RetainerProfile.c 64.5 KB
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/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 2001
 * Author: Sungwoo Park
 *
 * Retainer profiling.
 *
 * ---------------------------------------------------------------------------*/

#ifdef PROFILING

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// Turn off inlining when debugging - it obfuscates things
#ifdef DEBUG
#define INLINE
#else
#define INLINE inline
#endif

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#include "Rts.h"
#include "RtsUtils.h"
#include "RetainerProfile.h"
#include "RetainerSet.h"
#include "Schedule.h"
#include "Printer.h"
#include "Storage.h"
#include "RtsFlags.h"
#include "Weak.h"
#include "Sanity.h"
#include "Profiling.h"
#include "Stats.h"
#include "BlockAlloc.h"
#include "ProfHeap.h"
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#include "Apply.h"
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/*
  Note: what to change in order to plug-in a new retainer profiling scheme?
    (1) type retainer in ../includes/StgRetainerProf.h
    (2) retainer function R(), i.e., getRetainerFrom()
    (3) the two hashing functions, hashKeySingleton() and hashKeyAddElement(),
        in RetainerSet.h, if needed.
    (4) printRetainer() and printRetainerSetShort() in RetainerSet.c.
 */

/* -----------------------------------------------------------------------------
 * Declarations...
 * -------------------------------------------------------------------------- */

static nat retainerGeneration;	// generation

static nat numObjectVisited;	// total number of objects visited
static nat timesAnyObjectVisited; // number of times any objects are visited

/*
  The rs field in the profile header of any object points to its retainer
  set in an indirect way: if flip is 0, it points to the retainer set;
  if flip is 1, it points to the next byte after the retainer set (even
  for NULL pointers). Therefore, with flip 1, (rs ^ 1) is the actual
  pointer. See retainerSetOf().
 */

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StgWord flip = 0;     // flip bit
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                      // must be 0 if DEBUG_RETAINER is on (for static closures)

#define setRetainerSetToNull(c)   \
  (c)->header.prof.hp.rs = (RetainerSet *)((StgWord)NULL | flip)

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static void retainStack(StgClosure *, retainer, StgPtr, StgPtr);
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static void retainClosure(StgClosure *, StgClosure *, retainer);
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#ifdef DEBUG_RETAINER
static void belongToHeap(StgPtr p);
#endif

#ifdef DEBUG_RETAINER
/*
  cStackSize records how many times retainStack() has been invoked recursively,
  that is, the number of activation records for retainStack() on the C stack.
  maxCStackSize records its max value.
  Invariants:
    cStackSize <= maxCStackSize
 */
static nat cStackSize, maxCStackSize;

static nat sumOfNewCost;	// sum of the cost of each object, computed
				// when the object is first visited
static nat sumOfNewCostExtra;   // for those objects not visited during
                                // retainer profiling, e.g., MUT_VAR
static nat costArray[N_CLOSURE_TYPES];

nat sumOfCostLinear;		// sum of the costs of all object, computed
				// when linearly traversing the heap after
				// retainer profiling
nat costArrayLinear[N_CLOSURE_TYPES];
#endif

/* -----------------------------------------------------------------------------
 * Retainer stack - header
 *   Note:
 *     Although the retainer stack implementation could be separated *
 *     from the retainer profiling engine, there does not seem to be
 *     any advantage in doing that; retainer stack is an integral part
 *     of retainer profiling engine and cannot be use elsewhere at
 *     all.
 * -------------------------------------------------------------------------- */

typedef enum {
    posTypeStep,
    posTypePtrs,
    posTypeSRT,
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    posTypeLargeSRT,
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} nextPosType;

typedef union {
    // fixed layout or layout specified by a field in the closure
    StgWord step;

    // layout.payload
    struct {
    // See StgClosureInfo in InfoTables.h
#if SIZEOF_VOID_P == 8
	StgWord32 pos;
	StgWord32 ptrs;
#else
	StgWord16 pos;
	StgWord16 ptrs;
#endif
	StgPtr payload;
    } ptrs;

