https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48885
vries at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu.org,
| |vries at gcc dot gnu.org
--- Comment #10 from vries at gcc dot gnu.org ---
The current implementation of restrict is based on clique/base pairs.
For the example
...
void
test (int *a, int *b, int * restrict v)
{
*a = *v;
*b = *v;
}
...
we get *v annotated with clique/base 1/1.
I wonder if we can reserve a base in each clique as non-restrict base, and
annotate like this:
- *a : 1/non-restrict
- *b : 1/non-restrict
- *v : 1/1
This way:
- *a and *b would still potentially alias
- *a and *v would be disambiguated, and
- not annotated memory references would not be impacted
This would only work with top-level restrict though. We would have to take care
in an example like this:
...
void
f (int *__restrict__ &__restrict__ p, int *p2)
{
*p = 1;
*p2 = 2;
}
void
g (int *__restrict__ gp)
{
f (gp, gp);
}
...
Currently we annotate this as:
...
void f(int* __restrict__&, int*) (intD.9 * restrict & restrict pD.2252, intD.9
* p2D.2253)
{
intD.9 * _3;
# VUSE <.MEM_1(D)>
# PT = { D.2265 } (nonlocal)
_3 = MEM[(intD.9 * restrict &)p_2(D) clique 1 base 1];
# .MEM_4 = VDEF <.MEM_1(D)>
MEM[(intD.9 *)_3 clique 1 base 2] = 1;
# .MEM_6 = VDEF <.MEM_4>
*p2_5(D) = 2;
...
In this case, p2 cannot alias with clique 1/base 1, since it's a toplevel
restrict. But p2 can alias with clique 1/base 2, because it's not a toplevel
restrict.
So, if we f.i. register MR_DEPENDENCE_TOPLEVEL (in addition to
MR_DEPENDENCE_CLIQUE and MR_DEPENDENCE_BASE), we can disambiguate:
- normal bases within the same clique if they're different, and
- a non-restrict base vs a toplevel base.
