/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 1998-2004
 *
 * Performing updates.
 *
 * ---------------------------------------------------------------------------*/

#ifndef UPDATES_H
#define UPDATES_H

#ifndef CMINUSMINUS
BEGIN_RTS_PRIVATE
#endif

/* -----------------------------------------------------------------------------
   Updates

   We have two layers of update macros.  The top layer, UPD_IND() and
   friends perform all the work of an update.  In detail:

      - if the closure being updated is a blocking queue, then all the
        threads waiting on the blocking queue are updated.

      - then the lower level updateWithIndirection() macro is invoked 
        to actually replace the closure with an indirection (see below).

   -------------------------------------------------------------------------- */

#  define SEMI ;
# define UPD_IND(updclosure, heapptr) \
   UPD_REAL_IND(updclosure,INFO_PTR(stg_IND_info),heapptr,SEMI)
# define UPD_SPEC_IND(updclosure, ind_info, heapptr, and_then) \
   UPD_REAL_IND(updclosure,ind_info,heapptr,and_then)

/* These macros have to work in both C and C--, so here's the
 * impedance matching:
 */
#ifdef CMINUSMINUS
#define BLOCK_BEGIN
#define BLOCK_END
#define INFO_PTR(info)      info
#else
#define BLOCK_BEGIN         {
#define BLOCK_END           }
#define INFO_PTR(info)      &info
#define StgBlockingQueue_blocking_queue(closure) \
    (((StgBlockingQueue *)closure)->blocking_queue)
#endif

/* krc: there used to be an UPD_REAL_IND and an
   UPD_PERM_IND, the latter of which was used for
   ticky and cost-centre profiling.
   for now, we just have UPD_REAL_IND. */
#define UPD_REAL_IND(updclosure, ind_info, heapptr, and_then)	\
        BLOCK_BEGIN						\
	updateWithIndirection(ind_info,				\
			      updclosure,			\
			      heapptr,				\
			      and_then);			\
	BLOCK_END

/* -----------------------------------------------------------------------------
   Awaken any threads waiting on a blocking queue (BLACKHOLE_BQ).
   -------------------------------------------------------------------------- */

/* -----------------------------------------------------------------------------
   Updates: lower-level macros which update a closure with an
   indirection to another closure.

   There are several variants of this code.

       PROFILING:
   -------------------------------------------------------------------------- */

/* LDV profiling:
 * We call LDV_recordDead_FILL_SLOP_DYNAMIC(p1) regardless of the generation in 
 * which p1 resides.
 *
 * Note: 
 *   After all, we do *NOT* need to call LDV_RECORD_CREATE() for both IND and 
 *   IND_OLDGEN closures because they are inherently used. But, it corrupts
 *   the invariants that every closure keeps its creation time in the profiling
 *  field. So, we call LDV_RECORD_CREATE().
 */

/* In the DEBUG case, we also zero out the slop of the old closure,
 * so that the sanity checker can tell where the next closure is.
 *
 * Two important invariants: we should never try to update a closure
 * to point to itself, and the closure being updated should not
 * already have been updated (the mutable list will get messed up
 * otherwise).
 *
 * NB. We do *not* do this in THREADED_RTS mode, because when we have the
 * possibility of multiple threads entering the same closure, zeroing
 * the slop in one of the threads would have a disastrous effect on
 * the other (seen in the wild!).
 */
#ifdef CMINUSMINUS

#define FILL_SLOP(p)							\
  W_ inf;								\
  W_ sz;								\
  W_ i;									\
  inf = %GET_STD_INFO(p);						\
  if (%INFO_TYPE(inf) != HALF_W_(BLACKHOLE)				\
	&& %INFO_TYPE(inf) != HALF_W_(CAF_BLACKHOLE)) {			\
      if (%INFO_TYPE(inf) == HALF_W_(THUNK_SELECTOR)) {			\
	  sz = BYTES_TO_WDS(SIZEOF_StgSelector_NoThunkHdr);		\
     } else {								\
          if (%INFO_TYPE(inf) == HALF_W_(AP_STACK)) {			\
              sz = StgAP_STACK_size(p) + BYTES_TO_WDS(SIZEOF_StgAP_STACK_NoThunkHdr); \
          } else {							\
              if (%INFO_TYPE(inf) == HALF_W_(AP)) {			\
	          sz = TO_W_(StgAP_n_args(p)) +  BYTES_TO_WDS(SIZEOF_StgAP_NoThunkHdr);	\
              } else {							\
                  sz = TO_W_(%INFO_PTRS(inf)) + TO_W_(%INFO_NPTRS(inf)); \
	      }								\
          }								\
      }									\
      i = 0;								\
      for:								\
        if (i < sz) {							\
          StgThunk_payload(p,i) = 0;					\
          i = i + 1;							\
          goto for;							\
        }								\
  }

