpy has an optimization effect above 128 bytes, 18% improvement
for copies above 2K bytes, and 38% for larger bytes, such as 32M
bytes around.

And for memmove, there are two main changes: i) Q register is used
instead of  X register. ii) dst address is aligned instead of src
address aligned to improve store operation. Hence, memmove
implementation also has improvement above 128 bytes, that about 30%
for 2k to 8M bytes, and about 50% for 32M or more.
---
 sysdeps/aarch64/multiarch/Makefile          |   2 +-
 sysdeps/aarch64/multiarch/ifunc-impl-list.c |   4 +-
 sysdeps/aarch64/multiarch/memcpy.c          |   5 +-
 sysdeps/aarch64/multiarch/memcpy_kunpeng.S  | 468 ++++++++++++++++++++++++++++
 4 files changed, 476 insertions(+), 3 deletions(-)
 create mode 100644 sysdeps/aarch64/multiarch/memcpy_kunpeng.S

> Btw do you have any plans to post other string functions that you can discuss here? If so, would these
> add more ifuncs or improve the generic versions?

> Yes, memcmp, strlen, strnlen, strcpy, memrchr will be included, we will summited the patch and test results as soon as possible.

We have submitted the patches of string functions, see below:

[PATCH] aarch64: Optimized strnlen for Kunpeng processor
https://sourceware.org/ml/libc-alpha/2019-10/msg00528.html

[PATCH] aarch64: Optimized strlen for Kunpeng processor
https://sourceware.org/ml/libc-alpha/2019-10/msg00527.html

[PATCH] aarch64: Optimized implementation of memrchr
https://sourceware.org/ml/libc-alpha/2019-10/msg00526.html

[PATCH] aarch64: Optimized strcpy for Kunpeng processor.
https://sourceware.org/ml/libc-alpha/2019-10/msg00525.html

[PATCH] aarch64: Optimized memcmp for Kunpeng processor.
https://sourceware.org/ml/libc-alpha/2019-10/msg00524.html

