Richard Henderson writes: > On Fri, Sep 02, 2005 at 09:40:20PM -0400, DJ Delorie wrote: > http://gcc.gnu.org/ml/gcc/2005-09/msg00064.html > > So... why is it illegal to put a constant into a single bit field? > > Probably because it was more efficient to use some other pattern > for some other target. > > But there's absolutely zero chance you can reliably use a volatile > bit field to emit a given insn sequence necessary for accessing a > hardware register.
- Out of curiosity, how's that? As it would seem that as HW control/I/O registers are often typically mapped into a processor's data memory address space, they may be correspondingly addressable via a read/mask/write as any N bit field may be? Candidly the only potential problem I see may occur if multiple independent volatile bit fields of any size are defined within the same uniquely addressable UNIT, as then an access to any would necessitate an access to all (although even this is likely fine, as if in fact the bit fields were defined in this way, it would be unavoidably physically required).
