PrimOps.cmm 52.3 KB
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/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 1998-2004
 *
 * Out-of-line primitive operations
 *
 * This file contains the implementations of all the primitive
 * operations ("primops") which are not expanded inline.  See
 * ghc/compiler/prelude/primops.txt.pp for a list of all the primops;
 * this file contains code for most of those with the attribute
 * out_of_line=True.
 *
 * Entry convention: the entry convention for a primop is that all the
 * args are in Stg registers (R1, R2, etc.).  This is to make writing
 * the primops easier.  (see compiler/codeGen/CgCallConv.hs).
 *
 * Return convention: results from a primop are generally returned
 * using the ordinary unboxed tuple return convention.  The C-- parser
 * implements the RET_xxxx() macros to perform unboxed-tuple returns
 * based on the prevailing return convention.
 *
 * This file is written in a subset of C--, extended with various
 * features specific to GHC.  It is compiled by GHC directly.  For the
 * syntax of .cmm files, see the parser in ghc/compiler/cmm/CmmParse.y.
 *
 * ---------------------------------------------------------------------------*/

#include "Cmm.h"

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#ifdef __PIC__
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import pthread_mutex_lock;
import pthread_mutex_unlock;
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#endif
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import base_ControlziExceptionziBase_nestedAtomically_closure;
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import EnterCriticalSection;
import LeaveCriticalSection;
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import ghczmprim_GHCziBool_False_closure;
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/*-----------------------------------------------------------------------------
  Array Primitives

  Basically just new*Array - the others are all inline macros.

  The size arg is always passed in R1, and the result returned in R1.

  The slow entry point is for returning from a heap check, the saved
  size argument must be re-loaded from the stack.
  -------------------------------------------------------------------------- */

/* for objects that are *less* than the size of a word, make sure we
 * round up to the nearest word for the size of the array.
 */

newByteArrayzh_fast
{
    W_ words, payload_words, n, p;
    MAYBE_GC(NO_PTRS,newByteArrayzh_fast);
    n = R1;
    payload_words = ROUNDUP_BYTES_TO_WDS(n);
    words = BYTES_TO_WDS(SIZEOF_StgArrWords) + payload_words;
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    ("ptr" p) = foreign "C" allocateLocal(MyCapability() "ptr",words) [];
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    TICK_ALLOC_PRIM(SIZEOF_StgArrWords,WDS(payload_words),0);
    SET_HDR(p, stg_ARR_WORDS_info, W_[CCCS]);
    StgArrWords_words(p) = payload_words;
    RET_P(p);
}

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#define BA_ALIGN 16
#define BA_MASK  (BA_ALIGN-1)

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newPinnedByteArrayzh_fast
{
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    W_ words, bytes, payload_words, p;
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    MAYBE_GC(NO_PTRS,newPinnedByteArrayzh_fast);
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    bytes = R1;
    /* payload_words is what we will tell the profiler we had to allocate */
    payload_words = ROUNDUP_BYTES_TO_WDS(bytes);
    /* When we actually allocate memory, we need to allow space for the
       header: */
    bytes = bytes + SIZEOF_StgArrWords;
    /* And we want to align to BA_ALIGN bytes, so we need to allow space
       to shift up to BA_ALIGN - 1 bytes: */
    bytes = bytes + BA_ALIGN - 1;
    /* Now we convert to a number of words: */
    words = ROUNDUP_BYTES_TO_WDS(bytes);
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    ("ptr" p) = foreign "C" allocatePinned(words) [];
    TICK_ALLOC_PRIM(SIZEOF_StgArrWords,WDS(payload_words),0);

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    /* Now we need to move p forward so that the payload is aligned
       to BA_ALIGN bytes: */
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    p = p + ((-p - SIZEOF_StgArrWords) & BA_MASK);

    SET_HDR(p, stg_ARR_WORDS_info, W_[CCCS]);
    StgArrWords_words(p) = payload_words;
    RET_P(p);
}

newAlignedPinnedByteArrayzh_fast
{
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    W_ words, bytes, payload_words, p, alignment;
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    MAYBE_GC(NO_PTRS,newAlignedPinnedByteArrayzh_fast);
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    bytes = R1;
    alignment = R2;
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    /* payload_words is what we will tell the profiler we had to allocate */
    payload_words = ROUNDUP_BYTES_TO_WDS(bytes);
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    /* When we actually allocate memory, we need to allow space for the
       header: */
    bytes = bytes + SIZEOF_StgArrWords;
    /* And we want to align to <alignment> bytes, so we need to allow space
       to shift up to <alignment - 1> bytes: */
    bytes = bytes + alignment - 1;
    /* Now we convert to a number of words: */
    words = ROUNDUP_BYTES_TO_WDS(bytes);
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    ("ptr" p) = foreign "C" allocatePinned(words) [];
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    TICK_ALLOC_PRIM(SIZEOF_StgArrWords,WDS(payload_words),0);

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    /* Now we need to move p forward so that the payload is aligned
       to <alignment> bytes. Note that we are assuming that
       <alignment> is a power of 2, which is technically not guaranteed */
    p = p + ((-p - SIZEOF_StgArrWords) & (alignment - 1));
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    SET_HDR(p, stg_ARR_WORDS_info, W_[CCCS]);
    StgArrWords_words(p) = payload_words;
    RET_P(p);
}

newArrayzh_fast
{
    W_ words, n, init, arr, p;
    /* Args: R1 = words, R2 = initialisation value */

    n = R1;
    MAYBE_GC(R2_PTR,newArrayzh_fast);

    words = BYTES_TO_WDS(SIZEOF_StgMutArrPtrs) + n;
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    ("ptr" arr) = foreign "C" allocateLocal(MyCapability() "ptr",words) [R2];
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    TICK_ALLOC_PRIM(SIZEOF_StgMutArrPtrs, WDS(n), 0);

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    SET_HDR(arr, stg_MUT_ARR_PTRS_DIRTY_info, W_[CCCS]);
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    StgMutArrPtrs_ptrs(arr) = n;

