gistfile1.txt

diff --git a/mono/metadata/gc-internal.h b/mono/metadata/gc-internal.h
index f975762..cb8fb5a 100644
--- a/mono/metadata/gc-internal.h
+++ b/mono/metadata/gc-internal.h
@@ -74,6 +74,10 @@ void    mono_gc_remove_weak_track_handle (guint32 gchandle) MONO_INTERNAL;
 GSList* mono_gc_remove_weak_track_object (MonoDomain *domain, MonoObject *obj) MONO_INTERNAL;
 #endif
 
+/*Ephemeron functionality*/
+void    mono_gc_ephemeron_array_add (MonoObject *obj) MONO_INTERNAL;
+
+
 MonoBoolean
 GCHandle_CheckCurrentDomain (guint32 gchandle) MONO_INTERNAL;
 
diff --git a/mono/metadata/icall-def.h b/mono/metadata/icall-def.h
index 16c4347..ae90890 100644
--- a/mono/metadata/icall-def.h
+++ b/mono/metadata/icall-def.h
@@ -637,6 +637,10 @@ ICALL_TYPE(PARAMI, "System.Reflection.ParameterInfo", PARAMI_1)
 ICALL(PARAMI_1, "GetMetadataToken", mono_reflection_get_token)
 ICALL(PARAMI_2, "GetTypeModifiers", param_info_get_type_modifiers)
 
+ICALL_TYPE(EPHE, "System.Runtime.CompilerServices.Ephemeron", EPHE_1)
+ICALL(EPHE_1, "register_ephemeron_array", mono_gc_ephemeron_array_add)
+
+
 ICALL_TYPE(RUNH, "System.Runtime.CompilerServices.RuntimeHelpers", RUNH_1)
 ICALL(RUNH_1, "GetObjectValue", ves_icall_System_Runtime_CompilerServices_RuntimeHelpers_GetObjectValue)
 	 /* REMOVEME: no longer needed, just so we dont break things when not needed */
diff --git a/mono/metadata/object.c b/mono/metadata/object.c
index 59a6263..8e546c2 100644
--- a/mono/metadata/object.c
+++ b/mono/metadata/object.c
@@ -633,6 +633,15 @@ compute_class_bitmap (MonoClass *class, gsize *bitmap, int size, int offset, int
 		size = max_size;
 	}
 
+#ifdef HAVE_SGEN_GC
+	/*An Ephemeron cannot be marked by sgen*/
+	if (!static_fields && class->image == mono_defaults.corlib && !strcmp ("Ephemeron", class->name)) {
+		*max_set = 0;
+		memset (bitmap, 0, size / 8);
+		return bitmap;
+	}
+#endif
+
 	for (p = class; p != NULL; p = p->parent) {
 		gpointer iter = NULL;
 		while ((field = mono_class_get_fields (p, &iter))) {
diff --git a/mono/metadata/sgen-gc.c b/mono/metadata/sgen-gc.c
index a0d75b3..8a21402 100644
--- a/mono/metadata/sgen-gc.c
+++ b/mono/metadata/sgen-gc.c
@@ -330,6 +330,7 @@ enum {
 	INTERNAL_MEM_STORE_REMSET,
 	INTERNAL_MEM_MS_TABLES,
 	INTERNAL_MEM_MS_BLOCK_INFO,
+	INTERNAL_MEM_EPHEMERON_LINK,
 	INTERNAL_MEM_MAX
 };
 
@@ -734,6 +735,13 @@ struct _DisappearingLinkHashTable {
 	int num_links;
 };
 
+typedef struct _EphemeronLinkNode EphemeronLinkNode;
+
+struct _EphemeronLinkNode {
+	EphemeronLinkNode *next;
+	void **array;
+};
+
 #define LARGE_INTERNAL_MEM_HEADER_MAGIC	0x7d289f3a
 
 typedef struct _LargeInternalMemHeader LargeInternalMemHeader;
@@ -775,6 +783,8 @@ static FinalizeEntry *critical_fin_list = NULL;
 static DisappearingLinkHashTable minor_disappearing_link_hash;
 static DisappearingLinkHashTable major_disappearing_link_hash;
 
+static EphemeronLinkNode *ephemeron_list;
+
 static int num_ready_finalizers = 0;
 static int no_finalize = 0;
 
@@ -1025,6 +1035,9 @@ void mono_gc_scan_for_specific_ref (MonoObject *key);
 
 static void init_stats (void);
 
+static int ephemerons_in_range (CopyOrMarkObjectFunc copy_func, char *start, char *end);
+static void clear_unreachable_ephemerons (char *start, char *end);
+
 //#define BINARY_PROTOCOL
 #include "sgen-protocol.c"
 #include "sgen-pinning.c"
@@ -1454,8 +1467,8 @@ mono_gc_get_bitmap_for_descr (void *descr, int *numbits)
 		}	\
 	} while (0)
 
-//#include "sgen-major-copying.c"
-#include "sgen-marksweep.c"
+#include "sgen-major-copying.c"
+//#include "sgen-marksweep.c"
 
 static gboolean
 is_xdomain_ref_allowed (gpointer *ptr, char *obj, MonoDomain *domain)
@@ -2827,6 +2840,20 @@ finish_gray_stack (char *start_addr, char *end_addr, int generation)
 	TV_GETTIME (btv);
 	DEBUG (2, fprintf (gc_debug_file, "Finalize queue handling scan for %s generation: %d usecs\n", generation_name (generation), TV_ELAPSED (atv, btv)));
 
