On Thu, Nov 1, 2012 at 1:47 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> On Thu, Nov 01, 2012 at 12:34:54PM -0700, Xinliang David Li wrote:
>> On Thu, Nov 1, 2012 at 12:16 PM, Jakub Jelinek <ja...@redhat.com> wrote:
>> > On Thu, Nov 01, 2012 at 11:57:21AM -0700, Xinliang David Li wrote:
>> >> That is exactly related to tsan -- it should skip local variable that
>> >> is not address taken (though still addressable, which by addressable,
>> >> it means the variable has a memory home).
>> >>
>> >> The problem is that if 'addressable' bit is not equivalent to 'address
>> >> taken', it will be too conservative to use it --- as addressable
>> >> variables may not be address taken.
>> >
>> > But TREE_ADDRESSABLE is equivalent to address taken.
>>
>> It seems not -- unless our definition of them is different. I debugged
>> the following program:
>>
>>
>> int foo()
>> {
>> int a[1000];
>> int i, s;
>>
>> for (i = 0; i < 1000; i++)
>> a[i] = i;
>>
>> for (i = 0; i < 1000; i++)
>> s += a[i];
>>
>> return s;
>> }
>>
>> a's address is not taken (at source level), but it is marked as addressable.
>
> The question is when you are looking at TREE_ADDRESSABLE. Sure, the FE
> marks it as TREE_ADDRESSABLE conservatively, but if you compile with -O2,
> in execute_update_addresses_taken called after the ccp pass TREE_ADDRESSABLE
> is cleared. I thought the tsan pass was scheduled much later than that
> (around PRE pass).
I looked at it pretty late in the pipeline -- during cfgexpand and I
had specified -O2 in the command line.
>
>> > If you need it even less conservative, I guess you could do say:
>> > struct ptr_info_def pi;
>> > memset (&pi, 0, sizeof (pi));
>> > pi.escaped = 1;
>> > pi.nonlocal = 1;
>> > return pt_solution_includes (&pi, decl);
>> >
>>
>> That will be nice. Are points-to info exposed to client code like
>> this? Are there standard aliaser interfaces for them?
>
> pt_solution_includes is exported interface, though we'd need to ask richi
> when he returns whether he is fine with such an use.
yes, It is better to wrap it up in a simpler interface.
David
>
> Jakub
