DBC: Adds DecodeLoadObjectFromPoolOrThread, enables tests

runtime/vm/instructions_dbc.cc

 // Copyright (c) 2016, 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"  // Needed here to get TARGET_ARCH_DBC.
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/instructions.h"
 #include "vm/instructions_dbc.h"
 
@@ skipping 94 matching lines @@
                                                  Register* reg,
                                                  intptr_t* index) {
   UNIMPLEMENTED();
   return 0;
 }
 
 
 bool DecodeLoadObjectFromPoolOrThread(uword pc,
                                       const Code& code,
                                       Object* obj) {
-  UNIMPLEMENTED();
+  ASSERT(code.ContainsInstructionAt(pc));
+  Instr instr = Bytecode::At(pc);
+  if ((Bytecode::DecodeOpcode(instr) == Bytecode::kPushConstant) ||
+      (Bytecode::DecodeOpcode(instr) == Bytecode::kLoadConstant)) {

[Vyacheslav Egorov (Google), 2016/05/09 18:26:13]

There are more instructions that load stuff from pool:

StaticCall and InstanceCall* also load stuff from pool 

StoreStaticTOS, PushStatic load field from PP

Allocate D loads class from PP

InstantiateType, InstantiateTypeArgumentsTOS, AssertAssignable. 

I am not sure if this is important for the observatory use case or not. 

At least InstanceCall* might be important because they load ICData.

[zra, 2016/05/09 19:36:11]

Ah, yah, it looks like lots of these have potentially useful information, so
I've just included all of them.

+    uint16_t index = Bytecode::DecodeD(instr);
+    const ObjectPool& pool = ObjectPool::Handle(code.object_pool());
+    if (pool.InfoAt(index) == ObjectPool::kTaggedObject) {
+      *obj = pool.ObjectAt(index);
+      return true;
+    }
+  }
   return false;
 }
 
 
 RawICData* CallPattern::IcData() {
   UNIMPLEMENTED();
   return ICData::null();
 }
 
 
@@ skipping 45 matching lines @@
 
 
 bool ReturnPattern::IsValid() const {
   UNIMPLEMENTED();
   return false;
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC