Optimize division for two Smi-s as well. Gives ~ 15% speedup on NavierStokes.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 1017 matching lines @@
         operands_type = kSmiCid;
       } else if (ShouldSpecializeForDouble(ic_data)) {
         operands_type = kDoubleCid;
       } else if (HasOnlyTwoFloat32x4s(ic_data)) {
         operands_type = kFloat32x4Cid;
       } else {
         return false;
       }
       break;
     case Token::kDIV:
-      if (ShouldSpecializeForDouble(ic_data)) {
+      if (ShouldSpecializeForDouble(ic_data) || HasOnlyTwoSmis(ic_data)) {
         operands_type = kDoubleCid;
       } else if (HasOnlyTwoFloat32x4s(ic_data)) {
         operands_type = kFloat32x4Cid;
       } else {
         return false;
       }
       break;
     case Token::kMOD:
       if (HasOnlyTwoSmis(ic_data)) {
         operands_type = kSmiCid;
@@ skipping 46 matching lines @@
       break;
     default:
       UNREACHABLE();
   }
 
   ASSERT(call->ArgumentCount() == 2);
   Definition* left = call->ArgumentAt(0);
   Definition* right = call->ArgumentAt(1);
   if (operands_type == kDoubleCid) {
     // Check that either left or right are not a smi.  Result of a
-    // binary operation with two smis is a smi not a double.
-    InsertBefore(call,
-                 new CheckEitherNonSmiInstr(new Value(left),
-                                            new Value(right),
-                                            call->deopt_id()),
-                 call->env(),
-                 Definition::kEffect);
+    // binary operation with two smis is a smi not a double, except '/' which
+    // returns a double for two smis.
+    if (op_kind != Token::kDIV) {
+      InsertBefore(call,
+                   new CheckEitherNonSmiInstr(new Value(left),
+                                              new Value(right),
+                                              call->deopt_id()),
+                   call->env(),
+                   Definition::kEffect);
+    }
 
     BinaryDoubleOpInstr* double_bin_op =
         new BinaryDoubleOpInstr(op_kind, new Value(left), new Value(right),
                                 call->deopt_id());
     ReplaceCall(call, double_bin_op);
   } else if (operands_type == kMintCid) {
     if (!FlowGraphCompiler::SupportsUnboxedMints()) return false;
     if ((op_kind == Token::kSHR) || (op_kind == Token::kSHL)) {
       ShiftMintOpInstr* shift_op =
           new ShiftMintOpInstr(op_kind, new Value(left), new Value(right),
@@ skipping 6119 matching lines @@
 
   // Insert materializations at environment uses.
   const Class& cls = Class::Handle(alloc->constructor().Owner());
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, cls, *fields);
   }
 }
 
 
 }  // namespace dart