[Bug optimization/14312] [tree-ssa] [regression] tailcalls not being generated when functions contain pointers

["dnovillo at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From dnovillo at redhat dot com  2004-02-27 13:16 -------
Subject: Re:  [tree-ssa] [regression] tailcalls not
	being generated when functions contain pointers

On Fri, 2004-02-27 at 07:38, rth at gcc dot gnu dot org wrote:

> Will you please invent a way to recoginize them and ignore them in
> suitable_for_tail_opt_p?
>
There's nothing to invent, really.  suitable_for_tail_opt_p was doing a
very weak test.  It should really test whether the local variable is
call-clobbered, which is computed using escape analysis.

We ought to check other places in the optimizers where we use
addressability instead of is_call_clobbered.

Fixed with this patch.  Will commit if testing doesn't show any
regressions.


Diego.

        PR optimization/14312
        * tree-tailcall.c (suitable_for_tail_opt_p): Call
        is_call_clobbered instead of checking addressability.

Index: tree-tailcall.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-tailcall.c,v
retrieving revision 1.1.2.19
diff -d -c -p -r1.1.2.19 tree-tailcall.c
*** tree-tailcall.c     25 Feb 2004 03:22:47 -0000      1.1.2.19
--- tree-tailcall.c     27 Feb 2004 13:14:14 -0000
*************** suitable_for_tail_opt_p (void)
*** 72,87 ****
    if (current_function_stdarg)
      return false;

!   /* No local variable should have its address taken, as otherwise it might
!      be passed to the recursive call.  This of course is overly
!      conservative and should be replaced by a dataflow analysis later.  */
    for (i = 0; i < (int) VARRAY_ACTIVE_SIZE (referenced_vars); i++)
      {
        tree var = VARRAY_TREE (referenced_vars, i);

        if (decl_function_context (var) == current_function_decl
!         && !TREE_STATIC (var)
!         && TREE_ADDRESSABLE (var))
        return false;
      }

--- 72,86 ----
    if (current_function_stdarg)
      return false;

!   /* No local variable should be call-clobbered.  We ignore any kind
!      of memory tag, as these are not real variables.  */
    for (i = 0; i < (int) VARRAY_ACTIVE_SIZE (referenced_vars); i++)
      {
        tree var = VARRAY_TREE (referenced_vars, i);

        if (decl_function_context (var) == current_function_decl
!         && var_ann (var)->mem_tag_kind == NOT_A_TAG
!         && is_call_clobbered (var))
        return false;
      }



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14312