    // Initialise all elements of the the array with the value in R2
    init = R2;
    p = arr + SIZEOF_StgMutArrPtrs;
  for:
    if (p < arr + WDS(words)) {
	W_[p] = init;
	p = p + WDS(1);
	goto for;
    }

    RET_P(arr);
}

unsafeThawArrayzh_fast
{
  // SUBTLETY TO DO WITH THE OLD GEN MUTABLE LIST
  //
  // A MUT_ARR_PTRS lives on the mutable list, but a MUT_ARR_PTRS_FROZEN 
  // normally doesn't.  However, when we freeze a MUT_ARR_PTRS, we leave
  // it on the mutable list for the GC to remove (removing something from
  // the mutable list is not easy, because the mut_list is only singly-linked).
  // 
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  // So that we can tell whether a MUT_ARR_PTRS_FROZEN is on the mutable list,
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  // when we freeze it we set the info ptr to be MUT_ARR_PTRS_FROZEN0
  // to indicate that it is still on the mutable list.
  //
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  // So, when we thaw a MUT_ARR_PTRS_FROZEN, we must cope with two cases:
  // either it is on a mut_list, or it isn't.  We adopt the convention that
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  // the closure type is MUT_ARR_PTRS_FROZEN0 if it is on the mutable list,
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  // and MUT_ARR_PTRS_FROZEN otherwise.  In fact it wouldn't matter if
  // we put it on the mutable list more than once, but it would get scavenged
  // multiple times during GC, which would be unnecessarily slow.
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  //
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  if (StgHeader_info(R1) != stg_MUT_ARR_PTRS_FROZEN0_info) {
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	SET_INFO(R1,stg_MUT_ARR_PTRS_DIRTY_info);
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	recordMutable(R1, R1);
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	// must be done after SET_INFO, because it ASSERTs closure_MUTABLE()
	RET_P(R1);
  } else {
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	SET_INFO(R1,stg_MUT_ARR_PTRS_DIRTY_info);
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	RET_P(R1);
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  }
}

/* -----------------------------------------------------------------------------
   MutVar primitives
   -------------------------------------------------------------------------- */

newMutVarzh_fast
{
    W_ mv;
    /* Args: R1 = initialisation value */

    ALLOC_PRIM( SIZEOF_StgMutVar, R1_PTR, newMutVarzh_fast);

    mv = Hp - SIZEOF_StgMutVar + WDS(1);
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    SET_HDR(mv,stg_MUT_VAR_DIRTY_info,W_[CCCS]);
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    StgMutVar_var(mv) = R1;
    
    RET_P(mv);
}

atomicModifyMutVarzh_fast
{
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    W_ mv, f, z, x, y, r, h;
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    /* Args: R1 :: MutVar#,  R2 :: a -> (a,b) */

    /* If x is the current contents of the MutVar#, then 
       We want to make the new contents point to

         (sel_0 (f x))
 
       and the return value is
	 
	 (sel_1 (f x))

        obviously we can share (f x).

         z = [stg_ap_2 f x]  (max (HS + 2) MIN_UPD_SIZE)
	 y = [stg_sel_0 z]   (max (HS + 1) MIN_UPD_SIZE)
         r = [stg_sel_1 z]   (max (HS + 1) MIN_UPD_SIZE)
    */

#if MIN_UPD_SIZE > 1
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#define THUNK_1_SIZE (SIZEOF_StgThunkHeader + WDS(MIN_UPD_SIZE))
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#define TICK_ALLOC_THUNK_1() TICK_ALLOC_UP_THK(WDS(1),WDS(MIN_UPD_SIZE-1))
#else
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#define THUNK_1_SIZE (SIZEOF_StgThunkHeader + WDS(1))
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#define TICK_ALLOC_THUNK_1() TICK_ALLOC_UP_THK(WDS(1),0)
#endif

#if MIN_UPD_SIZE > 2
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#define THUNK_2_SIZE (SIZEOF_StgThunkHeader + WDS(MIN_UPD_SIZE))
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#define TICK_ALLOC_THUNK_2() TICK_ALLOC_UP_THK(WDS(2),WDS(MIN_UPD_SIZE-2))
#else
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#define THUNK_2_SIZE (SIZEOF_StgThunkHeader + WDS(2))
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#define TICK_ALLOC_THUNK_2() TICK_ALLOC_UP_THK(WDS(2),0)
#endif

#define SIZE (THUNK_2_SIZE + THUNK_1_SIZE + THUNK_1_SIZE)

   HP_CHK_GEN_TICKY(SIZE, R1_PTR & R2_PTR, atomicModifyMutVarzh_fast);

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   mv = R1;
   f = R2;
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   TICK_ALLOC_THUNK_2();
   CCCS_ALLOC(THUNK_2_SIZE);
   z = Hp - THUNK_2_SIZE + WDS(1);
   SET_HDR(z, stg_ap_2_upd_info, W_[CCCS]);
   LDV_RECORD_CREATE(z);
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   StgThunk_payload(z,0) = f;
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   TICK_ALLOC_THUNK_1();
   CCCS_ALLOC(THUNK_1_SIZE);
   y = z - THUNK_1_SIZE;
   SET_HDR(y, stg_sel_0_upd_info, W_[CCCS]);
   LDV_RECORD_CREATE(y);
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   StgThunk_payload(y,0) = z;
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   TICK_ALLOC_THUNK_1();
   CCCS_ALLOC(THUNK_1_SIZE);
   r = y - THUNK_1_SIZE;
   SET_HDR(r, stg_sel_1_upd_info, W_[CCCS]);
   LDV_RECORD_CREATE(r);
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   StgThunk_payload(r,0) = z;

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 retry:
   x = StgMutVar_var(mv);
   StgThunk_payload(z,1) = x;
#ifdef THREADED_RTS
   (h) = foreign "C" cas(mv + SIZEOF_StgHeader + OFFSET_StgMutVar_var, x, y) [];
   if (h != x) { goto retry; }
#else
   StgMutVar_var(mv) = y;
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#endif
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   if (GET_INFO(mv) == stg_MUT_VAR_CLEAN_info) {
     foreign "C" dirty_MUT_VAR(BaseReg "ptr", mv "ptr") [];
   }

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   RET_P(r);
}

/* -----------------------------------------------------------------------------
   Weak Pointer Primitives
   -------------------------------------------------------------------------- */

STRING(stg_weak_msg,"New weak pointer at %p\n")

mkWeakzh_fast
{
  /* R1 = key
     R2 = value
     R3 = finalizer (or NULL)
  */
  W_ w;

  if (R3 == NULL) {
    R3 = stg_NO_FINALIZER_closure;
  }

  ALLOC_PRIM( SIZEOF_StgWeak, R1_PTR & R2_PTR & R3_PTR, mkWeakzh_fast );

  w = Hp - SIZEOF_StgWeak + WDS(1);
  SET_HDR(w, stg_WEAK_info, W_[CCCS]);

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  // We don't care about cfinalizer here.
  // Should StgWeak_cfinalizer(w) be stg_NO_FINALIZER_closure or
  // something else?

