TODO_rebuild_alias and -O0

[Ludovic Courtès]

Richard Guenther <richard.guenther@gmail.com> skribis:

> On Mon, Oct 8, 2012 at 11:58 AM, Ludovic Courtès <ludo@gnu.org> wrote:
>> Richard Guenther <richard.guenther@gmail.com> skribis:
>>
>>> At -O0 no virtual operands are produced.  TODO_rebuild_alias only computes
>>> points-to sets which are in itself not useful.
>>>
>>> What do you want to achieve with TODO_rebuild_alias?
>>
>> I basically want to use ‘ptr_derefs_may_alias_p’ in this particular pass.
>
> That should work.

It actually does, except that ‘ptr_derefs_may_alias_p’ returns true for
two SSA names in cases like this:

  double *p, *q;
  p = malloc (123);
  q = malloc (234);

(Where ‘malloc’ has the ‘malloc’ attribute.)

For some reason, there’s no such false positive when using TODO_rebuild_alias.

Ludo’.