Interpreter.c 38.8 KB
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/* -----------------------------------------------------------------------------
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 * Bytecode interpreter
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 *
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 * Copyright (c) The GHC Team, 1994-2002.
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 * ---------------------------------------------------------------------------*/

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#include "PosixSource.h"
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#include "Rts.h"
#include "RtsAPI.h"
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#include "RtsUtils.h"
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#include "Closures.h"
#include "TSO.h"
#include "Schedule.h"
#include "RtsFlags.h"
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#include "LdvProfile.h"
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#include "Updates.h"
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#include "Sanity.h"
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#include "Liveness.h"
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#include "Bytecodes.h"
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#include "Printer.h"
#include "Disassembler.h"
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#include "Interpreter.h"
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#include <string.h>     /* for memcpy */
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif

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/* --------------------------------------------------------------------------
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 * The bytecode interpreter
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 * ------------------------------------------------------------------------*/

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/* Gather stats about entry, opcode, opcode-pair frequencies.  For
   tuning the interpreter. */

/* #define INTERP_STATS */


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/* Sp points to the lowest live word on the stack. */
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#define BCO_NEXT      instrs[bciPtr++]
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#define BCO_NEXT_32   (bciPtr += 2, (((StgWord) instrs[bciPtr-2]) << 16) + ((StgWord) instrs[bciPtr-1]))
#define BCO_NEXT_64   (bciPtr += 4, (((StgWord) instrs[bciPtr-4]) << 48) + (((StgWord) instrs[bciPtr-3]) << 32) + (((StgWord) instrs[bciPtr-2]) << 16) + ((StgWord) instrs[bciPtr-1]))
#if WORD_SIZE_IN_BITS == 32
#define BCO_NEXT_WORD BCO_NEXT_32
#elif WORD_SIZE_IN_BITS == 64
#define BCO_NEXT_WORD BCO_NEXT_64
#else
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#error Cannot cope with WORD_SIZE_IN_BITS being nether 32 nor 64
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#endif
#define BCO_GET_LARGE_ARG ((bci & bci_FLAG_LARGE_ARGS) ? BCO_NEXT_WORD : BCO_NEXT)

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#define BCO_PTR(n)    (W_)ptrs[n]
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#define BCO_LIT(n)    literals[n]
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#define LOAD_STACK_POINTERS					\
    Sp = cap->r.rCurrentTSO->sp;				\
    /* We don't change this ... */				\
    SpLim = cap->r.rCurrentTSO->stack + RESERVED_STACK_WORDS;
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#define SAVE_STACK_POINTERS			\
    cap->r.rCurrentTSO->sp = Sp
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#define RETURN_TO_SCHEDULER(todo,retcode)	\
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   SAVE_STACK_POINTERS;				\
   cap->r.rCurrentTSO->what_next = (todo);	\
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   threadPaused(cap,cap->r.rCurrentTSO);		\
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   cap->r.rRet = (retcode);			\
   return cap;
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#define RETURN_TO_SCHEDULER_NO_PAUSE(todo,retcode)	\
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   SAVE_STACK_POINTERS;					\
   cap->r.rCurrentTSO->what_next = (todo);		\
   cap->r.rRet = (retcode);				\
   return cap;
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STATIC_INLINE StgPtr
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allocate_NONUPD (int n_words)
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{
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    return allocate(stg_max(sizeofW(StgHeader)+MIN_PAYLOAD_SIZE, n_words));
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}

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rtsBool stop_next_breakpoint = rtsFalse;
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#ifdef INTERP_STATS
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/* Hacky stats, for tuning the interpreter ... */
int it_unknown_entries[N_CLOSURE_TYPES];
int it_total_unknown_entries;
int it_total_entries;

int it_retto_BCO;
int it_retto_UPDATE;
int it_retto_other;

int it_slides;
int it_insns;
int it_BCO_entries;

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int it_ofreq[27];
int it_oofreq[27][27];
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int it_lastopc;

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#define INTERP_TICK(n) (n)++

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void interp_startup ( void )
{
   int i, j;
   it_retto_BCO = it_retto_UPDATE = it_retto_other = 0;
   it_total_entries = it_total_unknown_entries = 0;
   for (i = 0; i < N_CLOSURE_TYPES; i++)
      it_unknown_entries[i] = 0;
   it_slides = it_insns = it_BCO_entries = 0;
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   for (i = 0; i < 27; i++) it_ofreq[i] = 0;
   for (i = 0; i < 27; i++) 
     for (j = 0; j < 27; j++)
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        it_oofreq[i][j] = 0;
   it_lastopc = 0;
}

void interp_shutdown ( void )
{
   int i, j, k, o_max, i_max, j_max;
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   debugBelch("%d constrs entered -> (%d BCO, %d UPD, %d ??? )\n",
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                   it_retto_BCO + it_retto_UPDATE + it_retto_other,
                   it_retto_BCO, it_retto_UPDATE, it_retto_other );
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   debugBelch("%d total entries, %d unknown entries \n", 
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                   it_total_entries, it_total_unknown_entries);
   for (i = 0; i < N_CLOSURE_TYPES; i++) {
     if (it_unknown_entries[i] == 0) continue;
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     debugBelch("   type %2d: unknown entries (%4.1f%%) == %d\n",
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	     i, 100.0 * ((double)it_unknown_entries[i]) / 
                        ((double)it_total_unknown_entries),
             it_unknown_entries[i]);
   }
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   debugBelch("%d insns, %d slides, %d BCO_entries\n", 
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                   it_insns, it_slides, it_BCO_entries);
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   for (i = 0; i < 27; i++) 
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      debugBelch("opcode %2d got %d\n", i, it_ofreq[i] );
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   for (k = 1; k < 20; k++) {
      o_max = 0;
      i_max = j_max = 0;
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      for (i = 0; i < 27; i++) {
         for (j = 0; j < 27; j++) {
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	    if (it_oofreq[i][j] > o_max) {
               o_max = it_oofreq[i][j];
	       i_max = i; j_max = j;
	    }
	 }
      }
      
