On Thu, Mar 21, 2019 at 11:25:38AM +0100, Richard Biener wrote:
> On Thu, 21 Mar 2019, Jakub Jelinek wrote:
> 
> > On Thu, Mar 21, 2019 at 11:13:41AM +0100, Richard Biener wrote:
> > > > Would you prefer to have say add_tree_to_fld_list that does what it 
> > > > does now
> > > > and has just 2 callers in find_decls_types_r and a new
> > > > maybe_add_tree_to_fld_list that would do
> > > >   if (!fld->pset.add (t))
> > > >     add_tree_to_fld_list (t, fld);
> > > > and change all the other add_tree_to_fld_list callers?
> > > 
> > > Not sure if that's needed, if you leave find_decls_types_r alone then
> > > always doing the check should work, no?
> > 
> > Well, find_decls_types_r uses add_tree_to_fld_list, so the if (fld->pset.add
> > (t)) return; can't be in that function.  If we want to simplify all the
> > other callers, so that they don't need to do it manually, then the only
> > options I see is call some other function in those spots that does this
> > additional check, or call another function that doesn't do that in the
> > two spots of find_decls_types_r, or add another argument to the function
> > say with default argument and test that argument before the fld->pset.add.
> > E.g. , bool do_add = true and if (do_add && fld->pset.add (t)) return;
> > and adjust the two calls in find_decls_types_r to call
> > add_tree_to_fld_list (t, fld, false);
> > Or keep the patch as is, do the tests before each but the two
> > add_tree_to_fld_list calls.
> 
> I'd have kept the patch but made the add_tree_to_fld_list following
> the new fld->pset.add (t) calls conditional on the result.

Ok, so incremental diff:
--- gcc/tree.c  2019-03-20 20:16:12.277091827 +0100
+++ gcc/tree.c  2019-03-21 11:33:17.008936452 +0100
@@ -5215,8 +5215,8 @@
   if (inner_type)
     TREE_TYPE (v) = inner_type;
   gcc_checking_assert (fld_type_variant_equal_p (t,v, inner_type));
-  fld->pset.add (v);
-  add_tree_to_fld_list (v, fld);
+  if (!fld->pset.add (v))
+    add_tree_to_fld_list (v, fld);
   return v;
 }
 
@@ -5324,8 +5324,8 @@
          copy = build_distinct_type_copy (t);
 
          /* It is possible that type was not seen by free_lang_data yet.  */
-         fld->pset.add (copy);
-         add_tree_to_fld_list (copy, fld);
+         if (!fld->pset.add (copy))
+           add_tree_to_fld_list (copy, fld);
          TYPE_SIZE (copy) = NULL;
          TYPE_USER_ALIGN (copy) = 0;
          TYPE_SIZE_UNIT (copy) = NULL;
@@ -5480,8 +5480,8 @@
                          & ~TYPE_QUAL_CONST
                          & ~TYPE_QUAL_VOLATILE;
              TREE_VALUE (p) = build_qualified_type (arg_type, quals);
-             fld->pset.add (TREE_VALUE (p));
-             free_lang_data_in_type (TREE_VALUE (p), fld);
+             if (!fld->pset.add (TREE_VALUE (p)))
+               free_lang_data_in_type (TREE_VALUE (p), fld);
            }
          /* C++ FE uses TREE_PURPOSE to store initial values.  */
          TREE_PURPOSE (p) = NULL;

and full patch below?  Ok for trunk if it passes bootstrap/regtest?

2019-03-21  Jan Hubicka  <hubi...@ucw.cz>
            Jakub Jelinek  <ja...@redhat.com>

        PR lto/89692
        * tree.c (fld_type_variant, fld_incomplete_type_of,
        fld_process_array_type): Call fld->pset.add and don't call
        add_tree_to_fld_list if it returns true.
        (free_lang_data_in_type): Likewise.  Purge non-marked types from
        TYPE_NEXT_VARIANT list.
        (find_decls_types_r): Call fld_worklist_push for TYPE_CANONICAL (t).

        * g++.dg/other/pr89692.C: New test.

