Implement class id checks as a separate instruction and add a local CSE optimization pass.

runtime/vm/hash_map.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_HASH_MAP_H_
+#define VM_HASH_MAP_H_
+
+namespace dart {
+

[srdjan, 2012/08/17 22:30:22]

Sidenote: what is your opinion of starting to use STL containers? Carl is quite
in favor of it, but we still have our doubts,

[Florian Schneider, 2012/08/20 12:09:37]

I'm also mostly in favor, if we are careful with memory management performance.
If we want to support a certain operation efficiently and there is no support
for that in STL, then we can always use our own implementation. e.g. in Chromium
there is both std::list and LinkedList
(http://src.chromium.org/svn/trunk/src/base/linked_list.h)

+template <typename T>
+class DirectChainedHashMap: public ValueObject {
+ public:
+  DirectChainedHashMap() : array_size_(0),
+                           lists_size_(0),
+                           count_(0),
+                           array_(NULL),
+                           lists_(NULL),
+                           free_list_head_(kNil) {
+    ResizeLists(kInitialSize);
+    Resize(kInitialSize);
+  }
+
+  void Insert(T* value);
+
+  T* Lookup(T* value) const;

[srdjan, 2012/08/17 22:30:22]

Please change specification so that DirectChainedHashMap<Name*> means that you
are storing Name* into it and not Name**.
See GrowableArray, BitField and others.

[Florian Schneider, 2012/08/20 12:09:37]

Done.

+
+  bool IsEmpty() const { return count_ == 0; }
+
+ private:
+  // A linked list of Computation* values.  Stored in arrays.

[srdjan, 2012/08/17 22:30:22]

s/Computation/T/

[Florian Schneider, 2012/08/20 12:09:37]

Done.

+  struct HashMapListElement {
+    T* value;
+    intptr_t next;  // Index in the array of the next list element.
+  };
+  static const intptr_t kNil = -1;  // The end of a linked list
+
+  // Must be a power of 2.
+  static const intptr_t kInitialSize = 16;
+
+  void Resize(intptr_t new_size);
+  void ResizeLists(intptr_t new_size);
+  uword Bound(uword value) const { return value & (array_size_ - 1); }
+
+  intptr_t array_size_;
+  intptr_t lists_size_;
+  intptr_t count_;  // The number of values stored in the HashMap.
+  HashMapListElement* array_;  // Primary store - contains the first value
+  // with a given hash.  Colliding elements are stored in linked lists.
+  HashMapListElement* lists_;  // The linked lists containing hash collisions.
+  intptr_t free_list_head_;  // Unused elements in lists_ are on the free list.
+
+  DISALLOW_COPY_AND_ASSIGN(DirectChainedHashMap);
+};
+
+
+template <typename T>
+T* DirectChainedHashMap<T>::Lookup(T* value) const {
+  uword hash = static_cast<uword>(value->Hashcode());
+  uword pos = Bound(hash);
+  if (array_[pos].value != NULL) {
+    if (array_[pos].value->Equals(value)) return array_[pos].value;
+    intptr_t next = array_[pos].next;
+    while (next != kNil) {
+      if (lists_[next].value->Equals(value)) return lists_[next].value;
+      next = lists_[next].next;
+    }
+  }
+  return NULL;
+}
+
+
+template <typename T>
+void DirectChainedHashMap<T>::Resize(intptr_t new_size) {
+  ASSERT(new_size > count_);
+  // Hashing the values into the new array has no more collisions than in the
+  // old hash map, so we can use the existing lists_ array, if we are careful.
+
+  // Make sure we have at least one free element.
+  if (free_list_head_ == kNil) {
+    ResizeLists(lists_size_ << 1);
+  }
+
+  HashMapListElement* new_array =
+      Isolate::Current()->current_zone()->Alloc<HashMapListElement>(new_size);
+  memset(new_array, 0, sizeof(HashMapListElement) * new_size);
+
+  HashMapListElement* old_array = array_;
+  intptr_t old_size = array_size_;
+
+  intptr_t old_count = count_;
+  count_ = 0;
+  array_size_ = new_size;
+  array_ = new_array;
+
+  if (old_array != NULL) {
+    // Iterate over all the elements in lists, rehashing them.
+    for (intptr_t i = 0; i < old_size; ++i) {
+      if (old_array[i].value != NULL) {
+        intptr_t current = old_array[i].next;
+        while (current != kNil) {
+          Insert(lists_[current].value);
+          intptr_t next = lists_[current].next;
+          lists_[current].next = free_list_head_;
+          free_list_head_ = current;
+          current = next;
+        }
+        // Rehash the directly stored value.
+        Insert(old_array[i].value);
+      }
+    }
+  }
+  USE(old_count);
+  ASSERT(count_ == old_count);
+}
+
+
+template <typename T>
+void DirectChainedHashMap<T>::ResizeLists(intptr_t new_size) {
+  ASSERT(new_size > lists_size_);
+
+  HashMapListElement* new_lists =
+      Isolate::Current()->current_zone()->
+      Alloc<HashMapListElement>(new_size);
+  memset(new_lists, 0, sizeof(HashMapListElement) * new_size);
+
+  HashMapListElement* old_lists = lists_;
+  intptr_t old_size = lists_size_;
+
+  lists_size_ = new_size;
+  lists_ = new_lists;
+
+  if (old_lists != NULL) {
+    memmove(lists_, old_lists, old_size * sizeof(HashMapListElement));
+  }
+  for (intptr_t i = old_size; i < lists_size_; ++i) {
+    lists_[i].next = free_list_head_;
+    free_list_head_ = i;
+  }
+}
+
+
+template <typename T>
+void DirectChainedHashMap<T>::Insert(T* value) {
+  ASSERT(value != NULL);
+  // Resizing when half of the hashtable is filled up.
+  if (count_ >= array_size_ >> 1) Resize(array_size_ << 1);
+  ASSERT(count_ < array_size_);
+  count_++;
+  uword pos = Bound(static_cast<uword>(value->Hashcode()));
+  if (array_[pos].value == NULL) {
+    array_[pos].value = value;
+    array_[pos].next = kNil;
+  } else {
+    if (free_list_head_ == kNil) {
+      ResizeLists(lists_size_ << 1);
+    }
+    intptr_t new_element_pos = free_list_head_;
+    ASSERT(new_element_pos != kNil);
+    free_list_head_ = lists_[free_list_head_].next;
+    lists_[new_element_pos].value = value;
+    lists_[new_element_pos].next = array_[pos].next;
+    ASSERT(array_[pos].next == kNil || lists_[array_[pos].next].value != NULL);
+    array_[pos].next = new_element_pos;
+  }
+}
+
+}  // namespace dart
+
+#endif  // VM_HASH_MAP_H_