The vector size chosen here is for V64DImode. The concept of this setting is
not well adapted for GCN, in which the vector size varies with the number of
lanes, not the other way around, but this is ok for now.
2020-04-24 Andrew Stubbs <ams@codesourcery.com>
gcc/testsuite/
* lib/target-supports.exp (available_vector_sizes): Add amdgcn.
(check_effective_target_vect_cmdline_needed): Disable for amdgcn.
(check_effective_target_vect_pack_trunc): Add amdgcn.