--- gcc/tree.c.jj       2019-03-20 12:24:56.443322228 +0100
+++ gcc/tree.c  2019-03-21 11:33:17.008936452 +0100
@@ -5215,7 +5215,8 @@ fld_type_variant (tree first, tree t, st
   if (inner_type)
     TREE_TYPE (v) = inner_type;
   gcc_checking_assert (fld_type_variant_equal_p (t,v, inner_type));
-  add_tree_to_fld_list (v, fld);
+  if (!fld->pset.add (v))
+    add_tree_to_fld_list (v, fld);
   return v;
 }
 
@@ -5253,7 +5254,8 @@ fld_process_array_type (tree t, tree t2,
       array = build_array_type_1 (t2, TYPE_DOMAIN (t),
                                  TYPE_TYPELESS_STORAGE (t), false);
       TYPE_CANONICAL (array) = TYPE_CANONICAL (t);
-      add_tree_to_fld_list (array, fld);
+      if (!fld->pset.add (array))
+       add_tree_to_fld_list (array, fld);
     }
   return array;
 }
@@ -5298,7 +5300,8 @@ fld_incomplete_type_of (tree t, struct f
                                                TYPE_REF_CAN_ALIAS_ALL (t));
          gcc_assert (TYPE_CANONICAL (t2) != t2
                      && TYPE_CANONICAL (t2) == TYPE_CANONICAL (TREE_TYPE (t)));
-         add_tree_to_fld_list (first, fld);
+         if (!fld->pset.add (first))
+           add_tree_to_fld_list (first, fld);
          return fld_type_variant (first, t, fld);
        }
       return t;
@@ -5321,7 +5324,8 @@ fld_incomplete_type_of (tree t, struct f
          copy = build_distinct_type_copy (t);
 
          /* It is possible that type was not seen by free_lang_data yet.  */
-         add_tree_to_fld_list (copy, fld);
+         if (!fld->pset.add (copy))
+           add_tree_to_fld_list (copy, fld);
          TYPE_SIZE (copy) = NULL;
          TYPE_USER_ALIGN (copy) = 0;
          TYPE_SIZE_UNIT (copy) = NULL;
@@ -5445,6 +5449,18 @@ free_lang_data_in_type (tree type, struc
 
   TYPE_NEEDS_CONSTRUCTING (type) = 0;
 
+  /* Purge non-marked variants from the variants chain, so that they
+     don't reappear in the IL after free_lang_data.  */
+  while (TYPE_NEXT_VARIANT (type)
+        && !fld->pset.contains (TYPE_NEXT_VARIANT (type)))
+    {
+      tree t = TYPE_NEXT_VARIANT (type);
+      TYPE_NEXT_VARIANT (type) = TYPE_NEXT_VARIANT (t);
+      /* Turn the removed types into distinct types.  */
+      TYPE_MAIN_VARIANT (t) = t;
+      TYPE_NEXT_VARIANT (t) = NULL_TREE;
+    }
+
   if (TREE_CODE (type) == FUNCTION_TYPE)
     {
       TREE_TYPE (type) = fld_simplified_type (TREE_TYPE (type), fld);
@@ -5464,7 +5480,8 @@ free_lang_data_in_type (tree type, struc
                          & ~TYPE_QUAL_CONST
                          & ~TYPE_QUAL_VOLATILE;
              TREE_VALUE (p) = build_qualified_type (arg_type, quals);
-             free_lang_data_in_type (TREE_VALUE (p), fld);
+             if (!fld->pset.add (TREE_VALUE (p)))
+               free_lang_data_in_type (TREE_VALUE (p), fld);
            }
          /* C++ FE uses TREE_PURPOSE to store initial values.  */
          TREE_PURPOSE (p) = NULL;
@@ -5886,8 +5903,7 @@ find_decls_types_r (tree *tp, int *ws, v
            ctx = BLOCK_SUPERCONTEXT (ctx);
          fld_worklist_push (ctx, fld);
        }
-      /* Do not walk TYPE_CANONICAL.  We do not stream it and thus do not
-        and want not to reach unused types this way.  */
+      fld_worklist_push (TYPE_CANONICAL (t), fld);
 
       if (RECORD_OR_UNION_TYPE_P (t) && TYPE_BINFO (t))
        {
--- gcc/testsuite/g++.dg/other/pr89692.C.jj     2019-03-20 20:20:10.233278697 
+0100
+++ gcc/testsuite/g++.dg/other/pr89692.C        2019-03-20 20:19:53.193551778 
+0100
@@ -0,0 +1,20 @@
+// PR lto/89692
+// { dg-do compile }
+// { dg-require-effective-target lto }
+// { dg-options "-flto -O2" }
+
+struct S {
+  short int a, b;
+  unsigned char c : 1;
+};
+
+bool
+foo (void)
+{
+  unsigned char d[sizeof (S)] = { 0 };
+  S e;
+
+  __builtin_memcpy (&e, d, sizeof (d));
+
+  return e.c == d[0];
+}


        Jakub

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