Xuelei Zhang <zhangxuelei4@huawei.com> 于2019年10月17日周四 下午9:16写道：
>
> This is an optimized implementation of the memcpy and memmove on the
> Huawei Kunpeng processor.
>
> Based on the prefetch mechanism on Kunpeng arch, branch to handle 96
> to 2K bytes in memcpy is written without prfm instruction. Hence,
> memcpy has an optimization effect above 128 bytes, 18% improvement
> for copies above 2K bytes, and 38% for larger bytes, such as 32M
> bytes around.
>
> And for memmove, there are two main changes: i) Q register is used
> instead of  X register. ii) dst address is aligned instead of src
> address aligned to improve store operation. Hence, memmove
> implementation also has improvement above 128 bytes, that about 30%
> for 2k to 8M bytes, and about 50% for 32M or more.
> ---
>  sysdeps/aarch64/multiarch/Makefile          |   2 +-
>  sysdeps/aarch64/multiarch/ifunc-impl-list.c |   4 +-
>  sysdeps/aarch64/multiarch/memcpy.c          |   5 +-
>  sysdeps/aarch64/multiarch/memcpy_kunpeng.S  | 468 ++++++++++++++++++++++++++++
>  4 files changed, 476 insertions(+), 3 deletions(-)
>  create mode 100644 sysdeps/aarch64/multiarch/memcpy_kunpeng.S
>
> diff --git a/sysdeps/aarch64/multiarch/Makefile b/sysdeps/aarch64/multiarch/Makefile
> index 4150b89a90..37ed49982d 100644
> --- a/sysdeps/aarch64/multiarch/Makefile
> +++ b/sysdeps/aarch64/multiarch/Makefile
> @@ -1,6 +1,6 @@
>  ifeq ($(subdir),string)
>  sysdep_routines += memcpy_generic memcpy_thunderx memcpy_thunderx2 \
> -                  memcpy_falkor memmove_falkor \
> +                  memcpy_falkor memcpy_kunpeng memmove_falkor \
>                    memset_generic memset_falkor memset_emag \
>                    memchr_generic memchr_nosimd \
>                    strlen_generic strlen_asimd
> diff --git a/sysdeps/aarch64/multiarch/ifunc-impl-list.c b/sysdeps/aarch64/multiarch/ifunc-impl-list.c
> index be13b916e5..dbbe19096a 100644
> --- a/sysdeps/aarch64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/aarch64/multiarch/ifunc-impl-list.c
> @@ -25,7 +25,7 @@
>  #include <stdio.h>
>
>  /* Maximum number of IFUNC implementations.  */
> -#define MAX_IFUNC      4
> +#define MAX_IFUNC      5
>
>  size_t
>  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> @@ -42,11 +42,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>               IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_thunderx)
>               IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_thunderx2)
>               IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_falkor)
> +             IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_kunpeng)
>               IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_generic))
>    IFUNC_IMPL (i, name, memmove,
>               IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_thunderx)
>               IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_thunderx2)
>               IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_falkor)
> +             IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_kunpeng)
>               IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_generic))
>    IFUNC_IMPL (i, name, memset,
>               /* Enable this on non-falkor processors too so that other cores
> diff --git a/sysdeps/aarch64/multiarch/memcpy.c b/sysdeps/aarch64/multiarch/memcpy.c
> index 13796f987f..b5929e2718 100644
> --- a/sysdeps/aarch64/multiarch/memcpy.c
> +++ b/sysdeps/aarch64/multiarch/memcpy.c
> @@ -32,9 +32,12 @@ extern __typeof (__redirect_memcpy) __memcpy_generic attribute_hidden;
>  extern __typeof (__redirect_memcpy) __memcpy_thunderx attribute_hidden;
>  extern __typeof (__redirect_memcpy) __memcpy_thunderx2 attribute_hidden;
>  extern __typeof (__redirect_memcpy) __memcpy_falkor attribute_hidden;
> +extern __typeof (__redirect_memcpy) __memcpy_kunpeng attribute_hidden;
>
>  libc_ifunc (__libc_memcpy,
> -            (IS_THUNDERX (midr)
> +            IS_KUNPENG(midr)
> +           ?__memcpy_kunpeng
> +           : (IS_THUNDERX (midr)
>              ? __memcpy_thunderx
>              : (IS_FALKOR (midr) || IS_PHECDA (midr) || IS_ARES (midr)
>                 ? __memcpy_falkor
> diff --git a/sysdeps/aarch64/multiarch/memcpy_kunpeng.S b/sysdeps/aarch64/multiarch/memcpy_kunpeng.S
> new file mode 100644
> index 0000000000..385f282224
> --- /dev/null
> +++ b/sysdeps/aarch64/multiarch/memcpy_kunpeng.S
> @@ -0,0 +1,468 @@
> +/* Optimized memcpy and memmove for Huawei Kunpeng processor.
> +   Copyright (C) 2018-2019 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
