On 09/18/2012 10:21 AM, Xiao Guangrong wrote:
> On 09/16/2012 08:07 PM, Avi Kivity wrote:
>
>> + /*
>> + * On a write fault, fold the dirty bit into accessed_dirty by shifting
>> it one
>> + * place right.
>> + *
>> + * On a read fault, do nothing.
>> + */
>> + accessed_dirty &= pte >> (write_fault >> ilog2(PFERR_WRITE_MASK));
>
> It is too trick: it depends on DIRTY_SHIFT = ACCESSED_SHIFT + 1. How about
> change it
> to:
> accessed_dirty &= pte >> (!!write_fault >> (DIRTY_SHIFT - ACCESSED_SHIFT)) ?
!! forces a branch, unless gcc is really clever. So I changed it to
shift = write_fault >> ilog2(PFERR_WRITE_MASK);
shift *= PT_DIRTY_SHIFT - PT_ACCESSED_SHIFT;
accessed_dirty &= pte >> shift;
which should result in the same code.
--
error compiling committee.c: too many arguments to function
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