Improve constant pool implementation in the assembler.

runtime/vm/assembler_arm64.cc

 // Copyright (c) 2014, 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.
 
 #include "vm/globals.h"  // NOLINT
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
@@ skipping 22 matching lines @@
       use_far_branches_(use_far_branches),
       comments_(),
       allow_constant_pool_(true) {
   if (Isolate::Current() != Dart::vm_isolate()) {
     object_pool_ = GrowableObjectArray::New(Heap::kOld);
 
     // These objects and labels need to be accessible through every pool-pointer
     // at the same index.
     object_pool_.Add(Object::null_object(), Heap::kOld);
     patchable_pool_entries_.Add(kNotPatchable);
-    // Not adding Object::null() to the index table. It is at index 0 in the
-    // object pool, but the HashMap uses 0 to indicate not found.
+    object_pool_index_table_.Insert(ObjIndexPair(&Object::null_object(), 0));

[Ivan Posva, 2015/01/15 23:59:58]

We have three data structures in the assembler that need to be kept in sync:
object_pool_, patchable_pool_entries_ and object_pool_index_table_

It would probably make sense to abstract that into an assembler helper class
AssemblerObjectPool and use it across all architectures.

 
     object_pool_.Add(Bool::True(), Heap::kOld);
     patchable_pool_entries_.Add(kNotPatchable);
-    object_pool_index_table_.Insert(ObjIndexPair(Bool::True().raw(), 1));
+    object_pool_index_table_.Insert(ObjIndexPair(&Bool::True(), 1));
 
     object_pool_.Add(Bool::False(), Heap::kOld);
     patchable_pool_entries_.Add(kNotPatchable);
-    object_pool_index_table_.Insert(ObjIndexPair(Bool::False().raw(), 2));
+    object_pool_index_table_.Insert(ObjIndexPair(&Bool::False(), 2));
 
     const Smi& vacant = Smi::Handle(Smi::New(0xfa >> kSmiTagShift));
     StubCode* stub_code = Isolate::Current()->stub_code();
 
     if (stub_code->UpdateStoreBuffer_entry() != NULL) {
       FindExternalLabel(&stub_code->UpdateStoreBufferLabel(), kNotPatchable);
     } else {
       object_pool_.Add(vacant, Heap::kOld);
       patchable_pool_entries_.Add(kNotPatchable);
     }
@@ skipping 385 matching lines @@
 
 
 intptr_t Assembler::FindObject(const Object& obj, Patchability patchable) {
   // The object pool cannot be used in the vm isolate.
   ASSERT(Isolate::Current() != Dart::vm_isolate());
   ASSERT(!object_pool_.IsNull());
 
   // If the object is not patchable, check if we've already got it in the
   // object pool.
   if (patchable == kNotPatchable) {
-    // Special case for Object::null(), which is always at object_pool_ index 0
-    // because Lookup() below returns 0 when the object is not mapped in the
-    // table.
-    if (obj.raw() == Object::null()) {
-      return 0;
-    }
-
-    intptr_t idx = object_pool_index_table_.Lookup(obj.raw());
-    if (idx != 0) {
+    intptr_t idx = object_pool_index_table_.Lookup(&obj);
+    if (idx != ObjIndexPair::kNoIndex) {
       ASSERT(patchable_pool_entries_[idx] == kNotPatchable);
       return idx;
     }
   }
 
   object_pool_.Add(obj, Heap::kOld);
   patchable_pool_entries_.Add(patchable);
   if (patchable == kNotPatchable) {
     // The object isn't patchable. Record the index for fast lookup.
     object_pool_index_table_.Insert(
-        ObjIndexPair(obj.raw(), object_pool_.Length() - 1));
+        ObjIndexPair(&obj, object_pool_.Length() - 1));
   }
   return object_pool_.Length() - 1;
 }
 
 
 intptr_t Assembler::FindImmediate(int64_t imm) {
   ASSERT(Isolate::Current() != Dart::vm_isolate());
   ASSERT(!object_pool_.IsNull());
   const Smi& smi = Smi::Handle(reinterpret_cast<RawSmi*>(imm));
   return FindObject(smi, kNotPatchable);
@@ skipping 1069 matching lines @@
     add(base, array, Operand(index, LSL, shift));
   }
   const OperandSize size = Address::OperandSizeFor(cid);
   ASSERT(Address::CanHoldOffset(offset, Address::Offset, size));
   return Address(base, offset, Address::Offset, size);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64