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      debugBelch("%d:  count (%4.1f%%) %6d   is %d then %d\n",
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                k, ((double)o_max) * 100.0 / ((double)it_insns), o_max,
                   i_max, j_max );
      it_oofreq[i_max][j_max] = 0;

   }
}

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#else // !INTERP_STATS

#define INTERP_TICK(n) /* nothing */

#endif
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static StgWord app_ptrs_itbl[] = {
    (W_)&stg_ap_p_info,
    (W_)&stg_ap_pp_info,
    (W_)&stg_ap_ppp_info,
    (W_)&stg_ap_pppp_info,
    (W_)&stg_ap_ppppp_info,
    (W_)&stg_ap_pppppp_info,
};

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HsStablePtr breakPointIOAction; // points to the IO action which is executed on a breakpoint
                                // it is set in main/GHC.hs:runStmt

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Capability *
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interpretBCO (Capability* cap)
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{
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    // Use of register here is primarily to make it clear to compilers
    // that these entities are non-aliasable.
    register StgPtr       Sp;    // local state -- stack pointer
    register StgPtr       SpLim; // local state -- stack lim pointer
    register StgClosure*  obj;
    nat n, m;
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    LOAD_STACK_POINTERS;

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    // ------------------------------------------------------------------------
    // Case 1:
    // 
    //       We have a closure to evaluate.  Stack looks like:
    //       
    //      	|   XXXX_info   |
    //      	+---------------+
    //       Sp |      -------------------> closure
    //      	+---------------+
    //       
    if (Sp[0] == (W_)&stg_enter_info) {
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       Sp++;
       goto eval;
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    }

    // ------------------------------------------------------------------------
    // Case 2:
    // 
    //       We have a BCO application to perform.  Stack looks like:
    //
    //      	|     ....      |
    //      	+---------------+
    //      	|     arg1      |
    //      	+---------------+
    //      	|     BCO       |
    //      	+---------------+
    //       Sp |   RET_BCO     |
    //      	+---------------+
    //       
    else if (Sp[0] == (W_)&stg_apply_interp_info) {
	obj = (StgClosure *)Sp[1];
	Sp += 2;
	goto run_BCO_fun;
    }

    // ------------------------------------------------------------------------
    // Case 3:
    //
    //       We have an unboxed value to return.  See comment before
    //       do_return_unboxed, below.
    //
    else {
	goto do_return_unboxed;
    }

    // Evaluate the object on top of the stack.
eval:
    obj = (StgClosure*)Sp[0]; Sp++;

eval_obj:
    INTERP_TICK(it_total_evals);

    IF_DEBUG(interpreter,
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             debugBelch(
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             "\n---------------------------------------------------------------\n");
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             debugBelch("Evaluating: "); printObj(obj);
             debugBelch("Sp = %p\n", Sp);
             debugBelch("\n" );
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             printStackChunk(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size);
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             debugBelch("\n\n");
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            );
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    IF_DEBUG(sanity,checkStackChunk(Sp, cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size));
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    switch ( get_itbl(obj)->type ) {
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    case IND:
    case IND_OLDGEN:
    case IND_PERM:
    case IND_OLDGEN_PERM:
    case IND_STATIC:
    { 
	obj = ((StgInd*)obj)->indirectee;
	goto eval_obj;
    }
    
    case CONSTR:
    case CONSTR_1_0:
    case CONSTR_0_1:
    case CONSTR_2_0:
    case CONSTR_1_1:
    case CONSTR_0_2:
    case CONSTR_STATIC:
    case CONSTR_NOCAF_STATIC:
    case FUN:
    case FUN_1_0:
    case FUN_0_1:
    case FUN_2_0:
    case FUN_1_1:
    case FUN_0_2:
    case FUN_STATIC:
    case PAP:
	// already in WHNF
	break;
	
    case BCO:
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    {
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	ASSERT(((StgBCO *)obj)->arity > 0);
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	break;
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    }
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    case AP:	/* Copied from stg_AP_entry. */
    {
	nat i, words;
	StgAP *ap;
	
	ap = (StgAP*)obj;
	words = ap->n_args;
	
	// Stack check
	if (Sp - (words+sizeofW(StgUpdateFrame)) < SpLim) {
	    Sp -= 2;
	    Sp[1] = (W_)obj;
	    Sp[0] = (W_)&stg_enter_info;
	    RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
	}
	
	/* Ok; we're safe.  Party on.  Push an update frame. */
	Sp -= sizeofW(StgUpdateFrame);
	{
	    StgUpdateFrame *__frame;
	    __frame = (StgUpdateFrame *)Sp;
	    SET_INFO(__frame, (StgInfoTable *)&stg_upd_frame_info);
	    __frame->updatee = (StgClosure *)(ap);
	}
	
	/* Reload the stack */
	Sp -= words;
	for (i=0; i < words; i++) {
	    Sp[i] = (W_)ap->payload[i];
	}

	obj = (StgClosure*)ap->fun;
	ASSERT(get_itbl(obj)->type == BCO);
	goto run_BCO_fun;
    }

    default:
#ifdef INTERP_STATS
    { 
	int j;
	
	j = get_itbl(obj)->type;
	ASSERT(j >= 0 && j < N_CLOSURE_TYPES);
	it_unknown_entries[j]++;
	it_total_unknown_entries++;
    }
#endif
    {
	// Can't handle this object; yield to scheduler
	IF_DEBUG(interpreter,
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		 debugBelch("evaluating unknown closure -- yielding to sched\n"); 
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		 printObj(obj);
	    );
	Sp -= 2;
	Sp[1] = (W_)obj;
	Sp[0] = (W_)&stg_enter_info;
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	RETURN_TO_SCHEDULER_NO_PAUSE(ThreadRunGHC, ThreadYielding);
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    }
    }

