riscv: optimized mem* functions

From: Matteo Croce <[email protected]>

Replace the assembly mem{cpy,move,set} with C equivalent.

Try to access RAM with the largest bit width possible, but without doing unaligned accesses.

A further improvement could be to use multiple read and writes as the assembly version was trying to do.

Tested on a BeagleV Starlight with a SiFive U74 core, where the improvement is noticeable.

v4 -> v5:
- call __memcpy() instead of memcpy() in memmove()

v3 -> v4:
- incorporate changes from proposed generic version:
https://lore.kernel.org/lkml/[email protected]/

v2 -> v3:
- alias mem* to __mem* and not viceversa
- use __alias instead of a tail call

v1 -> v2:
- reduce the threshold from 64 to 16 bytes
- fix KASAN build
- optimize memset

Matteo Croce (3):
riscv: optimized memcpy
riscv: optimized memmove
riscv: optimized memset

 arch/riscv/include/asm/string.h |  18 ++--
 arch/riscv/kernel/Makefile      |   1 -
 arch/riscv/kernel/riscv_ksyms.c |  17 ----
 arch/riscv/lib/Makefile         |   4 +-
 arch/riscv/lib/memcpy.S         | 108 ----------------------
 arch/riscv/lib/memmove.S        |  64 -------------
 arch/riscv/lib/memset.S         | 113 -----------------------
 arch/riscv/lib/string.c         | 154 ++++++++++++++++++++++++++++++++
 8 files changed, 164 insertions(+), 315 deletions(-)
 delete mode 100644 arch/riscv/kernel/riscv_ksyms.c
 delete mode 100644 arch/riscv/lib/memcpy.S
 delete mode 100644 arch/riscv/lib/memmove.S
 delete mode 100644 arch/riscv/lib/memset.S
 create mode 100644 arch/riscv/lib/string.c

2.31.1