This is pretty unlikely in real code, but similar to Arm, the AArch64

This is pretty unlikely in real code, but similar to Arm, the AArch64
ABI has a bug with the handling of 128-bit bit-fields, where if the
bit-field dominates the overall alignment the back-end code may end up
passing the argument correctly.  This is a regression that started in
gcc-6 when the ABI support code was updated to support overaligned
types.  The fix is very similar in concept to the Arm fix.  128-bit
bit-fields are fortunately extremely rare, so I'd be very surprised if
anyone has been bitten by this.

PR target/88469
gcc/
	* config/aarch64/aarch64.c (aarch64_function_arg_alignment): Add new
	argument ABI_BREAK.  Set to true if the calculated alignment has
	changed in gcc-9.  Check bit-fields for their base type alignment.
	(aarch64_layout_arg): Warn if argument passing has changed in gcc-9.
	(aarch64_function_arg_boundary): Likewise.
	(aarch64_gimplify_va_arg_expr): Likewise.

gcc/testsuite/
	* gcc.target/aarch64/aapcs64/test_align-10.c: New test.
	* gcc.target/aarch64/aapcs64/test_align-11.c: New test.
	* gcc.target/aarch64/aapcs64/test_align-12.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@268273 138bc75d-0d04-0410-961f-82ee72b054a4