    // ------------------------------------------------------------------------
    // We now have an evaluated object (obj).  The next thing to
    // do is return it to the stack frame on top of the stack.
do_return:
    ASSERT(closure_HNF(obj));

    IF_DEBUG(interpreter,
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             debugBelch(
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             "\n---------------------------------------------------------------\n");
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             debugBelch("Returning: "); printObj(obj);
             debugBelch("Sp = %p\n", Sp);
             debugBelch("\n" );
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             printStackChunk(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size);
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             debugBelch("\n\n");
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            );
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    IF_DEBUG(sanity,checkStackChunk(Sp, cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size));

    switch (get_itbl((StgClosure *)Sp)->type) {

    case RET_SMALL: {
	const StgInfoTable *info;

	// NOTE: not using get_itbl().
	info = ((StgClosure *)Sp)->header.info;
	if (info == (StgInfoTable *)&stg_ap_v_info) {
	    n = 1; m = 0; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_f_info) {
	    n = 1; m = 1; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_d_info) {
	    n = 1; m = sizeofW(StgDouble); goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_l_info) {
	    n = 1; m = sizeofW(StgInt64); goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_n_info) {
	    n = 1; m = 1; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_p_info) {
	    n = 1; m = 1; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_pp_info) {
	    n = 2; m = 2; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_ppp_info) {
	    n = 3; m = 3; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_pppp_info) {
	    n = 4; m = 4; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_ppppp_info) {
	    n = 5; m = 5; goto do_apply;
	}
	if (info == (StgInfoTable *)&stg_ap_pppppp_info) {
	    n = 6; m = 6; goto do_apply;
	}
	goto do_return_unrecognised;
    }

    case UPDATE_FRAME:
	// Returning to an update frame: do the update, pop the update
	// frame, and continue with the next stack frame.
	INTERP_TICK(it_retto_UPDATE);
	UPD_IND(((StgUpdateFrame *)Sp)->updatee, obj); 
	Sp += sizeofW(StgUpdateFrame);
	goto do_return;

    case RET_BCO:
	// Returning to an interpreted continuation: put the object on
	// the stack, and start executing the BCO.
	INTERP_TICK(it_retto_BCO);
	Sp--;
	Sp[0] = (W_)obj;
	obj = (StgClosure*)Sp[2];
	ASSERT(get_itbl(obj)->type == BCO);
	goto run_BCO_return;

    default:
    do_return_unrecognised:
    {
	// Can't handle this return address; yield to scheduler
	INTERP_TICK(it_retto_other);
	IF_DEBUG(interpreter,
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		 debugBelch("returning to unknown frame -- yielding to sched\n"); 
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		 printStackChunk(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size);
	    );
	Sp -= 2;
	Sp[1] = (W_)obj;
	Sp[0] = (W_)&stg_enter_info;
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	RETURN_TO_SCHEDULER_NO_PAUSE(ThreadRunGHC, ThreadYielding);
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    }
    }

    // -------------------------------------------------------------------------
    // Returning an unboxed value.  The stack looks like this:
    //
    // 	  |     ....      |
    // 	  +---------------+
    // 	  |     fv2       |
    // 	  +---------------+
    // 	  |     fv1       |
    // 	  +---------------+
    // 	  |     BCO       |
    // 	  +---------------+
    // 	  | stg_ctoi_ret_ |
    // 	  +---------------+
    // 	  |    retval     |
    // 	  +---------------+
    // 	  |   XXXX_info   |
    // 	  +---------------+
    //
    // where XXXX_info is one of the stg_gc_unbx_r1_info family.
    //
    // We're only interested in the case when the real return address
    // is a BCO; otherwise we'll return to the scheduler.

do_return_unboxed:
    { 
	int offset;
	
	ASSERT( Sp[0] == (W_)&stg_gc_unbx_r1_info
		|| Sp[0] == (W_)&stg_gc_unpt_r1_info
		|| Sp[0] == (W_)&stg_gc_f1_info
		|| Sp[0] == (W_)&stg_gc_d1_info
		|| Sp[0] == (W_)&stg_gc_l1_info
		|| Sp[0] == (W_)&stg_gc_void_info // VoidRep
	    );

	// get the offset of the stg_ctoi_ret_XXX itbl
	offset = stack_frame_sizeW((StgClosure *)Sp);

	switch (get_itbl((StgClosure *)Sp+offset)->type) {

	case RET_BCO:
	    // Returning to an interpreted continuation: put the object on
	    // the stack, and start executing the BCO.
	    INTERP_TICK(it_retto_BCO);
	    obj = (StgClosure*)Sp[offset+1];
	    ASSERT(get_itbl(obj)->type == BCO);
	    goto run_BCO_return_unboxed;

	default:
	{
	    // Can't handle this return address; yield to scheduler
	    INTERP_TICK(it_retto_other);
	    IF_DEBUG(interpreter,
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		     debugBelch("returning to unknown frame -- yielding to sched\n"); 
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		     printStackChunk(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size);
		);
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	    RETURN_TO_SCHEDULER_NO_PAUSE(ThreadRunGHC, ThreadYielding);
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	}
	}
    }
    // not reached.


