[Bug tree-optimization/86050] Inline break tail-call optimization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86050

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-06-05
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  It is because the address of 'value' escapes which is easier to
see when you instead do

    static void __attribute__((noinline)) stackConsume(const char*stack){
        char value;
        __builtin_putchar ((long)&value);
    }

this then causes us to hit

  /* Make sure the tail invocation of this function does not indirectly
     refer to local variables.  (Passing variables directly by value
     is OK.)  */
  FOR_EACH_LOCAL_DECL (cfun, idx, var)
    {
      if (TREE_CODE (var) != PARM_DECL
          && auto_var_in_fn_p (var, cfun->decl)
          && may_be_aliased (var)
          && (ref_maybe_used_by_stmt_p (call, var)
              || call_may_clobber_ref_p (call, var)))
        return;
    }

where we think that the recursive call might possibly access that very
escaped stack slot (for example via a global pointer).  We do not have
sophisticated enough analysis to fix that easily.