Hi,
The attached patch rearranges order of type-check for vec_perm_expr
and relaxes type checking for
lhs = vec_perm_expr<rhs1, rhs2, mask>

when:
rhs1 == rhs2,
lhs is variable length vector,
rhs1 is fixed length vector,
TREE_TYPE (lhs) == TREE_TYPE (rhs1)

I am not sure tho if this check is correct ? My intent was to capture
case when vec_perm_expr is used to "extend" fixed length vector to
it's VLA equivalent.

Thanks,
Prathamesh