  StgWeak_key(w)        = R1;
  StgWeak_value(w)      = R2;
  StgWeak_finalizer(w)  = R3;
  StgWeak_cfinalizer(w) = stg_NO_FINALIZER_closure;
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  StgWeak_link(w)	= W_[weak_ptr_list];
  W_[weak_ptr_list] 	= w;

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  IF_DEBUG(weak, foreign "C" debugBelch(stg_weak_msg,w) []);
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  RET_P(w);
}

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mkWeakForeignEnvzh_fast
{
  /* R1 = key
     R2 = value
     R3 = finalizer
     R4 = pointer
     R5 = has environment (0 or 1)
     R6 = environment
  */
  W_ w, payload_words, words, p;

  W_ key, val, fptr, ptr, flag, eptr;

  key  = R1;
  val  = R2;
  fptr = R3;
  ptr  = R4;
  flag = R5;
  eptr = R6;

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  ALLOC_PRIM( SIZEOF_StgWeak, R1_PTR & R2_PTR, mkWeakForeignEnvzh_fast );
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  w = Hp - SIZEOF_StgWeak + WDS(1);
  SET_HDR(w, stg_WEAK_info, W_[CCCS]);

  payload_words = 4;
  words         = BYTES_TO_WDS(SIZEOF_StgArrWords) + payload_words;
  ("ptr" p)     = foreign "C" allocateLocal(MyCapability() "ptr", words) [];

  TICK_ALLOC_PRIM(SIZEOF_StgArrWords,WDS(payload_words),0);
  SET_HDR(p, stg_ARR_WORDS_info, W_[CCCS]);

  StgArrWords_words(p)     = payload_words;
  StgArrWords_payload(p,0) = fptr;
  StgArrWords_payload(p,1) = ptr;
  StgArrWords_payload(p,2) = eptr;
  StgArrWords_payload(p,3) = flag;

  // We don't care about the value here.
  // Should StgWeak_value(w) be stg_NO_FINALIZER_closure or something else?

  StgWeak_key(w)        = key;
  StgWeak_value(w)      = val;
  StgWeak_finalizer(w)  = stg_NO_FINALIZER_closure;
  StgWeak_cfinalizer(w) = p;

  StgWeak_link(w)   = W_[weak_ptr_list];
  W_[weak_ptr_list] = w;

  IF_DEBUG(weak, foreign "C" debugBelch(stg_weak_msg,w) []);

  RET_P(w);
}
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finalizzeWeakzh_fast
{
  /* R1 = weak ptr
   */
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  W_ w, f, arr;
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  w = R1;

  // already dead?
  if (GET_INFO(w) == stg_DEAD_WEAK_info) {
      RET_NP(0,stg_NO_FINALIZER_closure);
  }

  // kill it
#ifdef PROFILING
  // @LDV profiling
  // A weak pointer is inherently used, so we do not need to call
  // LDV_recordDead_FILL_SLOP_DYNAMIC():
  //    LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)w);
  // or, LDV_recordDead():
  //    LDV_recordDead((StgClosure *)w, sizeofW(StgWeak) - sizeofW(StgProfHeader));
  // Furthermore, when PROFILING is turned on, dead weak pointers are exactly as 
  // large as weak pointers, so there is no need to fill the slop, either.
  // See stg_DEAD_WEAK_info in StgMiscClosures.hc.
#endif

  //
  // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
  //
  SET_INFO(w,stg_DEAD_WEAK_info);
  LDV_RECORD_CREATE(w);

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  f   = StgWeak_finalizer(w);
  arr = StgWeak_cfinalizer(w);

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  StgDeadWeak_link(w) = StgWeak_link(w);
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  if (arr != stg_NO_FINALIZER_closure) {
    foreign "C" runCFinalizer(StgArrWords_payload(arr,0),
                              StgArrWords_payload(arr,1),
                              StgArrWords_payload(arr,2),
                              StgArrWords_payload(arr,3)) [];
  }

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  /* return the finalizer */
  if (f == stg_NO_FINALIZER_closure) {
      RET_NP(0,stg_NO_FINALIZER_closure);
  } else {
      RET_NP(1,f);
  }
}

deRefWeakzh_fast
{
  /* R1 = weak ptr */
  W_ w, code, val;

  w = R1;
  if (GET_INFO(w) == stg_WEAK_info) {
    code = 1;
    val = StgWeak_value(w);
  } else {
    code = 0;
    val = w;
  }
  RET_NP(code,val);
}

/* -----------------------------------------------------------------------------
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   Floating point operations.
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   -------------------------------------------------------------------------- */

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decodeFloatzuIntzh_fast
{ 
    W_ p;
    F_ arg;
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    W_ mp_tmp1;
    W_ mp_tmp_w;

    STK_CHK_GEN( WDS(2), NO_PTRS, decodeFloatzuIntzh_fast );

    mp_tmp1  = Sp - WDS(1);
    mp_tmp_w = Sp - WDS(2);
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    /* arguments: F1 = Float# */
    arg = F1;
    
    /* Perform the operation */
    foreign "C" __decodeFloat_Int(mp_tmp1 "ptr", mp_tmp_w "ptr", arg) [];
    
