[PATCH v1 2/3] riscv: Add RVV implementation __strcpy_vector

[Yao Zihong]

> Also, I note the submitted patch uses m4. Why not m8?

On the two platforms I had access to (SpacemiT M1 and K230), using LMUL=8
did not show a clear throughput benefit compared to LMUL=4 in the measured
ranges. In fact, for very short strings (<=32B) the m8 variant sometimes
performed worse.

That said, I am not sure whether m4 should really be considered a balanced
choice, or if it also risks being an over-optimization tied to just a few
implementations. I’m happy to revisit this once we have results from a
broader set of platforms.

Zihong