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +
> +/* Assumptions:
> + *
> + * ARMv8-a, AArch64, unaligned accesses.
> + *
> + */
> +
> +#define dstin  x0
> +#define src    x1
> +#define count  x2
> +#define dst    x3
> +#define srcend x4
> +#define dstend x5
> +#define tmp2   x6
> +#define tmp3   x7
> +#define tmp3w   w7
> +#define A_l    x6
> +#define A_lw   w6
> +#define A_h    x7
> +#define A_hw   w7
> +#define B_l    x8
> +#define B_lw   w8
> +#define B_h    x9
> +#define C_l    x10
> +#define C_h    x11
> +#define D_l    x12
> +#define D_h    x13
> +#define E_l    src
> +#define E_h    count
> +#define F_l    srcend
> +#define F_h    dst
> +#define G_l    count
> +#define G_h    dst
> +#define tmp1   x14
> +
> +#define A_q    q0
> +#define B_q    q1
> +#define C_q    q2
> +#define D_q    q3
> +#define E_q    q4
> +#define F_q    q5
> +#define G_q    q6
> +#define H_q    q7
> +#define I_q    q16
> +#define J_q    q17
> +
> +#define A_v    v0
> +#define B_v    v1
> +#define C_v    v2
> +#define D_v    v3
> +#define E_v    v4
> +#define F_v    v5
> +#define G_v    v6
> +#define H_v    v7
> +#define I_v    v16
> +#define J_v    v17
> +
> +#ifndef MEMMOVE
> +# define MEMMOVE memmove
> +#endif
> +#ifndef MEMCPY
> +# define MEMCPY memcpy
> +#endif
> +
> +#if IS_IN (libc)
> +
> +#undef MEMCPY
> +#define MEMCPY __memcpy_kunpeng
> +#undef MEMMOVE
> +#define MEMMOVE __memmove_kunpeng
> +
> +
> +/* Overlapping large forward memmoves use a loop that copies backwards.
> +   Otherwise memcpy is used. Small moves branch to memcopy16 directly.
> +   The longer memcpy cases fall through to the memcpy head.
> +*/
> +
> +ENTRY_ALIGN (MEMMOVE, 6)
> +
> +       DELOUSE (0)
> +       DELOUSE (1)
> +       DELOUSE (2)
> +
> +       sub     tmp1, dstin, src
> +       cmp     count, 512
> +       ccmp    tmp1, count, 2, hi
> +       b.lo    L(move_long)
> +       cmp     count, 96
> +       ccmp    tmp1, count, 2, hi
> +       b.lo    L(move_middle)
> +
> +END (MEMMOVE)
> +libc_hidden_builtin_def (MEMMOVE)
> +
> +
> +/* Copies are split into 4 main cases: small copies of up to 16 bytes,
> +   medium copies of 17..96 bytes which are fully unrolled. Long copies
> +   of 97..2048 align dst address without prefetching. Large copies
> +   of more than 2048 bytes align the destination and use load-and-merge
> +   approach in the case src and dst addresses are unaligned not evenly,
> +   so that, actual loads and stores are always aligned.
> +   Large copies use the loops processing 64 bytes per iteration for
> +   unaligned case and 128 bytes per iteration for aligned ones.
> +*/
> +
> +#define MEMCPY_PREFETCH_LDR 640
> +
> +       .p2align 4
> +ENTRY (MEMCPY)
> +
> +       DELOUSE (0)
> +       DELOUSE (1)
> +       DELOUSE (2)
> +
> +       add     srcend, src, count
> +       cmp     count, 16
> +       b.ls    L(memcopy16)
> +       add     dstend, dstin, count
> +       cmp     count, 96
> +       b.hi    L(memcopy_long)
> +
> +       /* Medium copies: 17..96 bytes.  */
> +       ldr     A_q, [src], #16
> +       and     tmp1, src, 15
> +       ldr     E_q, [srcend, -16]
> +       cmp     count, 64
> +       b.gt    L(memcpy_copy96)
> +       cmp     count, 48
> +       b.le    L(bytes_17_to_48)
> +       /* 49..64 bytes */
> +       ldp     B_q, C_q, [src]
> +       str     E_q, [dstend, -16]
> +       stp     A_q, B_q, [dstin]
> +       str     C_q, [dstin, 32]
> +       ret
> +
> +L(bytes_17_to_48):
> +       /* 17..48 bytes*/
> +       cmp     count, 32
> +       b.gt    L(bytes_32_to_48)
> +       /* 17..32 bytes*/
> +       str     A_q, [dstin]
> +       str     E_q, [dstend, -16]
> +       ret
> +
> +L(bytes_32_to_48):
> +       /* 32..48 */
> +       ldr     B_q, [src]
> +       str     A_q, [dstin]
> +       str     E_q, [dstend, -16]
> +       str     B_q, [dstin, 16]
> +       ret
> +
> +       .p2align 4
> +       /* Small copies: 0..16 bytes.  */
> +L(memcopy16):
> +       cmp     count, 8
> +       b.lo    L(bytes_0_to_8)
> +       ldr     A_l, [src]
> +       ldr     A_h, [srcend, -8]
> +       add     dstend, dstin, count
> +       str     A_l, [dstin]
> +       str     A_h, [dstend, -8]
> +       ret
> +       .p2align 4
> +
> +L(bytes_0_to_8):
> +       tbz     count, 2, L(bytes_0_to_3)
> +       ldr     A_lw, [src]
> +       ldr     A_hw, [srcend, -4]
> +       add     dstend, dstin, count
> +       str     A_lw, [dstin]
> +       str     A_hw, [dstend, -4]
> +       ret
> +
> +       /* Copy 0..3 bytes.  Use a branchless sequence that copies the same
