text: /*
   * kmp_taskdeps.cpp
   * $Revision: 42539 $
   * $Date: 2013-07-17 11:20:01 -0500 (Wed, 17 Jul 2013) $
   */
  
  
  //===----------------------------------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is dual licensed under the MIT and the University of Illinois Open
  // Source Licenses. See LICENSE.txt for details.
  //
  //===----------------------------------------------------------------------===//
  
  
  //#define KMP_SUPPORT_GRAPH_OUTPUT 1
  
  #include "kmp.h"
  #include "kmp_io.h"
  #include "kmp_wait_release.h"
  
  #if OMP_40_ENABLED
  
  //TODO: Improve memory allocation? keep a list of pre-allocated structures? allocate in blocks? re-use list finished list entries?
  //TODO: don't use atomic ref counters for stack-allocated nodes.
  //TODO: find an alternate to atomic refs for heap-allocated nodes?
  //TODO: Finish graph output support
  //TODO: kmp_lock_t seems a tad to big (and heavy weight) for this. Check other runtime locks
  //TODO: Any ITT support needed?
  
  #ifdef KMP_SUPPORT_GRAPH_OUTPUT
  static kmp_int32 kmp_node_id_seed = 0;
  #endif
  
  static void
  __kmp_init_node ( kmp_depnode_t *node )
  {
      node->dn.task = NULL; // set to null initially, it will point to the right task once dependences have been processed
      node->dn.successors = NULL;
      __kmp_init_lock(&node->dn.lock);
      node->dn.nrefs = 1; // init creates the first reference to the node
  #ifdef KMP_SUPPORT_GRAPH_OUTPUT
      node->dn.id = KMP_TEST_THEN_INC32(&kmp_node_id_seed);
  #endif
  }
  
  static inline kmp_depnode_t *
  __kmp_node_ref ( kmp_depnode_t *node )
  {
      KMP_TEST_THEN_INC32(&node->dn.nrefs);
      return node;
  }
  
  static inline void
  __kmp_node_deref ( kmp_info_t *thread, kmp_depnode_t *node )
  {
      if (!node) return;
  
      kmp_int32 n = KMP_TEST_THEN_DEC32(&node->dn.nrefs) - 1;
      if ( n == 0 ) {
          KMP_ASSERT(node->dn.nrefs == 0);
  #if USE_FAST_MEMORY
          __kmp_fast_free(thread,node);
  #else
          __kmp_thread_free(thread,node);
  #endif
      }
  }
  
  #define KMP_ACQUIRE_DEPNODE(gtid,n) __kmp_acquire_lock(&(n)->dn.lock,(gtid))
  #define KMP_RELEASE_DEPNODE(gtid,n) __kmp_release_lock(&(n)->dn.lock,(gtid))
  
  static void
  __kmp_depnode_list_free ( kmp_info_t *thread, kmp_depnode_list *list );
  
  static const kmp_int32 kmp_dephash_log2 = 6;
  static const kmp_int32 kmp_dephash_size = (1 << kmp_dephash_log2);
  
  static inline kmp_int32
  __kmp_dephash_hash ( kmp_intptr_t addr )
  {
      //TODO alternate to try: set = (((Addr64)(addrUsefulBits * 9.618)) % m_num_sets );
      return ((addr >> kmp_dephash_log2) ^ addr) % kmp_dephash_size;
  }
  
  static kmp_dephash_t *
  __kmp_dephash_create ( kmp_info_t *thread )
  {
      kmp_dephash_t *h;
  
      kmp_int32 size = kmp_dephash_size * sizeof(kmp_dephash_entry_t) + sizeof(kmp_dephash_t);
  
  #if USE_FAST_MEMORY
      h = (kmp_dephash_t *) __kmp_fast_allocate( thread, size );
  #else
      h = (kmp_dephash_t *) __kmp_thread_malloc( thread, size );
  #endif
  
