[patch] Enable LTO support for Ada

[Eric Botcazou]

> +  if (CONTAINS_PLACEHOLDER_P (DECL_SIZE (expr)))
> +    lto_output_tree_or_ref (ob, build0 (PLACEHOLDER_EXPR, bitsizetype),
> ref_p); +  else
> +    lto_output_tree_or_ref (ob, DECL_SIZE (expr), ref_p);
>
> couldn't we just gimplify it that way?

I don't think that we can gimplify them because gimplification itself does 
SUBSTITUTE_PLACEHOLDER_IN_EXPR so we need to keep the original expressions as 
long as gimplification isn't entirely done.

> Or if that's too early do that in free_lang_data?

Let me try that.

> Thus, what are exprs containing PLACEHOLDER_EXPRs good for after
> gimplification (or lowering)? 

Nothing once gimplification is entirely done, but restoring INTEGER_CSTs 
instead of something variable leads to problems in useless_type_conversion_p.

-- 
Eric Botcazou