On 06/07/2015 13:42, Richard Henderson wrote:
> On 07/06/2015 09:43 AM, Paolo Bonzini wrote:
>>
>>
>> On 05/07/2015 23:08, Peter Crosthwaite wrote:
>>> There was a complicated subtractive arithmetic for determining the
>>> padding on the CPUTLBEntry structure. Simplify this with a union.
>>>
>>> Signed-off-by: Peter Crosthwaite <crosthwaite.pe...@gmail.com>
>>> ---
>>> include/exec/cpu-defs.h | 23 ++++++++++++-----------
>>> 1 file changed, 12 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h
>>> index 98b9cff..5093be2 100644
>>> --- a/include/exec/cpu-defs.h
>>> +++ b/include/exec/cpu-defs.h
>>> @@ -105,17 +105,18 @@ typedef struct CPUTLBEntry {
>>> bit 3 : indicates that the entry is
>>> invalid
>>> bit 2..0 : zero
>>> */
>>> - target_ulong addr_read;
>>> - target_ulong addr_write;
>>> - target_ulong addr_code;
>>> - /* Addend to virtual address to get host address. IO accesses
>>> - use the corresponding iotlb value. */
>>> - uintptr_t addend;
>>> - /* padding to get a power of two size */
>>> - uint8_t dummy[(1 << CPU_TLB_ENTRY_BITS) -
>>> - (sizeof(target_ulong) * 3 +
>>> - ((-sizeof(target_ulong) * 3) & (sizeof(uintptr_t)
>>> - 1)) +
>>> - sizeof(uintptr_t))];
>>> + union {
>>
>> The struct CPUTLBEntry can be changed to union CPUTLBEntry directly,
>> with no need for the anonymous struct.
>
> Um, no it can't. That would put all of the members at the same address.
Of course. :-( With no need for the anonymous _union_. *blush*.
>> Which compiler version started implementing anonymous structs?
>
> A long long time ago -- gcc 2 era.
Great. I now remember that the recent feature is anonymous tagged
structs, coming from the Plan 9 compiler.
Paolo
>> Or can we just add
>>
>> __attribute__((__aligned__(1 << CPU_TLB_ENTRY_BITS)))
>
> The structure isn't currently aligned, and it needn't be. We only need
> the size to be a power of two for the addressing.
>
>
>
> r~
