DBC: Support large offsets in optimized field access.

runtime/vm/simulator_dbc.cc

Index: runtime/vm/simulator_dbc.cc
diff --git a/runtime/vm/simulator_dbc.cc b/runtime/vm/simulator_dbc.cc
index 67c172866491999fea77fb29f5e5a6c145eb1760..a82d19a840c89a0e04b296fb05ba62c5d6c2c9e5 100644
--- a/runtime/vm/simulator_dbc.cc
+++ b/runtime/vm/simulator_dbc.cc
@@ -2367,7 +2367,20 @@ RawObject* Simulator::Call(const Code& code,
     const uint16_t value_reg = rC;
 
     RawInstance* instance = reinterpret_cast<RawInstance*>(FP[rA]);
-    RawObject* value = reinterpret_cast<RawObject*>(FP[value_reg]);
+    RawObject* value = FP[value_reg];
+
+    instance->StorePointer(
+        reinterpret_cast<RawObject**>(instance->ptr()) + offset_in_words,
+        value);
+    DISPATCH();
+  }
+
+  {
+    BYTECODE(StoreFieldExt, A_D);
+    // The offset is stored in the following nop-instruction which is skipped.
+    const uint16_t offset_in_words = Bytecode::DecodeD(*pc++);
+    RawInstance* instance = reinterpret_cast<RawInstance*>(FP[rA]);
+    RawObject* value = FP[rD];
 
     instance->StorePointer(
         reinterpret_cast<RawObject**>(instance->ptr()) + offset_in_words,
@@ -2398,6 +2411,16 @@ RawObject* Simulator::Call(const Code& code,
   }
 
   {
+    BYTECODE(LoadFieldExt, A_D);
+    // The offset is stored in the following nop-instruction which is skipped.
+    const uint16_t offset_in_words = Bytecode::DecodeD(*pc++);
+    const uint16_t instance_reg = rD;
+    RawInstance* instance = reinterpret_cast<RawInstance*>(FP[instance_reg]);
+    FP[rA] = reinterpret_cast<RawObject**>(instance->ptr())[offset_in_words];
+    DISPATCH();
+  }
+
+  {
     BYTECODE(LoadUntagged, A_B_C);
     const uint16_t instance_reg = rB;
     const uint16_t offset_in_words = rC;