Low-hanging C++-lexer speedup (PR c++/24208)

gcc/cp/ChangeLog:

	PR c++/24208
	* parser.c (LEXER_DEBUGGING_ENABLED_P): New macro.
	(cp_lexer_debugging_p): Use it.
	(cp_lexer_start_debugging): Likewise.
	(cp_lexer_stop_debugging): Likewise.

From-SVN: r232912

gcc/cp/ChangeLog

+2016-01-28  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/24208
+	* parser.c (LEXER_DEBUGGING_ENABLED_P): New macro.
+	(cp_lexer_debugging_p): Use it.
+	(cp_lexer_start_debugging): Likewise.
+	(cp_lexer_stop_debugging): Likewise.
+
 2016-01-27  Marek Polacek  <polacek@redhat.com>
 
 	PR c/68062

gcc/cp/parser.c

@@ -706,11 +706,21 @@ cp_lexer_destroy (cp_lexer *lexer)
   ggc_free (lexer);
 }
 
+/* This needs to be set to TRUE before the lexer-debugging infrastructure can
+   be used.  The point of this flag is to help the compiler to fold away calls
+   to cp_lexer_debugging_p within this source file at compile time, when the
+   lexer is not being debugged.  */
+
+#define LEXER_DEBUGGING_ENABLED_P false
+
 /* Returns nonzero if debugging information should be output.  */
 
 static inline bool
 cp_lexer_debugging_p (cp_lexer *lexer)
 {
+  if (!LEXER_DEBUGGING_ENABLED_P)
+    return false;
+
   return lexer->debugging_p;
 }
 
@@ -1296,6 +1306,10 @@ debug (cp_token *ptr)
 static void
 cp_lexer_start_debugging (cp_lexer* lexer)
 {
+  if (!LEXER_DEBUGGING_ENABLED_P)
+    fatal_error (input_location,
+		 "LEXER_DEBUGGING_ENABLED_P is not set to true");
+
   lexer->debugging_p = true;
   cp_lexer_debug_stream = stderr;
 }
@@ -1305,6 +1319,10 @@ cp_lexer_start_debugging (cp_lexer* lexer)
 static void
 cp_lexer_stop_debugging (cp_lexer* lexer)
 {
+  if (!LEXER_DEBUGGING_ENABLED_P)
+    fatal_error (input_location,
+		 "LEXER_DEBUGGING_ENABLED_P is not set to true");
+
   lexer->debugging_p = false;
   cp_lexer_debug_stream = NULL;
 }