Canonicalize generic types in an isolate specific hash table

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index a2f8d2143204ac0b8207e82621fffedec0c3fcd6..f6caa4eea982138bf4df1e7be32fd62892086804 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1717,8 +1717,8 @@ class TypeArguments : public Object {
 
   static intptr_t InstanceSize(intptr_t len) {
     // Ensure that the types() is not adding to the object size, which includes
-    // 2 fields: instantiations_ and length_.
-    ASSERT(sizeof(RawTypeArguments) == (sizeof(RawObject) + (2 * kWordSize)));
+    // 3 fields: instantiations_, length_ and hash_.
+    ASSERT(sizeof(RawTypeArguments) == (sizeof(RawObject) + (3 * kWordSize)));
     ASSERT(0 <= len && len <= kMaxElements);
     return RoundedAllocationSize(
         sizeof(RawTypeArguments) + (len * kBytesPerElement));
@@ -1729,6 +1729,9 @@ class TypeArguments : public Object {
   static RawTypeArguments* New(intptr_t len, Heap::Space space = Heap::kOld);
 
  private:
+  intptr_t ComputeHash() const;
+  void SetHash(intptr_t value) const;
+
   // Check if the subvector of length 'len' starting at 'from_index' of this
   // type argument vector consists solely of DynamicType.
   // If raw_instantiated is true, consider each type parameter to be first
@@ -5685,6 +5688,9 @@ class Type : public AbstractType {
                       Heap::Space space = Heap::kOld);
 
  private:
+  intptr_t ComputeHash() const;
+  void SetHash(intptr_t value) const;
+
   void set_token_pos(TokenPosition token_pos) const;
   void set_type_state(int8_t state) const;
 
@@ -5836,6 +5842,9 @@ class TypeParameter : public AbstractType {
                                TokenPosition token_pos);
 
  private:
+  intptr_t ComputeHash() const;
+  void SetHash(intptr_t value) const;
+
   void set_parameterized_class(const Class& value) const;
   void set_name(const String& value) const;
   void set_token_pos(TokenPosition token_pos) const;
@@ -5921,6 +5930,9 @@ class BoundedType : public AbstractType {
                              const TypeParameter& type_parameter);
 
  private:
+  intptr_t ComputeHash() const;
+  void SetHash(intptr_t value) const;
+
   void set_type(const AbstractType& value) const;
   void set_bound(const AbstractType& value) const;
   void set_type_parameter(const TypeParameter& value) const;
@@ -8528,6 +8540,72 @@ RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
+
+inline intptr_t Type::Hash() const {
+  intptr_t result = Smi::Value(raw_ptr()->hash_);
+  if (result != 0) {

[regis, 2016/05/10 18:14:26]

What if the hash is 0?

[siva, 2016/05/13 23:16:13]

I have fixed this similar to the StringHasher to return 1 if the has ever
becomes 0.

+    return result;
+  }
+  return ComputeHash();
+}
+
+
+inline void Type::SetHash(intptr_t value) const {
+  // This is only safe because we create a new Smi, which does not cause
+  // heap allocation.
+  StoreSmi(&raw_ptr()->hash_, Smi::New(value));
+}
+
+
+inline intptr_t TypeParameter::Hash() const {
+  ASSERT(IsFinalized());
+  intptr_t result = Smi::Value(raw_ptr()->hash_);
+  if (result != 0) {
+    return result;
+  }
+  return ComputeHash();
+}
+
+
+inline void TypeParameter::SetHash(intptr_t value) const {
+  // This is only safe because we create a new Smi, which does not cause
+  // heap allocation.
+  StoreSmi(&raw_ptr()->hash_, Smi::New(value));

[regis, 2016/05/10 18:14:26]

What if the value does not fit in a Smi?

[siva, 2016/05/13 23:16:13]

I have fixed this similar to the StringHasher by having a max hash bits which is
30 as it should be Smi consistently on all platforms where a snapshot can be
read

+}
+
+
+inline intptr_t BoundedType::Hash() const {
+  intptr_t result = Smi::Value(raw_ptr()->hash_);
+  if (result != 0) {
+    return result;
+  }
+  return ComputeHash();
+}
+
+
+inline void BoundedType::SetHash(intptr_t value) const {
+  // This is only safe because we create a new Smi, which does not cause
+  // heap allocation.
+  StoreSmi(&raw_ptr()->hash_, Smi::New(value));
+}
+
+
+inline intptr_t TypeArguments::Hash() const {
+  if (IsNull()) return 0;
+  intptr_t result = Smi::Value(raw_ptr()->hash_);
+  if (result != 0) {
+    return result;
+  }
+  return ComputeHash();
+}
+
+
+inline void TypeArguments::SetHash(intptr_t value) const {
+  // This is only safe because we create a new Smi, which does not cause
+  // heap allocation.
+  StoreSmi(&raw_ptr()->hash_, Smi::New(value));
+}
+
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_