adding GGC events for plugins.

[Basile STARYNKEVITCH <basile at starynkevitch dot net>]

Hello All

The attached patch to trunk rev147426 add some events in plugins for GGC 
(the GCC garbage collector).

In particular, it provides the following features to future plugins:

The plugin events PLUGIN_GGC_START and PLUGIN_GGC_END are called by 
ggc_collect at start and at end of garbage collection.

The plugin event PLUGIN_GGC_MARKING is called by ggc_mark_roots and 
could be used by the plugins which need to mark some extra data.

The function ggc_register_root_tab is added to register extra GGC roots, 
and can be used by plugins using the plugin event PLUGIN_REGISTER_GGC_ROOTS.
Of course, what is missing is some extension to gengtype to generate the 
marking routines; together, that would enable plugins to have their own 
GTY-ed stuff.

A real-case scenario for these would be to make the MELT branch a 
mega-plugin itself. I documented on the wiki on 
http://gcc.gnu.org/wiki/memory%20management%20in%20MELT why all these 
features (or something equivalent) are essential for making MELT a 
plugin. This page also explains precisely the memory management in MELT 
(which I believe few people understand in details).

For people interested in MELT, I am also writing on the wiki some 
tutorial pages.

Is the attached patch  ok for trunk.?


Respectful regards.

--
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
8, rue de la Faiencerie, 92340 Bourg La Reine, France
*** opinions {are only mines, sont seulement les miennes} ***

Index: gcc/doc/plugins.texi
===================================================================
--- gcc/doc/plugins.texi	(revision 147426)
+++ gcc/doc/plugins.texi	(working copy)
@@ -9,7 +9,7 @@
 
 @section Loading Plugins
 
-Plugins are supported on platforms that support @option{-ld
+Plugins are supported on platforms that support @option{-ldl
 -rdynamic}.  They are loaded by the compiler using @code{dlopen}
 and invoked at pre-determined locations in the compilation
 process.
@@ -71,6 +71,9 @@
   PLUGIN_FINISH_UNIT,           /* Useful for summary processing.  */
   PLUGIN_CXX_CP_PRE_GENERICIZE, /* Allows to see low level AST in C++ FE.  */
   PLUGIN_FINISH,                /* Called before GCC exits.  */
+  PLUGIN_GGC_START,		/* Called at start of Gcc Garbage Collection */
+  PLUGIN_GGC_MARKING,		/* To extend the GGC marking */
+  PLUGIN_GGC_END,		/* Called at end of GGC */
   PLUGIN_EVENT_LAST             /* Dummy event used for indexing callback
                                    array.  */
 @};
Index: gcc/ggc.h
===================================================================
--- gcc/ggc.h	(revision 147426)
+++ gcc/ggc.h	(working copy)
@@ -1,7 +1,8 @@
 /* Garbage collection for the GNU compiler.
-   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
-   Free Software Foundation, Inc.
 
+   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007,
+   2008, 2009 Free Software Foundation, Inc.
+
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify it under
@@ -270,6 +271,9 @@
    function is called, not during allocations.  */
 extern void ggc_collect	(void);
 
+/* Register an additional root tab. This can be useful to plugins */
+extern void ggc_register_root_tab (const struct ggc_root_tab*);
+
 /* Return the number of bytes allocated at the indicated address.  */
 extern size_t ggc_get_size (const void *);
 
Index: gcc/gcc-plugin.h
===================================================================
--- gcc/gcc-plugin.h	(revision 147426)
+++ gcc/gcc-plugin.h	(working copy)
@@ -29,6 +29,10 @@
   PLUGIN_CXX_CP_PRE_GENERICIZE, /* Allows to see low level AST in C++ FE.  */
   PLUGIN_FINISH,                /* Called before GCC exits.  */
   PLUGIN_INFO,                  /* Information about the plugin */
+  PLUGIN_GGC_START,		/* Called at start of Gcc Garbage Collection */
+  PLUGIN_GGC_MARKING,		/* To extend the GGC marking */
+  PLUGIN_GGC_END,		/* Called at end of GGC */
+  PLUGIN_REGISTER_GGC_ROOTS,	/* register an extra GGC root table */
   PLUGIN_EVENT_LAST             /* Dummy event used for indexing callback
                                    array.  */
 };
Index: gcc/ggc-common.c
===================================================================
--- gcc/ggc-common.c	(revision 147426)
+++ gcc/ggc-common.c	(working copy)
@@ -30,6 +30,7 @@
 #include "params.h"
 #include "hosthooks.h"
 #include "hosthooks-def.h"
+#include "plugin.h"
 
