For the bitfield access, MSVC apparently uses a right shift of the base type of the bitfield member. In our case, is is cased by IA32_PTE_4K and
IA32_PAGE_LEAF_ENTRY_BIG_PAGESIZE and other structures which uses uint64
bitfields and 32-bit x86 doesn't have a 64-bit integer shift (except using MMX or SSE2). With -Od (NOOPT) even for constant counts it puts
the data in EDX:EAX, the shift count in cl and calls __aullshr.
Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>