[Bug middle-end/26461] liveness of thread local references across function calls

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26461

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |torvald at gcc dot gnu.org

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Even if we have an option that avoids CSE of TLS addresses across function
calls (or attribute for specific function), what would you expect to happen
when user takes address of TLS variables himself:
__thread int a;
void
foo ()
{
  int *p = &a;
  *p = 10;
  bar (); // Changes threads
  *p += 10;
}
?  The address can be stored anywhere, so the compiler can't do anything with
it.  And of course such an option would cause major slowdown of anything using
TLS, not only it would need to stop CSEing TLS addresses late, but stop
treating TLS addresses as constant in all early optimizations as well.