+	/*handle ephemerons arrays*/
+	g_assert (gray_object_queue_is_empty ());
+	for (;;) {
+		int done = ephemerons_in_range (copy_func, start_addr, end_addr);
+		drain_gray_stack ();
+		if (done)
+			break;
+	}
+
+	clear_unreachable_ephemerons (start_addr, end_addr);
+
+	DEBUG (2, fprintf (gc_debug_file, "Finalize ephemeron handling scan for %s generation\n", generation_name (generation)));
+
+
 	/*
 	 * handle disappearing links
 	 * Note we do this after checking the finalization queue because if an object
@@ -4199,6 +4226,102 @@ finalize_in_range (CopyOrMarkObjectFunc copy_func, char *start, char *end, int g
 	}
 }
 
+static int
+object_is_reachable (char *object, char *start, char *end)
+{
+	if (object >= start && object < end && !object_is_fin_ready (object))
+		return 1;
+	return major_is_object_live (object);
+}
+
+/* LOCKING: requires that the GC lock is held */
+static void
+clear_unreachable_ephemerons (char *start, char *end)
+{
+	int i;
+	EphemeronLinkNode *current = ephemeron_list;
+
+	while (current) {
+		char *object = REVEAL_POINTER (current->array);
+		/*it has to be alive*/
+		if (!object_is_reachable (object, start, end)) {
+			current = current->next;
+			continue;
+		}
+
+		DEBUG (2, fprintf (gc_debug_file, "Clearing unreachable entries for ephemeron array at %p\n", object));
+		MonoArray *array = (MonoArray*)object;
+		gpointer *ptr = (gpointer*)mono_array_addr_with_size (array, sizeof (mword) * 2, 0);
+		for (i = 0; i < mono_array_length (array); ++i) {
+			char *key = ptr [0];
+			char *value = ptr [1];
+			if (key)
+				DEBUG (2, fprintf (gc_debug_file, "[%d] key %p (%s) value %p (%s)\n", i,
+					key, key && object_is_reachable (key, start, end) ? "reachable" : "unreachable",
+					value, value && object_is_reachable (value, start, end) ? "reachable" : "unreachable"));
+
+
+			if (key && !object_is_reachable (key, start, end)) {
+				ptr [0] = NULL;
+				ptr [1] = NULL;
+			}
+
+			ptr += 2;
+		}
+		current = current->next;
+	}
+}
+
+/* LOCKING: requires that the GC lock is held */
+static int
+ephemerons_in_range (CopyOrMarkObjectFunc copy_func, char *start, char *end)
+{
+	int i;
+	int nothing_marked = 1;
+	EphemeronLinkNode *current = ephemeron_list;
+
+	while (current) {
+		char *object = REVEAL_POINTER (current->array);
+		/*it has to be alive*/
+		if (!object_is_reachable (object, start, end)) {
+			DEBUG (2, fprintf (gc_debug_file, "Ephemeron array at %p is not reachable\n", object));
+			current = current->next;
+			continue;
+		}
+
+		copy_func ((void**)&object);
+		current->array = HIDE_POINTER (object, FALSE);
+
+		DEBUG (2, fprintf (gc_debug_file, "Processing Ephemeron array at %p\n", object));
+		MonoArray *array = (MonoArray*)object;
+		gpointer *ptr = (gpointer*)mono_array_addr_with_size (array, sizeof (mword) * 2, 0);
+		for (i = 0; i < mono_array_length (array); ++i) {
+			char *key = ptr [0];
+			char *value = ptr [1];
+			if (key)
+				DEBUG (2, fprintf (gc_debug_file, "[%d] key %p (%s) value %p (%s)\n", i,
+					key, key && object_is_reachable (key, start, end) ? "reachable" : "unreachable",
+					value, value && object_is_reachable (value, start, end) ? "reachable" : "unreachable"));
+
+
+			if (key && object_is_reachable (key, start, end)) {
+				copy_func (ptr); //move the key
+				if (value) {
+					if (!object_is_reachable (value, start, end)) {
+						nothing_marked = 0;
+						copy_func (ptr + 1); //;move the value
+					}
+				}
+			}
+
+			ptr += 2;
+		}
+		current = current->next;
+	}
+	DEBUG (2, fprintf (gc_debug_file, "Ephemeron run finished. Is it done %d\n", nothing_marked));
+	return nothing_marked;
+}
+
 /* LOCKING: requires that the GC lock is held */
 static void
 null_link_in_range (CopyOrMarkObjectFunc copy_func, char *start, char *end, int generation)
@@ -4537,6 +4660,18 @@ mono_gc_register_disappearing_link (MonoObject *obj, void **link, gboolean track
 	}
 }
 
+/* LOCKING: assumes the GC lock is held */
+void
+mono_gc_register_ephemeron_array (MonoObject *obj)
+{
+	EphemeronLinkNode *node = get_internal_mem (sizeof (EphemeronLinkNode), INTERNAL_MEM_EPHEMERON_LINK);
+	node->array = HIDE_POINTER (obj, FALSE);
+	node->next = ephemeron_list;
+	ephemeron_list = node;
+
+	DEBUG (2, fprintf (gc_debug_file, "Registered ephemeron array %p\n", obj));
+}
+
 int
 mono_gc_invoke_finalizers (void)
 {
@@ -6564,6 +6699,14 @@ mono_gc_weak_link_get (void **link_addr)
 	return (MonoObject*) REVEAL_POINTER (*link_addr);
 }
 
+void
+mono_gc_ephemeron_array_add (MonoObject *obj)
+{
+	LOCK_GC;
+	mono_gc_register_ephemeron_array (obj);
+	UNLOCK_GC;
+}
+
 void*
 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
 {