> +          byte 3 times if count==1, or the 2nd byte twice if count==2.  */
> +L(bytes_0_to_3):
> +       cbz     count, 1f
> +       lsr     tmp1, count, 1
> +       ldrb    A_lw, [src]
> +       ldrb    A_hw, [srcend, -1]
> +       add     dstend, dstin, count
> +       ldrb    B_lw, [src, tmp1]
> +       strb    B_lw, [dstin, tmp1]
> +       strb    A_hw, [dstend, -1]
> +       strb    A_lw, [dstin]
> +1:
> +       ret
> +
> +       .p2align 4
> +
> +L(memcpy_copy96):
> +       /* Copying 65..96 bytes. A_q (first 16 bytes) and
> +          E_q(last 16 bytes) are already loaded. The size
> +          is large enough to benefit from aligned loads */
> +       bic     src, src, 15
> +       ldp     B_q, C_q, [src]
> +       /* Loaded 64 bytes, second 16-bytes chunk can be
> +          overlapping with the first chunk by tmp1 bytes.
> +          Stored 16 bytes. */
> +       sub     dst, dstin, tmp1
> +       add     count, count, tmp1
> +       /* The range of count being [65..96] becomes [65..111]
> +          after tmp [0..15] gets added to it,
> +          count now is <bytes-left-to-load>+48 */
> +       cmp     count, 80
> +       b.gt    L(copy96_medium)
> +       ldr     D_q, [src, 32]
> +       stp     B_q, C_q, [dst, 16]
> +       str     D_q, [dst, 48]
> +       str     A_q, [dstin]
> +       str     E_q, [dstend, -16]
> +       ret
> +
> +       .p2align 4
> +L(copy96_medium):
> +       ldp     D_q, G_q, [src, 32]
> +       cmp     count, 96
> +       b.gt    L(copy96_large)
> +       stp     B_q, C_q, [dst, 16]
> +       stp     D_q, G_q, [dst, 48]
> +       str     A_q, [dstin]
> +       str     E_q, [dstend, -16]
> +       ret
> +
> +L(copy96_large):
> +       ldr     F_q, [src, 64]
> +       str     B_q, [dst, 16]
> +       stp     C_q, D_q, [dst, 32]
> +       stp     G_q, F_q, [dst, 64]
> +       str     A_q, [dstin]
> +       str     E_q, [dstend, -16]
> +       ret
> +
> +       .p2align 4
> +L(memcopy_long):
> +       cmp count, 2048
> +       b.ls L(copy2048_large)
> +       ldr     A_q, [src], #16
> +       and     tmp1, src, 15
> +       bic     src, src, 15
> +       ldp     B_q, C_q, [src], #32
> +       sub     dst, dstin, tmp1
> +       add     count, count, tmp1
> +       add     dst, dst, 16
> +       ldp     D_q, E_q, [src], #32
> +       str     A_q, [dstin]
> +
> +       /* Already loaded 64+16 bytes. Check if at
> +          least 64 more bytes left */
> +       subs    count, count, 64+64+16
> +       b.lt    L(loop128_exit0)
> +       cmp     count, MEMCPY_PREFETCH_LDR + 64 + 32
> +       b.lt    L(loop128)
> +       sub     count, count, MEMCPY_PREFETCH_LDR + 64 + 32
> +
> +       .p2align 4
> +
> +L(loop128_prefetch):
> +       prfm    pldl1strm, [src, MEMCPY_PREFETCH_LDR]
> +       ldp     F_q, G_q, [src], #32
> +       stp     B_q, C_q, [dst], #32
> +       ldp     H_q, I_q, [src], #32
> +       prfm    pldl1strm, [src, MEMCPY_PREFETCH_LDR]
> +       ldp     B_q, C_q, [src], #32
> +       stp     D_q, E_q, [dst], #32
> +       ldp     D_q, E_q, [src], #32
> +       stp     F_q, G_q, [dst], #32
> +       stp     H_q, I_q, [dst], #32
> +       subs    count, count, 128
> +       b.ge    L(loop128_prefetch)
> +
> +       add     count, count, MEMCPY_PREFETCH_LDR + 64 + 32
> +       .p2align 4
> +L(loop128):
> +       ldp     F_q, G_q, [src], #32
> +       ldp     H_q, I_q, [src], #32
> +       stp     B_q, C_q, [dst], #32
> +       stp     D_q, E_q, [dst], #32
> +       subs    count, count, 64
> +       b.lt    L(loop128_exit1)
> +       ldp     B_q, C_q, [src], #32
> +       ldp     D_q, E_q, [src], #32
> +       stp     F_q, G_q, [dst], #32
> +       stp     H_q, I_q, [dst], #32
> +       subs    count, count, 64
> +       b.ge    L(loop128)
> +L(loop128_exit0):
> +       ldp     F_q, G_q, [srcend, -64]
> +       ldp     H_q, I_q, [srcend, -32]
> +       stp     B_q, C_q, [dst], #32
> +       stp     D_q, E_q, [dst]
> +       stp     F_q, G_q, [dstend, -64]
> +       stp     H_q, I_q, [dstend, -32]
> +       ret
> +L(loop128_exit1):
> +       ldp     B_q, C_q, [srcend, -64]
> +       ldp     D_q, E_q, [srcend, -32]
> +       stp     F_q, G_q, [dst], #32
> +       stp     H_q, I_q, [dst]
> +       stp     B_q, C_q, [dstend, -64]
> +       stp     D_q, E_q, [dstend, -32]
> +       ret
> +
> +       /* long copies: 96..2048 bytes */
> +L(copy2048_large):
> +       and     tmp1, dstin, 15
> +       bic     dst, dstin, 15
> +       ldp     D_l, D_h, [src]
> +       sub     src, src, tmp1
> +       add     count, count, tmp1      /* Count is now 16 too large.  */
