Support unboxed input to indirect goto instruction.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index e7cd941e0a80c9f93153d1cc9d6bf5b690ba17dd..867c3354409cc7b6c5e1eefda2c256cd781defea 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -6216,7 +6216,9 @@ void IndirectGotoInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ movq(target_address_reg, Address(RBP, kPcMarkerSlotFromFp * kWordSize));
 
   // Calculate the final absolute address.
-  __ SmiUntag(offset_reg);
+  if (offset()->definition()->representation() == kTagged) {
+    __ SmiUntag(offset_reg);
+  }
   __ addq(target_address_reg, offset_reg);
 
   // Jump to the absolute address.