Convert MOD to AND for power-of-two positive constants.

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 450 matching lines @@
       }
       break;
     case Token::kDIV:
       if (ShouldSpecializeForDouble(ic_data)) {
         operands_type = kDoubleCid;
       } else {
         return false;
       }
       break;
     case Token::kMOD:
-      // TODO(vegorov): implement fast path code for modulo.
-      return false;
+      if (HasOnlyTwoSmi(ic_data)) {
+        operands_type = kSmiCid;
+      } else {
+        return false;
+      }
+      break;
     case Token::kBIT_AND:
       if (HasOnlyTwoSmi(ic_data)) {
         operands_type = kSmiCid;
       } else if (HasTwoMintOrSmi(ic_data)) {
         operands_type = kMintCid;
       } else {
         return false;
       }
       break;
     case Token::kBIT_OR:
@@ skipping 34 matching lines @@
     RemovePushArguments(call);
   } else if (operands_type == kMintCid) {
     Value* left = call->ArgumentAt(0)->value();
     Value* right = call->ArgumentAt(1)->value();
     BinaryMintOpInstr* bin_op = new BinaryMintOpInstr(op_kind,
                                                       call,
                                                       left,
                                                       right);
     call->ReplaceWith(bin_op, current_iterator());
     RemovePushArguments(call);
+  } else if (op_kind == Token::kMOD) {
+    // TODO(vegorov): implement fast path code for modulo.
+    ASSERT(operands_type == kSmiCid);
+    if (!call->ArgumentAt(1)->value()->BindsToConstant()) return false;
+    const Object& obj = call->ArgumentAt(1)->value()->BoundConstant();
+    if (!obj.IsSmi()) return false;
+    const intptr_t value = Smi::Cast(obj).Value();
+    if ((value > 0) && Utils::IsPowerOfTwo(value)) {
+      Value* left = call->ArgumentAt(0)->value();
+      // Insert smi check and attach a copy of the original
+      // environment because the smi operation can still deoptimize.
+      InsertBefore(call,
+                   new CheckSmiInstr(left->Copy(), call->deopt_id()),
+                   call->env(),
+                   Definition::kEffect);
+      ConstantInstr* c = new ConstantInstr(Smi::Handle(Smi::New(value - 1)));
+      InsertBefore(call, c, NULL, Definition::kValue);
+      BinarySmiOpInstr* bin_op =
+          new BinarySmiOpInstr(Token::kBIT_AND, call, left, new Value(c));
+      call->ReplaceWith(bin_op, current_iterator());
+      RemovePushArguments(call);
+    }
   } else {
     ASSERT(operands_type == kSmiCid);
     Value* left = call->ArgumentAt(0)->value();
     Value* right = call->ArgumentAt(1)->value();
     // Insert two smi checks and attach a copy of the original
     // environment because the smi operation can still deoptimize.
     InsertBefore(call,
                  new CheckSmiInstr(left->Copy(), call->deopt_id()),
                  call->env(),
                  Definition::kEffect);
@@ skipping 2554 matching lines @@
 
   if (FLAG_trace_constant_propagation) {
     OS::Print("\n==== After constant propagation ====\n");
     FlowGraphPrinter printer(*graph_);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart