[Bug tree-optimization/49279] [4.5/4.6/4.7 Regression] Optimization incorrectly presuming constant variable inside loop in g++ 4.5 and 4.6 with -O2 and -O3 for x86_64 targets

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49279

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-05 
15:52:49 UTC ---
(In reply to comment #10)
> with tag coming from allocate_decl_uid ().  We would use these copies
> as restrict tag sources using the specified UID.  Thus every inline
> copy (and clone) would share them.

Assuming we don't CSE over it (in particular, the LHS of such a builtin with
some non-restricted later pointers not based on it), perhaps it could work.
I wouldn't expose it to users, because how would users ensure uniqueness of the
tag over the whole CU?  __COUNTER__ or something similar?  That's going to lead
to bugs...

The FEs should probably add that for user __restrict variable initializers too.