Fixes slow object pool search on x64.

runtime/vm/assembler_x64.cc

 // Copyright (c) 2013, 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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/heap.h"
 #include "vm/memory_region.h"
@@ skipping 62 matching lines @@
       comments_() {
   // Far branching mode is only needed and implemented for MIPS and ARM.
   ASSERT(!use_far_branches);
   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::Handle(), 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_.Add(Bool::True(), Heap::kOld);
     patchable_pool_entries_.Add(kNotPatchable);
+    object_pool_index_table_.Insert(ObjIndexPair(Bool::True().raw(), 1));
 
     object_pool_.Add(Bool::False(), Heap::kOld);
     patchable_pool_entries_.Add(kNotPatchable);
+    object_pool_index_table_.Insert(ObjIndexPair(Bool::False().raw(), 2));
 
     if (StubCode::UpdateStoreBuffer_entry() != NULL) {
       FindExternalLabel(&StubCode::UpdateStoreBufferLabel(), kNotPatchable);
-      patchable_pool_entries_.Add(kNotPatchable);
     } else {
       object_pool_.Add(Object::Handle(), Heap::kOld);
       patchable_pool_entries_.Add(kNotPatchable);
     }
 
     if (StubCode::CallToRuntime_entry() != NULL) {
       FindExternalLabel(&StubCode::CallToRuntimeLabel(), kNotPatchable);
-      patchable_pool_entries_.Add(kNotPatchable);
     } else {
       object_pool_.Add(Object::Handle(), Heap::kOld);
       patchable_pool_entries_.Add(kNotPatchable);
     }
   }
 }
 
 
 void Assembler::InitializeMemoryWithBreakpoints(uword data, int length) {
   memset(reinterpret_cast<void*>(data), Instr::kBreakPointInstruction, length);
@@ skipping 2054 matching lines @@
   }
   addq(RSP, Immediate(stack_elements * kWordSize));
 }
 
 
 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());
 
-  // TODO(zra): This can be slow. Add a hash map from obj.raw() to
-  // object pool indexes to speed lookup.
-  for (int i = 0; i < object_pool_.Length(); i++) {
-    if ((object_pool_.At(i) == obj.raw()) &&
-        (patchable_pool_entries_[i] != kPatchable)) {
-      return i;
+  // 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) {
+      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));
+  }
   return object_pool_.Length() - 1;
 }
 
 
 intptr_t Assembler::FindExternalLabel(const ExternalLabel* label,
                                       Patchability patchable) {
   // The object pool cannot be used in the vm isolate.
   ASSERT(Isolate::Current() != Dart::vm_isolate());
   ASSERT(!object_pool_.IsNull());
   const uword address = label->address();
   ASSERT(Utils::IsAligned(address, 4));
   // The address is stored in the object array as a RawSmi.
   const Smi& smi = Smi::Handle(reinterpret_cast<RawSmi*>(address));
   if (patchable == kNotPatchable) {
+    // If the call site is not patchable, we can try to re-use an existing
+    // entry.
     return FindObject(smi, kNotPatchable);
   }
   // If the call is patchable, do not reuse an existing entry since each
   // reference may be patched independently.
   object_pool_.Add(smi, Heap::kOld);
   patchable_pool_entries_.Add(patchable);
   return object_pool_.Length() - 1;
 }
 
 
@@ skipping 652 matching lines @@
 
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64