Object pool with support for untagged entries.

runtime/vm/assembler_ia32.h

Index: runtime/vm/assembler_ia32.h
diff --git a/runtime/vm/assembler_ia32.h b/runtime/vm/assembler_ia32.h
index 5c0ec98110294aa572d36bedced98aeec2207d39..9035f6294911032296b3521d486f430c7a359d53 100644
--- a/runtime/vm/assembler_ia32.h
+++ b/runtime/vm/assembler_ia32.h
@@ -806,11 +806,9 @@ class Assembler : public ValueObject {
     return buffer_.pointer_offsets();
   }
 
-  const GrowableObjectArray& object_pool_data() const {
-    return object_pool_.data();
-  }
+  ObjectPoolHelper& object_pool() { return object_pool_; }
 
-  ObjectPool& object_pool() { return object_pool_; }
+  RawObjectPool* MakeObjectPool() { return object_pool_.MakeObjectPool(); }
 
   void FinalizeInstructions(const MemoryRegion& region) {
     buffer_.FinalizeInstructions(region);
@@ -992,7 +990,7 @@ class Assembler : public ValueObject {
   int32_t jit_cookie();
 
   AssemblerBuffer buffer_;
-  ObjectPool object_pool_;
+  ObjectPoolHelper object_pool_;
   intptr_t prologue_offset_;
   int32_t jit_cookie_;
   GrowableArray<CodeComment*> comments_;