risc-v memcpy, memset, memmove functions

Optimized memcpy, memset, memmove functions written in RISC-V assembler. Everyone wants to reduce the size of the code, so in order to comply with the compressed ISA specification, here preferably s0-s1, a0-a5 registers are used.

Minimal supported risc-v ISA: rv32e

code size

rv64gc: memset: 188 bytes, memcpy: 188 bytes, memmove: 266 bytes (324 with lh/sh)

performance

• rv64: memcpy(page1, page2, 4096) => 1178 instructions; 3.477 bytes per ins. (tends to 3.66)
• rv64: memset(page, 0, 4096) => 574 instructions; 7.13 bytes per ins. (tends to 7.31)
• memmove: 5 instructions per load/store LEN where LEN is depend on the mutual alignment of src/dst.