RISC-V and unaligned memory access

[ccawley2011]

The RISC-V chunkset code includes the line uint##elen##_t val = *(uint##elen##_t*)from; as part of the CHUNK_MEMSET_RVV_IMPL, however all the other chunkset implementations use alignment-safe reads here. RISC-V also doesn't define UNALIGNED_OK, and looking at the output from Compiler Explorer shows that both memcpy and __attribute__ ((__packed__, __may_alias__)) read one byte at a time for smaller sizes. Is using unaligned reads intentional here?

[mtl1979]

AFAIK RISC-V traps on unaligned loads and stores, but can handle them in M-mode. In case of reads, it will read more and shift the result to get the correct bytes. In case of unaligned writes, it will write byte by byte.