At least on aarch64, the gathers and scatters use (mem:BLK (scratch:P)),
i.e. a wildcard memory access. There's no good way in RTL to represent
multiplie distinct locations in a single reference.
(unspec on its own doesn't imply a memory access)
At first I thought if we only cared about element misalignment checking the
first element/pointer should be sufficient. But riscv's gathers as well as
strided loads allow byte offsets rather than element-sized offsets so there
could be 16-bit loads with a stride of e.g. 1 byte.
How would we query the target on whether it can handle the alignment
here?
I think for gathers, STRICT_ALIGNMENT rules apply: if STRICT_ALIGNMENT
is true then each scalar element must be aligned to its size, otherwise
the elements can be misaligned.
On riscv we can have separate strict-alignment values for scalar and vector.
A uarch can theoretically allow (element-)misaligned vector accesses but not
scalar ones.
--
Regards
Robin
