Ensure that compile time types for comparisons are recomputed once comparison are specialized.

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 2cd692a9142c32144ceb7abdf6fb38706a91d924..f18bb90db401ed22fa526e1d66b740de6dbb6d5d 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -959,7 +959,7 @@ void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-CompileType* LoadIndexedInstr::ComputeInitialType() const {
+CompileType LoadIndexedInstr::ComputeType() const {
   switch (class_id_) {
     case kArrayCid:
     case kImmutableArrayCid:
@@ -984,7 +984,7 @@ CompileType* LoadIndexedInstr::ComputeInitialType() const {
 
     default:
       UNIMPLEMENTED();
-      return NULL;
+      return CompileType::Dynamic();
   }
 }