    // SRT
    struct {
	StgClosure **srt;
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	StgWord    srt_bitmap;
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    } srt;
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    // Large SRT
    struct {
	StgLargeSRT *srt;
	StgWord offset;
    } large_srt;
	
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} nextPos;

typedef struct {
    nextPosType type;
    nextPos next;
} stackPos;

typedef struct {
    StgClosure *c;
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    retainer c_child_r;
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    stackPos info;
} stackElement;

/*
  Invariants:
    firstStack points to the first block group.
    currentStack points to the block group currently being used.
    currentStack->free == stackLimit.
    stackTop points to the topmost byte in the stack of currentStack.
    Unless the whole stack is empty, stackTop must point to the topmost
    object (or byte) in the whole stack. Thus, it is only when the whole stack
    is empty that stackTop == stackLimit (not during the execution of push()
    and pop()).
    stackBottom == currentStack->start.
    stackLimit == currentStack->start + BLOCK_SIZE_W * currentStack->blocks.
  Note:
    When a current stack becomes empty, stackTop is set to point to
    the topmost element on the previous block group so as to satisfy
    the invariants described above.
 */
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static bdescr *firstStack = NULL;
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static bdescr *currentStack;
static stackElement *stackBottom, *stackTop, *stackLimit;

/*
  currentStackBoundary is used to mark the current stack chunk.
  If stackTop == currentStackBoundary, it means that the current stack chunk
  is empty. It is the responsibility of the user to keep currentStackBoundary
  valid all the time if it is to be employed.
 */
static stackElement *currentStackBoundary;

/*
  stackSize records the current size of the stack.
  maxStackSize records its high water mark.
  Invariants:
    stackSize <= maxStackSize
  Note:
    stackSize is just an estimate measure of the depth of the graph. The reason
    is that some heap objects have only a single child and may not result
    in a new element being pushed onto the stack. Therefore, at the end of
    retainer profiling, maxStackSize + maxCStackSize is some value no greater
    than the actual depth of the graph.
 */
#ifdef DEBUG_RETAINER
static int stackSize, maxStackSize;
#endif

// number of blocks allocated for one stack
#define BLOCKS_IN_STACK 1

/* -----------------------------------------------------------------------------
 * Add a new block group to the stack.
 * Invariants:
 *  currentStack->link == s.
 * -------------------------------------------------------------------------- */
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static INLINE void
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newStackBlock( bdescr *bd )
{
    currentStack = bd;
    stackTop     = (stackElement *)(bd->start + BLOCK_SIZE_W * bd->blocks);
    stackBottom  = (stackElement *)bd->start;
    stackLimit   = (stackElement *)stackTop;
    bd->free     = (StgPtr)stackLimit;
}

/* -----------------------------------------------------------------------------
 * Return to the previous block group.
 * Invariants:
 *   s->link == currentStack.
 * -------------------------------------------------------------------------- */
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static INLINE void
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returnToOldStack( bdescr *bd )
{
    currentStack = bd;
    stackTop = (stackElement *)bd->free;
    stackBottom = (stackElement *)bd->start;
    stackLimit = (stackElement *)(bd->start + BLOCK_SIZE_W * bd->blocks);
    bd->free = (StgPtr)stackLimit;
}

/* -----------------------------------------------------------------------------
 *  Initializes the traverse stack.
 * -------------------------------------------------------------------------- */
static void
initializeTraverseStack( void )
{
    if (firstStack != NULL) {
	freeChain(firstStack);
    }

    firstStack = allocGroup(BLOCKS_IN_STACK);
    firstStack->link = NULL;
    firstStack->u.back = NULL;

    newStackBlock(firstStack);
}

/* -----------------------------------------------------------------------------
 * Frees all the block groups in the traverse stack.
 * Invariants:
 *   firstStack != NULL
 * -------------------------------------------------------------------------- */
static void
closeTraverseStack( void )
{
    freeChain(firstStack);
    firstStack = NULL;
}

/* -----------------------------------------------------------------------------
 * Returns rtsTrue if the whole stack is empty.
 * -------------------------------------------------------------------------- */
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static INLINE rtsBool
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isEmptyRetainerStack( void )
{
    return (firstStack == currentStack) && stackTop == stackLimit;
}

