Box values of LoadCodeUnits that fall outside of smi range on 32bit platforms.

runtime/vm/intermediate_language_arm64.cc

Index: runtime/vm/intermediate_language_arm64.cc
diff --git a/runtime/vm/intermediate_language_arm64.cc b/runtime/vm/intermediate_language_arm64.cc
index cdfba511e0d6178aa5d874b64972a600644b2045..47f908907f79f49d612154cde2a3d6cffb0746b4 100644
--- a/runtime/vm/intermediate_language_arm64.cc
+++ b/runtime/vm/intermediate_language_arm64.cc
@@ -1135,20 +1135,6 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-Representation LoadCodeUnitsInstr::representation() const {
-  switch (class_id()) {
-    case kOneByteStringCid:
-    case kTwoByteStringCid:
-    case kExternalOneByteStringCid:
-    case kExternalTwoByteStringCid:
-      return kTagged;
-    default:
-      UNIMPLEMENTED();
-      return kTagged;
-  }
-}
-
-
 LocationSummary* LoadCodeUnitsInstr::MakeLocationSummary(Isolate* isolate,
                                                          bool opt) const {
   const intptr_t kNumInputs = 2;