From: Lino Sanfilippo
> On 14.04.2015 00:07, Sergei Shtylyov wrote:
>
...
> > +#ifdef __LITTLE_ENDIAN
> > + u32 res: 16; /* Reserved bits */
> > + u32 ts_sh: 16; /* Timestamp high */
> > +#else
> > + u32 ts_sh: 16; /* Timestamp high */
> > + u32 res: 16; /* Reserved bits */
> > +#endif
> > +};
>
> I recall a thread in which the use of bitfields for structs that are
> shared with the hardware was considered a bad idea (because the compiler
> is free to reorder the fields). Shift operations are probably a better
> choice here.
The compiler itself isn't free to reorder the fields, but the order
is an implementation decision for the compiler/ABI.
An ABI will probably define a bit order, but it doesn't have to match
the endianness.
Shifting and masking also tends to generate better code.
David
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