    /* returns: (Int# (mantissa), Int# (exponent)) */
    RET_NN(W_[mp_tmp1], W_[mp_tmp_w]);
}

decodeDoublezu2Intzh_fast
{ 
    D_ arg;
    W_ p;
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    W_ mp_tmp1;
    W_ mp_tmp2;
    W_ mp_result1;
    W_ mp_result2;

    STK_CHK_GEN( WDS(4), NO_PTRS, decodeDoublezu2Intzh_fast );

    mp_tmp1    = Sp - WDS(1);
    mp_tmp2    = Sp - WDS(2);
    mp_result1 = Sp - WDS(3);
    mp_result2 = Sp - WDS(4);
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    /* arguments: D1 = Double# */
    arg = D1;

    /* Perform the operation */
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    foreign "C" __decodeDouble_2Int(mp_tmp1 "ptr", mp_tmp2 "ptr",
                                    mp_result1 "ptr", mp_result2 "ptr",
                                    arg) [];

    /* returns:
       (Int# (mant sign), Word# (mant high), Word# (mant low), Int# (expn)) */
    RET_NNNN(W_[mp_tmp1], W_[mp_tmp2], W_[mp_result1], W_[mp_result2]);
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}

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/* -----------------------------------------------------------------------------
 * Concurrency primitives
 * -------------------------------------------------------------------------- */

forkzh_fast
{
  /* args: R1 = closure to spark */
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  MAYBE_GC(R1_PTR, forkzh_fast);

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  W_ closure;
  W_ threadid;
  closure = R1;

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  ("ptr" threadid) = foreign "C" createIOThread( MyCapability() "ptr", 
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				RtsFlags_GcFlags_initialStkSize(RtsFlags), 
				closure "ptr") [];
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  /* start blocked if the current thread is blocked */
  StgTSO_flags(threadid) = 
     StgTSO_flags(threadid) |  (StgTSO_flags(CurrentTSO) & 
                                (TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32));

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  foreign "C" scheduleThread(MyCapability() "ptr", threadid "ptr") [];

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  // context switch soon, but not immediately: we don't want every
  // forkIO to force a context-switch.
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  Capability_context_switch(MyCapability()) = 1 :: CInt;
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  RET_P(threadid);
}

forkOnzh_fast
{
  /* args: R1 = cpu, R2 = closure to spark */

  MAYBE_GC(R2_PTR, forkOnzh_fast);

  W_ cpu;
  W_ closure;
  W_ threadid;
  cpu = R1;
  closure = R2;

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  ("ptr" threadid) = foreign "C" createIOThread( MyCapability() "ptr", 
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				RtsFlags_GcFlags_initialStkSize(RtsFlags), 
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				closure "ptr") [];
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  /* start blocked if the current thread is blocked */
  StgTSO_flags(threadid) = 
     StgTSO_flags(threadid) |  (StgTSO_flags(CurrentTSO) & 
                                (TSO_BLOCKEX::I32 | TSO_INTERRUPTIBLE::I32));

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  foreign "C" scheduleThreadOn(MyCapability() "ptr", cpu, threadid "ptr") [];
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  // context switch soon, but not immediately: we don't want every
  // forkIO to force a context-switch.
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  Capability_context_switch(MyCapability()) = 1 :: CInt;
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  RET_P(threadid);
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}

yieldzh_fast
{
  jump stg_yield_noregs;
}

myThreadIdzh_fast
{
  /* no args. */
  RET_P(CurrentTSO);
}

labelThreadzh_fast
{
  /* args: 
	R1 = ThreadId#
	R2 = Addr# */
#ifdef DEBUG
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  foreign "C" labelThread(R1 "ptr", R2 "ptr") [];
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#endif
  jump %ENTRY_CODE(Sp(0));
}

isCurrentThreadBoundzh_fast
{
  /* no args */
  W_ r;
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  (r) = foreign "C" isThreadBound(CurrentTSO) [];
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  RET_N(r);
}

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threadStatuszh_fast
{
    /* args: R1 :: ThreadId# */
    W_ tso;
    W_ why_blocked;
    W_ what_next;
    W_ ret;

    tso = R1;
    loop:
      if (TO_W_(StgTSO_what_next(tso)) == ThreadRelocated) {
          tso = StgTSO__link(tso);
          goto loop;
      }

    what_next   = TO_W_(StgTSO_what_next(tso));
    why_blocked = TO_W_(StgTSO_why_blocked(tso));
    // Note: these two reads are not atomic, so they might end up
    // being inconsistent.  It doesn't matter, since we
    // only return one or the other.  If we wanted to return the
    // contents of block_info too, then we'd have to do some synchronisation.

    if (what_next == ThreadComplete) {
        ret = 16;  // NB. magic, matches up with GHC.Conc.threadStatus
    } else {
        if (what_next == ThreadKilled) {
            ret = 17;
        } else {
            ret = why_blocked;
        }
    }
    RET_N(ret);
}
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/* -----------------------------------------------------------------------------
 * TVar primitives
 * -------------------------------------------------------------------------- */

#define SP_OFF 0

// Catch retry frame ------------------------------------------------------------

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INFO_TABLE_RET(stg_catch_retry_frame, CATCH_RETRY_FRAME,
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#if defined(PROFILING)
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  W_ unused1, W_ unused2,
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#endif
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  W_ unused3, P_ unused4, P_ unused5)
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{
   W_ r, frame, trec, outer;

