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/*
* sgen-minor-copy-object.h: Copy functions for nursery collections.
*
* Copyright 2001-2003 Ximian, Inc
* Copyright 2003-2010 Novell, Inc.
* Copyright (C) 2012 Xamarin Inc
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License 2.0 as published by the Free Software Foundation;
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License 2.0 along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#define collector_pin_object(obj, queue) sgen_pin_object (obj, queue);
#define COLLECTOR_SERIAL_ALLOC_FOR_PROMOTION alloc_for_promotion
#define COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION par_alloc_for_promotion

extern long long stat_nursery_copy_object_failed_to_space; /* from sgen-gc.c */

#include "sgen-copy-object.h"

/*
* This is how the copying happens from the nursery to the old generation.
* We assume that at this time all the pinned objects have been identified and
* marked as such.
* We run scan_object() for each pinned object so that each referenced
* objects if possible are copied. The new gray objects created can have
* scan_object() run on them right away, too.
* Then we run copy_object() for the precisely tracked roots. At this point
* all the roots are either gray or black. We run scan_object() on the gray
* objects until no more gray objects are created.
* At the end of the process we walk again the pinned list and we unmark
* the pinned flag. As we go we also create the list of free space for use
* in the next allocation runs.
*
* We need to remember objects from the old generation that point to the new one
* (or just addresses?).
*
* copy_object could be made into a macro once debugged (use inline for now).
*/

#ifdef _MSC_VER
static __forceinline void
#else
static inline void __attribute__((always_inline))
#endif
SERIAL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
{
char *forwarded;
char *obj = *obj_slot;

SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy from a %d generation collection", current_collection_generation);

HEAVY_STAT (++stat_copy_object_called_nursery);

if (!sgen_ptr_in_nursery (obj)) {
HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
return;
}

SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);

/*
* Before we can copy the object we must make sure that we are
* allowed to, i.e. that the object not pinned, not already
* forwarded or belongs to the nursery To Space.
*/

if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
SGEN_LOG (9, " (already forwarded to %p)", forwarded);
HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
*obj_slot = forwarded;
return;
}
if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
SGEN_LOG (9, " (pinned, no change)");
HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
return;
}

#ifndef SGEN_SIMPLE_NURSERY
if (sgen_nursery_is_to_space (obj)) {
SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
SGEN_LOG (9, " (tospace, no change)");
HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
return;
}
#endif

HEAVY_STAT (++stat_objects_copied_nursery);

*obj_slot = copy_object_no_checks (obj, queue);
}

/*
* SERIAL_COPY_OBJECT_FROM_OBJ:
*
* Similar to SERIAL_COPY_OBJECT, but assumes that OBJ_SLOT is part of an object, so it handles global remsets as well.
*/
#ifdef _MSC_VER
static __forceinline void
#else
static inline void __attribute__((always_inline))
#endif
SERIAL_COPY_OBJECT_FROM_OBJ (void **obj_slot, SgenGrayQueue *queue)
{
char *forwarded;
char *obj = *obj_slot;
void *copy;

SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy-from-obj from a %d generation collection", current_collection_generation);

HEAVY_STAT (++stat_copy_object_called_nursery);

if (!sgen_ptr_in_nursery (obj)) {
HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
return;
}

SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);

/*
* Before we can copy the object we must make sure that we are
* allowed to, i.e. that the object not pinned, not already
* forwarded or belongs to the nursery To Space.
*/

if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
SGEN_LOG (9, " (already forwarded to %p)", forwarded);
HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
*obj_slot = forwarded;
#ifndef SGEN_SIMPLE_NURSERY
if (G_UNLIKELY (sgen_ptr_in_nursery (forwarded) && !sgen_ptr_in_nursery (obj_slot)))
sgen_add_to_global_remset (obj_slot, forwarded);
#endif
return;
}
if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
SGEN_LOG (9, " (pinned, no change)");
HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
if (!sgen_ptr_in_nursery (obj_slot))
sgen_add_to_global_remset (obj_slot, obj);
return;
}

#ifndef SGEN_SIMPLE_NURSERY
if (sgen_nursery_is_to_space (obj)) {
SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
SGEN_LOG (9, " (tospace, no change)");
HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);

