[Bug c++/70594] [6 Regression] -fcompare-debug failure

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70594

--- Comment #47 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Ok, found one bug in the unused block pruning:
--- gcc/ipa-polymorphic-call.c.jj       2016-03-30 16:00:17.000000000 +0200
+++ gcc/ipa-polymorphic-call.c  2016-04-14 16:45:45.407754387 +0200
@@ -479,16 +479,12 @@ contains_type_p (tree outer_type, HOST_W
 }


-/* Return a FUNCTION_DECL if BLOCK represents a constructor or destructor.
+/* Return a FUNCTION_DECL if FN represent a constructor or destructor.
    If CHECK_CLONES is true, also check for clones of ctor/dtors.  */

 tree
-inlined_polymorphic_ctor_dtor_block_p (tree block, bool check_clones)
+polymorphic_ctor_dtor_p (tree fn, bool check_clones)
 {
-  tree fn = block_ultimate_origin (block);
-  if (fn == NULL || TREE_CODE (fn) != FUNCTION_DECL)
-    return NULL_TREE;
-
   if (TREE_CODE (TREE_TYPE (fn)) != METHOD_TYPE
       || (!DECL_CXX_CONSTRUCTOR_P (fn) && !DECL_CXX_DESTRUCTOR_P (fn)))
     {
@@ -510,6 +506,19 @@ inlined_polymorphic_ctor_dtor_block_p (t
   return fn;
 }

+/* Return a FUNCTION_DECL if BLOCK represents a constructor or destructor.
+   If CHECK_CLONES is true, also check for clones of ctor/dtors.  */
+
+tree
+inlined_polymorphic_ctor_dtor_block_p (tree block, bool check_clones)
+{
+  tree fn = block_ultimate_origin (block);
+  if (fn == NULL || TREE_CODE (fn) != FUNCTION_DECL)
+    return NULL_TREE;
+
+  return polymorphic_ctor_dtor_p (fn, check_clones);
+}
+

 /* We know that the instance is stored in variable or parameter
    (not dynamically allocated) and we want to disprove the fact
--- gcc/ipa-utils.h.jj  2016-01-04 14:55:51.000000000 +0100
+++ gcc/ipa-utils.h     2016-04-14 16:46:08.828444152 +0200
@@ -70,6 +70,7 @@ void dump_possible_polymorphic_call_targ
 bool possible_polymorphic_call_target_p (tree, HOST_WIDE_INT,
                                         const ipa_polymorphic_call_context &,
                                         struct cgraph_node *);
+tree polymorphic_ctor_dtor_p (tree, bool);
 tree inlined_polymorphic_ctor_dtor_block_p (tree, bool);
 bool decl_maybe_in_construction_p (tree, tree, gimple *, tree);
 tree vtable_pointer_value_to_binfo (const_tree);
--- gcc/tree-ssa-live.c.jj      2016-01-04 14:55:51.000000000 +0100
+++ gcc/tree-ssa-live.c 2016-04-14 16:47:33.343324654 +0200
@@ -855,7 +855,9 @@ remove_unused_locals (void)
       cfun->local_decls->truncate (dstidx);
     }

-  remove_unused_scope_block_p (DECL_INITIAL (current_function_decl), false);
+  remove_unused_scope_block_p (DECL_INITIAL (current_function_decl),
+                              polymorphic_ctor_dtor_p (current_function_decl,
+                                                       true) != NULL_TREE);
   clear_unused_block_pointer ();

   BITMAP_FREE (usedvars);

but sadly this still doesn't fix it (though, fixes at least the first case
where we nuke the needed BLOCK).