pass_manager: Fix ICE with -fdump-passes -fdisable-tree-* [PR93874]

dump_passes pushes a dummy function for which it evaluates the gates
and checks whether the pass is enabled or disabled.
Unfortunately, if any -fdisable-*-*/-fenable-*-* options were seen,
we ICE during is_pass_explicitly_enabled_or_disabled because slot
is non-NULL then and the code will do:
  cgraph_uid = func ? cgraph_node::get (func)->get_uid () : 0;
but the dummy function doesn't have a cgraph node.

So, either we need to create and then remove a cgraph node for the dummy
function like the following patch, or function.c would need to export the
in_dummy_function flag (or have some way to query that flag from other TUs)
and we'd need to check it in is_pass_explicitly_enabled_or_disabled.

2020-02-25  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/93874
	* passes.c (pass_manager::dump_passes): Create a cgraph node for the
	dummy function and remove it at the end.

	* gcc.dg/pr93874.c: New test.

gcc/ChangeLog

 2020-02-25  Jakub Jelinek  <jakub@redhat.com>
 
+	PR middle-end/93874
+	* passes.c (pass_manager::dump_passes): Create a cgraph node for the
+	dummy function and remove it at the end.
+
 	PR translation/93864
 	* config/lm32/lm32.c (lm32_setup_incoming_varargs): Fix comment typo
 	paramter -> parameter.

gcc/passes.c

@@ -950,6 +950,7 @@ void
 pass_manager::dump_passes () const
 {
   push_dummy_function (true);
+  cgraph_node *node = cgraph_node::get_create (current_function_decl);
 
   create_pass_tab ();
 
@@ -959,6 +960,7 @@ pass_manager::dump_passes () const
   dump_pass_list (all_late_ipa_passes, 1);
   dump_pass_list (all_passes, 1);
 
+  node->remove ();
   pop_dummy_function ();
 }
 

gcc/testsuite/ChangeLog

 2020-02-25  Jakub Jelinek  <jakub@redhat.com>
 
+	PR middle-end/93874
+	* gcc.dg/pr93874.c: New test.
+
 	PR ipa/93763
 	* gcc.dg/ipa/pr93763.c: Adjust the test so that it compiles without
 	warnings and still ICEs before the ipa-cp.c fix.

gcc/testsuite/gcc.dg/pr93874.c

+/* PR middle-end/93874 */
+/* { dg-do compile } */
+/* { dg-options "-fdisable-tree-dse3 -fdump-passes" } */
+/* { dg-prune-output ".*" } */
+
+int i;