  #ifdef KMP_DEBUG
      h->nelements = 0;
  #endif
      h->buckets = (kmp_dephash_entry **)(h+1);
  
      for ( kmp_int32 i = 0; i < kmp_dephash_size; i++ )
          h->buckets[i] = 0;
  
      return h;
  }
  
  static void
  __kmp_dephash_free ( kmp_info_t *thread, kmp_dephash_t *h )
  {
      for ( kmp_int32 i=0; i < kmp_dephash_size; i++ ) {
          if ( h->buckets[i] ) {
              kmp_dephash_entry_t *next;
              for ( kmp_dephash_entry_t *entry = h->buckets[i]; entry; entry = next ) {
                  next = entry->next_in_bucket;
                  __kmp_depnode_list_free(thread,entry->last_ins);
                  __kmp_node_deref(thread,entry->last_out);
  #if USE_FAST_MEMORY
                  __kmp_fast_free(thread,entry);
  #else
                  __kmp_thread_free(thread,entry);
  #endif
              }
          }
      }
  #if USE_FAST_MEMORY
      __kmp_fast_free(thread,h);
  #else
      __kmp_thread_free(thread,h);
  #endif
  }
  
  static kmp_dephash_entry *
  __kmp_dephash_find ( kmp_info_t *thread, kmp_dephash_t *h, kmp_intptr_t addr )
  {
      kmp_int32 bucket = __kmp_dephash_hash(addr);
  
      kmp_dephash_entry_t *entry;
      for ( entry = h->buckets[bucket]; entry; entry = entry->next_in_bucket )
          if ( entry->addr == addr ) break;
  
      if ( entry == NULL ) {
          // create entry. This is only done by one thread so no locking required
  #if USE_FAST_MEMORY
          entry = (kmp_dephash_entry_t *) __kmp_fast_allocate( thread, sizeof(kmp_dephash_entry_t) );
  #else
          entry = (kmp_dephash_entry_t *) __kmp_thread_malloc( thread, sizeof(kmp_dephash_entry_t) );
  #endif
          entry->addr = addr;
          entry->last_out = NULL;
          entry->last_ins = NULL;
          entry->next_in_bucket = h->buckets[bucket];
          h->buckets[bucket] = entry;
  #ifdef KMP_DEBUG
          h->nelements++;
          if ( entry->next_in_bucket ) h->nconflicts++;
  #endif
      }
      return entry;
  }
  
  static kmp_depnode_list_t *
  __kmp_add_node ( kmp_info_t *thread, kmp_depnode_list_t *list, kmp_depnode_t *node )
  {
      kmp_depnode_list_t *new_head;
  
  #if USE_FAST_MEMORY
      new_head = (kmp_depnode_list_t *) __kmp_fast_allocate(thread,sizeof(kmp_depnode_list_t));
  #else
      new_head = (kmp_depnode_list_t *) __kmp_thread_malloc(thread,sizeof(kmp_depnode_list_t));
  #endif
  
      new_head->node = __kmp_node_ref(node);
      new_head->next = list;
  
      return new_head;
  }
  
  static void
  __kmp_depnode_list_free ( kmp_info_t *thread, kmp_depnode_list *list )
  {
      kmp_depnode_list *next;
  
      for ( ; list ; list = next ) {
          next = list->next;
  
          __kmp_node_deref(thread,list->node);
  #if USE_FAST_MEMORY
          __kmp_fast_free(thread,list);
  #else
          __kmp_thread_free(thread,list);
  #endif
      }
  }
  
  static inline void
  __kmp_track_dependence ( kmp_depnode_t *source, kmp_depnode_t *sink )
  {
  #ifdef KMP_SUPPORT_GRAPH_OUTPUT
      kmp_taskdata_t * task_source = KMP_TASK_TO_TASKDATA(source->dn.task);
      kmp_taskdata_t * task_sink = KMP_TASK_TO_TASKDATA(sink->dn.task);    // this can be NULL when if(0) ...
  
      __kmp_printf("%d(%s) -> %d(%s)\n", source->dn.id, task_source->td_ident->psource, sink->dn.id, task_sink->td_ident->psource);
  #endif
  }
  
  template< bool filter >
  static inline kmp_int32
  __kmp_process_deps ( kmp_int32 gtid, kmp_depnode_t *node, kmp_dephash_t *hash,
                       bool dep_barrier,kmp_int32 ndeps, kmp_depend_info_t *dep_list)
  {
      KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d processing %d depencies : dep_barrier = %d\n", filter, gtid, ndeps, dep_barrier ) );
      
      kmp_info_t *thread = __kmp_threads[ gtid ];
      kmp_int32 npredecessors=0;
      for ( kmp_int32 i = 0; i < ndeps ; i++ ) {
          const kmp_depend_info_t * dep = &dep_list[i];
  
          KMP_DEBUG_ASSERT(dep->flags.in);
  
          if ( filter && dep->base_addr == 0 ) continue; // skip filtered entries
  
          kmp_dephash_entry_t *info = __kmp_dephash_find(thread,hash,dep->base_addr);
          kmp_depnode_t *last_out = info->last_out;
  
          if ( dep->flags.out && info->last_ins ) {
              for ( kmp_depnode_list_t * p = info->last_ins; p; p = p->next ) {
                  kmp_depnode_t * indep = p->node;
                  if ( indep->dn.task ) {
                      KMP_ACQUIRE_DEPNODE(gtid,indep);
                      if ( indep->dn.task ) {
                          __kmp_track_dependence(indep,node);
                          indep->dn.successors = __kmp_add_node(thread, indep->dn.successors, node);
                          KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p",
                                   filter,gtid, KMP_TASK_TO_TASKDATA(indep->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));
                          npredecessors++;
                      }
                      KMP_RELEASE_DEPNODE(gtid,indep);
                  }
              }
  
              __kmp_depnode_list_free(thread,info->last_ins);
              info->last_ins = NULL;
  
          } else if ( last_out && last_out->dn.task ) {
              KMP_ACQUIRE_DEPNODE(gtid,last_out);
              if ( last_out->dn.task ) {
                  __kmp_track_dependence(last_out,node);
                  last_out->dn.successors = __kmp_add_node(thread, last_out->dn.successors, node);
                  KA_TRACE(40,("__kmp_process_deps<%d>: T#%d adding dependence from %p to %p", 
                               filter,gtid, KMP_TASK_TO_TASKDATA(last_out->dn.task), KMP_TASK_TO_TASKDATA(node->dn.task)));
                  
                  npredecessors++;
              }
              KMP_RELEASE_DEPNODE(gtid,last_out);
          }
  
          if ( dep_barrier ) {
              // if this is a sync point in the serial sequence, then the previous outputs are guaranteed to be completed after
              // the execution of this task so the previous output nodes can be cleared.
              __kmp_node_deref(thread,last_out);
              info->last_out = NULL;
          } else {
              if ( dep->flags.out ) {
                  __kmp_node_deref(thread,last_out);
                  info->last_out = __kmp_node_ref(node);
              } else
                  info->last_ins = __kmp_add_node(thread, info->last_ins, node);
          }
  
      }
  
      KA_TRACE(30, ("__kmp_process_deps<%d>: T#%d found %d predecessors\n", filter, gtid, npredecessors ) );
  
      return npredecessors;
  }
  
  #define NO_DEP_BARRIER (false)
  #define DEP_BARRIER (true)
  
  // returns true if the task has any outstanding dependence
  static bool
  __kmp_check_deps ( kmp_int32 gtid, kmp_depnode_t *node, kmp_task_t *task, kmp_dephash_t *hash, bool dep_barrier,
                     kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                     kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
  {
      int i;
  
      kmp_taskdata_t * taskdata = KMP_TASK_TO_TASKDATA(task);
      KA_TRACE(20, ("__kmp_check_deps: T#%d checking dependencies for task %p : %d possibly aliased dependencies, %d non-aliased depedencies : dep_barrier=%d .\n", gtid, taskdata, ndeps, ndeps_noalias, dep_barrier ) );
  
      // Filter deps in dep_list
      // TODO: Different algorithm for large dep_list ( > 10 ? )
      for ( i = 0; i < ndeps; i ++ ) {
          if ( dep_list[i].base_addr != 0 )
              for ( int j = i+1; j < ndeps; j++ )
                  if ( dep_list[i].base_addr == dep_list[j].base_addr ) {
                      dep_list[i].flags.in |= dep_list[j].flags.in;
                      dep_list[i].flags.out |= dep_list[j].flags.out;
                      dep_list[j].base_addr = 0; // Mark j element as void
                  }
      }
  
      // doesn't need to be atomic as no other thread is going to be accessing this node just yet
      // npredecessors is set -1 to ensure that none of the releasing tasks queues this task before we have finished processing all the dependencies
      node->dn.npredecessors = -1;
  
      // used to pack all npredecessors additions into a single atomic operation at the end
      int npredecessors;
  
      npredecessors = __kmp_process_deps<true>(gtid, node, hash, dep_barrier, ndeps, dep_list);
      npredecessors += __kmp_process_deps<false>(gtid, node, hash, dep_barrier, ndeps_noalias, noalias_dep_list);
  
      node->dn.task = task;
      KMP_MB();
  
      // Account for our initial fake value
      npredecessors++;
  
      // Update predecessors and obtain current value to check if there are still any outstandig dependences (some tasks may have finished while we processed the dependences)
      npredecessors = KMP_TEST_THEN_ADD32(&node->dn.npredecessors, npredecessors) + npredecessors;
  
      KA_TRACE(20, ("__kmp_check_deps: T#%d found %d predecessors for task %p \n", gtid, npredecessors, taskdata ) );
  
      // beyond this point the task could be queued (and executed) by a releasing task...
      return npredecessors > 0 ? true : false;
  }
  
  void
  __kmp_release_deps ( kmp_int32 gtid, kmp_taskdata_t *task )
  {
      kmp_info_t *thread = __kmp_threads[ gtid ];
      kmp_depnode_t *node = task->td_depnode;
  
      if ( task->td_dephash ) {
          KA_TRACE(40, ("__kmp_realease_deps: T#%d freeing dependencies hash of task %p.\n", gtid, task ) );
          __kmp_dephash_free(thread,task->td_dephash);
      }
  
      if ( !node ) return;
  
      KA_TRACE(20, ("__kmp_realease_deps: T#%d notifying succesors of task %p.\n", gtid, task ) );
      
      KMP_ACQUIRE_DEPNODE(gtid,node);
      node->dn.task = NULL; // mark this task as finished, so no new dependencies are generated
      KMP_RELEASE_DEPNODE(gtid,node);
  
      kmp_depnode_list_t *next;
      for ( kmp_depnode_list_t *p = node->dn.successors; p; p = next ) {
          kmp_depnode_t *successor = p->node;
          kmp_int32 npredecessors = KMP_TEST_THEN_DEC32(&successor->dn.npredecessors) - 1;
  
          // successor task can be NULL for wait_depends or because deps are still being processed
          if ( npredecessors == 0 ) {
              KMP_MB();
              if ( successor->dn.task ) {            
                  KA_TRACE(20, ("__kmp_realease_deps: T#%d successor %p of %p scheduled for execution.\n", gtid, successor->dn.task, task ) );
                  __kmp_omp_task(gtid,successor->dn.task,false);
              }
          }
  
          next = p->next;
          __kmp_node_deref(thread,p->node);
  #if USE_FAST_MEMORY
          __kmp_fast_free(thread,p);
  #else
          __kmp_thread_free(thread,p);
  #endif
      }
  
      __kmp_node_deref(thread,node);
  
      KA_TRACE(20, ("__kmp_realease_deps: T#%d all successors of %p notified of completation\n", gtid, task ) );
  }
  
  /*!
  @ingroup TASKING
  @param loc_ref location of the original task directive
  @param gtid Global Thread ID of encountering thread
  @param new_task task thunk allocated by __kmp_omp_task_alloc() for the ''new task''
  @param ndeps Number of depend items with possible aliasing
  @param dep_list List of depend items with possible aliasing
  @param ndeps_noalias Number of depend items with no aliasing
  @param noalias_dep_list List of depend items with no aliasing
  
  @return Returns either TASK_CURRENT_NOT_QUEUED if the current task was not suspendend and queued, or TASK_CURRENT_QUEUED if it was suspended and queued
  
  Schedule a non-thread-switchable task with dependences for execution
  */
  kmp_int32
  __kmpc_omp_task_with_deps( ident_t *loc_ref, kmp_int32 gtid, kmp_task_t * new_task,
                              kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                              kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
  {
  
      kmp_taskdata_t * new_taskdata = KMP_TASK_TO_TASKDATA(new_task);
      KA_TRACE(10, ("__kmpc_omp_task_with_deps(enter): T#%d loc=%p task=%p\n",
                    gtid, loc_ref, new_taskdata ) );
  
      kmp_info_t *thread = __kmp_threads[ gtid ];
      kmp_taskdata_t * current_task = thread->th.th_current_task;
  
      bool serial = current_task->td_flags.team_serial || current_task->td_flags.tasking_ser || current_task->td_flags.final;
  
      if ( !serial && ( ndeps > 0 || ndeps_noalias > 0 )) {
          /* if no dependencies have been tracked yet, create the dependence hash */
          if ( current_task->td_dephash == NULL )
              current_task->td_dephash = __kmp_dephash_create(thread);
  
