Implement a hash based look-up to speed up containing address check in large

src/spaces.cc

Index: src/spaces.cc
===================================================================
--- src/spaces.cc	(revision 10961)
+++ src/spaces.cc	(working copy)
@@ -2520,7 +2520,11 @@
 
 // -----------------------------------------------------------------------------
 // LargeObjectSpace
+static bool ComparePointers(void* key1, void* key2) {
+    return key1 == key2;
+}
 
+
 LargeObjectSpace::LargeObjectSpace(Heap* heap,
                                    intptr_t max_capacity,
                                    AllocationSpace id)
@@ -2529,7 +2533,8 @@
       first_page_(NULL),
       size_(0),
       page_count_(0),
-      objects_size_(0) {}
+      objects_size_(0),
+      chunk_map_(ComparePointers, 1024) {}
 
 
 bool LargeObjectSpace::SetUp() {
@@ -2537,6 +2542,7 @@
   size_ = 0;
   page_count_ = 0;
   objects_size_ = 0;
+  chunk_map_.Clear();
   return true;
 }
 
@@ -2580,6 +2586,17 @@
   page->set_next_page(first_page_);
   first_page_ = page;
 
+  // Register all MemoryChunk::kAlignment-aligned chunks covered by
+  // this large page in the chunk map.
+  uintptr_t base = reinterpret_cast<uintptr_t>(page)/MemoryChunk::kAlignment;
+  uintptr_t limit = base + (page->size()-1)/MemoryChunk::kAlignment;
+  for (uintptr_t key = base; key <= limit; key++) {
+    HashMap::Entry* entry = chunk_map_.Lookup(reinterpret_cast<void*>(key),
+                                              key, true);
+    ASSERT(entry != NULL);
+    entry->value = page;
+  }
+
   HeapObject* object = page->GetObject();
 
 #ifdef DEBUG
@@ -2596,27 +2613,24 @@
 
 // GC support
 MaybeObject* LargeObjectSpace::FindObject(Address a) {
-  for (LargePage* page = first_page_;
-       page != NULL;
-       page = page->next_page()) {
-    Address page_address = page->address();
-    if (page_address <= a && a < page_address + page->size()) {
-      return page->GetObject();
-    }
+  LargePage* page = FindPage(a);
+  if (page != NULL) {
+    return page->GetObject();
   }
   return Failure::Exception();
 }
 
 
-LargePage* LargeObjectSpace::FindPageContainingPc(Address pc) {
-  // TODO(853): Change this implementation to only find executable
-  // chunks and use some kind of hash-based approach to speed it up.
-  for (LargePage* chunk = first_page_;
-       chunk != NULL;
-       chunk = chunk->next_page()) {
-    Address chunk_address = chunk->address();
-    if (chunk_address <= pc && pc < chunk_address + chunk->size()) {
-      return chunk;
+LargePage* LargeObjectSpace::FindPage(Address a) {
+  uintptr_t key = reinterpret_cast<uintptr_t>(a) / MemoryChunk::kAlignment;
+  HashMap::Entry* e = chunk_map_.Lookup(reinterpret_cast<void*>(key),
+                                        key, false);
+  if (e != NULL) {
+    ASSERT(e->value != NULL);
+    LargePage* page = reinterpret_cast<LargePage*>(e->value);
+    ASSERT(page->is_valid());
+    if (page->Contains(a)) {
+      return page;
     }
   }
   return NULL;
@@ -2654,6 +2668,16 @@
       objects_size_ -= object->Size();
       page_count_--;
 
+      // Remove entries belonging to this page.
+      // Use variable alignment to help pass length check (<= 80 characters)
+      // of single line in tools/presubmit.py.
+      const intptr_t alignment = MemoryChunk::kAlignment;
+      uintptr_t base = reinterpret_cast<uintptr_t>(page)/alignment;
+      uintptr_t limit = base + (page->size()-1)/alignment;
+      for (uintptr_t key = base; key <= limit; key++) {
+        chunk_map_.Remove(reinterpret_cast<void*>(key), key);
+      }
+
       if (is_pointer_object) {
         heap()->QueueMemoryChunkForFree(page);
       } else {