VM: Fix bug in constant propagation with integer division and modulo.

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 6401 matching lines @@
   const Object& left = left_val.definition()->constant_value();
   const Object& right = right_val.definition()->constant_value();
   if (IsNonConstant(left) || IsNonConstant(right)) {
     // TODO(srdjan): Add arithemtic simplifications, e.g, add with 0.
     SetValue(instr, non_constant_);
   } else if (IsConstant(left) && IsConstant(right)) {
     if (left.IsInteger() && right.IsInteger()) {
       const Integer& left_int = Integer::Cast(left);
       const Integer& right_int = Integer::Cast(right);
       switch (op_kind) {
+        case Token::kTRUNCDIV:
+        case Token::kMOD:
+          // Check right value for zero.
+          if (right_int.AsInt64Value() == 0) {
+            SetValue(instr, non_constant_);
+            break;
+          }
+          // Fall through.
         case Token::kADD:
         case Token::kSUB:
-        case Token::kMUL:
-        case Token::kTRUNCDIV:
-        case Token::kMOD: {
+        case Token::kMUL: {
           Instance& result = Integer::ZoneHandle(
               left_int.ArithmeticOp(op_kind, right_int));
           result = result.CheckAndCanonicalize(NULL);
           ASSERT(!result.IsNull());
           SetValue(instr, result);
           break;
         }
         case Token::kSHL:
         case Token::kSHR:
           if (left.IsSmi() && right.IsSmi()) {
@@ skipping 1210 matching lines @@
   }
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, alloc->cls(), *fields);
   }
 }
 
 
 }  // namespace dart