cgraph: add selftest::symbol_table_test

This patch adds a selftest fixture for overriding the "symtab" global,
so that selftests involving symtab nodes can be isolated from each
other: each selftest can have its own symbol_table instance.

In particular, this ensures that nodes can have a predictable "order"
and thus predictable dump names within selftests.

gcc/ChangeLog:
	* cgraph.c: Include "selftest.h".
	(saved_symtab): New variable.
	(selftest::symbol_table_test::symbol_table_test): New ctor.
	(selftest::symbol_table_test::~symbol_table_test): New dtor.
	(selftest::test_symbol_table_test): New test.
	(selftest::cgraph_c_tests): New.
	* cgraph.h (saved_symtab): New decl.
	(selftest::symbol_table_test): New class.
	* selftest-run-tests.c (selftest::run_tests): Call
	selftest::cgraph_c_tests.
	* selftest.h (selftest::cgraph_c_tests): New decl.

From-SVN: r265915

gcc/ChangeLog

+2018-11-08  David Malcolm  <dmalcolm@redhat.com>
+
+	* cgraph.c: Include "selftest.h".
+	(saved_symtab): New variable.
+	(selftest::symbol_table_test::symbol_table_test): New ctor.
+	(selftest::symbol_table_test::~symbol_table_test): New dtor.
+	(selftest::test_symbol_table_test): New test.
+	(selftest::cgraph_c_tests): New.
+	* cgraph.h (saved_symtab): New decl.
+	(selftest::symbol_table_test): New class.
+	* selftest-run-tests.c (selftest::run_tests): Call
+	selftest::cgraph_c_tests.
+	* selftest.h (selftest::cgraph_c_tests): New decl.
+
 2018-11-08  Richard Biener  <rguenther@suse.de>
 
 	* tree-data-ref.h (lambda_int): New typedef.

gcc/cgraph.c

@@ -62,6 +62,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "stringpool.h"
 #include "attribs.h"
+#include "selftest.h"
 
 /* FIXME: Only for PROP_loops, but cgraph shouldn't have to know about this.  */
 #include "tree-pass.h"
@@ -3765,4 +3766,70 @@ cgraph_edge::sreal_frequency ()
 			       : caller->count);
 }
 
+/* A stashed copy of "symtab" for use by selftest::symbol_table_test.
+   This needs to be a global so that it can be a GC root, and thus
+   prevent the stashed copy from being garbage-collected if the GC runs
+   during a symbol_table_test.  */
+
+symbol_table *saved_symtab;
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* class selftest::symbol_table_test.  */
+
+/* Constructor.  Store the old value of symtab, and create a new one.  */
+
+symbol_table_test::symbol_table_test ()
+{
+  gcc_assert (saved_symtab == NULL);
+  saved_symtab = symtab;
+  symtab = new (ggc_cleared_alloc <symbol_table> ()) symbol_table ();
+}
+
+/* Destructor.  Restore the old value of symtab.  */
+
+symbol_table_test::~symbol_table_test ()
+{
+  gcc_assert (saved_symtab != NULL);
+  symtab = saved_symtab;
+  saved_symtab = NULL;
+}
+
+/* Verify that symbol_table_test works.  */
+
+static void
+test_symbol_table_test ()
+{
+  /* Simulate running two selftests involving symbol tables.  */
+  for (int i = 0; i < 2; i++)
+    {
+      symbol_table_test stt;
+      tree test_decl = build_decl (UNKNOWN_LOCATION, FUNCTION_DECL,
+				   get_identifier ("test_decl"),
+				   build_function_type_list (void_type_node,
+							     NULL_TREE));
+      cgraph_node *node = cgraph_node::get_create (test_decl);
+      gcc_assert (node);
+
+      /* Verify that the node has order 0 on both iterations,
+	 and thus that nodes have predictable dump names in selftests.  */
+      ASSERT_EQ (node->order, 0);
+      ASSERT_STREQ (node->dump_name (), "test_decl/0");
+    }
+}
+
+/* Run all of the selftests within this file.  */
+
+void
+cgraph_c_tests ()
+{
+  test_symbol_table_test ();
+}
+
+} // namespace selftest
+
+#endif /* CHECKING_P */
+
 #include "gt-cgraph.h"

gcc/cgraph.h

@@ -3353,4 +3353,27 @@ xstrdup_for_dump (const char *transient_str)
   return ggc_strdup (transient_str);
 }
 
+extern GTY(()) symbol_table *saved_symtab;
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* An RAII-style class for use in selftests for temporarily using a different
+   symbol_table, so that such tests can be isolated from each other.  */
+
+class symbol_table_test
+{
+ public:
+  /* Constructor.  Override "symtab".  */
+  symbol_table_test ();
+
+  /* Destructor.  Restore the saved_symtab.  */
+  ~symbol_table_test ();
+};
+
+} // namespace selftest
+
+#endif /* CHECKING_P */
+
 #endif  /* GCC_CGRAPH_H  */

gcc/selftest-run-tests.c

@@ -73,6 +73,7 @@ selftest::run_tests ()
   unique_ptr_tests_cc_tests ();
   opt_proposer_c_tests ();
   json_cc_tests ();
+  cgraph_c_tests ();
   optinfo_emit_json_cc_tests ();
   opt_problem_cc_tests ();
 

gcc/selftest.h

@@ -215,6 +215,7 @@ class test_runner
    alphabetical order.  */
 extern void attribute_c_tests ();
 extern void bitmap_c_tests ();
+extern void cgraph_c_tests ();
 extern void diagnostic_c_tests ();
 extern void diagnostic_show_locus_c_tests ();
 extern void dumpfile_c_tests ();