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/* -----------------------------------------------------------------------------
 * Returns size of stack
 * -------------------------------------------------------------------------- */
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#ifdef DEBUG
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lnat
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retainerStackBlocks( void )
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{
    bdescr* bd;
    lnat res = 0;

    for (bd = firstStack; bd != NULL; bd = bd->link) 
      res += bd->blocks;

    return res;
}
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#endif
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/* -----------------------------------------------------------------------------
 * Returns rtsTrue if stackTop is at the stack boundary of the current stack,
 * i.e., if the current stack chunk is empty.
 * -------------------------------------------------------------------------- */
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static INLINE rtsBool
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isOnBoundary( void )
{
    return stackTop == currentStackBoundary;
}

/* -----------------------------------------------------------------------------
 * Initializes *info from ptrs and payload.
 * Invariants:
 *   payload[] begins with ptrs pointers followed by non-pointers.
 * -------------------------------------------------------------------------- */
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static INLINE void
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init_ptrs( stackPos *info, nat ptrs, StgPtr payload )
{
    info->type              = posTypePtrs;
    info->next.ptrs.pos     = 0;
    info->next.ptrs.ptrs    = ptrs;
    info->next.ptrs.payload = payload;
}

/* -----------------------------------------------------------------------------
 * Find the next object from *info.
 * -------------------------------------------------------------------------- */
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static INLINE StgClosure *
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find_ptrs( stackPos *info )
{
    if (info->next.ptrs.pos < info->next.ptrs.ptrs) {
	return (StgClosure *)info->next.ptrs.payload[info->next.ptrs.pos++];
    } else {
	return NULL;
    }
}

/* -----------------------------------------------------------------------------
 *  Initializes *info from SRT information stored in *infoTable.
 * -------------------------------------------------------------------------- */
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static INLINE void
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init_srt_fun( stackPos *info, StgFunInfoTable *infoTable )
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{
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    if (infoTable->i.srt_bitmap == (StgHalfWord)(-1)) {
	info->type = posTypeLargeSRT;
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	info->next.large_srt.srt = (StgLargeSRT *)GET_FUN_SRT(infoTable);
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	info->next.large_srt.offset = 0;
    } else {
	info->type = posTypeSRT;
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	info->next.srt.srt = (StgClosure **)GET_FUN_SRT(infoTable);
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	info->next.srt.srt_bitmap = infoTable->i.srt_bitmap;
    }
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}

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static INLINE void
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init_srt_thunk( stackPos *info, StgThunkInfoTable *infoTable )
{
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    if (infoTable->i.srt_bitmap == (StgHalfWord)(-1)) {
	info->type = posTypeLargeSRT;
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	info->next.large_srt.srt = (StgLargeSRT *)GET_SRT(infoTable);
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	info->next.large_srt.offset = 0;
    } else {
	info->type = posTypeSRT;
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	info->next.srt.srt = (StgClosure **)GET_SRT(infoTable);
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	info->next.srt.srt_bitmap = infoTable->i.srt_bitmap;
    }
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}

/* -----------------------------------------------------------------------------
 * Find the next object from *info.
 * -------------------------------------------------------------------------- */
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static INLINE StgClosure *
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find_srt( stackPos *info )
{
    StgClosure *c;
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    StgWord bitmap;
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    if (info->type == posTypeSRT) {
	// Small SRT bitmap
	bitmap = info->next.srt.srt_bitmap;
	while (bitmap != 0) {
	    if ((bitmap & 1) != 0) {
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#ifdef ENABLE_WIN32_DLL_SUPPORT
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		if ((unsigned long)(*(info->next.srt.srt)) & 0x1)
		    c = (* (StgClosure **)((unsigned long)*(info->next.srt.srt)) & ~0x1);
		else
		    c = *(info->next.srt.srt);
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#else
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		c = *(info->next.srt.srt);
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#endif
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		bitmap = bitmap >> 1;
		info->next.srt.srt++;
		info->next.srt.srt_bitmap = bitmap;
		return c;
	    }
	    bitmap = bitmap >> 1;
	    info->next.srt.srt++;
	}
	// bitmap is now zero...
	return NULL;
    }
    else {
	// Large SRT bitmap
	nat i = info->next.large_srt.offset;
	StgWord bitmap;

