mask
#define mask $0
#define mask $0
#define mask r7
#define mask r7
union decode_item mask;
masks->str, masks->res0, masks->res1, masks->mask, masks->nmask);
#define mask x13
#define mask R8 /* mask used to determine prolog size */
#define mask(x,sz) ((x) & ~((1<<(sz))-1))
#define mask(w) ((1 << (w)) - 1)
#define mask(w) ((1 << (w)) - 1)
#define mask(bitfield) __mask(bitfield)
#define mask(width) ((u64)~0 >> (64 - (width)))