   frame = Sp;
   trec = StgTSO_trec(CurrentTSO);
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   ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
   (r) = foreign "C" stmCommitNestedTransaction(MyCapability() "ptr", trec "ptr") [];
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   if (r != 0) {
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     /* Succeeded (either first branch or second branch) */
     StgTSO_trec(CurrentTSO) = outer;
     Sp = Sp + SIZEOF_StgCatchRetryFrame;
     jump %ENTRY_CODE(Sp(SP_OFF));
   } else {
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     /* Did not commit: re-execute */
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     W_ new_trec;
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     ("ptr" new_trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", outer "ptr") [];
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     StgTSO_trec(CurrentTSO) = new_trec;
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     if (StgCatchRetryFrame_running_alt_code(frame) != 0::I32) {
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       R1 = StgCatchRetryFrame_alt_code(frame);
     } else {
       R1 = StgCatchRetryFrame_first_code(frame);
     }
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     jump stg_ap_v_fast;
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   }
}
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// Atomically frame ------------------------------------------------------------
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INFO_TABLE_RET(stg_atomically_frame, ATOMICALLY_FRAME,
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#if defined(PROFILING)
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  W_ unused1, W_ unused2,
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#endif
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  P_ code, P_ next_invariant_to_check, P_ result)
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{
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  W_ frame, trec, valid, next_invariant, q, outer;
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  frame  = Sp;
  trec   = StgTSO_trec(CurrentTSO);
  result = R1;
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  ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
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  if (outer == NO_TREC) {
    /* First time back at the atomically frame -- pick up invariants */
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    ("ptr" q) = foreign "C" stmGetInvariantsToCheck(MyCapability() "ptr", trec "ptr") [];
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    StgAtomicallyFrame_next_invariant_to_check(frame) = q;
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    StgAtomicallyFrame_result(frame) = result;
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  } else {
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    /* Second/subsequent time back at the atomically frame -- abort the
     * tx that's checking the invariant and move on to the next one */
    StgTSO_trec(CurrentTSO) = outer;
    q = StgAtomicallyFrame_next_invariant_to_check(frame);
    StgInvariantCheckQueue_my_execution(q) = trec;
    foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
    /* Don't free trec -- it's linked from q and will be stashed in the
     * invariant if we eventually commit. */
    q = StgInvariantCheckQueue_next_queue_entry(q);
    StgAtomicallyFrame_next_invariant_to_check(frame) = q;
    trec = outer;
  }

  q = StgAtomicallyFrame_next_invariant_to_check(frame);

  if (q != END_INVARIANT_CHECK_QUEUE) {
    /* We can't commit yet: another invariant to check */
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    ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", trec "ptr") [];
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    StgTSO_trec(CurrentTSO) = trec;
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    next_invariant = StgInvariantCheckQueue_invariant(q);
    R1 = StgAtomicInvariant_code(next_invariant);
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    jump stg_ap_v_fast;
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  } else {

    /* We've got no more invariants to check, try to commit */
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    (valid) = foreign "C" stmCommitTransaction(MyCapability() "ptr", trec "ptr") [];
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    if (valid != 0) {
      /* Transaction was valid: commit succeeded */
      StgTSO_trec(CurrentTSO) = NO_TREC;
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      R1 = StgAtomicallyFrame_result(frame);
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      Sp = Sp + SIZEOF_StgAtomicallyFrame;
      jump %ENTRY_CODE(Sp(SP_OFF));
    } else {
      /* Transaction was not valid: try again */
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      ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
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      StgTSO_trec(CurrentTSO) = trec;
      StgAtomicallyFrame_next_invariant_to_check(frame) = END_INVARIANT_CHECK_QUEUE;
      R1 = StgAtomicallyFrame_code(frame);
      jump stg_ap_v_fast;
    }
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  }
}

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INFO_TABLE_RET(stg_atomically_waiting_frame, ATOMICALLY_FRAME,
#if defined(PROFILING)
  W_ unused1, W_ unused2,
#endif
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  P_ code, P_ next_invariant_to_check, P_ result)
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{
  W_ frame, trec, valid;

  frame = Sp;

  /* The TSO is currently waiting: should we stop waiting? */
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  (valid) = foreign "C" stmReWait(MyCapability() "ptr", CurrentTSO "ptr") [];
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  if (valid != 0) {
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    /* Previous attempt is still valid: no point trying again yet */
    jump stg_block_noregs;
  } else {
    /* Previous attempt is no longer valid: try again */
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    ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
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    StgTSO_trec(CurrentTSO) = trec;
    StgHeader_info(frame) = stg_atomically_frame_info;
    R1 = StgAtomicallyFrame_code(frame);
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    jump stg_ap_v_fast;
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  }
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}
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// STM catch frame --------------------------------------------------------------

#define SP_OFF 0

/* Catch frames are very similar to update frames, but when entering
 * one we just pop the frame off the stack and perform the correct
 * kind of return to the activation record underneath us on the stack.
 */

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INFO_TABLE_RET(stg_catch_stm_frame, CATCH_STM_FRAME,
#if defined(PROFILING)
  W_ unused1, W_ unused2,
#endif
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  P_ unused3, P_ unused4)
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   {
      W_ r, frame, trec, outer;
      frame = Sp;
      trec = StgTSO_trec(CurrentTSO);
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      ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
      (r) = foreign "C" stmCommitNestedTransaction(MyCapability() "ptr", trec "ptr") [];
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      if (r != 0) {
        /* Commit succeeded */
        StgTSO_trec(CurrentTSO) = outer;
        Sp = Sp + SIZEOF_StgCatchSTMFrame;
        jump Sp(SP_OFF);
      } else {
        /* Commit failed */
        W_ new_trec;
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        ("ptr" new_trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", outer "ptr") [];
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        StgTSO_trec(CurrentTSO) = new_trec;
        R1 = StgCatchSTMFrame_code(frame);
        jump stg_ap_v_fast;
      }
   }
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// Primop definition ------------------------------------------------------------

atomicallyzh_fast
{
  W_ frame;
  W_ old_trec;
  W_ new_trec;
  
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  // stmStartTransaction may allocate
  MAYBE_GC (R1_PTR, atomicallyzh_fast); 

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  /* Args: R1 = m :: STM a */
  STK_CHK_GEN(SIZEOF_StgAtomicallyFrame + WDS(1), R1_PTR, atomicallyzh_fast);

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  old_trec = StgTSO_trec(CurrentTSO);

  /* Nested transactions are not allowed; raise an exception */
  if (old_trec != NO_TREC) {
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     R1 = base_ControlziExceptionziBase_nestedAtomically_closure;
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     jump raisezh_fast;
  }

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  /* Set up the atomically frame */
  Sp = Sp - SIZEOF_StgAtomicallyFrame;
  frame = Sp;