	// Follow the pattern from GC.c:scavenge_large_srt_bitmap().
	bitmap = info->next.large_srt.srt->l.bitmap[i / BITS_IN(W_)];
	bitmap = bitmap >> (i % BITS_IN(StgWord));
	while (i < info->next.large_srt.srt->l.size) {
	    if ((bitmap & 1) != 0) {
		c = ((StgClosure **)info->next.large_srt.srt->srt)[i];
		i++;
		info->next.large_srt.offset = i;
		return c;
	    }
	    i++;
	    if (i % BITS_IN(W_) == 0) {
		bitmap = info->next.large_srt.srt->l.bitmap[i / BITS_IN(W_)];
	    } else {
		bitmap = bitmap >> 1;
	    }
	}
	// reached the end of this bitmap.
	info->next.large_srt.offset = i;
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	return NULL;
    }
}

/* -----------------------------------------------------------------------------
 *  push() pushes a stackElement representing the next child of *c
 *  onto the traverse stack. If *c has no child, *first_child is set
 *  to NULL and nothing is pushed onto the stack. If *c has only one
 *  child, *c_chlid is set to that child and nothing is pushed onto
 *  the stack.  If *c has more than two children, *first_child is set
 *  to the first child and a stackElement representing the second
 *  child is pushed onto the stack.

 *  Invariants:
 *     *c_child_r is the most recent retainer of *c's children.
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 *     *c is not any of TSO, AP, PAP, AP_STACK, which means that
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 *        there cannot be any stack objects.
 *  Note: SRTs are considered to  be children as well.
 * -------------------------------------------------------------------------- */
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static INLINE void
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push( StgClosure *c, retainer c_child_r, StgClosure **first_child )
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{
    stackElement se;
    bdescr *nbd;      // Next Block Descriptor

#ifdef DEBUG_RETAINER
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    // debugBelch("push(): stackTop = 0x%x, currentStackBoundary = 0x%x\n", stackTop, currentStackBoundary);
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#endif

    ASSERT(get_itbl(c)->type != TSO);
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    ASSERT(get_itbl(c)->type != AP_STACK);
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    //
    // fill in se
    //

    se.c = c;
    se.c_child_r = c_child_r;

    // fill in se.info
    switch (get_itbl(c)->type) {
	// no child, no SRT
    case CONSTR_0_1:
    case CONSTR_0_2:
    case CAF_BLACKHOLE:
    case BLACKHOLE:
    case SE_BLACKHOLE:
    case SE_CAF_BLACKHOLE:
    case ARR_WORDS:
	*first_child = NULL;
	return;

	// one child (fixed), no SRT
    case MUT_VAR:
	*first_child = ((StgMutVar *)c)->var;
	return;
    case THUNK_SELECTOR:
	*first_child = ((StgSelector *)c)->selectee;
	return;
    case IND_PERM:
    case IND_OLDGEN_PERM:
    case IND_OLDGEN:
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	*first_child = ((StgInd *)c)->indirectee;
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	return;
    case CONSTR_1_0:
    case CONSTR_1_1:
	*first_child = c->payload[0];
	return;

	// For CONSTR_2_0 and MVAR, we use se.info.step to record the position
	// of the next child. We do not write a separate initialization code.
	// Also we do not have to initialize info.type;

	// two children (fixed), no SRT
	// need to push a stackElement, but nothing to store in se.info
    case CONSTR_2_0:
	*first_child = c->payload[0];         // return the first pointer
	// se.info.type = posTypeStep;
	// se.info.next.step = 2;            // 2 = second
	break;

	// three children (fixed), no SRT
	// need to push a stackElement
    case MVAR:
	// head must be TSO and the head of a linked list of TSOs.
	// Shoule it be a child? Seems to be yes.
	*first_child = (StgClosure *)((StgMVar *)c)->head;
	// se.info.type = posTypeStep;
	se.info.next.step = 2;            // 2 = second
	break;

