Add gcc_assert that &global_options are not dirty modified.

gcc/ChangeLog:

2020-03-20  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/92860
	* optc-save-gen.awk: Generate new function cl_optimization_compare.
	* opth-gen.awk: Generate declaration of the function.

gcc/c-family/ChangeLog:

2020-03-20  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/92860
	* c-attribs.c (handle_optimize_attribute):
	Save global options and compare it after parsing of function
	attribute.
	* c-pragma.c (opt_stack::saved_global_options): New field.
	(handle_pragma_push_options): Save global_options.
	(handle_pragma_pop_options): Compare them after pop.

gcc/c-family/c-attribs.c

@@ -4452,6 +4452,13 @@ handle_optimize_attribute (tree *node, tree name, tree args,
 
       /* If we previously had some optimization options, use them as the
 	 default.  */
+      gcc_options *saved_global_options = NULL;
+      if (flag_checking)
+	{
+	  saved_global_options = XNEW (gcc_options);
+	  *saved_global_options = global_options;
+	}
+
       if (old_opts)
 	cl_optimization_restore (&global_options,
 				 TREE_OPTIMIZATION (old_opts));
@@ -4463,6 +4470,11 @@ handle_optimize_attribute (tree *node, tree name, tree args,
 
       /* Restore current options.  */
       cl_optimization_restore (&global_options, &cur_opts);
+      if (saved_global_options != NULL)
+	{
+	  cl_optimization_compare (saved_global_options, &global_options);
+	  free (saved_global_options);
+	}
     }
 
   return NULL_TREE;

gcc/c-family/c-pragma.c

@@ -1003,6 +1003,7 @@ struct GTY(()) opt_stack {
   tree target_strings;
   tree optimize_binary;
   tree optimize_strings;
+  gcc_options * GTY ((skip)) saved_global_options;
 };
 
 static GTY(()) struct opt_stack * options_stack;
@@ -1028,6 +1029,11 @@ handle_pragma_push_options (cpp_reader *ARG_UNUSED(dummy))
   options_stack = p;
 
   /* Save optimization and target flags in binary format.  */
+  if (flag_checking)
+    {
+      p->saved_global_options = XNEW (gcc_options);
+      *p->saved_global_options = global_options;
+    }
   p->optimize_binary = build_optimization_node (&global_options);
   p->target_binary = build_target_option_node (&global_options);
 
@@ -1079,6 +1085,11 @@ handle_pragma_pop_options (cpp_reader *ARG_UNUSED(dummy))
 				      p->optimize_binary);
       optimization_current_node = p->optimize_binary;
     }
+  if (flag_checking)
+    {
+      cl_optimization_compare (p->saved_global_options, &global_options);
+      free (p->saved_global_options);
+    }
 
   current_target_pragma = p->target_strings;
   current_optimize_pragma = p->optimize_strings;

gcc/optc-save-gen.awk

@@ -945,5 +945,30 @@ for (i = 0; i < n_opt_val; i++) {
 	      print "    free (const_cast <char *>(ptr->" name"));";
 	}
 }
+print "}";
+
+print "void";
+print "cl_optimization_compare (gcc_options *ptr1, gcc_options *ptr2)"
+print "{"
+
+# all these options are mentioned in PR92860
+checked_options["flag_merge_constants"]++
+checked_options["param_max_fields_for_field_sensitive"]++
+checked_options["flag_omit_frame_pointer"]++
+checked_options["unroll_only_small_loops"]++
+
+for (i = 0; i < n_opts; i++) {
+	name = var_name(flags[i]);
+	if (name == "")
+		continue;
+
+	if (name in checked_options)
+		continue;
+	checked_options[name]++
+
+	print "  if (ptr1->x_" name " != ptr2->x_" name ")"
+	print "    internal_error (\"Error: global_options are modified in local context\\n\");";
+}
+
 print "}";
 }

gcc/opth-gen.awk

@@ -318,6 +318,9 @@ print "";
 print "/* Free heap memory used by optimization options.  */";
 print "extern void cl_optimization_option_free (cl_optimization *ptr1);"
 print "";
+print "/* Compare and report difference for a part of cl_optimization options.  */";
+print "extern void cl_optimization_compare (gcc_options *ptr1, gcc_options *ptr2);";
+print "";
 print "/* Generator files may not have access to location_t, and don't need these.  */"
 print "#if defined(UNKNOWN_LOCATION)"
 print "bool                                                                  "