iverilog/vvp/vthread.cc

/*
 * Copyright (c) 2001 Stephen Williams (steve@icarus.com)
 *
 *    This source code is free software; you can redistribute it
 *    and/or modify it in source code form under the terms of the GNU
 *    General Public License as published by the Free Software
 *    Foundation; either version 2 of the License, or (at your option)
 *    any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */
#if !defined(WINNT)
#ident "$Id: vthread.cc,v 1.33 2001/05/02 01:57:26 steve Exp $"
#endif

# include  "vthread.h"
# include  "codes.h"
# include  "schedule.h"
# include  "functor.h"
# include  "vpi_priv.h"
# include  <malloc.h>
# include  <string.h>
# include  <assert.h>

/*
 * This vhtread_s structure describes all there is to know about a
 * thread, including its program counter, all the private bits it
 * holds, and its place in other lists.
 *
 *
 * ** Notes On The Interactions of %fork/%join/%end:
 *
 * The %fork instruction creates a new thread and pushes that onto the
 * stack of children for the thread. This new thread, then, becomes
 * the new direct descendent of the thread. This new thread is
 * therefore also the first thread to be reaped when the parent does a
 * %join.
 *
 * It is a programming error for a thread that created threads to not
 * %join as many as it created before it %ends. The linear stack for
 * tracking thread relationships will create a mess otherwise. For
 * example, if A creates B then C, the stack is:
 *
 *       A --> C --> B
 *
 * If C then %forks X, the stack is:
 *
 *       A --> C --> X --> B
 *
 * If C %ends without a join, then the stack is:
 *
 *       A --> C(zombie) --> X --> B
 *
 * If A then executes 2 %joins, it will read C and X (when it ends)
 * leaving B in purgatory. What's worse, A will block on the schedules
 * of X and C instead of C and B, possibly creating incorrect timing.
 *
 * The schedule_parent_on_end flag is used by threads to tell their
 * children that they are waiting for it to end. It is set by a %join
 * instruction if the child is not already done. The thread that
 * executes a %join instruction sets the flag in its child.
 *
 * The i_have_ended flag, on the other hand, is used by threads to
 * tell their parents that they are already dead. A thread that
 * executes %end will set its own i_have_ended flag and let its parent
 * reap it when the parent does the %join. If a thread has its
 * schedule_parent_on_end flag set already when it %ends, then it
 * reaps itself and simply schedules its parent. If a child has its
 * i_have_ended flag set when a thread executes %join, then it is free
 * to reap the child immediately.
 */

struct vthread_s {
	/* This is the program counter. */
      unsigned long pc;
	/* These hold the private thread bits. */
      unsigned char *bits;
      long index[4];
      unsigned nbits :16;
	/* My parent sets this when it wants me to wake it up. */
      unsigned schedule_parent_on_end :1;
      unsigned i_have_ended      :1;
      unsigned waiting_for_event :1;
      unsigned is_scheduled      :1;
	/* This points to the sole child of the thread. */
      struct vthread_s*child;
	/* This points to my parent, if I have one. */
      struct vthread_s*parent;
	/* This is used for keeping wait queues. */
      struct vthread_s*wait_next;
	/* These are used to keep the thread in a scope. */
      struct vthread_s*scope_next, *scope_prev;
};

static void thr_check_addr(struct vthread_s*thr, unsigned addr)
{
      if (addr < thr->nbits)
	    return;
      assert(addr < 0x10000);
      while (thr->nbits <= addr) {
	    thr->bits = (unsigned char*)realloc(thr->bits, thr->nbits/4 + 16);
	    memset(thr->bits + thr->nbits/4, 0xaa, 16);
	    thr->nbits += 16*4;
      }
}

static inline unsigned thr_get_bit(struct vthread_s*thr, unsigned addr)
{
      assert(addr < thr->nbits);
      unsigned idx = addr % 4;
      addr /= 4;
      return (thr->bits[addr] >> (idx*2)) & 3;
}

static inline void thr_put_bit(struct vthread_s*thr,
			       unsigned addr, unsigned val)
{
      thr_check_addr(thr, addr);
      unsigned idx = addr % 4;
      addr /= 4;
      unsigned mask = 3 << (idx*2);

      thr->bits[addr] = (thr->bits[addr] & ~mask) | (val << (idx*2));
}

/*
 * Create a new thread with the given start address.
 */
vthread_t vthread_new(unsigned long pc, struct __vpiScope*scope)
{
      vthread_t thr = new struct vthread_s;
      thr->pc     = pc;
      thr->bits   = (unsigned char*)malloc(16);
      thr->nbits  = 16*4;
      thr->child  = 0;
      thr->parent = 0;
      thr->wait_next   = 0;