	// three children (fixed), no SRT
    case WEAK:
	*first_child = ((StgWeak *)c)->key;
	// se.info.type = posTypeStep;
	se.info.next.step = 2;
	break;

	// layout.payload.ptrs, no SRT
    case CONSTR:
    case FOREIGN:
    case STABLE_NAME:
    case BCO:
    case CONSTR_STATIC:
	init_ptrs(&se.info, get_itbl(c)->layout.payload.ptrs,
		  (StgPtr)c->payload);
	*first_child = find_ptrs(&se.info);
	if (*first_child == NULL)
	    return;   // no child
	break;

	// StgMutArrPtr.ptrs, no SRT
    case MUT_ARR_PTRS:
    case MUT_ARR_PTRS_FROZEN:
	init_ptrs(&se.info, ((StgMutArrPtrs *)c)->ptrs,
		  (StgPtr)(((StgMutArrPtrs *)c)->payload));
	*first_child = find_ptrs(&se.info);
	if (*first_child == NULL)
	    return;
	break;

    // layout.payload.ptrs, SRT
    case FUN:           // *c is a heap object.
    case FUN_2_0:
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	init_ptrs(&se.info, get_itbl(c)->layout.payload.ptrs, (StgPtr)c->payload);
	*first_child = find_ptrs(&se.info);
	if (*first_child == NULL)
	    // no child from ptrs, so check SRT
	    goto fun_srt_only;
	break;

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    case THUNK:
    case THUNK_2_0:
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	init_ptrs(&se.info, get_itbl(c)->layout.payload.ptrs, 
		  (StgPtr)((StgThunk *)c)->payload);
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	*first_child = find_ptrs(&se.info);
	if (*first_child == NULL)
	    // no child from ptrs, so check SRT
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	    goto thunk_srt_only;
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	break;

	// 1 fixed child, SRT
    case FUN_1_0:
    case FUN_1_1:
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	*first_child = c->payload[0];
	ASSERT(*first_child != NULL);
	init_srt_fun(&se.info, get_fun_itbl(c));
	break;

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    case THUNK_1_0:
    case THUNK_1_1:
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	*first_child = ((StgThunk *)c)->payload[0];
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	ASSERT(*first_child != NULL);
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	init_srt_thunk(&se.info, get_thunk_itbl(c));
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	break;

    case FUN_STATIC:      // *c is a heap object.
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	ASSERT(get_itbl(c)->srt_bitmap != 0);
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    case FUN_0_1:
    case FUN_0_2:
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    fun_srt_only:
        init_srt_fun(&se.info, get_fun_itbl(c));
	*first_child = find_srt(&se.info);
	if (*first_child == NULL)
	    return;     // no child
	break;

    // SRT only
    case THUNK_STATIC:
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	ASSERT(get_itbl(c)->srt_bitmap != 0);
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    case THUNK_0_1:
    case THUNK_0_2:
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    thunk_srt_only:
        init_srt_thunk(&se.info, get_thunk_itbl(c));
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	*first_child = find_srt(&se.info);
	if (*first_child == NULL)
	    return;     // no child
	break;

	// cannot appear
    case PAP:
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    case AP:
    case AP_STACK:
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    case TSO:
    case IND_STATIC:
    case CONSTR_INTLIKE:
    case CONSTR_CHARLIKE:
    case CONSTR_NOCAF_STATIC:
	// stack objects
    case UPDATE_FRAME:
    case CATCH_FRAME:
    case STOP_FRAME:
    case RET_DYN:
    case RET_BCO:
    case RET_SMALL:
    case RET_VEC_SMALL:
    case RET_BIG:
    case RET_VEC_BIG:
	// invalid objects
    case IND:
    case BLOCKED_FETCH:
    case FETCH_ME:
    case FETCH_ME_BQ:
    case RBH:
    case REMOTE_REF:
    case EVACUATED:
    case INVALID_OBJECT:
    default:
	barf("Invalid object *c in push()");
	return;
    }

