This is another fix I postponed for 4.8 (or 4.7.1 if it doesn't have
any fallout). We fail to honor the (unwritten) rule that type
variants ought to share their TYPE_FIELDs. Which breaks users
that compare FIELD_DECLs by pointers.
This should also save some memory at WPA/LTRANS stage.
LTO bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2012-03-06 Richard Guenther <rguent...@suse.de>
PR lto/52097
* lto.c (uniquify_nodes): Merge TYPE_FIELDS of variant types.
* gcc.dg/lto/pr52097_0.c: New testcase.
Index: gcc/lto/lto.c
===================================================================
--- gcc/lto/lto.c (revision 184200)
+++ gcc/lto/lto.c (working copy)
@@ -805,6 +805,41 @@ uniquify_nodes (struct data_in *data_in,
TYPE_NEXT_VARIANT (mv) = t;
if (RECORD_OR_UNION_TYPE_P (t))
TYPE_BINFO (t) = TYPE_BINFO (mv);
+ /* Preserve the invariant that type variants share their
+ TYPE_FIELDS. */
+ if (RECORD_OR_UNION_TYPE_P (t)
+ && TYPE_FIELDS (mv) != TYPE_FIELDS (t))
+ {
+ tree f1, f2;
+ for (f1 = TYPE_FIELDS (mv), f2 = TYPE_FIELDS (t);
+ f1 && f2; f1 = TREE_CHAIN (f1), f2 = TREE_CHAIN (f2))
+ {
+ unsigned ix;
+ gcc_assert (f1 != f2
+ && DECL_NAME (f1) == DECL_NAME (f2));
+ if (!streamer_tree_cache_lookup (cache, f2, &ix))
+ gcc_unreachable ();
+ /* If we're going to replace an element which we'd
+ still visit in the next iterations, we wouldn't
+ handle it, so do it here. We do have to handle it
+ even though the field_decl itself will be removed,
+ as it could refer to e.g. integer_cst which we
+ wouldn't reach via any other way, hence they
+ (and their type) would stay uncollected. */
+ /* ??? We should rather make sure to replace all
+ references to f2 with f1. That means handling
+ COMPONENT_REFs and CONSTRUCTOR elements in
+ lto_fixup_types and special-case the field-decl
+ operand handling. */
+ /* ??? Not sure the above is all relevant in this
+ path canonicalizing TYPE_FIELDS to that of the
+ main variant. */
+ if (ix < i)
+ lto_fixup_types (f2);
+ streamer_tree_cache_insert_at (cache, f1, ix);
+ }
+ TYPE_FIELDS (t) = TYPE_FIELDS (mv);
+ }
}
/* Finally adjust our main variant and fix it up. */
Index: gcc/testsuite/gcc.dg/lto/pr52097_0.c
===================================================================
--- gcc/testsuite/gcc.dg/lto/pr52097_0.c (revision 0)
+++ gcc/testsuite/gcc.dg/lto/pr52097_0.c (revision 0)
@@ -0,0 +1,20 @@
+/* { dg-lto-do link } */
+/* { dg-lto-options { { -O -flto -fexceptions -fnon-call-exceptions --param
allow-store-data-races=0 } } } */
+
+typedef struct { unsigned int e0 : 16; } s1;
+typedef struct { unsigned int e0 : 16; } s2;
+typedef struct { s1 i1; s2 i2; } io;
+
+static io *i;
+
+void f1 (void)
+{
+ s1 x0;
+ i->i1 = x0;
+}
+
+int main ()
+{
+ f1 ();
+ return 0;
+}
