On Thu, Jun 20, 2013 at 10:47:57AM +0100, David Laight wrote:
> > The C ABI reverses the bitfield fill order when compiled as
> > little-endian.
>
> No - it is completely implementation defined.
> The general concensus is not to use bitfields if you
> care at all about the bit assignments.
FWIW, bitfields often alow things to be expressed more nicely. Just the
endian-dependent definition suck, so I came up with this little hack
for arch/mips/include/uapi/asm/inst.h:
#ifdef __MIPSEB__
#define BITFIELD_FIELD(field, more) \
field; \
more
#elif defined(__MIPSEL__)
#define BITFIELD_FIELD(field, more) \
more \
field;
#endif
struct i_format { /* signed immediate format */
BITFIELD_FIELD(unsigned int opcode : 6,
BITFIELD_FIELD(unsigned int rs : 5,
BITFIELD_FIELD(unsigned int rt : 5,
BITFIELD_FIELD(signed int simmediate : 16,
;))))
};
Ralf
