[Bug tree-optimization/81009] missing aliasing optimization for const restrict pointers

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81009

Richard Biener  changed:

   What|Removed |Added

 CC||rguenth at gcc dot gnu.org

--- Comment #1 from Richard Biener  ---
const qualification doesn't mean anything to the middle-end and it would be
dangerous to interpret it that way given we support more than just C as input
language.  So the C FE would have to communicate this in a more explict way.

Anyway, doesn't this even apply to

void f (int *);

void g (const int* restrict p)
{
  int x = *p;
  f ((int *)p); // f() cannot modify *p here
  if (x != *p)   // cannot be true
__builtin_abort ();
}

?

[Bug tree-optimization/81009] missing aliasing optimization for const restrict pointers

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81009

--- Comment #2 from Martin Sebor  ---
Yes, the constness can be cast away without changing the effect of the rule.

Similar to the C++ rule we discussed in bug 80794 I feel that constness is an
underappreciated opportunity to generate better code in both languages.  I
agree that constness alone is not sufficient to rely on for optimization
because it can be cast away and the object modified, but in conjunction with
restrict in C and with other rules in C++ (as discussed in bug 80794) I think
it's worth looking into.

[Bug tree-optimization/81009] missing aliasing optimization for const restrict pointers

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81009

Marc Glisse  changed:

   What|Removed |Added

 CC||eyalroz at technion dot ac.il

--- Comment #3 from Marc Glisse  ---
*** Bug 89479 has been marked as a duplicate of this bug. ***