    // -------------------------------------------------------------------------
    // Application...

do_apply:
    // we have a function to apply (obj), and n arguments taking up m
    // words on the stack.  The info table (stg_ap_pp_info or whatever)
    // is on top of the arguments on the stack.
    {
	switch (get_itbl(obj)->type) {

	case PAP: {
	    StgPAP *pap;
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	    nat i, arity;
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	    pap = (StgPAP *)obj;

	    // we only cope with PAPs whose function is a BCO
	    if (get_itbl(pap->fun)->type != BCO) {
		goto defer_apply_to_sched;
	    }
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	    Sp++;
	    arity = pap->arity;
	    ASSERT(arity > 0);
	    if (arity < n) {
		// n must be greater than 1, and the only kinds of
		// application we support with more than one argument
		// are all pointers...
		//
		// Shuffle the args for this function down, and put
		// the appropriate info table in the gap.
		for (i = 0; i < arity; i++) {
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		    Sp[(int)i-1] = Sp[i];
		    // ^^^^^ careful, i-1 might be negative, but i in unsigned
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		}
		Sp[arity-1] = app_ptrs_itbl[n-arity-1];
		Sp--;
		// unpack the PAP's arguments onto the stack
		Sp -= pap->n_args;
		for (i = 0; i < pap->n_args; i++) {
		    Sp[i] = (W_)pap->payload[i];
		}
		obj = pap->fun;
		goto run_BCO_fun;
	    } 
	    else if (arity == n) {
		Sp -= pap->n_args;
		for (i = 0; i < pap->n_args; i++) {
		    Sp[i] = (W_)pap->payload[i];
		}
		obj = pap->fun;
		goto run_BCO_fun;
	    } 
	    else /* arity > n */ {
		// build a new PAP and return it.
		StgPAP *new_pap;
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		new_pap = (StgPAP *)allocate(PAP_sizeW(pap->n_args + m));
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		SET_HDR(new_pap,&stg_PAP_info,CCCS);
		new_pap->arity = pap->arity - n;
		new_pap->n_args = pap->n_args + m;
		new_pap->fun = pap->fun;
		for (i = 0; i < pap->n_args; i++) {
		    new_pap->payload[i] = pap->payload[i];
		}
		for (i = 0; i < m; i++) {
		    new_pap->payload[pap->n_args + i] = (StgClosure *)Sp[i];
		}
		obj = (StgClosure *)new_pap;
		Sp += m;
		goto do_return;
	    }
	}	    

	case BCO: {
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	    nat arity, i;
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	    Sp++;
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	    arity = ((StgBCO *)obj)->arity;
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	    ASSERT(arity > 0);
	    if (arity < n) {
		// n must be greater than 1, and the only kinds of
		// application we support with more than one argument
		// are all pointers...
		//
		// Shuffle the args for this function down, and put
		// the appropriate info table in the gap.
		for (i = 0; i < arity; i++) {
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		    Sp[(int)i-1] = Sp[i];
		    // ^^^^^ careful, i-1 might be negative, but i in unsigned
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		}
		Sp[arity-1] = app_ptrs_itbl[n-arity-1];
		Sp--;
		goto run_BCO_fun;
	    } 
	    else if (arity == n) {
		goto run_BCO_fun;
	    }
	    else /* arity > n */ {
		// build a PAP and return it.
		StgPAP *pap;
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		nat i;
		pap = (StgPAP *)allocate(PAP_sizeW(m));
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		SET_HDR(pap, &stg_PAP_info,CCCS);
		pap->arity = arity - n;
		pap->fun = obj;
		pap->n_args = m;
		for (i = 0; i < m; i++) {
		    pap->payload[i] = (StgClosure *)Sp[i];
		}
		obj = (StgClosure *)pap;
		Sp += m;
		goto do_return;
	    }
	}

	// No point in us applying machine-code functions
	default:
	defer_apply_to_sched:
	    Sp -= 2;
	    Sp[1] = (W_)obj;
	    Sp[0] = (W_)&stg_enter_info;
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	    RETURN_TO_SCHEDULER_NO_PAUSE(ThreadRunGHC, ThreadYielding);
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    }

    // ------------------------------------------------------------------------
    // Ok, we now have a bco (obj), and its arguments are all on the
    // stack.  We can start executing the byte codes.
    //
    // The stack is in one of two states.  First, if this BCO is a
    // function:
    //
    // 	  |     ....      |
    // 	  +---------------+
    // 	  |     arg2      |
    // 	  +---------------+
    // 	  |     arg1      |
    // 	  +---------------+
    //
    // Second, if this BCO is a continuation:
    //
    // 	  |     ....      |
    // 	  +---------------+
    // 	  |     fv2       |
    // 	  +---------------+
    // 	  |     fv1       |
    // 	  +---------------+
    // 	  |     BCO       |
    // 	  +---------------+
    // 	  | stg_ctoi_ret_ |
    // 	  +---------------+
    // 	  |    retval     |
    // 	  +---------------+
    // 
    // where retval is the value being returned to this continuation.
    // In the event of a stack check, heap check, or context switch,
    // we need to leave the stack in a sane state so the garbage
    // collector can find all the pointers.
    //
    //  (1) BCO is a function:  the BCO's bitmap describes the
    //      pointerhood of the arguments.
    //
    //  (2) BCO is a continuation: BCO's bitmap describes the
    //      pointerhood of the free variables.
    //
    // Sadly we have three different kinds of stack/heap/cswitch check
    // to do:

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run_BCO_return:
    // Heap check
    if (doYouWantToGC()) {
	Sp--; Sp[0] = (W_)&stg_enter_info;
	RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
    }
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    // Stack checks aren't necessary at return points, the stack use
    // is aggregated into the enclosing function entry point.
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    goto run_BCO;
    
run_BCO_return_unboxed:
    // Heap check
    if (doYouWantToGC()) {
	RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
    }
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    // Stack checks aren't necessary at return points, the stack use
    // is aggregated into the enclosing function entry point.
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    goto run_BCO;
    
run_BCO_fun:
    IF_DEBUG(sanity,
	     Sp -= 2; 
	     Sp[1] = (W_)obj; 
	     Sp[0] = (W_)&stg_apply_interp_info;
	     checkStackChunk(Sp,SpLim);
	     Sp += 2;
	);

    // Heap check
    if (doYouWantToGC()) {
	Sp -= 2; 
	Sp[1] = (W_)obj; 
	Sp[0] = (W_)&stg_apply_interp_info; // placeholder, really
	RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
    }
    
