Update string_constant for new const initializer code

[Richard Guenther]

On Sat, 4 Sep 2010, Jan Hubicka wrote:

> Hi,
> while disabling initializer folding in expr.c I noticed that string-constant is
> actually used by builtin folding and thus it needs to be updated for new
> varppol initializer code.  Unfortunately folding also happens early from
> frntend and thus we need to  behave sanely when varpool is not ready yet.  The
> patch removes TREE_SIDE_EFFECTS check since we don't do it elsewhere
> (and I have problems to think of volatile constant string having some meaning)
> and also makes us to use DECL_REPLACEABLE_P instead of targetm.binds_local_p
> like we do elsewhere now too.
> 
> Bootstrapped/regtested x86_64-linx, OK?
> 
> Honza
> 
> 	* expr.c (string_constant): Use varpool to figure out if value
> 	is known.
> Index: expr.c
> ===================================================================
> --- expr.c	(revision 163859)
> +++ expr.c	(working copy)
> @@ -9815,10 +9837,12 @@ string_constant (tree arg, tree *ptr_off
>  	  || TREE_CODE (DECL_INITIAL (array)) != STRING_CST)
>  	return 0;
>  
> -      /* If they are read-only, non-volatile and bind locally.  */
> +      /* If they are read-only and non-replaceable.  */
>        if (! TREE_READONLY (array)
> -	  || TREE_SIDE_EFFECTS (array)
> -	  || ! targetm.binds_local_p (array))
> +	  || ((!cgraph_function_flags_ready
> +	       && !DECL_REPLACEABLE_P (array))
> +	      || (cgraph_function_flags_ready
> +		  && !varpool_get_node (array)->const_value_known)))

So DECL_REPLACEABLE_P isn't kept up-to-date?  Why does

  || !DECL_REPLACEABLE_P (array)

not work?

Richard.