 #ifdef HAVE_SYS_RESOURCE_H
 # include <sys/resource.h>
@@ -86,6 +87,37 @@
   return 1;
 }
 
+
+/* extra table of dynamically registers root tab, its count and allocated length */
+static const struct ggc_root_tab**extra_root_tab;
+static size_t extra_root_count;
+static size_t extra_root_length;
+
+void 
+ggc_register_root_tab (const struct ggc_root_tab* rt)
+{
+  if (!rt)
+    return;
+  if (!extra_root_tab) 
+    {
+      extra_root_length = 32;
+      extra_root_count = 0;
+      extra_root_tab = XNEWVEC (const struct ggc_root_tab*, extra_root_length);
+      memset(extra_root_tab, 0, sizeof(extra_root_tab[0]) * extra_root_length);
+    }
+  else if (extra_root_count >= extra_root_length)
+    {
+      const struct ggc_root_tab** oldtab = extra_root_tab;
+      size_t oldlen = extra_root_length;
+      extra_root_length *= 2;
+      extra_root_tab = XNEWVEC (const struct ggc_root_tab*, extra_root_length);
+      memcpy (extra_root_tab, oldtab, sizeof(extra_root_tab[0]) * extra_root_count);
+      memset (extra_root_tab + extra_root_count, 0, 
+	      sizeof(extra_root_tab[0]) * (extra_root_length - extra_root_count));
+    };
+  extra_root_tab[extra_root_count++] = rt;
+}
+
 /* Iterate through all registered roots and mark each element.  */
 
 void
@@ -106,6 +138,18 @@
       for (i = 0; i < rti->nelt; i++)
 	(*rti->cb)(*(void **)((char *)rti->base + rti->stride * i));
 
+  if (extra_root_tab)
+    {
+      i = 0;
+      for (i=0; i<extra_root_count; i++) 
+	{
+	  rt = extra_root_tab[i];
+	  for (rti = *rt; rti->base != NULL; rti++)
+	    for (i = 0; i < rti->nelt; i++)
+	      (*rti->cb)(*(void **)((char *)rti->base + rti->stride * i));
+	}
+    }
+
   if (ggc_protect_identifiers)
     ggc_mark_stringpool ();
 
@@ -123,6 +167,10 @@
 
   if (! ggc_protect_identifiers)
     ggc_purge_stringpool ();
+
+  /* some plugins may need to register their routine mark additional
+     data */
+  invoke_plugin_callbacks (PLUGIN_GGC_MARKING, NULL);
 }
 
 /* Allocate a block of memory, then clear it.  */
Index: gcc/ggc-zone.c
===================================================================
--- gcc/ggc-zone.c	(revision 147426)
+++ gcc/ggc-zone.c	(working copy)
@@ -2029,6 +2029,9 @@
 	}
     }
 
+  /* Some plugins may need to know when GGC is really starting */
+  invoke_plugin_callbacks (PLUGIN_GGC_START, NULL);
+
   /* Start by possibly collecting the main zone.  */
   main_zone.was_collected = false;
   marked |= ggc_collect_1 (&main_zone, true);
@@ -2093,6 +2096,9 @@
 	}
     }
 
+  /* Some plugins may need to know when GGC ended */
+  invoke_plugin_callbacks (PLUGIN_GGC_END, NULL);
+
   timevar_pop (TV_GC);
 }
 
Index: gcc/ggc-page.c
===================================================================
--- gcc/ggc-page.c	(revision 147426)
+++ gcc/ggc-page.c	(working copy)
@@ -31,6 +31,7 @@
 #include "timevar.h"
 #include "params.h"
 #include "tree-flow.h"
+#include "plugin.h"
 
 /* Prefer MAP_ANON(YMOUS) to /dev/zero, since we don't need to keep a
    file open.  Prefer either to valloc.  */
@@ -1937,6 +1938,9 @@
   /* Indicate that we've seen collections at this context depth.  */
   G.context_depth_collections = ((unsigned long)1 << (G.context_depth + 1)) - 1;
 
+  /* Some plugins may need to know when GGC is really starting */
+  invoke_plugin_callbacks (PLUGIN_GGC_START, NULL);
+
   clear_marks ();
   ggc_mark_roots ();
 #ifdef GATHER_STATISTICS
@@ -1948,6 +1952,9 @@
 
   G.allocated_last_gc = G.allocated;
 
