tree level aliasing and call clobber

[Andrew Pinski]

I noticed that if I try not to mark a variable as escaping, we don't 
get the function
call to have V_MAY_DEF for that variable.

For an example in this Fortran code:
function i()
INTEGER :: i
INTEGER :: t
call f(t)
t = 2;
call g()
if (t .ne. 2) then
  call abort ()
end if
i = t
end function

t cannot escape from the function as the variable is not marked as a 
TARGET.
Is there a way to mark the function call for f as clobbering t but not 
escaping?
Or do I have to modify tree-ssa-operands code to do it correctly?

PS I attached the patch which I am currently working on to make the 
variable as not
being call clobbered.  I use an attribute instead of a bit in the 
decls' structure
since it seems only to happen for Fortran code.

Thanks,
Andrew Pinski

Index: fortran/trans-decl.c
===================================================================
--- fortran/trans-decl.c        (revision 109033)
+++ fortran/trans-decl.c        (working copy)
@@ -447,6 +447,7 @@ gfc_finish_decl (tree decl, tree init)
 
 }
 
+static GTY(()) tree noescape_attribute = NULL_TREE;
 
 /* Apply symbol attributes to a variable, and add it to the function scope.  */
 
@@ -457,13 +458,26 @@ gfc_finish_var_decl (tree decl, gfc_symb
      This is the equivalent of the TARGET variables.
      We also need to set this if the variable is passed by reference in a
      CALL statement.  */
-
+     
   /* Set DECL_VALUE_EXPR for Cray Pointees.  */
   if (sym->attr.cray_pointee)
     gfc_finish_cray_pointee (decl, sym);
 
   if (sym->attr.target)
     TREE_ADDRESSABLE (decl) = 1;
+  
+  /* Add the attribute to tell the middle-end this variable can never 
+     escape.  */
+  if (!sym->attr.target && !sym->attr.cray_pointee)
+    {
+      if (noescape_attribute == NULL_TREE)
+        {
+         tree noescape = get_identifier ("no escape");
+         noescape_attribute = build_tree_list (noescape, NULL_TREE);
+       }
+      DECL_ATTRIBUTES (decl) = noescape_attribute;
+    }
+  
   /* If it wasn't used we wouldn't be getting it.  */
   TREE_USED (decl) = 1;
 
Index: tree-ssa-structalias.c
===================================================================
--- tree-ssa-structalias.c      (revision 109033)
+++ tree-ssa-structalias.c      (working copy)
@@ -2965,7 +2965,11 @@ update_alias_info (tree stmt, struct ali
          unsigned i;
 
          EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
-           mark_call_clobbered (referenced_var (i));
+           {
+             tree decl = referenced_var (i);
+             if (!lookup_attribute ("no escape", DECL_ATTRIBUTES (decl)))
+               mark_call_clobbered (decl);
+           }
        }
     }