Re: Use ODR for canonical types construction in LTO

[Nathan Sidwell]

On 6/19/19 9:28 AM, Jan Hubicka wrote:
Jason,
I also wonder if something like this would make sense:
        * decl.c (build_clobber_this): Use original basetype if they
        match.

Index: decl.c
===================================================================
--- decl.c      (revision 272381)
+++ decl.c      (working copy)
@@ -15210,7 +15210,11 @@ build_clobber_this ()
  
    tree ctype = current_class_type;
    if (!vbases)
-    ctype = CLASSTYPE_AS_BASE (ctype);
+    {
+      if (!tree_int_cst_equal (TYPE_SIZE (ctype),
+                              TYPE_SIZE (CLASSTYPE_AS_BASE (ctype))))
+        ctype = CLASSTYPE_AS_BASE (ctype);
+    }
  
    tree clobber = build_clobber (ctype);

I have noticed we build a distinct as-base type in rather more cases 
than strictly necessary.  For instance when there's a member of 
reference type or we have a non-trivial dtor. 
(CLASSTYPE_NON_LAYOUT_POD_P gets set by a bunch of things that don't 
affect ABI layout)

nathan

--
Nathan Sidwell