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

#ifndef UPDATES_H
#define UPDATES_H

#ifndef CMINUSMINUS
#include "BeginPrivate.h"
#endif

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

/* 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 IND
* 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)) { \
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:
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 updateWithIndirection(p1, p2, and_then) \
W_ bd; \
\
DEBUG_FILL_SLOP(p1); \
LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(p1); \
StgInd_indirectee(p1) = p2; \
prim %write_barrier() []; \
SET_INFO(p1, stg_BLACKHOLE_info); \
LDV_RECORD_CREATE(p1); \
bd = Bdescr(p1); \
if (bdescr_gen_no(bd) != 0 :: bits16) { \
recordMutableCap(p1, TO_W_(bdescr_gen_no(bd)), R1); \
TICK_UPD_OLD_IND(); \
and_then; \
} else { \
TICK_UPD_NEW_IND(); \
and_then; \
}

#else /* !CMINUSMINUS */

INLINE_HEADER void updateWithIndirection (Capability *cap,
                                          StgClosure *p1,
                                          StgClosure *p2)
{
    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();
    SET_INFO(p1, &stg_BLACKHOLE_info);
    LDV_RECORD_CREATE(p1);
    bd = Bdescr((StgPtr)p1);
    if (bd->gen_no != 0) {
        recordMutableCap(p1, cap, bd->gen_no);
        TICK_UPD_OLD_IND();
    } else {
        TICK_UPD_NEW_IND();
    }
}

#endif /* CMINUSMINUS */

#ifndef CMINUSMINUS
#include "EndPrivate.h"
#endif

#endif /* UPDATES_H */
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