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    // Stack check
    if (Sp - INTERP_STACK_CHECK_THRESH < SpLim) {
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	Sp -= 2; 
	Sp[1] = (W_)obj; 
	Sp[0] = (W_)&stg_apply_interp_info; // placeholder, really
	RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
    }
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    goto run_BCO;
    
    // Now, actually interpret the BCO... (no returning to the
    // scheduler again until the stack is in an orderly state).
run_BCO:
    INTERP_TICK(it_BCO_entries);
    {
	register int       bciPtr     = 1; /* instruction pointer */
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        register StgWord16 bci;
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	register StgBCO*   bco        = (StgBCO*)obj;
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	register StgWord16* instrs    = (StgWord16*)(bco->instrs->payload);
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	register StgWord*  literals   = (StgWord*)(&bco->literals->payload[0]);
	register StgPtr*   ptrs       = (StgPtr*)(&bco->ptrs->payload[0]);
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#ifdef INTERP_STATS
	it_lastopc = 0; /* no opcode */
#endif
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    nextInsn:
	ASSERT(bciPtr <= instrs[0]);
	IF_DEBUG(interpreter,
		 //if (do_print_stack) {
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		 //debugBelch("\n-- BEGIN stack\n");
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		 //printStack(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size,iSu);
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		 //debugBelch("-- END stack\n\n");
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		 //}
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		 debugBelch("Sp = %p   pc = %d      ", Sp, bciPtr);
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		 disInstr(bco,bciPtr);
		 if (0) { int i;
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		 debugBelch("\n");
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		 for (i = 8; i >= 0; i--) {
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		     debugBelch("%d  %p\n", i, (StgPtr)(*(Sp+i)));
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		 }
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		 debugBelch("\n");
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		 }
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		 //if (do_print_stack) checkStack(Sp,cap->r.rCurrentTSO->stack+cap->r.rCurrentTSO->stack_size,iSu);
	    );
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	INTERP_TICK(it_insns);

#ifdef INTERP_STATS
	ASSERT( (int)instrs[bciPtr] >= 0 && (int)instrs[bciPtr] < 27 );
	it_ofreq[ (int)instrs[bciPtr] ] ++;
	it_oofreq[ it_lastopc ][ (int)instrs[bciPtr] ] ++;
	it_lastopc = (int)instrs[bciPtr];
#endif

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	bci = BCO_NEXT;
    /* We use the high 8 bits for flags, only the highest of which is
     * currently allocated */
    ASSERT((bci & 0xFF00) == (bci & 0x8000));

    switch (bci & 0xFF) {
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        /* check for a breakpoint on the beginning of a let binding */
        case bci_BRK_FUN: 
        {
            int arg1_brk_array, arg2_array_index, arg3_freeVars;
            StgArrWords *breakPoints;
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            int returning_from_break;     // are we resuming execution from a breakpoint?
                                          //  if yes, then don't break this time around
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            StgClosure *ioAction;         // the io action to run at a breakpoint

            StgAP_STACK *new_aps;         // a closure to save the top stack frame on the heap
            int i;
            int size_words;

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            arg1_brk_array      = BCO_NEXT;  // 1st arg of break instruction
            arg2_array_index    = BCO_NEXT;  // 2nd arg of break instruction
            arg3_freeVars       = BCO_NEXT;  // 3rd arg of break instruction
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            // check if we are returning from a breakpoint - this info
            // is stored in the flags field of the current TSO
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            returning_from_break = cap->r.rCurrentTSO->flags & TSO_STOPPED_ON_BREAKPOINT; 

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            // if we are returning from a break then skip this section
            // and continue executing
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            if (!returning_from_break)
            {
               breakPoints = (StgArrWords *) BCO_PTR(arg1_brk_array);

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               // stop the current thread if either the
               // "stop_next_breakpoint" flag is true OR if the
               // breakpoint flag for this particular expression is
               // true
               if (stop_next_breakpoint == rtsTrue || 
                   breakPoints->payload[arg2_array_index] == rtsTrue)
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               {
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                  // make sure we don't automatically stop at the
                  // next breakpoint
                  stop_next_breakpoint = rtsFalse;

                  // allocate memory for a new AP_STACK, enough to
                  // store the top stack frame plus an
                  // stg_apply_interp_info pointer and a pointer to
                  // the BCO
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                  size_words = BCO_BITMAP_SIZE(obj) + 2;
                  new_aps = (StgAP_STACK *) allocate (AP_STACK_sizeW(size_words));
                  SET_HDR(new_aps,&stg_AP_STACK_info,CCS_SYSTEM); 
                  new_aps->size = size_words;
                  new_aps->fun = &stg_dummy_ret_closure; 

                  // fill in the payload of the AP_STACK 
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                  new_aps->payload[0] = (StgClosure *)&stg_apply_interp_info;
                  new_aps->payload[1] = (StgClosure *)obj;
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                  // copy the contents of the top stack frame into the AP_STACK
                  for (i = 2; i < size_words; i++)
                  {
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                     new_aps->payload[i] = (StgClosure *)Sp[i-2];
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                  }

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                  // prepare the stack so that we can call the
                  // breakPointIOAction and ensure that the stack is
                  // in a reasonable state for the GC and so that
                  // execution of this BCO can continue when we resume
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                  ioAction = (StgClosure *) deRefStablePtr (breakPointIOAction);
                  Sp -= 7;
                  Sp[6] = (W_)obj;   
                  Sp[5] = (W_)&stg_apply_interp_info;
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                  Sp[4] = (W_)new_aps;                 // the AP_STACK
                  Sp[3] = (W_)BCO_PTR(arg3_freeVars);  // the info about local vars of the breakpoint
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                  Sp[2] = (W_)&stg_ap_ppv_info;
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                  Sp[1] = (W_)ioAction;                // apply the IO action to its two arguments above
                  Sp[0] = (W_)&stg_enter_info;         // get ready to run the IO action
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                  // set the flag in the TSO to say that we are now
                  // stopping at a breakpoint so that when we resume
                  // we don't stop on the same breakpoint that we
                  // already stopped at just now
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                  cap->r.rCurrentTSO->flags |= TSO_STOPPED_ON_BREAKPOINT;