	/* If the target scope never held a thread, then create a
	   header cell for it. This is a stub to make circular lists
	   easier to work with. */
      if (scope->threads == 0) {
	    scope->threads = new struct vthread_s;
	    scope->threads->pc = 0;
	    scope->threads->bits   = 0;
	    scope->threads->nbits  = 0;
	    scope->threads->child  = 0;
	    scope->threads->parent = 0;
	    scope->threads->scope_prev = scope->threads;
	    scope->threads->scope_next = scope->threads;
      }

      { vthread_t tmp = scope->threads;
        thr->scope_next = tmp->scope_next;
	thr->scope_prev = tmp;
	thr->scope_next->scope_prev = thr;
	thr->scope_prev->scope_next = thr;
      }

      thr->schedule_parent_on_end = 0;
      thr->is_scheduled = 0;
      thr->i_have_ended = 0;
      thr->waiting_for_event = 0;

      thr_put_bit(thr, 0, 0);
      thr_put_bit(thr, 1, 1);
      thr_put_bit(thr, 2, 2);
      thr_put_bit(thr, 3, 3);

      return thr;
}

static void vthread_reap(vthread_t thr)
{
      assert(thr->wait_next == 0);
      assert(thr->child == 0);

      free(thr->bits);
      thr->bits = 0;

      if (thr->child)
	    thr->child->parent = thr->parent;
      if (thr->parent)
	    thr->parent->child = thr->child;

      thr->child = 0;
      thr->parent = 0;

      thr->scope_next->scope_prev = thr->scope_prev;
      thr->scope_prev->scope_next = thr->scope_next;

      thr->pc = 0;

	/* If this thread is not scheduled, then is it safe to delete
	   it now. Otherwise, let the schedule event (which will
	   execute the thread at of_ZOMBIE) delete the object. */
      if (thr->is_scheduled == 0)
	    delete thr;
}

void vthread_mark_scheduled(vthread_t thr)
{
      assert(thr->is_scheduled == 0);
      thr->is_scheduled = 1;
}

/*
 * This function runs a thread by fetching an instruction,
 * incrementing the PC, and executing the instruction.
 */
void vthread_run(vthread_t thr)
{
      assert(thr->is_scheduled);
      thr->is_scheduled = 0;

      for (;;) {
	    vvp_code_t cp = codespace_index(thr->pc);
	    thr->pc += 1;

	    assert(cp->opcode);

	      /* Run the opcode implementation. If the execution of
		 the opcode returns false, then the thread is meant to
		 be paused, so break out of the loop. */
	    bool rc = (cp->opcode)(thr, cp);
	    if (rc == false)
		  return;
      }
}

/*
 * This is called by an event functor to wake up all the threads on
 * its list. I in fact created that list in the %wait instruction, and
 * I also am certain that the waiting_for_event flag is set.
 */
void vthread_schedule_list(vthread_t thr)
{
      while (thr) {
	    vthread_t tmp = thr;
	    thr = thr->wait_next;
	    assert(tmp->waiting_for_event);
	    tmp->waiting_for_event = 0;
	    tmp->wait_next = 0;
	    schedule_vthread(tmp, 0);
      }
}


bool of_AND(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {

	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb == 0) || (rb == 0)) {
		  thr_put_bit(thr, idx1, 0);

	    } else if ((lb == 1) && (rb == 1)) {
		  thr_put_bit(thr, idx1, 1);

	    } else {
		  thr_put_bit(thr, idx1, 2);
	    }

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      return true;
}

bool of_ADD(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);
      assert(cp->number <= 8*sizeof(unsigned long));

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;
      unsigned long lv = 0, rv = 0;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb | rb) & 2)
		  goto x_out;

	    lv |= lb << idx;
	    rv |= rb << idx;

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      lv += rv;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    thr_put_bit(thr, cp->bit_idx1+idx, (lv&1) ? 1 : 0);
	    lv >>= 1;
      }

      return true;

 x_out:
      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1)
	    thr_put_bit(thr, cp->bit_idx1+idx, 2);

      return true;
}

bool of_ASSIGN(vthread_t thr, vvp_code_t cp)
{
      unsigned char bit_val = thr_get_bit(thr, cp->bit_idx2);
      schedule_assign(cp->iptr, bit_val, cp->bit_idx1);
      return true;
}

bool of_ASSIGN_MEM(vthread_t thr, vvp_code_t cp)
{
      unsigned char bit_val = thr_get_bit(thr, cp->bit_idx2);
      schedule_memory(cp->mem, thr->index[3], bit_val, cp->bit_idx1);
      return true;
}

bool of_CMPS(vthread_t thr, vvp_code_t cp)
{
      unsigned eq = 1;
      unsigned eeq = 1;
      unsigned lt = 0;

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      unsigned sig1 = thr_get_bit(thr, idx1 + cp->number - 1);
      unsigned sig2 = thr_get_bit(thr, idx2 + cp->number - 1);

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lv = thr_get_bit(thr, idx1);
	    unsigned rv = thr_get_bit(thr, idx2);

	    if (lv > rv) {
		  lt = 0;
		  eeq = 0;
	    } else if (lv < rv) {
		  lt = 1;
		  eeq = 0;
	    }
	    if (eq != 2) {
		  if ((lv == 0) && (rv != 0))
			eq = 0;
		  if ((lv == 1) && (rv != 1))
			eq = 0;
		  if ((lv | rv) >= 2)
			eq = 2;
	    }

	    if (idx1 >= 4) idx1 += 1;
	    if (idx2 >= 4) idx2 += 1;
      }

      if (eq == 2)
	    lt = 2;
      else if ((sig1 == 1) && (sig2 == 0))
	    lt = 1;
      else if ((sig1 == 0) && (sig2 == 1))
	    lt = 0;

      thr_put_bit(thr, 4, eq);
      thr_put_bit(thr, 5, lt);
      thr_put_bit(thr, 6, eeq);

      return true;
}

bool of_CMPU(vthread_t thr, vvp_code_t cp)
{
      unsigned eq = 1;
      unsigned eeq = 1;
      unsigned lt = 0;

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lv = thr_get_bit(thr, idx1);
	    unsigned rv = thr_get_bit(thr, idx2);

	    if (lv > rv) {
		  lt = 0;
		  eeq = 0;
	    } else if (lv < rv) {
		  lt = 1;
		  eeq = 0;
	    }
	    if (eq != 2) {
		  if ((lv == 0) && (rv != 0))
			eq = 0;
		  if ((lv == 1) && (rv != 1))
			eq = 0;
		  if ((lv | rv) >= 2)
			eq = 2;
	    }

	    if (idx1 >= 4) idx1 += 1;
	    if (idx2 >= 4) idx2 += 1;
      }

      if (eq == 2)
	    lt = 2;

      thr_put_bit(thr, 4, eq);
      thr_put_bit(thr, 5, lt);
      thr_put_bit(thr, 6, eeq);

      return true;
}

bool of_CMPX(vthread_t thr, vvp_code_t cp)
{
      unsigned eq = 1;

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lv = thr_get_bit(thr, idx1);
	    unsigned rv = thr_get_bit(thr, idx2);

	    if ((lv < 2) && (rv < 2) && (lv != rv)) {
		  eq = 0;
		  break;
	    }

	    if (idx1 >= 4) idx1 += 1;
	    if (idx2 >= 4) idx2 += 1;
      }

      thr_put_bit(thr, 4, eq);

      return true;
}

bool of_CMPZ(vthread_t thr, vvp_code_t cp)
{
      unsigned eq = 1;

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lv = thr_get_bit(thr, idx1);
	    unsigned rv = thr_get_bit(thr, idx2);

	    if ((lv < 3) && (rv < 3) && (lv != rv)) {
		  eq = 0;
		  break;
	    }

	    if (idx1 >= 4) idx1 += 1;
	    if (idx2 >= 4) idx2 += 1;
      }

      thr_put_bit(thr, 4, eq);

      return true;
}

bool of_DELAY(vthread_t thr, vvp_code_t cp)
{
	//printf("thread %p: %%delay %lu\n", thr, cp->number);
      schedule_vthread(thr, cp->number);
      return false;
}

