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Re: TODO_rebuild_alias and -O0
On Mon, Oct 8, 2012 at 1:42 PM, Ludovic Courtès <firstname.lastname@example.org> wrote:
> Richard Guenther <email@example.com> skribis:
>> On Mon, Oct 8, 2012 at 11:58 AM, Ludovic Courtès <firstname.lastname@example.org> wrote:
>>> Richard Guenther <email@example.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.
Well, "that should work" means it works non-conservatively with
TODO_rebuild_alias, of course.