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                  // stop this thread and return to the scheduler -
                  // eventually we will come back and the IO action on
                  // the top of the stack will be executed
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                  RETURN_TO_SCHEDULER_NO_PAUSE(ThreadRunGHC, ThreadYielding);
               }
            }
            // record that this thread is not stopped at a breakpoint anymore
            cap->r.rCurrentTSO->flags &= ~TSO_STOPPED_ON_BREAKPOINT;

            // continue normal execution of the byte code instructions
	    goto nextInsn;
        }

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	case bci_STKCHECK: {
	    // Explicit stack check at the beginning of a function
	    // *only* (stack checks in case alternatives are
	    // propagated to the enclosing function).
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	    StgWord stk_words_reqd = BCO_GET_LARGE_ARG + 1;
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	    if (Sp - stk_words_reqd < SpLim) {
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		Sp -= 2; 
		Sp[1] = (W_)obj; 
		Sp[0] = (W_)&stg_apply_interp_info;
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		RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
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	    } else {
		goto nextInsn;
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	    }
	}

	case bci_PUSH_L: {
	    int o1 = BCO_NEXT;
	    Sp[-1] = Sp[o1];
	    Sp--;
	    goto nextInsn;
	}

	case bci_PUSH_LL: {
	    int o1 = BCO_NEXT;
	    int o2 = BCO_NEXT;
	    Sp[-1] = Sp[o1];
	    Sp[-2] = Sp[o2];
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_LLL: {
	    int o1 = BCO_NEXT;
	    int o2 = BCO_NEXT;
	    int o3 = BCO_NEXT;
	    Sp[-1] = Sp[o1];
	    Sp[-2] = Sp[o2];
	    Sp[-3] = Sp[o3];
	    Sp -= 3;
	    goto nextInsn;
	}

	case bci_PUSH_G: {
	    int o1 = BCO_NEXT;
	    Sp[-1] = BCO_PTR(o1);
	    Sp -= 1;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_R1p_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_P: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_R1unpt_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_N: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_R1n_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_F: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_F1_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_D: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_D1_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_L: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_L1_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_ALTS_V: {
	    int o_bco  = BCO_NEXT;
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	    Sp[-2] = (W_)&stg_ctoi_V_info;
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	    Sp[-1] = BCO_PTR(o_bco);
	    Sp -= 2;
	    goto nextInsn;
	}

	case bci_PUSH_APPLY_N:
	    Sp--; Sp[0] = (W_)&stg_ap_n_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_V:
	    Sp--; Sp[0] = (W_)&stg_ap_v_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_F:
	    Sp--; Sp[0] = (W_)&stg_ap_f_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_D:
	    Sp--; Sp[0] = (W_)&stg_ap_d_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_L:
	    Sp--; Sp[0] = (W_)&stg_ap_l_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_P:
	    Sp--; Sp[0] = (W_)&stg_ap_p_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_PP:
	    Sp--; Sp[0] = (W_)&stg_ap_pp_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_PPP:
	    Sp--; Sp[0] = (W_)&stg_ap_ppp_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_PPPP:
	    Sp--; Sp[0] = (W_)&stg_ap_pppp_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_PPPPP:
	    Sp--; Sp[0] = (W_)&stg_ap_ppppp_info;
	    goto nextInsn;
	case bci_PUSH_APPLY_PPPPPP:
	    Sp--; Sp[0] = (W_)&stg_ap_pppppp_info;
	    goto nextInsn;
	    
	case bci_PUSH_UBX: {
	    int i;
	    int o_lits = BCO_NEXT;
	    int n_words = BCO_NEXT;
	    Sp -= n_words;
	    for (i = 0; i < n_words; i++) {
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		Sp[i] = (W_)BCO_LIT(o_lits+i);
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	    }
	    goto nextInsn;
	}

	case bci_SLIDE: {
	    int n  = BCO_NEXT;
	    int by = BCO_NEXT;
	    /* a_1, .. a_n, b_1, .. b_by, s => a_1, .. a_n, s */
	    while(--n >= 0) {
		Sp[n+by] = Sp[n];
	    }
	    Sp += by;
	    INTERP_TICK(it_slides);
	    goto nextInsn;
	}

	case bci_ALLOC_AP: {
	    StgAP* ap; 
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	    int n_payload = BCO_NEXT;
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	    ap = (StgAP*)allocate(AP_sizeW(n_payload));
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	    Sp[-1] = (W_)ap;
	    ap->n_args = n_payload;
	    SET_HDR(ap, &stg_AP_info, CCS_SYSTEM/*ToDo*/)
	    Sp --;
	    goto nextInsn;
	}

	case bci_ALLOC_PAP: {
	    StgPAP* pap; 
	    int arity = BCO_NEXT;
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	    int n_payload = BCO_NEXT;
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	    pap = (StgPAP*)allocate(PAP_sizeW(n_payload));
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	    Sp[-1] = (W_)pap;
	    pap->n_args = n_payload;
	    pap->arity = arity;
	    SET_HDR(pap, &stg_PAP_info, CCS_SYSTEM/*ToDo*/)
	    Sp --;
	    goto nextInsn;
	}

	case bci_MKAP: {
	    int i;
	    int stkoff = BCO_NEXT;
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	    int n_payload = BCO_NEXT;
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	    StgAP* ap = (StgAP*)Sp[stkoff];
	    ASSERT((int)ap->n_args == n_payload);
	    ap->fun = (StgClosure*)Sp[0];
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	    // The function should be a BCO, and its bitmap should
	    // cover the payload of the AP correctly.
	    ASSERT(get_itbl(ap->fun)->type == BCO
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		   && BCO_BITMAP_SIZE(ap->fun) == ap->n_args);
	    
