On Ia32 optimistically assume that results from int32 and uint32 array loads fit into Smi. Only if …

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 17771)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -733,6 +733,8 @@
 
 bool FlowGraphOptimizer::TryReplaceWithLoadIndexed(InstanceCallInstr* call) {
   const intptr_t class_id = ReceiverClassId(call);
+  // Set deopt_id to a valid id if the LoadIndexedInstr can cause deopt.
+  intptr_t deopt_id = Isolate::kNoDeoptId;
   switch (class_id) {
     case kArrayCid:
     case kImmutableArrayCid:
@@ -753,6 +755,17 @@
       if ((kSmiBits < 32) && !FlowGraphCompiler::SupportsUnboxedMints()) {
         return false;
       }
+      // Set deopt_id if we can optimistically assume that the result is Smi.
+      // TODO(srdjan): Add better signal if this instruction caused

[Florian Schneider, 2013/01/29 19:57:58]

call->ic_data().deopt_reason() should contain the last deopt reason-id. It can
be used to fall back to mint representation in the non-smi case.

+      // deoptimization. This solution: only if no deoptimization occured in
+      // this method is it guaranteed that this instruction did not cause
+      // deoptimization.
+      if (flow_graph_->parsed_function().function().deoptimization_counter()
+          > 0) {
+        deopt_id = Isolate::kNoDeoptId;
+      } else {
+        deopt_id = call->deopt_id();
+      }
       break;
     default:
       return false;
@@ -760,7 +773,8 @@
   Value* array = NULL;
   Value* index = NULL;
   intptr_t array_cid = PrepareIndexedOp(call, class_id, &array, &index);
-  Definition* array_op = new LoadIndexedInstr(array, index, array_cid);
+  Definition* array_op =
+      new LoadIndexedInstr(array, index, array_cid, deopt_id);
   call->ReplaceWith(array_op, current_iterator());
   RemovePushArguments(call);
   return true;
@@ -1289,7 +1303,7 @@
                  call->env(),
                  Definition::kEffect);
   }
-  return new LoadIndexedInstr(str, index, cid);
+  return new LoadIndexedInstr(str, index, cid, Isolate::kNoDeoptId);
 }