  #if USE_FAST_MEMORY
          kmp_depnode_t *node = (kmp_depnode_t *) __kmp_fast_allocate(thread,sizeof(kmp_depnode_t));
  #else
          kmp_depnode_t *node = (kmp_depnode_t *) __kmp_thread_malloc(thread,sizeof(kmp_depnode_t));
  #endif
  
          __kmp_init_node(node);
          new_taskdata->td_depnode = node;
  
          if ( __kmp_check_deps( gtid, node, new_task, current_task->td_dephash, NO_DEP_BARRIER,
                                 ndeps, dep_list, ndeps_noalias,noalias_dep_list ) ) {
              KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had blocking dependencies: "
                    "loc=%p task=%p, return: TASK_CURRENT_NOT_QUEUED\n", gtid, loc_ref,
                    new_taskdata ) );
              return TASK_CURRENT_NOT_QUEUED;
          }
      }
  
      KA_TRACE(10, ("__kmpc_omp_task_with_deps(exit): T#%d task had no blocking dependencies : "
                    "loc=%p task=%p, transferring to __kmpc_omp_task\n", gtid, loc_ref,
                    new_taskdata ) );    
  
      return __kmpc_omp_task(loc_ref,gtid,new_task);
  }
  
  /*!
  @ingroup TASKING
  @param loc_ref location of the original task directive
  @param gtid Global Thread ID of encountering thread
  @param ndeps Number of depend items with possible aliasing
  @param dep_list List of depend items with possible aliasing
  @param ndeps_noalias Number of depend items with no aliasing
  @param noalias_dep_list List of depend items with no aliasing
  
  Blocks the current task until all specifies dependencies have been fulfilled.
  */
  void
  __kmpc_omp_wait_deps ( ident_t *loc_ref, kmp_int32 gtid, kmp_int32 ndeps, kmp_depend_info_t *dep_list,
                         kmp_int32 ndeps_noalias, kmp_depend_info_t *noalias_dep_list )
  {
      KA_TRACE(10, ("__kmpc_omp_wait_deps(enter): T#%d loc=%p\n", gtid, loc_ref) );
  
      if ( ndeps == 0 && ndeps_noalias == 0 ) {
          KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no dependencies to wait upon : loc=%p\n", gtid, loc_ref) );
          return;
      }
  
      kmp_info_t *thread = __kmp_threads[ gtid ];
      kmp_taskdata_t * current_task = thread->th.th_current_task;
  
      // We can return immediately as:
      //   - dependences are not computed in serial teams
      //   - if the dephash is not yet created it means we have nothing to wait for
      if ( current_task->td_flags.team_serial || current_task->td_flags.tasking_ser || current_task->td_flags.final || current_task->td_dephash == NULL ) {
          KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
          return;
      }
  
      kmp_depnode_t node;
      __kmp_init_node(&node);
  
      if (!__kmp_check_deps( gtid, &node, NULL, current_task->td_dephash, DEP_BARRIER,
                             ndeps, dep_list, ndeps_noalias, noalias_dep_list )) {
          KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d has no blocking dependencies : loc=%p\n", gtid, loc_ref) );
          return;
      }
  
      int thread_finished = FALSE;
      kmp_flag_32 flag((volatile kmp_uint32 *)&(node.dn.npredecessors), 0U);
      while ( node.dn.npredecessors > 0 ) {
          flag.execute_tasks(thread, gtid, FALSE, &thread_finished,
  #if USE_ITT_BUILD
                             NULL,
  #endif
                             __kmp_task_stealing_constraint );
      }
  
      KA_TRACE(10, ("__kmpc_omp_wait_deps(exit): T#%d finished waiting : loc=%p\n", gtid, loc_ref) );
  }
  
  #endif /* OMP_40_ENABLED */
  
  