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	    for (i = 0; i < n_payload; i++)
		ap->payload[i] = (StgClosure*)Sp[i+1];
	    Sp += n_payload+1;
	    IF_DEBUG(interpreter,
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		     debugBelch("\tBuilt "); 
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		     printObj((StgClosure*)ap);
		);
	    goto nextInsn;
	}

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1096
1097
1098
1099
1100
1101
1102
1103
1104
	case bci_MKPAP: {
	    int i;
	    int stkoff = BCO_NEXT;
	    int n_payload = BCO_NEXT;
	    StgPAP* pap = (StgPAP*)Sp[stkoff];
	    ASSERT((int)pap->n_args == n_payload);
	    pap->fun = (StgClosure*)Sp[0];
	    
	    // The function should be a BCO
	    ASSERT(get_itbl(pap->fun)->type == BCO);
	    
	    for (i = 0; i < n_payload; i++)
		pap->payload[i] = (StgClosure*)Sp[i+1];
	    Sp += n_payload+1;
	    IF_DEBUG(interpreter,
		     debugBelch("\tBuilt "); 
		     printObj((StgClosure*)pap);
		);
	    goto nextInsn;
	}

1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
	case bci_UNPACK: {
	    /* Unpack N ptr words from t.o.s constructor */
	    int i;
	    int n_words = BCO_NEXT;
	    StgClosure* con = (StgClosure*)Sp[0];
	    Sp -= n_words;
	    for (i = 0; i < n_words; i++) {
		Sp[i] = (W_)con->payload[i];
	    }
	    goto nextInsn;
	}

	case bci_PACK: {
	    int i;
	    int o_itbl         = BCO_NEXT;
	    int n_words        = BCO_NEXT;
1121
	    StgInfoTable* itbl = INFO_PTR_TO_STRUCT(BCO_LIT(o_itbl));
1122
1123
1124
1125
	    int request        = CONSTR_sizeW( itbl->layout.payload.ptrs, 
					       itbl->layout.payload.nptrs );
	    StgClosure* con = (StgClosure*)allocate_NONUPD(request);
	    ASSERT( itbl->layout.payload.ptrs + itbl->layout.payload.nptrs > 0);
1126
	    SET_HDR(con, (StgInfoTable*)BCO_LIT(o_itbl), CCS_SYSTEM/*ToDo*/);
1127
1128
1129
1130
1131
1132
1133
	    for (i = 0; i < n_words; i++) {
		con->payload[i] = (StgClosure*)Sp[i];
	    }
	    Sp += n_words;
	    Sp --;
	    Sp[0] = (W_)con;
	    IF_DEBUG(interpreter,
1134
		     debugBelch("\tBuilt "); 
1135
1136
1137
1138
1139
1140
		     printObj((StgClosure*)con);
		);
	    goto nextInsn;
	}

	case bci_TESTLT_P: {
1141
	    unsigned int discr  = BCO_NEXT;
1142
1143
	    int failto = BCO_NEXT;
	    StgClosure* con = (StgClosure*)Sp[0];
1144
	    if (GET_TAG(con) >= discr) {
1145
1146
1147
1148
1149
1150
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTEQ_P: {
1151
	    unsigned int discr  = BCO_NEXT;
1152
1153
	    int failto = BCO_NEXT;
	    StgClosure* con = (StgClosure*)Sp[0];
1154
	    if (GET_TAG(con) != discr) {
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTLT_I: {
	    // There should be an Int at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    I_ stackInt = (I_)Sp[1];
	    if (stackInt >= (I_)BCO_LIT(discr))
		bciPtr = failto;
	    goto nextInsn;
	}

	case bci_TESTEQ_I: {
	    // There should be an Int at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    I_ stackInt = (I_)Sp[1];
	    if (stackInt != (I_)BCO_LIT(discr)) {
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTLT_D: {
	    // There should be a Double at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    StgDouble stackDbl, discrDbl;
	    stackDbl = PK_DBL( & Sp[1] );
	    discrDbl = PK_DBL( & BCO_LIT(discr) );
	    if (stackDbl >= discrDbl) {
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTEQ_D: {
	    // There should be a Double at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    StgDouble stackDbl, discrDbl;
	    stackDbl = PK_DBL( & Sp[1] );
	    discrDbl = PK_DBL( & BCO_LIT(discr) );
	    if (stackDbl != discrDbl) {
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTLT_F: {
	    // There should be a Float at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    StgFloat stackFlt, discrFlt;
	    stackFlt = PK_FLT( & Sp[1] );
	    discrFlt = PK_FLT( & BCO_LIT(discr) );
	    if (stackFlt >= discrFlt) {
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	case bci_TESTEQ_F: {
	    // There should be a Float at Sp[1], and an info table at Sp[0].
	    int discr   = BCO_NEXT;
	    int failto  = BCO_NEXT;
	    StgFloat stackFlt, discrFlt;
	    stackFlt = PK_FLT( & Sp[1] );
	    discrFlt = PK_FLT( & BCO_LIT(discr) );
	    if (stackFlt != discrFlt) {
		bciPtr = failto;
	    }
	    goto nextInsn;
	}