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  SET_HDR(frame,stg_atomically_frame_info, W_[CCCS]);
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  StgAtomicallyFrame_code(frame) = R1;
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  StgAtomicallyFrame_result(frame) = NO_TREC;
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  StgAtomicallyFrame_next_invariant_to_check(frame) = END_INVARIANT_CHECK_QUEUE;
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  /* Start the memory transcation */
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  ("ptr" new_trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", old_trec "ptr") [R1];
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  StgTSO_trec(CurrentTSO) = new_trec;

  /* Apply R1 to the realworld token */
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  jump stg_ap_v_fast;
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}


catchSTMzh_fast
{
  W_ frame;
  
  /* Args: R1 :: STM a */
  /* Args: R2 :: Exception -> STM a */
  STK_CHK_GEN(SIZEOF_StgCatchSTMFrame + WDS(1), R1_PTR & R2_PTR, catchSTMzh_fast);

  /* Set up the catch frame */
  Sp = Sp - SIZEOF_StgCatchSTMFrame;
  frame = Sp;

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  SET_HDR(frame, stg_catch_stm_frame_info, W_[CCCS]);
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  StgCatchSTMFrame_handler(frame) = R2;
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  StgCatchSTMFrame_code(frame) = R1;

  /* Start a nested transaction to run the body of the try block in */
  W_ cur_trec;  
  W_ new_trec;
  cur_trec = StgTSO_trec(CurrentTSO);
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  ("ptr" new_trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", cur_trec "ptr");
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  StgTSO_trec(CurrentTSO) = new_trec;
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  /* Apply R1 to the realworld token */
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  jump stg_ap_v_fast;
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}


catchRetryzh_fast
{
  W_ frame;
  W_ new_trec;
  W_ trec;

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  // stmStartTransaction may allocate
  MAYBE_GC (R1_PTR & R2_PTR, catchRetryzh_fast); 

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  /* Args: R1 :: STM a */
  /* Args: R2 :: STM a */
  STK_CHK_GEN(SIZEOF_StgCatchRetryFrame + WDS(1), R1_PTR & R2_PTR, catchRetryzh_fast);

  /* Start a nested transaction within which to run the first code */
  trec = StgTSO_trec(CurrentTSO);
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  ("ptr" new_trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", trec "ptr") [R1,R2];
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  StgTSO_trec(CurrentTSO) = new_trec;

  /* Set up the catch-retry frame */
  Sp = Sp - SIZEOF_StgCatchRetryFrame;
  frame = Sp;
  
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  SET_HDR(frame, stg_catch_retry_frame_info, W_[CCCS]);
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  StgCatchRetryFrame_running_alt_code(frame) = 0 :: CInt; // false;
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  StgCatchRetryFrame_first_code(frame) = R1;
  StgCatchRetryFrame_alt_code(frame) = R2;

  /* Apply R1 to the realworld token */
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  jump stg_ap_v_fast;
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}


retryzh_fast
{
  W_ frame_type;
  W_ frame;
  W_ trec;
  W_ outer;
  W_ r;

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  MAYBE_GC (NO_PTRS, retryzh_fast); // STM operations may allocate
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  // Find the enclosing ATOMICALLY_FRAME or CATCH_RETRY_FRAME
retry_pop_stack:
  StgTSO_sp(CurrentTSO) = Sp;
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  (frame_type) = foreign "C" findRetryFrameHelper(CurrentTSO "ptr") [];
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  Sp = StgTSO_sp(CurrentTSO);
  frame = Sp;
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  trec = StgTSO_trec(CurrentTSO);
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  ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
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  if (frame_type == CATCH_RETRY_FRAME) {
    // The retry reaches a CATCH_RETRY_FRAME before the atomic frame
    ASSERT(outer != NO_TREC);
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    // Abort the transaction attempting the current branch
    foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
    foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
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    if (!StgCatchRetryFrame_running_alt_code(frame) != 0::I32) {
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      // Retry in the first branch: try the alternative
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      ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", outer "ptr") [];
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      StgTSO_trec(CurrentTSO) = trec;
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      StgCatchRetryFrame_running_alt_code(frame) = 1 :: CInt; // true;
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      R1 = StgCatchRetryFrame_alt_code(frame);
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      jump stg_ap_v_fast;
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    } else {
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      // Retry in the alternative code: propagate the retry
      StgTSO_trec(CurrentTSO) = outer;
      Sp = Sp + SIZEOF_StgCatchRetryFrame;
      goto retry_pop_stack;
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    }
  }

  // We've reached the ATOMICALLY_FRAME: attempt to wait 
  ASSERT(frame_type == ATOMICALLY_FRAME);
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  if (outer != NO_TREC) {
    // We called retry while checking invariants, so abort the current
    // invariant check (merging its TVar accesses into the parents read
    // set so we'll wait on them)
    foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
    foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
    trec = outer;
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    StgTSO_trec(CurrentTSO) = trec;
    ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
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  }
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  ASSERT(outer == NO_TREC);
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  (r) = foreign "C" stmWait(MyCapability() "ptr", CurrentTSO "ptr", trec "ptr") [];
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  if (r != 0) {
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    // Transaction was valid: stmWait put us on the TVars' queues, we now block
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    StgHeader_info(frame) = stg_atomically_waiting_frame_info;
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    Sp = frame;
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    // Fix up the stack in the unregisterised case: the return convention is different.
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    R3 = trec; // passing to stmWaitUnblock()
    jump stg_block_stmwait;
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  } else {
    // Transaction was not valid: retry immediately
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    ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", outer "ptr") [];
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    StgTSO_trec(CurrentTSO) = trec;
    R1 = StgAtomicallyFrame_code(frame);
    Sp = frame;
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    jump stg_ap_v_fast;
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  }
}


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checkzh_fast
{
  W_ trec, closure;

  /* Args: R1 = invariant closure */
  MAYBE_GC (R1_PTR, checkzh_fast); 

  trec = StgTSO_trec(CurrentTSO);
  closure = R1;
  foreign "C" stmAddInvariantToCheck(MyCapability() "ptr", 
                                     trec "ptr",
                                     closure "ptr") [];

  jump %ENTRY_CODE(Sp(0));
}


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newTVarzh_fast
{
  W_ tv;
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  W_ new_value;
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  /* Args: R1 = initialisation value */

