UnboxDouble: convert smi constants to doubles at compile time instead of at runtime.

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/flow_graph_compiler.h"
@@ skipping 174 matching lines @@
     InsertBefore(instr, boxed, NULL, Definition::kValue);
     const intptr_t deopt_id = (deopt_target != NULL) ?
         deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
     converted = new UnboxDoubleInstr(new Value(boxed), deopt_id);
   } else if ((from == kUnboxedDouble) && (to == kTagged)) {
     converted = new BoxDoubleInstr(new Value(def), NULL);
   } else if ((from == kTagged) && (to == kUnboxedDouble)) {
     const intptr_t deopt_id = (deopt_target != NULL) ?
         deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
     ASSERT((deopt_target != NULL) || (def->GetPropagatedCid() == kDoubleCid));
-    converted = new UnboxDoubleInstr(new Value(def), deopt_id);
+    if (def->IsConstant() && def->AsConstant()->value().IsSmi()) {
+      const double dbl_val =
+          Smi::Cast(def->AsConstant()->value()).AsDoubleValue();
+      const Double& dbl_obj =
+          Double::ZoneHandle(Double::New(dbl_val, Heap::kOld));
+      ConstantInstr* double_const = new ConstantInstr(dbl_obj);
+      InsertBefore(instr, double_const, NULL, Definition::kValue);
+      converted = new UnboxDoubleInstr(new Value(double_const), deopt_id);
+    } else {
+      converted = new UnboxDoubleInstr(new Value(def), deopt_id);
+    }
   }
   ASSERT(converted != NULL);
   InsertBefore(instr, converted, use->instruction()->env(),
                Definition::kValue);
   use->set_definition(converted);
 }
 
 
 void FlowGraphOptimizer::InsertConversionsFor(Definition* def) {
   const Representation from_rep = def->representation();
@@ skipping 4077 matching lines @@
 
   if (FLAG_trace_constant_propagation) {
     OS::Print("\n==== After constant propagation ====\n");
     FlowGraphPrinter printer(*graph_);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart