root/rts/Apply.cmm

/* -----------------------------------------------------------------------------
 *
 * (c) The University of Glasgow 2004
 *
 * Application-related bits.
 *
 * 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"

/* ----------------------------------------------------------------------------
 * Evaluate a closure and return it.
 *
 * There isn't an info table / return address version of stg_ap_0, because
 * everything being returned is guaranteed evaluated, so it would be a no-op.
 */

STRING(stg_ap_0_ret_str,"stg_ap_0_ret... ")

stg_ap_0_fast
{ 
    // fn is in R1, no args on the stack

    IF_DEBUG(apply,
        foreign "C" debugBelch(stg_ap_0_ret_str) [R1];
        foreign "C" printClosure(R1 "ptr") [R1]);

    IF_DEBUG(sanity,
        foreign "C" checkStackFrame(Sp "ptr") [R1]);

    ENTER();
}

/* -----------------------------------------------------------------------------
   Entry Code for a PAP.

   This entry code is *only* called by one of the stg_ap functions.
   On entry: Sp points to the remaining arguments on the stack.  If
   the stack check fails, we can just push the PAP on the stack and
   return to the scheduler.

   On entry: R1 points to the PAP.  The rest of the function's
   arguments (apart from those that are already in the PAP) are on the
   stack, starting at Sp(0).  R2 contains an info table which
   describes these arguments, which is used in the event that the
   stack check in the entry code below fails.  The info table is
   currently one of the stg_ap_*_ret family, as this code is always
   entered from those functions.

   The idea is to copy the chunk of stack from the PAP object onto the
   stack / into registers, and enter the function.
   -------------------------------------------------------------------------- */

INFO_TABLE(stg_PAP,/*special layout*/0,0,PAP,"PAP","PAP")
{  foreign "C" barf("PAP object entered!") never returns; }
    
stg_PAP_apply
{
  W_ Words;
  W_ pap;
    
  pap = R1;

  Words = TO_W_(StgPAP_n_args(pap));

  //
  // Check for stack overflow and bump the stack pointer.
  // We have a hand-rolled stack check fragment here, because none of
  // the canned ones suit this situation.
  //
  if ((Sp - WDS(Words)) < SpLim) {
      // there is a return address in R2 in the event of a
      // stack check failure.  The various stg_apply functions arrange
      // this before calling stg_PAP_entry.
      Sp_adj(-1); 
      Sp(0) = R2;
      jump stg_gc_unpt_r1;
  }
  Sp_adj(-Words);

  // profiling
  TICK_ENT_PAP();
  LDV_ENTER(pap);
#ifdef PROFILING
  foreign "C" enterFunCCS(BaseReg "ptr", StgHeader_ccs(pap) "ptr");
#endif

  // Reload the stack 
  W_ i;
  W_ p;
  p = pap + SIZEOF_StgHeader + OFFSET_StgPAP_payload;
  i = 0;
for:
  if (i < Words) {
    Sp(i) = W_[p];
    p = p + WDS(1);
    i = i + 1;
    goto for;
  }

  R1 = StgPAP_fun(pap);

/* DEBUGGING CODE, ensures that arity 1 and 2 functions are entered tagged
  if (TO_W_(StgFunInfoExtra_arity(%FUN_INFO(%INFO_PTR(UNTAG(R1))))) == 1 ) {
    if (GETTAG(R1)!=1) {
        W_[0]=1;
    }
  }

  if (TO_W_(StgFunInfoExtra_arity(%FUN_INFO(%INFO_PTR(UNTAG(R1))))) == 2 ) {
    if (GETTAG(R1)!=2) {
        W_[0]=1;
    }
  }
*/

  // Off we go! 
  TICK_ENT_VIA_NODE();

#ifdef NO_ARG_REGS
  jump %GET_ENTRY(UNTAG(R1));
#else
      W_ info;
      info = %GET_FUN_INFO(UNTAG(R1));
      W_ type;
      type = TO_W_(StgFunInfoExtra_fun_type(info));
      if (type == ARG_GEN) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_GEN_BIG) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_BCO) {
          Sp_adj(-2);
          Sp(1) = R1;
          Sp(0) = stg_apply_interp_info;
          jump stg_yield_to_interpreter;
      }
      jump W_[stg_ap_stack_entries + 
                WDS(TO_W_(StgFunInfoExtra_fun_type(info)))];
#endif
}

/* -----------------------------------------------------------------------------
   Entry Code for an AP (a PAP with arity zero).