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  MAYBE_GC (R1_PTR, newTVarzh_fast); 
  new_value = R1;
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  ("ptr" tv) = foreign "C" stmNewTVar(MyCapability() "ptr", new_value "ptr") [];
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  RET_P(tv);
}


readTVarzh_fast
{
  W_ trec;
  W_ tvar;
  W_ result;

  /* Args: R1 = TVar closure */

  MAYBE_GC (R1_PTR, readTVarzh_fast); // Call to stmReadTVar may allocate
  trec = StgTSO_trec(CurrentTSO);
  tvar = R1;
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  ("ptr" result) = foreign "C" stmReadTVar(MyCapability() "ptr", trec "ptr", tvar "ptr") [];
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  RET_P(result);
}

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readTVarIOzh_fast
{
    W_ result;

again:
    result = StgTVar_current_value(R1);
    if (%INFO_PTR(result) == stg_TREC_HEADER_info) {
        goto again;
    }
    RET_P(result);
}
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writeTVarzh_fast
{
  W_ trec;
  W_ tvar;
  W_ new_value;
  
  /* Args: R1 = TVar closure */
  /*       R2 = New value    */

  MAYBE_GC (R1_PTR & R2_PTR, writeTVarzh_fast); // Call to stmWriteTVar may allocate
  trec = StgTSO_trec(CurrentTSO);
  tvar = R1;
  new_value = R2;
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  foreign "C" stmWriteTVar(MyCapability() "ptr", trec "ptr", tvar "ptr", new_value "ptr") [];
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  jump %ENTRY_CODE(Sp(0));
}


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/* -----------------------------------------------------------------------------
 * MVar primitives
 *
 * take & putMVar work as follows.  Firstly, an important invariant:
 *
 *    If the MVar is full, then the blocking queue contains only
 *    threads blocked on putMVar, and if the MVar is empty then the
 *    blocking queue contains only threads blocked on takeMVar.
 *
 * takeMvar:
 *    MVar empty : then add ourselves to the blocking queue
 *    MVar full  : remove the value from the MVar, and
 *                 blocking queue empty     : return
 *                 blocking queue non-empty : perform the first blocked putMVar
 *                                            from the queue, and wake up the
 *                                            thread (MVar is now full again)
 *
 * putMVar is just the dual of the above algorithm.
 *
 * How do we "perform a putMVar"?  Well, we have to fiddle around with
 * the stack of the thread waiting to do the putMVar.  See
 * stg_block_putmvar and stg_block_takemvar in HeapStackCheck.c for
 * the stack layout, and the PerformPut and PerformTake macros below.
 *
 * It is important that a blocked take or put is woken up with the
 * take/put already performed, because otherwise there would be a
 * small window of vulnerability where the thread could receive an
 * exception and never perform its take or put, and we'd end up with a
 * deadlock.
 *
 * -------------------------------------------------------------------------- */

isEmptyMVarzh_fast
{
    /* args: R1 = MVar closure */

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    if (StgMVar_value(R1) == stg_END_TSO_QUEUE_closure) {
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	RET_N(1);
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    } else {
	RET_N(0);
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    }
}

newMVarzh_fast
{
    /* args: none */
    W_ mvar;

    ALLOC_PRIM ( SIZEOF_StgMVar, NO_PTRS, newMVarzh_fast );
  
    mvar = Hp - SIZEOF_StgMVar + WDS(1);
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    SET_HDR(mvar,stg_MVAR_DIRTY_info,W_[CCCS]);
        // MVARs start dirty: generation 0 has no mutable list
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    StgMVar_head(mvar)  = stg_END_TSO_QUEUE_closure;
    StgMVar_tail(mvar)  = stg_END_TSO_QUEUE_closure;
    StgMVar_value(mvar) = stg_END_TSO_QUEUE_closure;
    RET_P(mvar);
}


#define PerformTake(tso, value)				\
    W_[StgTSO_sp(tso) + WDS(1)] = value;		\
    W_[StgTSO_sp(tso) + WDS(0)] = stg_gc_unpt_r1_info;

#define PerformPut(tso,lval)			\
    StgTSO_sp(tso) = StgTSO_sp(tso) + WDS(3);	\
    lval = W_[StgTSO_sp(tso) - WDS(1)];

takeMVarzh_fast
{
    W_ mvar, val, info, tso;

    /* args: R1 = MVar closure */
    mvar = R1;

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#if defined(THREADED_RTS)
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    ("ptr" info) = foreign "C" lockClosure(mvar "ptr") [];
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#else
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    info = GET_INFO(mvar);
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#endif
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    if (info == stg_MVAR_CLEAN_info) {
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        foreign "C" dirty_MVAR(BaseReg "ptr", mvar "ptr") [];
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    }
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    /* If the MVar is empty, put ourselves on its blocking queue,
     * and wait until we're woken up.
     */
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    if (StgMVar_value(mvar) == stg_END_TSO_QUEUE_closure) {
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	if (StgMVar_head(mvar) == stg_END_TSO_QUEUE_closure) {
	    StgMVar_head(mvar) = CurrentTSO;
	} else {
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            foreign "C" setTSOLink(MyCapability() "ptr", 
                                   StgMVar_tail(mvar) "ptr",
                                   CurrentTSO) [];
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	}
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	StgTSO__link(CurrentTSO)       = stg_END_TSO_QUEUE_closure;
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	StgTSO_block_info(CurrentTSO)  = mvar;
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        // write barrier for throwTo(), which looks at block_info
        // if why_blocked==BlockedOnMVar.
        prim %write_barrier() [];
	StgTSO_why_blocked(CurrentTSO) = BlockedOnMVar::I16;
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	StgMVar_tail(mvar) = CurrentTSO;
	
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        R1 = mvar;
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	jump stg_block_takemvar;
  }

