[PATCH v2 0/1] riscv: add vectorized memset, memcpy and memmove

Hi all,

This v2 patch adds RISC-V Vector (RVV) optimized implementations for
memset, memcpy and memmove.

Changes since v1:
- Switch the conditional compilation macro from __riscv_v to __riscv_vector.
- Replaced '.option arch,+v' with '.option arch,+zve32x'.
- Removed an unnecessary unconditional jump instruction in memmove-asm.S
- In memcpy and memmove, when __riscv_misaligned_fast is not defined,
  the destination address is now aligned to SZREG to improve performance
  on systems with slow misaligned accesses.

These implementations use the RVV extension with e8 element size and m8
LMUL, and are conditionally compiled only when __riscv_vector is
defined, ensuring compatibility with non-vector RISC-V systems.

Benchmark results on Spacemit X60 (Muse-pi) and Canaan K230 show significant
improvements.

memcpy: Up to 4.84x on Muse-pi and 4.66x on K230.
memset: Up to 4.31x on Muse-pi and 3.14x on K230.
memmove: Up to 2.87x on Muse-pi and 1.48x on K230. 

With newly added alignment handling, these improvements are consistent
across both aligned and misaligned memory acesses.

In the v1 review thread, Kito suggested removing the 'sub' instruction in
the RVV memcpy loop and relying solely on the end-pointer-based loop
condition. After careful consideration, I would like to clarify that in
this specific context, the 'sub' cannot actually be eliminated since the
RVV loop still requires the exact number of remaining bytes to be
provided to vsetvli. Therefore, I have retained the orignial loop
structure.

Comments and suggestions are greatly appreciated, Thank you for your
time and review!

Thanks,
Pincheng Wang

Pincheng Wang (1):
  riscv: add vectorized memset, memcpy and memmove

 newlib/libc/machine/riscv/memcpy-asm.S  | 54 +++++++++++++-
 newlib/libc/machine/riscv/memcpy.c      |  2 +-
 newlib/libc/machine/riscv/memmove-asm.S | 95 ++++++++++++++++++++++++-
 newlib/libc/machine/riscv/memmove.c     |  2 +-
 newlib/libc/machine/riscv/memset.S      | 21 +++++-
 5 files changed, 169 insertions(+), 5 deletions(-)

-- 
2.39.5