On 7/25/19 7:01 AM, Alex Bennée wrote:
>> + union {
>> + /*
>> + * Offsets of the secure and non-secure fields in CPUARMState for
>> + * the register if it is banked. These fields are only used during
>> + * the static registration of a register. During hashing the bank
>> + * associated with a given security state is copied to fieldoffset
>> + * which is used from there on out.
>> + *
>> + * It is expected that register definitions use either fieldoffset
>> + * or bank_fieldoffsets in the definition but not both. It is also
>> + * expected that both bank offsets are set when defining a banked
>> + * register. This use indicates that a register is banked.
>> + */
>> + ptrdiff_t bank_fieldoffsets[2];
>
> It seems a bit off that we are compressing this structure into a union
> when we didn't bother with the above fieldoffset despite the statement
> that only one or the other is used.
...
> Is 2 pointers enough saving? Will we never see a re-directed register
> that was using the banked fieldoffsets? Can we protect against that?
It's because bank_fieldoffsets[] is only used before instantiation.
Before the structure is given to add_cpreg_to_hashtable, we have copied the
structure, copied bank_fieldoffsets into fieldoffset, and adjusted the secure
state flag.
After instantiation, those two pointers are unused, and I thought I could
reclaim it. However, you may have a point re total memory savings not making
the complication worthwhile.
r~
