using prefetch on all architectures (#166)

* changing _mm_prefetch to __builtin_prefetch

* removing #ifdef USE_SSE from HNSW 

* removed unnecessary cast

Author: GuyAv46

src/VecSim/algorithms/hnsw/hnsw_batch_iterator.cpp

@@ -106,20 +106,18 @@ candidatesMaxHeap HNSW_BatchIterator::scanGraph(candidatesMinHeap &candidates,
             this->hnsw_index->get_linklist_at_level(curr_node_id, 0);
         unsigned short links_num = this->hnsw_index->getListCount(cur_node_links_header);
         auto *node_links = (unsigned int *)(cur_node_links_header + 1);
-#ifdef USE_SSE
-        _mm_prefetch((char *)(visited_list->getElementsTags() + *node_links), _MM_HINT_T0);
-        _mm_prefetch((char *)(visited_list->getElementsTags() + *node_links + 64), _MM_HINT_T0);
-        _mm_prefetch(hnsw_index->getDataByInternalId(*node_links), _MM_HINT_T0);
-        _mm_prefetch(hnsw_index->getDataByInternalId(*(node_links + 1)), _MM_HINT_T0);
-#endif
+
+        __builtin_prefetch(visited_list->getElementsTags() + *node_links);
+        __builtin_prefetch(visited_list->getElementsTags() + *node_links + 64);
+        __builtin_prefetch(hnsw_index->getDataByInternalId(*node_links));
+        __builtin_prefetch(hnsw_index->getDataByInternalId(*(node_links + 1)));
 
         for (size_t j = 0; j < links_num; j++) {
             unsigned int candidate_id = *(node_links + j);
-#ifdef USE_SSE
-            _mm_prefetch((char *)(visited_list->getElementsTags() + *(node_links + j + 1)),
-                         _MM_HINT_T0);
-            _mm_prefetch(hnsw_index->getDataByInternalId(*(node_links + j + 1)), _MM_HINT_T0);
-#endif
+
+            __builtin_prefetch(visited_list->getElementsTags() + *(node_links + j + 1));
+            __builtin_prefetch(hnsw_index->getDataByInternalId(*(node_links + j + 1)));
+
             if (this->hasVisitedNode(candidate_id)) {
                 continue;
             }

src/VecSim/algorithms/hnsw/hnswlib.h

@@ -4,7 +4,6 @@
 #include "VecSim/spaces/L2_space.h"
 #include "VecSim/spaces/IP_space.h"
 #include "VecSim/spaces/space_interface.h"
-#include "VecSim/spaces/space_includes.h"
 #include "VecSim/utils/arr_cpp.h"
 #include "VecSim/memory/vecsim_malloc.h"
 #include "VecSim/utils/vecsim_stl.h"
@@ -362,21 +361,18 @@ dist_t HierarchicalNSW<dist_t>::processCandidate(tableint curNodeId, const void
     linklistsizeint *node_ll = get_linklist_at_level(curNodeId, layer);
     size_t links_num = getListCount(node_ll);
     auto *node_links = (tableint *)(node_ll + 1);
-#ifdef USE_SSE
-    _mm_prefetch((char *)(visited_nodes_handler->getElementsTags() + *(node_ll + 1)), _MM_HINT_T0);
-    _mm_prefetch((char *)(visited_nodes_handler->getElementsTags() + *(node_ll + 1) + 64),
-                 _MM_HINT_T0);
-    _mm_prefetch(getDataByInternalId(*node_links), _MM_HINT_T0);
-    _mm_prefetch(getDataByInternalId(*(node_links + 1)), _MM_HINT_T0);
-#endif
+
+    __builtin_prefetch(visited_nodes_handler->getElementsTags() + *(node_ll + 1));
+    __builtin_prefetch(visited_nodes_handler->getElementsTags() + *(node_ll + 1) + 64);
+    __builtin_prefetch(getDataByInternalId(*node_links));
+    __builtin_prefetch(getDataByInternalId(*(node_links + 1)));
 
     for (size_t j = 0; j < links_num; j++) {
         tableint candidate_id = *(node_links + j);
-#ifdef USE_SSE
-        _mm_prefetch((char *)(visited_nodes_handler->getElementsTags() + *(node_links + j + 1)),
-                     _MM_HINT_T0);
-        _mm_prefetch(getDataByInternalId(*(node_links + j + 1)), _MM_HINT_T0);
-#endif
+
+        __builtin_prefetch(visited_nodes_handler->getElementsTags() + *(node_links + j + 1));
+        __builtin_prefetch(getDataByInternalId(*(node_links + j + 1)));
+
         if (this->visited_nodes_handler->getNodeTag(candidate_id) == visited_tag)
             continue;
         this->visited_nodes_handler->tagNode(candidate_id, visited_tag);
@@ -385,9 +381,9 @@ dist_t HierarchicalNSW<dist_t>::processCandidate(tableint curNodeId, const void
         dist_t dist1 = fstdistfunc_(data_point, currObj1, dist_func_param_);
         if (top_candidates.size() < ef || lowerBound > dist1) {
             candidate_set.emplace(-dist1, candidate_id);
-#ifdef USE_SSE
-            _mm_prefetch(getDataByInternalId(candidate_set.top().second), _MM_HINT_T0);
-#endif
+
+            __builtin_prefetch(getDataByInternalId(candidate_set.top().second));
+
             top_candidates.emplace(dist1, candidate_id);
 
             if (top_candidates.size() > ef)