    if (stackTop - 1 < stackBottom) {
#ifdef DEBUG_RETAINER
627
	// debugBelch("push() to the next stack.\n");
628
629
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655
#endif
	// currentStack->free is updated when the active stack is switched
	// to the next stack.
	currentStack->free = (StgPtr)stackTop;

	if (currentStack->link == NULL) {
	    nbd = allocGroup(BLOCKS_IN_STACK);
	    nbd->link = NULL;
	    nbd->u.back = currentStack;
	    currentStack->link = nbd;
	} else
	    nbd = currentStack->link;

	newStackBlock(nbd);
    }

    // adjust stackTop (acutal push)
    stackTop--;
    // If the size of stackElement was huge, we would better replace the
    // following statement by either a memcpy() call or a switch statement
    // on the type of the element. Currently, the size of stackElement is
    // small enough (5 words) that this direct assignment seems to be enough.
    *stackTop = se;

#ifdef DEBUG_RETAINER
    stackSize++;
    if (stackSize > maxStackSize) maxStackSize = stackSize;
    // ASSERT(stackSize >= 0);
656
    // debugBelch("stackSize = %d\n", stackSize);
657
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660
661
662
663
664
665
666
667
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669
#endif
}

/* -----------------------------------------------------------------------------
 *  popOff() and popOffReal(): Pop a stackElement off the traverse stack.
 *  Invariants:
 *    stackTop cannot be equal to stackLimit unless the whole stack is
 *    empty, in which case popOff() is not allowed.
 *  Note:
 *    You can think of popOffReal() as a part of popOff() which is
 *    executed at the end of popOff() in necessary. Since popOff() is
 *    likely to be executed quite often while popOffReal() is not, we
 *    separate popOffReal() from popOff(), which is declared as an
670
 *    INLINE function (for the sake of execution speed).  popOffReal()
671
672
673
674
675
676
677
678
 *    is called only within popOff() and nowhere else.
 * -------------------------------------------------------------------------- */
static void
popOffReal(void)
{
    bdescr *pbd;    // Previous Block Descriptor

#ifdef DEBUG_RETAINER
679
    // debugBelch("pop() to the previous stack.\n");
680
681
682
683
684
685
686
687
688
689
690
691
692
693
#endif

    ASSERT(stackTop + 1 == stackLimit);
    ASSERT(stackBottom == (stackElement *)currentStack->start);

    if (firstStack == currentStack) {
	// The stack is completely empty.
	stackTop++;
	ASSERT(stackTop == stackLimit);
#ifdef DEBUG_RETAINER
	stackSize--;
	if (stackSize > maxStackSize) maxStackSize = stackSize;
	/*
	  ASSERT(stackSize >= 0);
694
	  debugBelch("stackSize = %d\n", stackSize);
695
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701
702
703
704
705
706
707
708
709
710
711
712
713
714
	*/
#endif
	return;
    }

    // currentStack->free is updated when the active stack is switched back
    // to the previous stack.
    currentStack->free = (StgPtr)stackLimit;

    // find the previous block descriptor
    pbd = currentStack->u.back;
    ASSERT(pbd != NULL);

    returnToOldStack(pbd);

#ifdef DEBUG_RETAINER
    stackSize--;
    if (stackSize > maxStackSize) maxStackSize = stackSize;
    /*
      ASSERT(stackSize >= 0);
715
      debugBelch("stackSize = %d\n", stackSize);
716
717
718
719
    */
#endif
}

720
static INLINE void
721
722
popOff(void) {
#ifdef DEBUG_RETAINER
723
    // debugBelch("\tpopOff(): stackTop = 0x%x, currentStackBoundary = 0x%x\n", stackTop, currentStackBoundary);
724
725
726
727
728
729
730
731
732
733
734
735
736
#endif

    ASSERT(stackTop != stackLimit);
    ASSERT(!isEmptyRetainerStack());

