Re: push parser

[Joel E. Denny]

On Tue, 19 Dec 2006, Joel E. Denny wrote:

> We can adjust this small change later if it proves problematic, so I went 
> ahead and committed it.  I'll soon post a patch that takes another step in 
> implementing my larger patch.  It will depend on the small patch I just 
> committed.
> 
> By taking these smaller steps, I plan to document all parts of that larger 
> patch that I didn't document before.

Here's the next one, not yet committed.  I've tried to make this patch 
small so that it's intelligible, but that's not easy for this kind of 
reorganization.  For this reason, I've intentionally left some cleanup for 
later patches.

Index: ChangeLog
===================================================================
RCS file: /sources/bison/bison/ChangeLog,v
retrieving revision 1.1631
diff -p -u -r1.1631 ChangeLog
--- ChangeLog   19 Dec 2006 21:40:14 -0000      1.1631
+++ ChangeLog   19 Dec 2006 22:07:55 -0000
@@ -1,5 +1,35 @@
 2006-12-19  Joel E. Denny  <address@hidden>
 
+       Encapsulate the push parser state variables into an M4 macro so the
+       push skeleton doesn't have to list them again for pull mode's yyparse.
+       For push mode, remove yypush_parse's local equivalents of these
+       variables to eliminate unnecessary copying between the two sets at
+       run-time.  This patch also fixes at least a bug related to multiple
+       %initial-action invocations in push mode.
+       * data/push.c (b4_declare_parser_variables): Rename to...
+       (b4_declare_scanner_communication_variables): ... this for clarity and
+       update both uses.
+       (b4_declare_yyparse_variables): Remove and move its contents to the one
+       spot where it was invoked.
+       (b4_declare_parser_state_variables): New macro containing the parser
+       state variables required by push mode.
+       (struct yypstate): Replace all fields but yynew with
+       b4_declare_parser_state_variables.
+       (yystate, yyn, yyresult, yyerrstatus, yytoken, yyss, yyssp, yyvs,
+       yyvsp, yyls, yylsp, yystacksize, yyval, yyloc): For push mode, #define
+       each NAME in this list to yyps->NAME so it can be used in yypush_parse.
+       (yyparse or yypush_parse): For yyparse in pull mode, replace local
+       parser state variable declarations with
+       b4_declare_parser_state_variables.
+       Don't initialize parser state variables when calling yypush_parse since
+       yypstate_new already does that.
+       Invoke the user's initial action only upon the first yypush_parse
+       invocation.
+       Remove all code that copies between the local parser state variables
+       and the yypstate.
+
+2006-12-19  Joel E. Denny  <address@hidden>
+
        * data/push.c (union yyalloc): Rename yyss, yyvs, and yyls fields to
        prevent a name collision in a future patch where these names will
        sometimes be #define'd.
Index: data/push.c
===================================================================
RCS file: /sources/bison/bison/data/push.c,v
retrieving revision 1.18
diff -p -u -r1.18 push.c
--- data/push.c 19 Dec 2006 21:40:14 -0000      1.18
+++ data/push.c 19 Dec 2006 22:07:56 -0000
@@ -981,11 +981,11 @@ enum { YYPUSH_MORE = 4 };
 #endif /* ! YYPARSE_PARAM */])[
 
 ]m4_divert_push([KILL])# ======================== M4 code.
-# b4_declare_parser_variables
-# ---------------------------
+# b4_declare_scanner_communication_variables
+# ------------------------------------------
 # Declare the variables that are global, or local to YYPARSE if
 # pure-parser.
-m4_define([b4_declare_parser_variables],
+m4_define([b4_declare_scanner_communication_variables],
 [/* The lookahead symbol.  */
 int yychar;
 
@@ -1002,19 +1002,19 @@ YYLTYPE yylloc;])
 m4_define([b4_yyssa],b4_push_if([yyps->yyssa],[yyssa]))
 m4_define([b4_yyerror_range],b4_push_if([yyps->yyerror_range],[yyerror_range]))
 
-# b4_declare_yyparse_variables
-# ----------------------------
-# Declare all the variables that are needed local to YYPARSE
-m4_define([b4_declare_yyparse_variables],
-[[struct yypstate
-  {
+# b4_declare_parser_state_variables
+# ---------------------------------
+# Declare all the variables that are needed to maintain the parser state
+# between calls to yypush_parse.
+m4_define([b4_declare_parser_state_variables],
+[[
     int yystate;
     int yyn;
     int yyresult;
     /* Number of tokens to shift before error messages enabled.  */
     int yyerrstatus;
     /* Look-ahead token as an internal (translated) token number.  */
-    int yytoken;
+    int yytoken]b4_push_if([], [[ = 0]])[;
 
     /* Three stacks and their tools:
        `yyss': related to states,
@@ -1026,26 +1026,37 @@ m4_define([b4_declare_yyparse_variables]
 
     /* The state stack.  */
     yytype_int16 yyssa[YYINITDEPTH];
-    yytype_int16 *yyss;
+    yytype_int16 *yyss]b4_push_if([], [[ = yyssa]])[;
     yytype_int16 *yyssp;
 