	// Control-flow ish things
	case bci_ENTER:
	    // Context-switch check.  We put it here to ensure that
	    // the interpreter has done at least *some* work before
	    // context switching: sometimes the scheduler can invoke
	    // the interpreter with context_switch == 1, particularly
	    // if the -C0 flag has been given on the cmd line.
	    if (context_switch) {
		Sp--; Sp[0] = (W_)&stg_enter_info;
		RETURN_TO_SCHEDULER(ThreadInterpret, ThreadYielding);
	    }
	    goto eval;

	case bci_RETURN:
	    obj = (StgClosure *)Sp[0];
	    Sp++;
	    goto do_return;

	case bci_RETURN_P:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_unpt_r1_info;
	    goto do_return_unboxed;
	case bci_RETURN_N:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_unbx_r1_info;
	    goto do_return_unboxed;
	case bci_RETURN_F:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_f1_info;
	    goto do_return_unboxed;
	case bci_RETURN_D:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_d1_info;
	    goto do_return_unboxed;
	case bci_RETURN_L:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_l1_info;
	    goto do_return_unboxed;
	case bci_RETURN_V:
	    Sp--;
	    Sp[0] = (W_)&stg_gc_void_info;
	    goto do_return_unboxed;

	case bci_SWIZZLE: {
	    int stkoff = BCO_NEXT;
	    signed short n = (signed short)(BCO_NEXT);
	    Sp[stkoff] += (W_)n;
	    goto nextInsn;
	}

	case bci_CCALL: {
1284
	    void *tok;
1285
1286
1287
	    int stk_offset            = BCO_NEXT;
	    int o_itbl                = BCO_NEXT;
	    void(*marshall_fn)(void*) = (void (*)(void*))BCO_LIT(o_itbl);
1288
1289
1290
	    int ret_dyn_size = 
		RET_DYN_BITMAP_SIZE + RET_DYN_NONPTR_REGS_SIZE
		+ sizeofW(StgRetDyn);
1291

1292
#ifdef THREADED_RTS
1293
1294
1295
1296
1297
	    // Threaded RTS:
	    // Arguments on the TSO stack are not good, because garbage
	    // collection might move the TSO as soon as we call
	    // suspendThread below.

1298
	    W_ arguments[stk_offset];
1299
1300
1301
	    
	    memcpy(arguments, Sp, sizeof(W_) * stk_offset);
#endif
1302

1303
1304
1305
	    // Restore the Haskell thread's current value of errno
	    errno = cap->r.rCurrentTSO->saved_errno;

1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
	    // There are a bunch of non-ptr words on the stack (the
	    // ccall args, the ccall fun address and space for the
	    // result), which we need to cover with an info table
	    // since we might GC during this call.
	    //
	    // We know how many (non-ptr) words there are before the
	    // next valid stack frame: it is the stk_offset arg to the
	    // CCALL instruction.   So we build a RET_DYN stack frame
	    // on the stack frame to describe this chunk of stack.
	    //
1316
	    Sp -= ret_dyn_size;
1317
	    ((StgRetDyn *)Sp)->liveness = NO_PTRS | N_NONPTRS(stk_offset);
1318
1319
	    ((StgRetDyn *)Sp)->info = (StgInfoTable *)&stg_gc_gen_info;

1320
	    SAVE_STACK_POINTERS;
1321
	    tok = suspendThread(&cap->r);
1322

1323
#ifndef THREADED_RTS
1324
1325
	    // Careful:
	    // suspendThread might have shifted the stack
1326
	    // around (stack squeezing), so we have to grab the real
1327
	    // Sp out of the TSO to find the ccall args again.
1328

1329
	    marshall_fn ( (void*)(cap->r.rCurrentTSO->sp + ret_dyn_size) );
1330
1331
#else
	    // Threaded RTS:
1332
	    // We already made a copy of the arguments above.
1333
1334
1335
1336

	    marshall_fn ( arguments );
#endif

1337
	    // And restart the thread again, popping the RET_DYN frame.
1338
	    cap = (Capability *)((void *)((unsigned char*)resumeThread(tok) - sizeof(StgFunTable)));
1339
	    LOAD_STACK_POINTERS;
1340
	    Sp += ret_dyn_size;
1341
	    
1342
1343
1344
	    // Save the Haskell thread's current value of errno
	    cap->r.rCurrentTSO->saved_errno = errno;
		
1345
#ifdef THREADED_RTS
1346
1347
1348
1349
1350
1351
1352
	    // Threaded RTS:
	    // Copy the "arguments", which might include a return value,
	    // back to the TSO stack. It would of course be enough to
	    // just copy the return value, but we don't know the offset.
	    memcpy(Sp, arguments, sizeof(W_) * stk_offset);
#endif

1353
1354
1355
1356
1357
1358
1359
1360
1361
	    goto nextInsn;
	}

	case bci_JMP: {
	    /* BCO_NEXT modifies bciPtr, so be conservative. */
	    int nextpc = BCO_NEXT;
	    bciPtr     = nextpc;
	    goto nextInsn;
	}
1362
 
1363
1364
1365
1366
1367
	case bci_CASEFAIL:
	    barf("interpretBCO: hit a CASEFAIL");
	    
	    // Errors
	default: 
1368
1369
	    barf("interpretBCO: unknown or unimplemented opcode %d",
                 (int)BCO_NEXT);
1370
1371
1372
1373
1374
1375

	} /* switch on opcode */
    }
    }

    barf("interpretBCO: fell off end of the interpreter");
1376
}
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392

/* temporary code for peeking inside a AP_STACK and pulling out values
   based on their stack offset - used in the debugger for inspecting
   the local values of a breakpoint
*/
HsStablePtr rts_getApStackVal (HsStablePtr, int);
HsStablePtr rts_getApStackVal (HsStablePtr apStackSptr, int offset)
{
   HsStablePtr resultSptr;
   StgAP_STACK *apStack;
   StgClosure **payload;
   StgClosure *val;

   apStack = (StgAP_STACK *) deRefStablePtr (apStackSptr);
   payload = apStack->payload;
   val = (StgClosure *) payload[offset+2];
1393
   resultSptr = getStablePtr ((P_)val); 
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
   return resultSptr;
}

/* set the single step flag for the debugger to True -
   it gets set back to false in the interpreter everytime
   we hit a breakpoint
*/
void rts_setStepFlag (void);
void rts_setStepFlag (void)
{
   stop_next_breakpoint = rtsTrue;
}