Can realloc be marked as a mallloc-like function?

[Daniel Berlin]

On 7/18/07, Richard Guenther <richard.guenther@gmail.com> wrote:
> On 7/18/07, Richard Henderson <rth@twiddle.net> wrote:
> > On Tue, Jul 17, 2007 at 09:53:30AM -0000, Wolfram Gloger wrote:
> > > Surely you agree that in my second example, "*p = 0" _cannot_ be moved
> > > after the call to destroy_something_and_allocate_anotherthing(p)?
> >
> > It can't be moved after, but it could be removed entirely as dead code.
> >
> > I don't think we have a pass that will do that presently, but I see no
> > reason why it couldn't happen some day, more or less automatically, with
> > a pass that analyzes lifetimes of dynamic allocations.
>
> Currently, the only thing that does prevent this optimization is the fact
> that passing p to realloc makes p escape and the memory pointed to
> clobbered.  But the alias analysis code already has special case code
> that would prevent this from happening (just maybe not in all places right
> now) - whether this is a good idea or not is another question.

We could use zdenek's builtin function table to mention which
arguments are not just written to, but *destroyed* for alias purposes,
and then just directly get that info into aliasing.
Boom, problem solved.