diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3e000cd424fb..7e580c723486 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -4,6 +4,12 @@
 	* loop-invariant.c (calculate_loop_reg_pressure): Don't count regs
 	referenced just in DEBUG_INSNs.
 
+2009-10-20  Richard Guenther  <rguenther@suse.de>
+
+	PR lto/41761
+	* gimple.c (gimple_register_type): Make sure we register
+	the types main variant first.
+
 2009-10-20  Richard Guenther  <rguenther@suse.de>
 
 	* gimple.c (gimple_types_compatible_p): Simplify.  Move
diff --git a/gcc/gimple.c b/gcc/gimple.c
index d5b1cf7f1c77..f725a347bac0 100644
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -3809,6 +3809,12 @@ gimple_register_type (tree t)
 
   gcc_assert (TYPE_P (t));
 
+  /* Always register the main variant first.  This is important so we
+     pick up the non-typedef variants as canonical, otherwise we'll end
+     up taking typedef ids for structure tags during comparison.  */
+  if (TYPE_MAIN_VARIANT (t) != t)
+    gimple_register_type (TYPE_MAIN_VARIANT (t));
+
   if (gimple_types == NULL)
     gimple_types = htab_create (16381, gimple_type_hash, gimple_type_eq, 0);
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7a862affcbb5..0e4f1aff52c2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2009-10-20  Richard Guenther  <rguenther@suse.de>
+
+	PR lto/41761
+	* gcc.dg/lto/20091020-1_0.c: New testcase.
+	* gcc.dg/lto/20091020-1_1.c: Likewise.
+	* gcc.dg/lto/20091020-2_0.c: Likewise.
+	* gcc.dg/lto/20091020-2_1.c: Likewise.
+
 2009-10-20  Jakub Jelinek  <jakub@redhat.com>
 
 	PR debug/41340
diff --git a/gcc/testsuite/gcc.dg/lto/20091020-1_0.c b/gcc/testsuite/gcc.dg/lto/20091020-1_0.c
new file mode 100644
index 000000000000..ef61e98b4cca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/20091020-1_0.c
@@ -0,0 +1,8 @@
+/* { dg-lto-do link } */
+/* { dg-lto-options {{-fPIC -shared -flto}} } */
+
+typedef struct {
+    int NumPackStreams;
+} CSzAr;
+void cli_7unz (CSzAr db) { }
+
diff --git a/gcc/testsuite/gcc.dg/lto/20091020-1_1.c b/gcc/testsuite/gcc.dg/lto/20091020-1_1.c
new file mode 100644
index 000000000000..899183a2459b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/20091020-1_1.c
@@ -0,0 +1,15 @@
+typedef struct {
+    int NumPackStreams;
+} CSzAr;
+typedef struct {
+    CSzAr db;
+} CSzArEx;
+int SzArEx_Init(CSzArEx *p)
+{
+  return p->db.NumPackStreams;
+}
+int SzArEx_GetFolderFullPackSize(const CSzArEx *p)
+{
+  return p->db.NumPackStreams;
+}
+
diff --git a/gcc/testsuite/gcc.dg/lto/20091020-2_0.c b/gcc/testsuite/gcc.dg/lto/20091020-2_0.c
new file mode 100644
index 000000000000..7dcbb2da2ca5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/20091020-2_0.c
@@ -0,0 +1,18 @@
+/* { dg-lto-do link } */
+/* { dg-lto-options {{-fPIC -shared -flto}} } */
+
+typedef struct {
+    int NumPackStreams;
+} CSzAr;
+typedef struct {
+    CSzAr db;
+} CSzArEx;
+int SzArEx_Init(CSzArEx *p)
+{
+  return p->db.NumPackStreams;
+}
+int SzArEx_GetFolderFullPackSize(const CSzArEx *p)
+{
+  return p->db.NumPackStreams;
+}
+
diff --git a/gcc/testsuite/gcc.dg/lto/20091020-2_1.c b/gcc/testsuite/gcc.dg/lto/20091020-2_1.c
new file mode 100644
index 000000000000..9174f26c35c1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/20091020-2_1.c
@@ -0,0 +1,5 @@
+typedef struct {
+    int NumPackStreams;
+} CSzAr;
+void cli_7unz (CSzAr db) { }
+