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..27d1c26f6204a34e8f87f3629b5e1afc4980c41c 100644
--- a/runtime/vm/assembler_ia32.h
+++ b/runtime/vm/assembler_ia32.h
@@ -806,11 +806,11 @@ class Assembler : public ValueObject {
     return buffer_.pointer_offsets();
   }
 
-  const GrowableObjectArray& object_pool_data() const {
-    return object_pool_.data();
-  }
+  ObjectPoolWrapper& object_pool_wrapper() { return object_pool_wrapper_; }
 
-  ObjectPool& object_pool() { return object_pool_; }
+  RawObjectPool* MakeObjectPool() {
+    return object_pool_wrapper_.MakeObjectPool();
+  }
 
   void FinalizeInstructions(const MemoryRegion& region) {
     buffer_.FinalizeInstructions(region);
@@ -992,7 +992,7 @@ class Assembler : public ValueObject {
   int32_t jit_cookie();
 
   AssemblerBuffer buffer_;
-  ObjectPool object_pool_;
+  ObjectPoolWrapper object_pool_wrapper_;
   intptr_t prologue_offset_;
   int32_t jit_cookie_;
   GrowableArray<CodeComment*> comments_;