tm.texi says for BIGGEST_ALIGNMENT (from which
__BIGGEST_ALIGNMENT__ is derived): "Biggest alignment that
any data type can require on this machine, in bits."
That is, using that value might be too strict for alignment
of *functions* and CRIS requires at least 16-bit alignment
for functions. But, one purpose of the test is to test that
alignment can be set to a large but valid value, so pick
512, which has some use as a historically required alignment
for certain I/O descriptors.
* gcc.dg/attr-aligned.c: Adjust comment for ALIGN_MAX_STATIC.
(ALIGN_MAX_STATIC): Set to 512 for CRIS.