> +       ldp     A_l, A_h, [src, 16]
> +       stp     D_l, D_h, [dstin]
> +       ldp     B_l, B_h, [src, 32]
> +       ldp     C_l, C_h, [src, 48]
> +       ldp     D_l, D_h, [src, 64]!
> +       subs    count, count, 128 + 16  /* Test and readjust count.  */
> +       b.ls    L(last64)
> +
> +L(loop64):
> +       stp     A_l, A_h, [dst, 16]
> +       ldp     A_l, A_h, [src, 16]
> +       stp     B_l, B_h, [dst, 32]
> +       ldp     B_l, B_h, [src, 32]
> +       stp     C_l, C_h, [dst, 48]
> +       ldp     C_l, C_h, [src, 48]
> +       stp     D_l, D_h, [dst, 64]
> +       ldp     D_l, D_h, [src, 64]
> +       add dst, dst, 64
> +       add src, src, 64
> +       subs    count, count, 64
> +       b.hi    L(loop64)
> +
> +       /* Write the last full set of 64 bytes.  The remainder is at most 64
> +          bytes, so it is safe to always copy 64 bytes from the end even if
> +          there is just 1 byte left.  */
> +L(last64):
> +       ldp     E_l, E_h, [srcend, -64]
> +       stp     A_l, A_h, [dst, 16]
> +       ldp     A_l, A_h, [srcend, -48]
> +       stp     B_l, B_h, [dst, 32]
> +       ldp     B_l, B_h, [srcend, -32]
> +       stp     C_l, C_h, [dst, 48]
> +       ldp     C_l, C_h, [srcend, -16]
> +       stp     D_l, D_h, [dst, 64]
> +       stp     E_l, E_h, [dstend, -64]
> +       stp     A_l, A_h, [dstend, -48]
> +       stp     B_l, B_h, [dstend, -32]
> +       stp     C_l, C_h, [dstend, -16]
> +       ret
> +
> +       /* long move: more than 512 bytes align the dstend */
> +       .p2align 4
> +L(move_long):
> +1:
> +       add     srcend, src, count
> +       add     dstend, dstin, count
> +
> +       and     tmp1, dstend, 15
> +       ldr     D_q, [srcend, -16]
> +       sub     srcend, srcend, tmp1
> +       sub     count, count, tmp1
> +       ldp     A_q, B_q, [srcend, -32]
> +       str     D_q, [dstend, -16]
> +       ldp     C_q, D_q, [srcend, -64]!
> +       sub     dstend, dstend, tmp1
> +       subs    count, count, 128
> +       b.ls    2f
> +
> +       .p2align 4
> +1:
> +       subs    count, count, 64
> +       stp     A_q, B_q, [dstend, -32]
> +       ldp     A_q, B_q, [srcend, -32]
> +       stp     C_q, D_q, [dstend, -64]!
> +       ldp     C_q, D_q, [srcend, -64]!
> +       b.hi    1b
> +
> +       /* Write the last full set of 64 bytes.  The remainder is at most 64
> +          bytes, so it is safe to always copy 64 bytes from the start even if
> +          there is just 1 byte left.  */
> +2:
> +       ldp     E_q, F_q, [src, 32]
> +       ldp     G_q, H_q, [src]
> +       stp     A_q, B_q, [dstend, -32]
> +       stp     C_q, D_q, [dstend, -64]
> +       stp     E_q, F_q, [dstin, 32]
> +       stp     G_q, H_q, [dstin]
> +3:     ret
> +
> +       /* midlle move: 96..512 bytes */
> +       .p2align 4
> +L(move_middle):
> +       cbz     tmp1, 3f
> +       add     srcend, src, count
> +       prfm    PLDL1STRM, [srcend, -64]
> +       add     dstend, dstin, count
> +       and     tmp1, dstend, 15
> +       ldr D_q, [srcend, -16]
> +       sub     srcend, srcend, tmp1
> +       sub     count, count, tmp1
> +       ldr     A_q, [srcend, -16]
> +       str     D_q, [dstend, -16]
> +       ldr     B_q, [srcend, -32]
> +       ldr     C_q, [srcend, -48]
> +       ldr     D_q, [srcend, -64]!
> +       sub     dstend, dstend, tmp1
> +       subs    count, count, 128
> +       b.ls    2f
> +
> +1:
> +       str     A_q, [dstend, -16]
> +       ldr     A_q, [srcend, -16]
> +       str     B_q, [dstend, -32]
> +       ldr     B_q, [srcend, -32]
> +       str     C_q, [dstend, -48]
> +       ldr     C_q, [srcend, -48]
> +       str     D_q, [dstend, -64]!
> +       ldr     D_q, [srcend, -64]!
> +       subs    count, count, 64
> +       b.hi    1b
> +
> +       /* Write the last full set of 64 bytes.  The remainder is at most 64
> +          bytes, so it is safe to always copy 64 bytes from the start even if
> +          there is just 1 byte left.  */
> +2:
> +       ldr     G_q, [src, 48]
> +       str     A_q, [dstend, -16]
> +       ldr     A_q, [src, 32]
> +       str     B_q, [dstend, -32]
> +       ldr     B_q, [src, 16]
> +       str     C_q, [dstend, -48]
> +       ldr     C_q, [src]
> +       str     D_q, [dstend, -64]
> +       str     G_q, [dstin, 48]
> +       str     A_q, [dstin, 32]
> +       str     B_q, [dstin, 16]
> +       str     C_q, [dstin]
> +3:     ret
> +
> +
> +END (MEMCPY)
> +       .section        .rodata
> +       .p2align        4
> +
> +libc_hidden_builtin_def (MEMCPY)
> +#endif
> --
> 2.14.1.windows.1
>
>