  /* we got the value... */
  val = StgMVar_value(mvar);

  if (StgMVar_head(mvar) != stg_END_TSO_QUEUE_closure)
  {
      /* There are putMVar(s) waiting... 
       * wake up the first thread on the queue
       */
      ASSERT(StgTSO_why_blocked(StgMVar_head(mvar)) == BlockedOnMVar::I16);

      /* actually perform the putMVar for the thread that we just woke up */
      tso = StgMVar_head(mvar);
      PerformPut(tso,StgMVar_value(mvar));
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      if (TO_W_(StgTSO_flags(tso)) & TSO_DIRTY == 0) {
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          foreign "C" dirty_TSO(MyCapability() "ptr", tso "ptr") [];
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      }
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      ("ptr" tso) = foreign "C" unblockOne_(MyCapability() "ptr", 
                                            StgMVar_head(mvar) "ptr", 1) [];
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      StgMVar_head(mvar) = tso;
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      if (StgMVar_head(mvar) == stg_END_TSO_QUEUE_closure) {
	  StgMVar_tail(mvar) = stg_END_TSO_QUEUE_closure;
      }
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#if defined(THREADED_RTS)
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      unlockClosure(mvar, stg_MVAR_DIRTY_info);
#else
      SET_INFO(mvar,stg_MVAR_DIRTY_info);
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#endif
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      RET_P(val);
  } 
  else
  {
      /* No further putMVars, MVar is now empty */
      StgMVar_value(mvar) = stg_END_TSO_QUEUE_closure;
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#if defined(THREADED_RTS)
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      unlockClosure(mvar, stg_MVAR_DIRTY_info);
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#else
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      SET_INFO(mvar,stg_MVAR_DIRTY_info);
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#endif
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      RET_P(val);
  }
}


tryTakeMVarzh_fast
{
    W_ mvar, val, info, tso;

    /* args: R1 = MVar closure */

    mvar = R1;

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#if defined(THREADED_RTS)
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    ("ptr" info) = foreign "C" lockClosure(mvar "ptr") [];
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#else
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    info = GET_INFO(mvar);
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#endif
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    if (StgMVar_value(mvar) == stg_END_TSO_QUEUE_closure) {
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#if defined(THREADED_RTS)
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        unlockClosure(mvar, info);
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#endif
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	/* HACK: we need a pointer to pass back, 
	 * so we abuse NO_FINALIZER_closure
	 */
	RET_NP(0, stg_NO_FINALIZER_closure);
    }

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    if (info == stg_MVAR_CLEAN_info) {
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        foreign "C" dirty_MVAR(BaseReg "ptr", mvar "ptr");
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    }

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    /* we got the value... */
    val = StgMVar_value(mvar);

    if (StgMVar_head(mvar) != stg_END_TSO_QUEUE_closure) {
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	/* There are putMVar(s) waiting... 
	 * wake up the first thread on the queue
	 */
	ASSERT(StgTSO_why_blocked(StgMVar_head(mvar)) == BlockedOnMVar::I16);

	/* actually perform the putMVar for the thread that we just woke up */
	tso = StgMVar_head(mvar);
	PerformPut(tso,StgMVar_value(mvar));
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        if (TO_W_(StgTSO_flags(tso)) & TSO_DIRTY == 0) {
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            foreign "C" dirty_TSO(MyCapability() "ptr", tso "ptr") [];
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        }
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        ("ptr" tso) = foreign "C" unblockOne_(MyCapability() "ptr", 
                                              StgMVar_head(mvar) "ptr", 1) [];
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	StgMVar_head(mvar) = tso;

	if (StgMVar_head(mvar) == stg_END_TSO_QUEUE_closure) {
	    StgMVar_tail(mvar) = stg_END_TSO_QUEUE_closure;
	}
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#if defined(THREADED_RTS)
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        unlockClosure(mvar, stg_MVAR_DIRTY_info);
#else
        SET_INFO(mvar,stg_MVAR_DIRTY_info);
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#endif
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    }
    else 
    {
	/* No further putMVars, MVar is now empty */
	StgMVar_value(mvar) = stg_END_TSO_QUEUE_closure;
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#if defined(THREADED_RTS)
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    	unlockClosure(mvar, stg_MVAR_DIRTY_info);
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#else
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	SET_INFO(mvar,stg_MVAR_DIRTY_info);
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#endif
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    }
    
    RET_NP(1, val);
}


putMVarzh_fast
{
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    W_ mvar, val, info, tso;
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    /* args: R1 = MVar, R2 = value */
    mvar = R1;
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    val  = R2;
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#if defined(THREADED_RTS)
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    ("ptr" info) = foreign "C" lockClosure(mvar "ptr") [];
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#else
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    info = GET_INFO(mvar);
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#endif
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    if (info == stg_MVAR_CLEAN_info) {
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        foreign "C" dirty_MVAR(BaseReg "ptr", mvar "ptr");
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    }

    if (StgMVar_value(mvar) != stg_END_TSO_QUEUE_closure) {
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	if (StgMVar_head(mvar) == stg_END_TSO_QUEUE_closure) {
	    StgMVar_head(mvar) = CurrentTSO;
	} else {
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            foreign "C" setTSOLink(MyCapability() "ptr", 
                                   StgMVar_tail(mvar) "ptr",
                                   CurrentTSO) [];
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	}
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	StgTSO__link(CurrentTSO)       = stg_END_TSO_QUEUE_closure;
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	StgTSO_block_info(CurrentTSO)  = mvar;
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        // write barrier for throwTo(), which looks at block_info
        // if why_blocked==BlockedOnMVar.
        prim %write_barrier() [];
	StgTSO_why_blocked(CurrentTSO) = BlockedOnMVar::I16;
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	StgMVar_tail(mvar) = CurrentTSO;
	
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        R1 = mvar;
        R2 = val;
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	jump stg_block_putmvar;
    }
  
    if (StgMVar_head(mvar) != stg_END_TSO_QUEUE_closure) {
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	/* There are takeMVar(s) waiting: wake up the first one
	 */
	ASSERT(StgTSO_why_blocked(StgMVar_head(mvar)) == BlockedOnMVar::I16);

	/* actually perform the takeMVar */
	tso = StgMVar_head(mvar);
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	PerformTake(tso, val);