     /* The semantic value stack.  */
     YYSTYPE yyvsa[YYINITDEPTH];
-    YYSTYPE *yyvs;
-    YYSTYPE *yyvsp;]]b4_locations_if([[[
+    YYSTYPE *yyvs]b4_push_if([], [[ = yyvsa]])[;
+    YYSTYPE *yyvsp;]b4_locations_if([[
     /* The location stack.  */
     YYLTYPE yylsa[YYINITDEPTH];
-    YYLTYPE *yyls;
+    YYLTYPE *yyls]b4_push_if([], [[ = yylsa]])[;
     YYLTYPE *yylsp;
     /* The locations where the error started and ended.  */
-    YYLTYPE yyerror_range[2];]]])[
-    YYSIZE_T yystacksize;
+    YYLTYPE yyerror_range[2];]])[
+    YYSIZE_T yystacksize]b4_push_if([], [[ = YYINITDEPTH]])[;
     /* The variables used to return semantic value and location from the
        action routines.  */
-    YYSTYPE yyval;
+    YYSTYPE yyval;]b4_locations_if([[
+    YYLTYPE yyloc;]])
+])
+
+m4_divert_pop([KILL])dnl# ====================== End of M4 code.
+
+b4_pure_if([], [b4_declare_scanner_communication_variables])
+
+b4_push_if(
+[[struct yypstate
+  {
+    ]b4_declare_parser_state_variables[
     /* Used to determine if this is the first time this instance has
        been used.  */
-    int yynew;]b4_locations_if([YYLTYPE yyloc;])[
+    int yynew;
   };
 
 /* Initialize the parser data structure.  */
@@ -1079,18 +1090,28 @@ m4_define([b4_declare_yyparse_variables]
 {
   free (yyps);
 }
-])
-m4_divert_pop([KILL])dnl# ====================== End of M4 code.
-
-b4_pure_if([], [b4_declare_parser_variables])
 
-b4_push_if([b4_declare_yyparse_variables])
+#define yystate yyps->yystate
+#define yyn yyps->yyn
+#define yyresult yyps->yyresult
+#define yyerrstatus yyps->yyerrstatus
+#define yytoken yyps->yytoken
+#define yyss yyps->yyss
+#define yyssp yyps->yyssp
+#define yyvs yyps->yyvs
+#define yyvsp yyps->yyvsp
+]b4_locations_if([[#define yyls yyps->yyls
+#define yylsp yyps->yylsp
+]])[#define yystacksize yyps->yystacksize
+#define yyval yyps->yyval
+]b4_locations_if([[#define yyloc yyps->yyloc
+]])])[
 
 /*-------------------------.
 | yyparse or yypush_parse.  |
 `-------------------------*/
 
-b4_push_if([
+]b4_push_if([
 b4_c_function_def([yypush_parse], [int], [[yypstate *yyps], [yyps]], 
                   [[int yynchar], [yynchar]],
                   [[YYSTYPE const *yynlval], [yynlval]]
@@ -1100,16 +1121,11 @@ b4_c_function_def([yypush_parse], [int],
 b4_c_function_def([yyparse], [int], [[void *YYPARSE_PARAM], [YYPARSE_PARAM]])
 #else /* ! YYPARSE_PARAM */
 b4_c_function_def([yyparse], [int], b4_parse_param)
-#endif])
-{[
-  ]b4_pure_if([b4_declare_parser_variables])[
-  int yystate;
-  int yyn;
-  int yyresult;
-  /* Number of tokens to shift before error messages enabled.  */
-  int yyerrstatus;
-  /* Lookahead token as an internal (translated) token number.  */
-  int yytoken = 0;
+#endif])[
+{
+  ]b4_pure_if([b4_declare_scanner_communication_variables])
+  b4_push_if([], [b4_declare_parser_state_variables])[
+
 #if YYERROR_VERBOSE
   /* Buffer for error messages, and its allocated size.  */
   char yymsgbuf[128];
@@ -1117,50 +1133,14 @@ b4_c_function_def([yyparse], [int], b4_p
   YYSIZE_T yymsg_alloc = sizeof yymsgbuf;
 #endif
 
-  /* Three stacks and their tools:
-     `yyss': related to states,
-     `yyvs': related to semantic values,
-     `yyls': related to locations.
-
-     Refer to the stacks thru separate pointers, to allow yyoverflow
-     to reallocate them elsewhere.  */
-
-  /* The state stack.  */
-  yytype_int16 yyssa[YYINITDEPTH];
-  yytype_int16 *yyss = yyssa;
-  yytype_int16 *yyssp;
-
-  /* The semantic value stack.  */
-  YYSTYPE yyvsa[YYINITDEPTH];
-  YYSTYPE *yyvs = yyvsa;
-  YYSTYPE *yyvsp;
-
-]b4_locations_if(
-[[  /* The location stack.  */
-  YYLTYPE yylsa[YYINITDEPTH];
-  YYLTYPE *yyls = yylsa;
-  YYLTYPE *yylsp;
-  /* The locations where the error started and ended.  */
-  ]b4_push_if([],[YYLTYPE yyerror_range[[2]]])[;
-  ]])[
-
 #define YYPOPSTACK(N)   (yyvsp -= (N), yyssp -= (N)]b4_locations_if([, yylsp 
-= (N)])[)
 
