Hi,
The attached prototype patch extends fold_vec_perm to fold VEC_PERM_EXPR
in VLA manner, and currently handles the following cases:
(a) fixed len arg0, arg1 and fixed len sel.
(b) fixed len arg0, arg1 and vla sel
(c) vla arg0, arg1 and vla sel with arg0, arg1 being VECTOR_CST.

It seems to work for the VLA tests written in
test_vec_perm_vla_folding (), and am working thru the fallout observed in
regression testing.

Does the approach taken in the patch look in the right direction ?
I am not sure if I have got the conversion from "sel_index"
to index of either arg0, or arg1 entirely correct.
I would be grateful for suggestions on the patch.

Thanks,
Prathamesh