/*
 * Implement the %disable instruction by scanning the target scope for
 * all the target threads. Kill the target threads and wake up a
 * parent that is attempting a %join.
 *
 * XXXX BUG BUG!
 * The scheduler probably still has a pointer to me, and this reaping
 * will destroy this object. The result: dangling pointer.
 */
bool of_DISABLE(vthread_t thr, vvp_code_t cp)
{
      struct __vpiScope*scope = (struct __vpiScope*)cp->handle;
      if (scope->threads == 0)
	    return true;

      struct vthread_s*head = scope->threads;

      while (head->scope_next != head) {
	    vthread_t tmp = head->scope_next;

	      /* Pull the target thread out of the scope. */
	    tmp->scope_next->scope_prev = tmp->scope_prev;
	    tmp->scope_prev->scope_next = tmp->scope_next;

	      /* XXXX I don't support disabling threads with children. */
	    assert(tmp->child == 0);
	    assert(tmp != thr);
	      /* XXXX Not supported yet. */
	    assert(tmp->waiting_for_event == 0);

	    tmp->pc = 0;
	    tmp->i_have_ended = 1;

	    if (tmp->schedule_parent_on_end) {
		    /* If a parent is waiting in a %join, wake it up. */
		  assert(tmp->parent);
		  schedule_vthread(tmp->parent, 0);
		  vthread_reap(tmp);

	    } else if (tmp->parent) {
		    /* If the parent is yet to %join me, let its %join
		       do the reaping. */
		    //assert(tmp->is_scheduled == 0);

	    } else {
		    /* No parent at all. Goodby. */
		  vthread_reap(tmp);
	    }
      }

      return true;
}

/*
 * This terminates the current thread. If there is a parent who is
 * waiting for me to die, then I schedule it. At any rate, I mark
 * myself as a zombie by setting my pc to 0.
 */
bool of_END(vthread_t thr, vvp_code_t)
{
      assert(! thr->waiting_for_event);

      thr->i_have_ended = 1;
      thr->pc = 0;

	/* If this thread has children, then there is a programming
	   error as there were not enough %join instructions to reap
	   all the children. */
      assert(thr->child == 0);


	/* If I have a parent who is waiting for me, then mark that I
	   have ended, and schedule that parent. Also, finish the
	   %join for the parent. */
      if (thr->schedule_parent_on_end) {
	    assert(thr->parent);
	    schedule_vthread(thr->parent, 0);
	    vthread_reap(thr);
	    return false;
      }

	/* If I have no parents, then no one can %join me and there is
	   no reason to stick around. This can happen, for example if
	   I am an ``initial'' thread. */
      if (thr->parent == 0) {
	    vthread_reap(thr);
	    return false;
      }

	/* If I make it this far, then I have a parent who may wish
	   to %join me. Remain a zombie so that it can. */

      return false;
}

/*
 * The %fork instruction causes a new child to be created and pushed
 * in front of any existing child. This causes the new child to be the
 * parent of any previous children, and for me to be the parent of the
 * new child.
 */
bool of_FORK(vthread_t thr, vvp_code_t cp)
{
      vthread_t child = vthread_new(cp->fork->cptr, cp->fork->scope);

      child->child  = thr->child;
      child->parent = thr;
      thr->child = child;
      if (child->child) {
	    assert(child->child->parent == thr);
	    child->child->parent = child;
      }
      schedule_vthread(child, 0);
      return true;
}

bool of_INV(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);
      for (unsigned idx = 0 ;  idx < cp->bit_idx2 ;  idx += 1) {
	    unsigned val = thr_get_bit(thr, cp->bit_idx1+idx);
	    switch (val) {
		case 0:
		  val = 1;
		  break;
		case 1:
		  val = 0;
		  break;
		default:
		  val = 2;
		  break;
	    }
	    thr_put_bit(thr, cp->bit_idx1+idx, val);
      }
      return true;
}


/*
** Index registers, signed arithmetic.
*/

bool of_IX_ADD(vthread_t thr, vvp_code_t cp)
{
  int number = (int)cp->number; // signed
  thr->index[cp->bit_idx1 & 3] += number;
  return true;
}

bool of_IX_MUL(vthread_t thr, vvp_code_t cp)
{
  int number = (int)cp->number; // signed
  thr->index[cp->bit_idx1 & 3] *= number;
  return true;
}

bool of_IX_LOAD(vthread_t thr, vvp_code_t cp)
{
      thr->index[cp->bit_idx1 & 3] = cp->number;
      return true;
}


