[PATCH] Don't eliminate used pointer typedefs from debuginfo as unused (PR debug/43190)

[Jakub Jelinek]

Hi!

I've been wondering why when debugging var-tracking I can't use
(variable_tracking_info)(bb->aux) and have to instead use
(struct variable_tracking_info_def *)(bb->aux).  Also, VTI (bb) doesn't
work even when built with -g3.  The problem is that variable_tracking_info
is a typedef to struct variable_tracking_info_def * and no variable nor
field has such type.  It is used heavily in the source though for casts
(through the VTI macro), but gcc does eliminate it as unused type anyway.
The problem seems to be that used_types_insert skips through POINTER_TYPEs
and to main variant of the type, while IMHO we want to stop when we find a
named type and record that named type as used into the hash table.

This is a regression from say 3.2 which didn't do any unused type
elimination from the debug info.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux.  Ok for
trunk?

2010-02-26  Jakub Jelinek  <jakub@redhat.com>

	PR debug/43190
	* function.c (used_types_insert): Don't skip through named pointer
	types.  Don't use TYPE_MAIN_VARIANT if the original type has a name
	and it is different from the main variant's type.

	* c-c++-common/dwarf2/pr43190.c: New test.

--- gcc/function.c.jj	2010-01-22 18:47:21.000000000 +0100
+++ gcc/function.c	2010-02-26 11:43:13.000000000 +0100
@@ -5469,8 +5469,13 @@ void
 used_types_insert (tree t)
 {
   while (POINTER_TYPE_P (t) || TREE_CODE (t) == ARRAY_TYPE)
-    t = TREE_TYPE (t);
-  t = TYPE_MAIN_VARIANT (t);
+    if (TYPE_NAME (t))
+      break;
+    else
+      t = TREE_TYPE (t);
+  if (TYPE_NAME (t) == NULL_TREE
+      || TYPE_NAME (t) == TYPE_NAME (TYPE_MAIN_VARIANT (t)))
+    t = TYPE_MAIN_VARIANT (t);
   if (debug_info_level > DINFO_LEVEL_NONE)
     {
       if (cfun)
--- gcc/testsuite/c-c++-common/dwarf2/pr43190.c.jj	2010-02-26 12:22:09.000000000 +0100
+++ gcc/testsuite/c-c++-common/dwarf2/pr43190.c	2010-02-26 12:22:26.000000000 +0100
@@ -0,0 +1,13 @@
+/* PR debug/43190 */
+/* { dg-options "-gdwarf-2 -dA" } */
+/* { dg-final { scan-assembler "DW_TAG_structure_type\[^\\r\\n\]*\[\\r\\n\]+\[^\\r\\n\]*\"S\[^\\r\\n\]*DW_AT_name" } } */
+/* { dg-final { scan-assembler "DW_TAG_typedef\[^\\r\\n\]*\[\\r\\n\]+\[^\\r\\n\]*\"T\[^\\r\\n\]*DW_AT_name" } } */
+
+typedef struct S { int i; } *T;
+#define M(p) ((T) (p))
+
+void
+foo (void *p)
+{
+  M (p)->i++;
+}

	Jakub