Optimize code for bound checks if array is constant. Skip unnecessary Smi checks if they still surv…

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2012, 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/flow_graph_builder.h"
 #include "vm/hash_map.h"
@@ skipping 345 matching lines @@
     case kGrowableObjectArrayCid: {
       Value* array = call->ArgumentAt(0)->value();
       Value* index = call->ArgumentAt(1)->value();
       // Insert class check and index smi checks and attach a copy of the
       // original environment because the operation can still deoptimize.
       AddCheckClass(call, array->Copy());
       InsertBefore(call,
                    new CheckSmiInstr(index->Copy(), call->deopt_id()),
                    call->env(),
                    Definition::kEffect);
-      // Insert array bounds check.
-      InsertBefore(call,
-                   new CheckArrayBoundInstr(array->Copy(),
-                                            index->Copy(),
-                                            class_id,
-                                            call),
-                   call->env(),
-                   Definition::kEffect);
+      // If both index and array are constants, then the bound check always
+      // succeeded.
+      if (!(array->BindsToConstant() && index->BindsToConstant())) {

[Vyacheslav Egorov (Google), 2012/09/13 09:27:51]

Please add todo so that we remove it when constant propagation lands.

[srdjan, 2012/09/13 09:46:45]

Done.

+        // Insert array bounds check.
+        InsertBefore(call,
+                     new CheckArrayBoundInstr(array->Copy(),
+                                              index->Copy(),
+                                              class_id,
+                                              call),
+                     call->env(),
+                     Definition::kEffect);
+      }
       if (class_id == kGrowableObjectArrayCid) {
         // Insert data elements load.
         LoadFieldInstr* elements =
             new LoadFieldInstr(array->Copy(),
                                GrowableObjectArray::data_offset(),
                                Type::ZoneHandle(Type::DynamicType()));
         elements->set_result_cid(kArrayCid);
         InsertBefore(call, elements, NULL, Definition::kValue);
         array = new Value(elements);
       }
@@ skipping 1183 matching lines @@
       DirectChainedHashMap<Definition*> child_map(*map);  // Copy map.
       OptimizeRecursive(child, &child_map);
     } else {
       OptimizeRecursive(child, map);  // Reuse map for the last child.
     }
   }
 }
 
 
 }  // namespace dart