rts/Updates.h

   1 /* -----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 1998-2004
   4  *
   5  * Performing updates.
   6  *
   7  * ---------------------------------------------------------------------------*/
   8
   9 #ifndef UPDATES_H
  10 #define UPDATES_H
  11
  12 #ifndef CMINUSMINUS
  13 BEGIN_RTS_PRIVATE
  14 #endif
  15
  16 /* -----------------------------------------------------------------------------
  17    Updates
  18    -------------------------------------------------------------------------- */
  19
  20 /* LDV profiling:
  21  * We call LDV_recordDead_FILL_SLOP_DYNAMIC(p1) regardless of the generation in
  22  * which p1 resides.
  23  *
  24  * Note:
  25  *   After all, we do *NOT* need to call LDV_RECORD_CREATE() for both IND and
  26  *   IND_OLDGEN closures because they are inherently used. But, it corrupts
  27  *   the invariants that every closure keeps its creation time in the profiling
  28  *  field. So, we call LDV_RECORD_CREATE().
  29  */
  30
  31 /* In the DEBUG case, we also zero out the slop of the old closure,
  32  * so that the sanity checker can tell where the next closure is.
  33  *
  34  * Two important invariants: we should never try to update a closure
  35  * to point to itself, and the closure being updated should not
  36  * already have been updated (the mutable list will get messed up
  37  * otherwise).
  38  *
  39  * NB. We do *not* do this in THREADED_RTS mode, because when we have the
  40  * possibility of multiple threads entering the same closure, zeroing
  41  * the slop in one of the threads would have a disastrous effect on
  42  * the other (seen in the wild!).
  43  */
  44 #ifdef CMINUSMINUS
  45
  46 #define FILL_SLOP(p)                                                    \
  47   W_ inf;                                                               \
  48   W_ sz;                                                                \
  49   W_ i;                                                                 \
  50   inf = %GET_STD_INFO(p);                                               \
  51   if (%INFO_TYPE(inf) != HALF_W_(BLACKHOLE)) {                          \
  52       if (%INFO_TYPE(inf) == HALF_W_(THUNK_SELECTOR)) {                 \
  53           sz = BYTES_TO_WDS(SIZEOF_StgSelector_NoThunkHdr);             \
  54      } else {                                                           \
  55           if (%INFO_TYPE(inf) == HALF_W_(AP_STACK)) {                   \
  56               sz = StgAP_STACK_size(p) + BYTES_TO_WDS(SIZEOF_StgAP_STACK_NoThunkHdr); \
  57           } else {                                                      \
  58               if (%INFO_TYPE(inf) == HALF_W_(AP)) {                     \
  59                   sz = TO_W_(StgAP_n_args(p)) +  BYTES_TO_WDS(SIZEOF_StgAP_NoThunkHdr); \
  60               } else {                                                  \
  61                   sz = TO_W_(%INFO_PTRS(inf)) + TO_W_(%INFO_NPTRS(inf)); \
  62               }                                                         \
  63           }                                                             \
  64       }                                                                 \
  65       i = 0;                                                            \
  66       for:                                                              \
  67         if (i < sz) {                                                   \
  68           StgThunk_payload(p,i) = 0;                                    \
  69           i = i + 1;                                                    \
  70           goto for;                                                     \
  71         }                                                               \
  72   }
  73
  74 #else /* !CMINUSMINUS */
  75
  76 INLINE_HEADER void
  77 FILL_SLOP(StgClosure *p)
  78 {
  79     StgInfoTable *inf = get_itbl(p);
  80     nat i, sz;
  81
  82     switch (inf->type) {
  83     case BLACKHOLE:
  84         goto no_slop;
  85         // we already filled in the slop when we overwrote the thunk
  86         // with BLACKHOLE, and also an evacuated BLACKHOLE is only the
  87         // size of an IND.
  88     case THUNK_SELECTOR:
  89         sz = sizeofW(StgSelector) - sizeofW(StgThunkHeader);
  90         break;
  91     case AP:
  92         sz = ((StgAP *)p)->n_args + sizeofW(StgAP) - sizeofW(StgThunkHeader);
  93         break;
  94     case AP_STACK:
  95         sz = ((StgAP_STACK *)p)->size + sizeofW(StgAP_STACK) - sizeofW(StgThunkHeader);
  96         break;
  97     default:
  98         sz = inf->layout.payload.ptrs + inf->layout.payload.nptrs;
  99         break;
 100     }
 101     for (i = 0; i < sz; i++) {
 102         ((StgThunk *)p)->payload[i] = 0;
 103     }
 104 no_slop:
 105     ;
 106 }
 107
 108 #endif /* CMINUSMINUS */
 109
 110 #if !defined(DEBUG) || defined(THREADED_RTS)
 111 #define DEBUG_FILL_SLOP(p) /* do nothing */
 112 #else
 113 #define DEBUG_FILL_SLOP(p) FILL_SLOP(p)
 114 #endif
 115
 116 /* We have two versions of this macro (sadly), one for use in C-- code,
 117  * and the other for C.
 118  *
 119  * The and_then argument is a performance hack so that we can paste in
 120  * the continuation code directly.  It helps shave a couple of
 121  * instructions off the common case in the update code, which is
 122  * worthwhile (the update code is often part of the inner loop).
 123  * (except that gcc now appears to common up this code again and
 124  * invert the optimisation.  Grrrr --SDM).
 125  */
 126 #ifdef CMINUSMINUS
 127
 128 #define updateWithIndirection(p1, p2, and_then) \
 129     W_ bd;                                                      \
 130                                                                 \
 131     DEBUG_FILL_SLOP(p1);                                        \
 132     LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(p1);                      \
 133     StgInd_indirectee(p1) = p2;                                 \
 134     prim %write_barrier() [];                                   \
 135     SET_INFO(p1, stg_BLACKHOLE_info);                           \
 136     LDV_RECORD_CREATE(p1);                                      \
 137     bd = Bdescr(p1);                                            \
 138     if (bdescr_gen_no(bd) != 0 :: bits16) {                     \
 139       recordMutableCap(p1, TO_W_(bdescr_gen_no(bd)), R1);       \
 140       TICK_UPD_OLD_IND();                                       \
 141       and_then;                                                 \
 142     } else {                                                    \
 143       TICK_UPD_NEW_IND();                                       \
 144       and_then;                                                 \
 145   }
 146
 147 #else /* !CMINUSMINUS */
 148
 149 INLINE_HEADER void updateWithIndirection (Capability *cap,
 150                                           StgClosure *p1,
 151                                           StgClosure *p2)
 152 {
 153     bdescr *bd;
 154
 155     ASSERT( (P_)p1 != (P_)p2 );
 156     /* not necessarily true: ASSERT( !closure_IND(p1) ); */
 157     /* occurs in RaiseAsync.c:raiseAsync() */
 158     DEBUG_FILL_SLOP(p1);
 159     LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(p1);
 160     ((StgInd *)p1)->indirectee = p2;
 161     write_barrier();
 162     SET_INFO(p1, &stg_BLACKHOLE_info);
 163     LDV_RECORD_CREATE(p1);
 164     bd = Bdescr((StgPtr)p1);
 165     if (bd->gen_no != 0) {
 166         recordMutableCap(p1, cap, bd->gen_no);
 167         TICK_UPD_OLD_IND();
 168     } else {
 169         TICK_UPD_NEW_IND();
 170     }
 171 }
 172
 173 #endif /* CMINUSMINUS */
 174
 175 #ifndef CMINUSMINUS
 176 END_RTS_PRIVATE
 177 #endif
 178
 179 #endif /* UPDATES_H */