    // <= (instead of <) is wrong!
    if (stackTop + 1 < stackLimit) {
	stackTop++;
#ifdef DEBUG_RETAINER
	stackSize--;
	if (stackSize > maxStackSize) maxStackSize = stackSize;
	/*
	  ASSERT(stackSize >= 0);
737
	  debugBelch("stackSize = %d\n", stackSize);
738
739
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741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
	*/
#endif
	return;
    }

    popOffReal();
}

/* -----------------------------------------------------------------------------
 *  Finds the next object to be considered for retainer profiling and store
 *  its pointer to *c.
 *  Test if the topmost stack element indicates that more objects are left,
 *  and if so, retrieve the first object and store its pointer to *c. Also,
 *  set *cp and *r appropriately, both of which are stored in the stack element.
 *  The topmost stack element then is overwritten so as for it to now denote
 *  the next object.
 *  If the topmost stack element indicates no more objects are left, pop
 *  off the stack element until either an object can be retrieved or
 *  the current stack chunk becomes empty, indicated by rtsTrue returned by
 *  isOnBoundary(), in which case *c is set to NULL.
 *  Note:
 *    It is okay to call this function even when the current stack chunk
 *    is empty.
 * -------------------------------------------------------------------------- */
762
static INLINE void
763
pop( StgClosure **c, StgClosure **cp, retainer *r )
764
765
766
767
{
    stackElement *se;

#ifdef DEBUG_RETAINER
768
    // debugBelch("pop(): stackTop = 0x%x, currentStackBoundary = 0x%x\n", stackTop, currentStackBoundary);
769
770
771
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822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
#endif

    do {
	if (isOnBoundary()) {     // if the current stack chunk is depleted
	    *c = NULL;
	    return;
	}

	se = stackTop;

	switch (get_itbl(se->c)->type) {
	    // two children (fixed), no SRT
	    // nothing in se.info
	case CONSTR_2_0:
	    *c = se->c->payload[1];
	    *cp = se->c;
	    *r = se->c_child_r;
	    popOff();
	    return;

	    // three children (fixed), no SRT
	    // need to push a stackElement
	case MVAR:
	    if (se->info.next.step == 2) {
		*c = (StgClosure *)((StgMVar *)se->c)->tail;
		se->info.next.step++;             // move to the next step
		// no popOff
	    } else {
		*c = ((StgMVar *)se->c)->value;
		popOff();
	    }
	    *cp = se->c;
	    *r = se->c_child_r;
	    return;

	    // three children (fixed), no SRT
	case WEAK:
	    if (se->info.next.step == 2) {
		*c = ((StgWeak *)se->c)->value;
		se->info.next.step++;
		// no popOff
	    } else {
		*c = ((StgWeak *)se->c)->finalizer;
		popOff();
	    }
	    *cp = se->c;
	    *r = se->c_child_r;
	    return;

	case CONSTR:
	case FOREIGN:
	case STABLE_NAME:
	case BCO:
	case CONSTR_STATIC:
	    // StgMutArrPtr.ptrs, no SRT
	case MUT_ARR_PTRS:
	case MUT_ARR_PTRS_FROZEN:
	    *c = find_ptrs(&se->info);
	    if (*c == NULL) {
		popOff();
		break;
	    }
	    *cp = se->c;
	    *r = se->c_child_r;
	    return;

	    // layout.payload.ptrs, SRT
	case FUN:         // always a heap object
	case FUN_2_0:
838
839
840
841
842
843
844
845
846
847
848
	    if (se->info.type == posTypePtrs) {
		*c = find_ptrs(&se->info);
		if (*c != NULL) {
		    *cp = se->c;
		    *r = se->c_child_r;
		    return;
		}
		init_srt_fun(&se->info, get_fun_itbl(se->c));
	    }
	    goto do_srt;

849
850
851
852
853
854
855
856
857
	case THUNK:
	case THUNK_2_0:
	    if (se->info.type == posTypePtrs) {
		*c = find_ptrs(&se->info);
		if (*c != NULL) {
		    *cp = se->c;
		    *r = se->c_child_r;
		    return;
		}
858
		init_srt_thunk(&se->info, get_thunk_itbl(se->c));
859
	    }
860
	    goto do_srt;
861
862