/*
* FIXME:
*
* The card table scanning code sometimes clears cards
* that have just been set for a global remset. In
* the split nursery the following situation can
* occur:
*
* Let's say object A starts in card C but continues
* into C+1. Within A, at offset O there's a
* reference to a new nursery object X. A+O is in
* card C+1. Now card C is scanned, and as part of
* it, object A. The reference at A+O is processed by
* copying X into nursery to-space at Y. Since it's
* still in the nursery, a global remset must be added
* for A+O, so card C+1 is marked. Now, however, card
* C+1 is scanned, which means that it's cleared
* first. This wouldn't be terribly bad if reference
* A+O were re-scanned and the global remset re-added,
* but since the reference points to to-space, that
* doesn't happen, and C+1 remains cleared: the remset
* is lost.
*
* There's at least two ways to fix this. The easy
* one is to re-add the remset on the re-scan. This
* is that - the following two lines of code.
*
* The proper solution appears to be to first make a
* copy of the cards before scanning a block, then to
* clear all the cards and scan from the copy, so no
* remsets will be overwritten. Scanning objects at
* most once would be the icing on the cake.
*/
if (!sgen_ptr_in_nursery (obj_slot))
sgen_add_to_global_remset (obj_slot, obj);

return;
}
#endif

HEAVY_STAT (++stat_objects_copied_nursery);

copy = copy_object_no_checks (obj, queue);
*obj_slot = copy;
#ifndef SGEN_SIMPLE_NURSERY
if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
sgen_add_to_global_remset (obj_slot, copy);
#else
/* copy_object_no_checks () can return obj on OOM */
if (G_UNLIKELY (obj == copy)) {
if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
sgen_add_to_global_remset (obj_slot, copy);
}
#endif
}

static void
PARALLEL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
{
char *obj = *obj_slot;
mword vtable_word, objsize;
MonoVTable *vt;
void *destination;
gboolean has_references;

SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-par-copy from a %d generation collection", current_collection_generation);

HEAVY_STAT (++stat_copy_object_called_nursery);

if (!sgen_ptr_in_nursery (obj)) {
HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
return;
}

vtable_word = *(mword*)obj;
vt = (MonoVTable*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);

/*
* Before we can copy the object we must make sure that we are
* allowed to, i.e. that the object not pinned, not already
* forwarded and not in the nursery To Space.
*/

if (vtable_word & SGEN_FORWARDED_BIT) {
HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
*obj_slot = vt;
return;
}
if (vtable_word & SGEN_PINNED_BIT) {
HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
return;
}

if (sgen_nursery_is_to_space (obj)) {
HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
return;
}

HEAVY_STAT (++stat_objects_copied_nursery);

objsize = SGEN_ALIGN_UP (sgen_par_object_get_size (vt, (MonoObject*)obj));
has_references = SGEN_VTABLE_HAS_REFERENCES (vt);

destination = COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION (vt, obj, objsize, has_references);

if (G_UNLIKELY (!destination)) {
sgen_parallel_pin_or_update (obj_slot, obj, vt, queue);
return;
}

*(MonoVTable**)destination = vt;

if (SGEN_CAS_PTR ((void*)obj, (void*)((mword)destination | SGEN_FORWARDED_BIT), vt) == vt) {
par_copy_object_no_checks (destination, vt, obj, objsize, has_references ? queue : NULL);
obj = destination;
*obj_slot = obj;
} else {
/* FIXME: unify with code in major_copy_or_mark_object() */

/* FIXME: Give destination back to the allocator. */
/*The major collector only needs the first word zeroed and nursery requires all bits to be. */
if (!sgen_ptr_in_nursery (destination))
*(void**)destination = NULL;
else
memset (destination, 0, objsize);

vtable_word = *(mword*)obj;
g_assert (vtable_word & SGEN_FORWARDED_BIT);

obj = (void*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);

*obj_slot = obj;

HEAVY_STAT (++stat_slots_allocated_in_vain);
}
}

#define FILL_MINOR_COLLECTOR_COPY_OBJECT(collector) do { \
(collector)->serial_ops.copy_or_mark_object = SERIAL_COPY_OBJECT; \
(collector)->parallel_ops.copy_or_mark_object = PARALLEL_COPY_OBJECT; \
} while (0)
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