   The entry code is very similar to a PAP, except there are no
   further arguments on the stack to worry about, so the stack check
   is simpler.  We must also push an update frame on the stack before
   applying the function.
   -------------------------------------------------------------------------- */

INFO_TABLE(stg_AP,/*special layout*/0,0,AP,"AP","AP")
{
  W_ Words;
  W_ ap;
    
  ap = R1;
  
  Words = TO_W_(StgAP_n_args(ap));

  /* 
   * Check for stack overflow.  IMPORTANT: use a _NP check here,
   * because if the check fails, we might end up blackholing this very
   * closure, in which case we must enter the blackhole on return rather
   * than continuing to evaluate the now-defunct closure.
   */
  STK_CHK_NP(WDS(Words) + SIZEOF_StgUpdateFrame);

  PUSH_UPD_FRAME(Sp - SIZEOF_StgUpdateFrame, R1);
  Sp = Sp - SIZEOF_StgUpdateFrame - WDS(Words);

  TICK_ENT_AP();
  LDV_ENTER(ap);
  ENTER_CCS_THUNK(ap);

  // Reload the stack
  W_ i;
  W_ p;
  p = ap + SIZEOF_StgHeader + OFFSET_StgAP_payload;
  i = 0;
for:
  if (i < Words) {
    Sp(i) = W_[p];
    p = p + WDS(1);
    i = i + 1;
    goto for;
  }

  R1 = StgAP_fun(ap);

  // Off we go! 
  TICK_ENT_VIA_NODE();

#ifdef NO_ARG_REGS
  jump %GET_ENTRY(UNTAG(R1));
#else
      W_ info;
      info = %GET_FUN_INFO(UNTAG(R1));
      W_ type;
      type = TO_W_(StgFunInfoExtra_fun_type(info));
      if (type == ARG_GEN) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_GEN_BIG) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_BCO) {
          Sp_adj(-2);
          Sp(1) = R1;
          Sp(0) = stg_apply_interp_info;
          jump stg_yield_to_interpreter;
      }
      jump W_[stg_ap_stack_entries + 
                WDS(TO_W_(StgFunInfoExtra_fun_type(info)))];
#endif
}

/* AP_NOUPD is exactly like AP, except that no update frame is pushed.
   Use for thunks that are guaranteed to be entered once only, such as 
   those generated by the byte-code compiler for inserting breakpoints. */

INFO_TABLE(stg_AP_NOUPD,/*special layout*/0,0,AP,"AP_NOUPD","AP_NOUPD")
{
  W_ Words;
  W_ ap;
    
  ap = R1;
  
  Words = TO_W_(StgAP_n_args(ap));

  /* 
   * Check for stack overflow.  IMPORTANT: use a _NP check here,
   * because if the check fails, we might end up blackholing this very
   * closure, in which case we must enter the blackhole on return rather
   * than continuing to evaluate the now-defunct closure.
   */
  STK_CHK_NP(WDS(Words));
  Sp = Sp - WDS(Words);

  TICK_ENT_AP();
  LDV_ENTER(ap);
  ENTER_CCS_THUNK(ap);

  // Reload the stack
  W_ i;
  W_ p;
  p = ap + SIZEOF_StgHeader + OFFSET_StgAP_payload;
  i = 0;
for:
  if (i < Words) {
    Sp(i) = W_[p];
    p = p + WDS(1);
    i = i + 1;
    goto for;
  }

  R1 = StgAP_fun(ap);

  // Off we go! 
  TICK_ENT_VIA_NODE();