	    // SRT
863
	do_srt:
864
865
866
867
868
869
870
871
872
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890
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893
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899
	case THUNK_STATIC:
	case FUN_STATIC:
	case FUN_0_1:
	case FUN_0_2:
	case THUNK_0_1:
	case THUNK_0_2:
	case FUN_1_0:
	case FUN_1_1:
	case THUNK_1_0:
	case THUNK_1_1:
	    *c = find_srt(&se->info);
	    if (*c != NULL) {
		*cp = se->c;
		*r = se->c_child_r;
		return;
	    }
	    popOff();
	    break;

	    // no child (fixed), no SRT
	case CONSTR_0_1:
	case CONSTR_0_2:
	case CAF_BLACKHOLE:
	case BLACKHOLE:
	case SE_BLACKHOLE:
	case SE_CAF_BLACKHOLE:
	case ARR_WORDS:
	    // one child (fixed), no SRT
	case MUT_VAR:
	case THUNK_SELECTOR:
	case IND_PERM:
	case IND_OLDGEN_PERM:
	case IND_OLDGEN:
	case CONSTR_1_1:
	    // cannot appear
	case PAP:
900
901
	case AP:
	case AP_STACK:
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
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926
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931
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946
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958
959
960
961
962
963
964
965
966
967
968
	case TSO:
	case IND_STATIC:
	case CONSTR_INTLIKE:
	case CONSTR_CHARLIKE:
	case CONSTR_NOCAF_STATIC:
	    // stack objects
	case RET_DYN:
	case UPDATE_FRAME:
	case CATCH_FRAME:
	case STOP_FRAME:
	case RET_BCO:
	case RET_SMALL:
	case RET_VEC_SMALL:
	case RET_BIG:
	case RET_VEC_BIG:
	    // invalid objects
	case IND:
	case BLOCKED_FETCH:
	case FETCH_ME:
	case FETCH_ME_BQ:
	case RBH:
	case REMOTE_REF:
	case EVACUATED:
	case INVALID_OBJECT:
	default:
	    barf("Invalid object *c in pop()");
	    return;
	}
    } while (rtsTrue);
}

/* -----------------------------------------------------------------------------
 * RETAINER PROFILING ENGINE
 * -------------------------------------------------------------------------- */

void
initRetainerProfiling( void )
{
    initializeAllRetainerSet();
    retainerGeneration = 0;
}

/* -----------------------------------------------------------------------------
 *  This function must be called before f-closing prof_file.
 * -------------------------------------------------------------------------- */
void
endRetainerProfiling( void )
{
#ifdef SECOND_APPROACH
    outputAllRetainerSet(prof_file);
#endif
}

/* -----------------------------------------------------------------------------
 *  Returns the actual pointer to the retainer set of the closure *c.
 *  It may adjust RSET(c) subject to flip.
 *  Side effects:
 *    RSET(c) is initialized to NULL if its current value does not
 *    conform to flip.
 *  Note:
 *    Even though this function has side effects, they CAN be ignored because
 *    subsequent calls to retainerSetOf() always result in the same return value
 *    and retainerSetOf() is the only way to retrieve retainerSet of a given
 *    closure.
 *    We have to perform an XOR (^) operation each time a closure is examined.
 *    The reason is that we do not know when a closure is visited last.
 * -------------------------------------------------------------------------- */
969
static INLINE void
970
971
972
973
974
975
976
977
978
979
maybeInitRetainerSet( StgClosure *c )
{
    if (!isRetainerSetFieldValid(c)) {
	setRetainerSetToNull(c);
    }
}

/* -----------------------------------------------------------------------------
 * Returns rtsTrue if *c is a retainer.
 * -------------------------------------------------------------------------- */
980
static INLINE rtsBool
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
isRetainer( StgClosure *c )
{
    switch (get_itbl(c)->type) {
	//
	//  True case
	//
	// TSOs MUST be retainers: they constitute the set of roots.
    case TSO:

	// mutable objects
    case MVAR:
    case MUT_VAR:
    case MUT_ARR_PTRS:
    case MUT_ARR_PTRS_FROZEN:

	// thunks are retainers.
    case THUNK:
    case THUNK_1_0:
    case THUNK_0_1:
    case THUNK_2_0:
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