#else /* !CMINUSMINUS */

INLINE_HEADER void
FILL_SLOP(StgClosure *p)
{						
    StgInfoTable *inf = get_itbl(p);		
    nat i, sz;

    switch (inf->type) {
    case BLACKHOLE:
    case CAF_BLACKHOLE:
	goto no_slop;
	// we already filled in the slop when we overwrote the thunk
	// with BLACKHOLE, and also an evacuated BLACKHOLE is only the
	// size of an IND.
    case THUNK_SELECTOR:
	sz = sizeofW(StgSelector) - sizeofW(StgThunkHeader);
	break;
    case AP:
	sz = ((StgAP *)p)->n_args + sizeofW(StgAP) - sizeofW(StgThunkHeader);
	break;
    case AP_STACK:
	sz = ((StgAP_STACK *)p)->size + sizeofW(StgAP_STACK) - sizeofW(StgThunkHeader);
	break;
    default:
	sz = inf->layout.payload.ptrs + inf->layout.payload.nptrs;
        break;
    }
    for (i = 0; i < sz; i++) {
	((StgThunk *)p)->payload[i] = 0;
    }
no_slop:
    ;
}

#endif /* CMINUSMINUS */

#if !defined(DEBUG) || defined(THREADED_RTS)
#define DEBUG_FILL_SLOP(p) /* do nothing */
#else
#define DEBUG_FILL_SLOP(p) FILL_SLOP(p)
#endif

/* We have two versions of this macro (sadly), one for use in C-- code,
 * and the other for C.
 *
 * The and_then argument is a performance hack so that we can paste in
 * the continuation code directly.  It helps shave a couple of
 * instructions off the common case in the update code, which is
 * worthwhile (the update code is often part of the inner loop).
 * (except that gcc now appears to common up this code again and
 * invert the optimisation.  Grrrr --SDM).
 */
#ifdef CMINUSMINUS
#define generation(n) (W_[generations] + n*SIZEOF_generation)
#define updateWithIndirection(ind_info, p1, p2, and_then)	\
    W_ bd;							\
								\
    DEBUG_FILL_SLOP(p1);					\
    LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(p1);			\
    StgInd_indirectee(p1) = p2;					\
    prim %write_barrier() [];					\
    bd = Bdescr(p1);						\
    if (bdescr_gen_no(bd) != 0 :: CInt) {			\
      recordMutableCap(p1, TO_W_(bdescr_gen_no(bd)), R1);  	\
      SET_INFO(p1, stg_IND_OLDGEN_info);			\
      LDV_RECORD_CREATE(p1);					\
      TICK_UPD_OLD_IND();					\
      and_then;							\
    } else {							\
      SET_INFO(p1, ind_info);					\
      LDV_RECORD_CREATE(p1);					\
      TICK_UPD_NEW_IND();					\
      and_then;							\
  }
#else
#define updateWithIndirection(ind_info, p1, p2, and_then)	\
  {								\
    bdescr *bd;							\
								\
    ASSERT( (P_)p1 != (P_)p2 );                                 \
    /* not necessarily true: ASSERT( !closure_IND(p1) ); */     \
    /* occurs in RaiseAsync.c:raiseAsync() */                   \
    DEBUG_FILL_SLOP(p1);					\
    LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(p1);			\
    ((StgInd *)p1)->indirectee = p2;				\
    write_barrier();						\
    bd = Bdescr((P_)p1);					\
    if (bd->gen_no != 0) {					\
      recordMutableGenLock(p1, bd->gen_no);			\
      SET_INFO(p1, &stg_IND_OLDGEN_info);			\
      TICK_UPD_OLD_IND();					\
      and_then;							\
    } else {							\
      SET_INFO(p1, ind_info);					\
      LDV_RECORD_CREATE(p1);					\
      TICK_UPD_NEW_IND();					\
      and_then;							\
    }								\
  }
#endif /* CMINUSMINUS */

#ifndef CMINUSMINUS
END_RTS_PRIVATE
#endif

#endif /* UPDATES_H */