[RFC][IPA-VRP] ADDR_EXPR and nonnull

Richard Biener rguenther@suse.de
Fri Oct 21 08:08:00 GMT 2016


On Fri, 21 Oct 2016, kugan wrote:

> 
> 
> On 21/10/16 18:16, Richard Biener wrote:
> > On Fri, 21 Oct 2016, kugan wrote:
> > 
> > > Hi,
> > > 
> > > On 20/10/16 23:15, Jan Hubicka wrote:
> > > > > Hi Richard,
> > > > > 
> > > > > 
> > > > > On 20/10/16 18:41, Richard Biener wrote:
> > > > > > On Thu, 20 Oct 2016, kugan wrote:
> > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > On 20/10/16 01:26, Jan Hubicka wrote:
> > > > > > > > > > Would excluding weak symbols (I believe I can check
> > > > > > > > > > DECL_WEAK
> > > > > > > > > > for this)
> > > > > > > > > > good
> > > > > > > > > > enough. Or looking for acceptable subset would work?
> > > > > > > > > 
> > > > > > > > > I think we should add a symtab helper to tell if
> > > > > > > > > address_nonzero_p
> > > > > > > > > (if
> > > > > > > > > that doesn't aleady exist).
> > > > > > > > 
> > > > > > > > We have node->nonzero_address()
> > > > > > > 
> > > > > > > Thanks for the pointer. Here is an attempt. Does this look OK?
> > > > > > > 
> > > > > > > +	  if (TREE_CODE (arg) == ADDR_EXPR)
> > > > > > > +	    {
> > > > > > > +	      /* See if the AADR_EXPR is nonnull.  */
> > > > > > > +	      varpool_node *node = NULL;
> > > > > > > +	      tree base = TREE_OPERAND (arg, 0);
> > > > > > > +	      base = get_base_address (base);
> > > > > > > +
> > > > > > > +	      if (decl_address_ip_invariant_p (base)
> > > > > > > +		  || !is_global_var (base))
> > > > > > > +		{
> > > > > > > +		  /* If the symbol address is local or
> > > > > > > +		     constant.  */
> > > > > > 
> > > > > > "constant" doesn't matter.  You want
> > > > > > 
> > > > > >   if (TREE_CODE (base) == CONST_DECL
> > > > > > || TREE_CODE (base) == PARM_DECL
> > > > > > || TREE_CODE (base) == RESULT_DECL)
> > > > > >  addr_nonzero = true;
> > > > > >   else if (VAR_P (base))
> > > > Better to check decl_in_symtab_p (decl)
> > > > > >     addr_nonzero = ! is_global_var (base) || (varpool_node::get
> > > > > > (base)->nonzero_address ());
> > > > and symtab_node::get.
> > > > 
> > > > I wonder if we can't unify the logic with tree_expr_nonzero_warnv_p
> > > > and corresponding vrp code?
> > > Are you saying that we should export tree_expr_nonzero_warnv_p and use
> > > here
> > > with the logic from above added to tree_expr_nonzero_warnv_p as shown in
> > > the
> > > attached patch?
> > 
> > tree_single_nonzero_warnv_p already handles this correctly via
> > maybe_nonzero_address.  And tree_single_nonzero_warnv_p is already
> > exported.
> Indeed. maybe_nonzero_address does look at node->nonzero_address () but we
> still seems to miss TREE_CODE (base) == PARM_DECL and TREE_CODE (base) ==
> RESULT_DECL.

Should be handled by

        /* Function local objects are never NULL.  */
        if (DECL_P (base)
            && (DECL_CONTEXT (base)
                && TREE_CODE (DECL_CONTEXT (base)) == FUNCTION_DECL
                && auto_var_in_fn_p (base, DECL_CONTEXT (base))))
          return true;

> Does the attached patch looks OK if no regressions?

+         else if (tree_single_nonzero_warnv_p (arg, &strict_overflow))
+           {
+             if (!strict_overflow)
+               addr_nonzero = true;

you don't need to care for strict_overflow here.

The patch is ok with that removed and the fold-const.c changes dropped.

Richard.

> Thanks,
> Kugan
> 
> 
> > 
> > Richard.
> > 
> > > Thanks,
> > > Kugan
> > > 
> > > > 
> > > > Otherwise the patch looks fine to me.
> > > > Honza
> > > > 
> > > 
> > 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)



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