/*
 * The various JMP instruction work simply by pulling the new program
 * counter from the instruction and resuming. If the jump is
 * conditional, then test the bit for the expected value first.
 */
bool of_JMP(vthread_t thr, vvp_code_t cp)
{
      thr->pc = cp->cptr;
      return true;
}

bool of_JMP0(vthread_t thr, vvp_code_t cp)
{
      if (thr_get_bit(thr, cp->bit_idx1) == 0)
	    thr->pc = cp->cptr;
      return true;
}

bool of_JMP0XZ(vthread_t thr, vvp_code_t cp)
{
      if (thr_get_bit(thr, cp->bit_idx1) != 1)
	    thr->pc = cp->cptr;
      return true;
}

bool of_JMP1(vthread_t thr, vvp_code_t cp)
{
      if (thr_get_bit(thr, cp->bit_idx1) == 1)
	    thr->pc = cp->cptr;
      return true;
}

/*
 * The %join instruction causes the thread to wait for the one and
 * only child to die.  If it is already dead (and a zombie) then I
 * reap it and go on. Otherwise, I tell the child that I am ready for
 * it to die, and it will reschedule me when it does.
 */
bool of_JOIN(vthread_t thr, vvp_code_t cp)
{
      assert(thr->child);
      assert(thr->child->parent == thr);

	/* If the child has already ended, reap it now. */
      if (thr->child->i_have_ended) {
	    vthread_reap(thr->child);
	    return true;
      }

	/* Otherwise, I get to start waiting. */
      thr->child->schedule_parent_on_end = 1;
      return false;
}

bool of_LOAD(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);
      thr_put_bit(thr, cp->bit_idx1, functor_get(cp->iptr));
      return true;
}

bool of_LOAD_MEM(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);
      assert(cp->bit_idx2 < 4);
      unsigned char val = memory_get(cp->mem, thr->index[cp->bit_idx1]);
      thr_put_bit(thr, cp->bit_idx2, val);
      return true;
}

bool of_MOV(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      if (cp->bit_idx2 >= 4) {
	    for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1)
		  thr_put_bit(thr,
			      cp->bit_idx1+idx,
			      thr_get_bit(thr, cp->bit_idx2+idx));

      } else {
	    for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1)
		  thr_put_bit(thr,
			      cp->bit_idx1+idx,
			      thr_get_bit(thr, cp->bit_idx2));
      }

      return true;
}

bool of_NOOP(vthread_t thr, vvp_code_t cp)
{
      return true;
}

bool of_NORR(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      unsigned lb = 0;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {

	    unsigned rb = thr_get_bit(thr, idx2);
	    if (rb == 1) {
		  lb = 1;
		  break;
	    }

	    if (rb != 0)
		  lb = 2;
      }

      thr_put_bit(thr, cp->bit_idx1, lb);

      return true;
}

bool of_OR(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {

	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb == 1) || (rb == 1)) {
		  thr_put_bit(thr, idx1, 1);

	    } else if ((lb == 0) && (rb == 0)) {
		  thr_put_bit(thr, idx1, 0);

	    } else {
		  thr_put_bit(thr, idx1, 2);
	    }

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      return true;
}

bool of_SET(vthread_t thr, vvp_code_t cp)
{
      unsigned char bit_val = thr_get_bit(thr, cp->bit_idx1);
      functor_set(cp->iptr, bit_val, true);

      return true;
}

bool of_SET_MEM(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx2 < 4);
      unsigned char val = thr_get_bit(thr, cp->bit_idx2);
      memory_set(cp->mem, thr->index[cp->bit_idx1], val);

      return true;
}

bool of_SUB(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);
      assert(cp->number <= 8*sizeof(unsigned long));

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;
      unsigned long lv = 0, rv = 0;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb | rb) & 2)
		  goto x_out;

	    lv |= lb << idx;
	    rv |= rb << idx;

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      lv -= rv;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {
	    thr_put_bit(thr, cp->bit_idx1+idx, (lv&1) ? 1 : 0);
	    lv >>= 1;
      }

      return true;

 x_out:
      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1)
	    thr_put_bit(thr, cp->bit_idx1+idx, 2);

      return true;
}

bool of_VPI_CALL(vthread_t thr, vvp_code_t cp)
{
	// printf("thread %p: %%vpi_call\n", thr);
      vpip_execute_vpi_call(cp->handle);
      return schedule_finished()? false : true;
}