#ifdef NO_ARG_REGS
  jump %GET_ENTRY(UNTAG(R1));
#else
      W_ info;
      info = %GET_FUN_INFO(UNTAG(R1));
      W_ type;
      type = TO_W_(StgFunInfoExtra_fun_type(info));
      if (type == ARG_GEN) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_GEN_BIG) {
          jump StgFunInfoExtra_slow_apply(info);
      }
      if (type == ARG_BCO) {
          Sp_adj(-2);
          Sp(1) = R1;
          Sp(0) = stg_apply_interp_info;
          jump stg_yield_to_interpreter;
      }
      jump W_[stg_ap_stack_entries + 
                WDS(TO_W_(StgFunInfoExtra_fun_type(info)))];
#endif
}

/* -----------------------------------------------------------------------------
   Entry Code for an AP_STACK.

   Very similar to a PAP and AP.  The layout is the same as PAP
   and AP, except that the payload is a chunk of stack instead of
   being described by the function's info table.  Like an AP,
   there are no further arguments on the stack to worry about.
   However, the function closure (ap->fun) does not necessarily point
   directly to a function, so we have to enter it using stg_ap_0.
   -------------------------------------------------------------------------- */

INFO_TABLE(stg_AP_STACK,/*special layout*/0,0,AP_STACK,"AP_STACK","AP_STACK")
{
  W_ Words;
  W_ ap;

  ap = R1;
  
  Words = StgAP_STACK_size(ap);

  /* 
   * Check for stack overflow.  IMPORTANT: use a _NP check here,
   * because if the check fails, we might end up blackholing this very
   * closure, in which case we must enter the blackhole on return rather
   * than continuing to evaluate the now-defunct closure.
   */
  STK_CHK_NP(WDS(Words) + SIZEOF_StgUpdateFrame + WDS(AP_STACK_SPLIM));
  /* ensure there is at least AP_STACK_SPLIM words of headroom available
   * after unpacking the AP_STACK. See bug #1466 */

  PUSH_UPD_FRAME(Sp - SIZEOF_StgUpdateFrame, R1);
  Sp = Sp - SIZEOF_StgUpdateFrame - WDS(Words);

  TICK_ENT_AP();
  LDV_ENTER(ap);
  ENTER_CCS_THUNK(ap);

  // Reload the stack
  W_ i;
  W_ p;
  p = ap + SIZEOF_StgHeader + OFFSET_StgAP_STACK_payload;
  i = 0;
for:
  if (i < Words) {
    Sp(i) = W_[p];
    p = p + WDS(1);
    i = i + 1;
    goto for;
  }

  // Off we go!
  TICK_ENT_VIA_NODE();

  R1 = StgAP_STACK_fun(ap);

  ENTER();
}

/* -----------------------------------------------------------------------------
   AP_STACK_NOUPD - exactly like AP_STACK, but doesn't push an update frame.
   -------------------------------------------------------------------------- */

INFO_TABLE(stg_AP_STACK_NOUPD,/*special layout*/0,0,AP_STACK,
                                        "AP_STACK_NOUPD","AP_STACK_NOUPD")
{
  W_ Words;
  W_ ap;

  ap = R1;
  
  Words = StgAP_STACK_size(ap);

  /* 
   * Check for stack overflow.  IMPORTANT: use a _NP check here,
   * because if the check fails, we might end up blackholing this very
   * closure, in which case we must enter the blackhole on return rather
   * than continuing to evaluate the now-defunct closure.
   */
  STK_CHK_NP(WDS(Words) + WDS(AP_STACK_SPLIM));
  /* ensure there is at least AP_STACK_SPLIM words of headroom available
   * after unpacking the AP_STACK. See bug #1466 */

  Sp = Sp - WDS(Words);

  TICK_ENT_AP();
  LDV_ENTER(ap);
  ENTER_CCS_THUNK(ap);

  // Reload the stack
  W_ i;
  W_ p;
  p = ap + SIZEOF_StgHeader + OFFSET_StgAP_STACK_payload;
  i = 0;
for:
  if (i < Words) {
    Sp(i) = W_[p];
    p = p + WDS(1);
    i = i + 1;
    goto for;
  }

  // Off we go!
  TICK_ENT_VIA_NODE();

  R1 = StgAP_STACK_fun(ap);

  ENTER();
}