[Bug tree-optimization/79547] duplicate strlen calls with same argument not folded

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79547

--- Comment #6 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 16 Feb 2017, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79547
> 
> --- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> Actually the last 4 not, they return addresses into it.
> But also strspn and strcspn?

Yeah, and __builtin_object_size (which is pure, not const - huh).
and __builtin_constant_p.  Then there's bcmp.

Just looking at the list of BT_FN_{INT,SIZE}_ in builtins.def.

Note that other functions like popcount can cause similar leakage,
say for

  foo (popcountl ((uintptr_t)s));

but as they do return some property of the pointer value I'm nervous
that a combination of such info can be used to restore the actual
pointer value (which is the only reason we track pointers through
integers - and floats!).

Richard.