Hi,
The patch folds:
lhs = svld1rq ({-1, -1, -1, ...}, &v[0])
into:
lhs = vec_perm_expr<v, v, {0, 1, 2, 3, ... }>
and expands above vec_perm_expr using aarch64_expand_sve_dupq.

With patch, for following test:
#include <arm_sve.h>
#include <arm_neon.h>

svint32_t
foo (int32x4_t x)
{
  return svld1rq (svptrue_b8 (), &x[0]);
}

it generates following code:
foo:
.LFB4350:
        dup     z0.q, z0.q[0]
        ret

and passes bootstrap+test on aarch64-linux-gnu.
But I am not sure if the changes to aarch64_evpc_sve_tbl
are correct.

Thanks,
Prathamesh