/*
 * Implement the wait by locating the functor for the event, and
 * adding this thread to the threads list for the event.
 */
bool of_WAIT(vthread_t thr, vvp_code_t cp)
{
      assert(! thr->waiting_for_event);
      thr->waiting_for_event = 1;
      functor_t fp = functor_index(cp->iptr);
      assert((fp->mode == 1) || (fp->mode == 2));
      vvp_event_t ep = fp->event;
      thr->wait_next = ep->threads;
      ep->threads = thr;

      return false;
}


bool of_XNOR(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {

	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb == 1) && (rb == 1)) {
		  thr_put_bit(thr, idx1, 1);

	    } else if ((lb == 0) && (rb == 0)) {
		  thr_put_bit(thr, idx1, 1);

	    } else if ((lb == 1) && (rb == 0)) {
		  thr_put_bit(thr, idx1, 0);

	    } else if ((lb == 0) && (rb == 1)) {
		  thr_put_bit(thr, idx1, 0);

	    } else {
		  thr_put_bit(thr, idx1, 2);
	    }

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      return true;
}


bool of_XOR(vthread_t thr, vvp_code_t cp)
{
      assert(cp->bit_idx1 >= 4);

      unsigned idx1 = cp->bit_idx1;
      unsigned idx2 = cp->bit_idx2;

      for (unsigned idx = 0 ;  idx < cp->number ;  idx += 1) {

	    unsigned lb = thr_get_bit(thr, idx1);
	    unsigned rb = thr_get_bit(thr, idx2);

	    if ((lb == 1) && (rb == 1)) {
		  thr_put_bit(thr, idx1, 0);

	    } else if ((lb == 0) && (rb == 0)) {
		  thr_put_bit(thr, idx1, 0);

	    } else if ((lb == 1) && (rb == 0)) {
		  thr_put_bit(thr, idx1, 1);

	    } else if ((lb == 0) && (rb == 1)) {
		  thr_put_bit(thr, idx1, 1);

	    } else {
		  thr_put_bit(thr, idx1, 2);
	    }

	    idx1 += 1;
	    if (idx2 >= 4)
		  idx2 += 1;
      }

      return true;
}


bool of_ZOMBIE(vthread_t thr, vvp_code_t)
{
      thr->pc = 0;
      if ((thr->parent == 0) && (thr->child == 0))
	    delete thr;

      return false;
}

/*
 * $Log: vthread.cc,v $
 * Revision 1.33  2001/05/02 01:57:26  steve
 *  Support behavioral subtraction.
 *
 * Revision 1.32  2001/05/02 01:37:38  steve
 *  initialize is_schedule.
 *
 * Revision 1.31  2001/05/01 05:00:02  steve
 *  Implement %ix/load.
 *
 * Revision 1.30  2001/05/01 01:09:39  steve
 *  Add support for memory objects. (Stephan Boettcher)
 *
 * Revision 1.29  2001/04/21 00:34:39  steve
 *  Working %disable and reap handling references from scheduler.
 *
 * Revision 1.28  2001/04/18 05:04:19  steve
 *  %end complete the %join for the parent.
 *
 * Revision 1.27  2001/04/18 04:21:23  steve
 *  Put threads into scopes.
 *
 * Revision 1.26  2001/04/15 16:37:48  steve
 *  add XOR support.
 *
 * Revision 1.25  2001/04/15 04:07:56  steve
 *  Add support for behavioral xnor.
 *
 * Revision 1.24  2001/04/14 05:10:05  steve
 *  Initialize the waiting_for_event member.
 *
 * Revision 1.23  2001/04/13 03:55:18  steve
 *  More complete reap of all threads.
 *
 * Revision 1.22  2001/04/05 01:12:28  steve
 *  Get signed compares working correctly in vvp.
 *
 * Revision 1.21  2001/04/03 03:18:34  steve
 *  support functor_set push for blocking assignment.
 *
 * Revision 1.20  2001/04/01 22:25:33  steve
 *  Add the reduction nor instruction.
 *
 * Revision 1.19  2001/04/01 07:22:08  steve
 *  Implement the less-then and %or instructions.
 */