* common.opt (-fstrict-volatile-bitfields): new.
* doc/invoke.texi: Document it.
* fold-const.c (optimize_bit_field_compare): For volatile
bitfields, use the field's type to determine the mode, not the
field's size.
* expr.c (expand_assignment): Likewise.
(get_inner_reference): Likewise.
(expand_expr_real_1): Likewise.
* expmed.c (store_fixed_bit_field): Likewise.
(extract_bit_field_1): Likewise.
(extract_fixed_bit_field): Likewise.

* gcc.target/i386/volatile-bitfields-1.c: New.
* gcc.target/i386/volatile-bitfields-2.c: New.

From-SVN: r160865