-  YYSIZE_T yystacksize = YYINITDEPTH;
-
-  /* The variables used to return semantic value and location from the
-     action routines.  */
-  YYSTYPE yyval;
-]b4_locations_if([  YYLTYPE yyloc;])[
-
   /* The number of symbols on the RHS of the reduced rule.
      Keep to zero when no symbol should be popped.  */
   int yylen = 0;
 
   YYDPRINTF ((stderr, "Starting parse\n"));
 
-  yystate = 0;
-  yyerrstatus = 0;
 ]b4_push_if([  yychar = yynchar;
   if (yynlval)
     yylval = *yynlval;
@@ -1168,6 +1148,10 @@ b4_c_function_def([yyparse], [int], b4_p
      yylloc = *yynlloc;])[],[yynerrs = 0;
   yychar = YYEMPTY; /* Cause a token to be read.  */])[
 
+]b4_push_if([],[[
+  yystate = 0;
+  yyerrstatus = 0;
+
   /* Initialize stack pointers.
      Waste one element of value and location stack
      so that they stay on the same level as the state stack.
@@ -1176,13 +1160,18 @@ b4_c_function_def([yyparse], [int], b4_p
   yyssp = yyss;
   yyvsp = yyvs;
 ]b4_locations_if([[  yylsp = yyls;
-]b4_push_if([],[
 #if YYLTYPE_IS_TRIVIAL
   /* Initialize the default location before parsing starts.  */
   yylloc.first_line   = yylloc.last_line   = ]b4_location_initial_line[;
   yylloc.first_column = yylloc.last_column = ]b4_location_initial_column[;
-#endif])[
-]])
+#endif]])
+])
+[  ]b4_push_if([
+      if (yyps->yynew == 0)
+      {
+       goto gottoken;
+      }
+      yyps->yynew= 0;])
 m4_ifdef([b4_initial_action], [
 m4_pushdef([b4_at_dollar],     [m4_define([b4_at_dollar_used])yylloc])dnl
 m4_pushdef([b4_dollar_dollar], [m4_define([b4_dollar_dollar_used])yylval])dnl
@@ -1194,32 +1183,7 @@ m4_ifdef([b4_dollar_dollar_used],[[  yyv
 ]])dnl
 m4_ifdef([b4_at_dollar_used], [[  yylsp[0] = yylloc;
 ]])dnl
-[  ]b4_push_if([
-       /* Initialize the locals to the current context. */
-       yystate = yyps->yystate;
-       yyn = yyps->yyn;
-       yyresult = yyps->yyresult;
-       yyerrstatus = yyps->yyerrstatus;
-       yytoken = yyps->yytoken;
-
-       yyss = yyps->yyss;
-       yyssp = yyps->yyssp;
-
-       yyvs = yyps->yyvs;
-       yyvsp = yyps->yyvsp;
-
-       ]b4_locations_if([[  /* The location stack.  */
-       yyls = yyps->yyls;
-       yylsp = yyps->yylsp;]])[
-
-       yystacksize = yyps->yystacksize;
-       yyval = yyps->yyval;
-       ]b4_locations_if([yyloc = yyps->yyloc;])[
-      if (yyps->yynew == 0)
-      {
-       goto gottoken;
-      }
-      yyps->yynew= 0;])[
+[
   goto yysetstate;
 
 /*------------------------------------------------------------.
@@ -1326,25 +1290,6 @@ yybackup:
       ]b4_push_if([
        YYDPRINTF ((stderr, "Return for a new token:\n"));
        yyresult = YYPUSH_MORE;
-       /* Initialize the locals to the current context. */
-       yyps->yystate = yystate;
-       yyps->yyn = yyn;
-       yyps->yyerrstatus = yyerrstatus;
-       yyps->yytoken = yytoken;
-
-       yyps->yyss = yyss;
-       yyps->yyssp = yyssp;
-
-       yyps->yyvs = yyvs;
-       yyps->yyvsp = yyvsp;
-
-       ]b4_locations_if([[  /* The location stack.  */
-       yyps->yyls = yyls;
-       yyps->yylsp = yylsp;]])[
-
-       yyps->yystacksize = yystacksize;
-       yyps->yyval = yyval;
-       ]b4_locations_if([yyps->yyloc = yyloc;])[
        goto yypushreturn;
 gottoken:])[
       YYDPRINTF ((stderr, "Reading a token: "));
@@ -1639,7 +1584,6 @@ yyreturn:
   if (yymsg != yymsgbuf)
     YYSTACK_FREE (yymsg);
 #endif
-  ]b4_push_if([yyps->yyresult = YYID (yyresult);])[
   /* Make sure YYID is used.  */
   return YYID (yyresult);
 ]}