Hi Yikun,

>> Btw do you have any plans to post other string functions that you can discuss here? If so, would these
>> add more ifuncs or improve the generic versions?
>
> Yes, memcmp, strlen, strnlen, strcpy, memrchr will be included, we will summited the patch and test results as soon as possible.
>
>We have submitted the patches of string functions, see below:

Thanks, that makes it easier to discuss in more detail. So in almost all cases these
patches add new ifuncs. There are general issues with ifuncs which make adding
lots of similar ifuncs a bad idea. The key problem is that ifuncs are not used inside
GLIBC itself. For example the strstr implementation benefits from a fast memcmp
but it always uses the generic memcmp, so it won't get any gains from the Kunpeng
optimized one.

So this makes it highly desirable to improve the generic versions of string functions.
From what I see, all of the changes are fairly simple and generic improvements, so
can be done easily to the generic versions. I think it would be a very bad idea to add
lots of ifunc variants which are almost identical to existing versions and differ in
minor details like unrolling.

For example strlen and memcmp add unrolling to existing code. Note that memchr_strlen
significantly outperforms the fastest strlen on sizes larger than 256, so I don't think that
using uminv to test for zeroes is the fastest approach.

Cheers,
Wilco

Hi Xuelei,

In order to select the right memmove implementation, multiarch/memmove.c needs
similar changes as multiarch/memcpy.c.

Also since the memmove entry sequence does both check for medium and large cases, the
full overlap check should be done in both. Currently only sizes 96-512 benefit, not the
move_long case:

+       /* long move: more than 512 bytes align the dstend */
+       .p2align 4
+L(move_long):
+1:
+       add     srcend, src, count
+       add     dstend, dstin, count

This should do the same as move_middle:

+L(move_middle):
+       cbz     tmp1, 3f

Wilco