* expr.c (target_align): New function.  Alignment the TARGET of an
	assignment may be assume to have.
	(highest_pow2_factor_for_target): Use it instead of relying on
	immediate tree attributes of TARGET, not necessarily honored when
	intermediate bitfields are involved.

	testsuite/
	* gcc.c-torture/execute/align-nest.c: New testcase.
	* gnat.dg/misaligned_nest.adb: New testcase.


Co-Authored-By: Eric Botcazou <ebotcazou@adacore.com>

From-SVN: r147916