+  /* Some plugins may need to know when GGC ended */
+  invoke_plugin_callbacks (PLUGIN_GGC_END, NULL);
+
   timevar_pop (TV_GC);
 
   if (!quiet_flag)
Index: gcc/plugin.c
===================================================================
--- gcc/plugin.c	(revision 147426)
+++ gcc/plugin.c	(working copy)
@@ -38,6 +38,8 @@
 #include "intl.h"
 #include "plugin.h"
 #include "timevar.h"
+#include "ggc.h"
+
 #ifdef ENABLE_PLUGIN
 #include "plugin-version.h"
 #endif
@@ -51,6 +53,10 @@
   "PLUGIN_CXX_CP_PRE_GENERICIZE",
   "PLUGIN_FINISH",
   "PLUGIN_INFO",
+  "PLUGIN_GGC_START",
+  "PLUGIN_GGC_MARKING",
+  "PLUGIN_GGC_END",
+  "PLUGIN_REGISTER_GGC_ROOTS",
   "PLUGIN_EVENT_LAST"
 };
 
@@ -490,9 +496,15 @@
       case PLUGIN_INFO:
 	register_plugin_info (plugin_name, (struct plugin_info *) user_data);
 	break;
+      case PLUGIN_REGISTER_GGC_ROOTS:
+        ggc_register_root_tab ((const struct ggc_root_tab*) user_data);
+	break;
       case PLUGIN_FINISH_TYPE:
       case PLUGIN_FINISH_UNIT:
       case PLUGIN_CXX_CP_PRE_GENERICIZE:
+      case PLUGIN_GGC_START:
+      case PLUGIN_GGC_MARKING:
+      case PLUGIN_GGC_END:
       case PLUGIN_FINISH:
         {
           struct callback_info *new_callback;
@@ -535,6 +547,9 @@
       case PLUGIN_FINISH_UNIT:
       case PLUGIN_CXX_CP_PRE_GENERICIZE:
       case PLUGIN_FINISH:
+      case PLUGIN_GGC_START:
+      case PLUGIN_GGC_MARKING:
+      case PLUGIN_GGC_END:
         {
           /* Iterate over every callback registered with this event and
              call it.  */
@@ -546,6 +561,7 @@
 
       case PLUGIN_PASS_MANAGER_SETUP:
       case PLUGIN_EVENT_LAST:
+      case PLUGIN_REGISTER_GGC_ROOTS:
       default:
         gcc_assert (false);
     }
Index: gcc/Makefile.in
===================================================================
--- gcc/Makefile.in	(revision 147426)
+++ gcc/Makefile.in	(working copy)
@@ -2481,7 +2481,7 @@
    gt-passes.h $(DF_H) $(PREDICT_H)
 
 plugin.o : plugin.c $(PLUGIN_H) $(CONFIG_H) $(SYSTEM_H) coretypes.h \
-   $(TOPLEV_H) $(TREE_H) $(TREE_PASS_H) intl.h $(PLUGIN_VERSION_H)
+   $(TOPLEV_H) $(TREE_H) $(TREE_PASS_H) intl.h $(PLUGIN_VERSION_H) $(GGC_H)
 
 main.o : main.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(TOPLEV_H)
 

2009-05-12  Basile Starynkevitch  <basile@starynkevitch.net>
	* gcc/doc/plugins.texi: Mentioned PLUGIN_GGC_START,
	PLUGIN_GGC_MARKING, PLUGIN_GGC_END.
	* gcc/ggc.h: Declared ggc_register_root_tab.
	* gcc/gcc-plugin.h (enum plugin_event): Added PLUGIN_GGC_START,
	PLUGIN_GGC_MARKING, PLUGIN_GGC_END, PLUGIN_REGISTER_GGC_ROOTS.
	* gcc/ggc-common.c: including "plugin.h".
	(extra_root_tab, extra_root_count, extra_root_length): new static
	variables.
	(ggc_register_root_tab): added new function.
	(ggc_mark_roots): scan the extra_root_tab if needed, and do the
	PLUGIN_GGC_MARKING callback.
	* gcc/ggc-zone.c (ggc_collect): call PLUGIN_GGC_START &
	PLUGIN_GGC_END callbacks.
	* gcc/ggc-page.c (ggc_collect): likewise.
	* gcc/plugin.c (plugin_event_name, register_callback)
	(invoke_plugin_callbacks): handle PLUGIN_GGC_START,
	PLUGIN_GGC_MARKING, PLUGIN_GGC_END, PLUGIN_REGISTER_GGC_ROOTS.
	* gcc/Makefile.in: plugin.o also depends upon $(GGC_H).