Remove StringCharCodeAtInstr and handle it as part of LoadIndexed.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 17219)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -1220,7 +1220,7 @@
 }
 
 
-StringCharCodeAtInstr* FlowGraphOptimizer::BuildStringCharCodeAt(
+LoadIndexedInstr* FlowGraphOptimizer::BuildStringCharCodeAt(
     InstanceCallInstr* call,
     intptr_t cid) {
   Value* str = call->ArgumentAt(0)->value();
@@ -1253,7 +1253,7 @@
                  call->env(),
                  Definition::kEffect);
   }
-  return new StringCharCodeAtInstr(str, index, cid);
+  return new LoadIndexedInstr(str, index, cid);
 }
 
 
@@ -1274,7 +1274,7 @@
       (ic_data.NumberOfChecks() == 1) &&
       ((class_ids[0] == kOneByteStringCid) ||
        (class_ids[0] == kTwoByteStringCid))) {
-    StringCharCodeAtInstr* instr = BuildStringCharCodeAt(call, class_ids[0]);
+    LoadIndexedInstr* instr = BuildStringCharCodeAt(call, class_ids[0]);
     call->ReplaceWith(instr, current_iterator());
     RemovePushArguments(call);
     return true;
@@ -1283,7 +1283,7 @@
       (ic_data.NumberOfChecks() == 1) &&
       (class_ids[0] == kOneByteStringCid)) {
     // TODO(fschneider): Handle TwoByteString.
-    StringCharCodeAtInstr* load_char_code =
+    LoadIndexedInstr* load_char_code =
         BuildStringCharCodeAt(call, class_ids[0]);
     InsertBefore(call, load_char_code, NULL, Definition::kValue);
     StringFromCharCodeInstr* char_at =
@@ -4036,11 +4036,6 @@
 }
 
 
-void ConstantPropagator::VisitStringCharCodeAt(StringCharCodeAtInstr* instr) {
-  SetValue(instr, non_constant_);
-}
-
-
 void ConstantPropagator::VisitStringFromCharCode(
     StringFromCharCodeInstr* instr) {
   SetValue(instr, non_constant_);