DBC: Fix not-stopping/crashing at fast Smi op breakpoints.

runtime/vm/constants_dbc.h

 // Copyright (c) 2016, 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.
 
 #ifndef VM_CONSTANTS_DBC_H_
 #define VM_CONSTANTS_DBC_H_
 
 #include "platform/globals.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 736 matching lines @@
       case Bytecode::kInstanceCall1Opt:
       case Bytecode::kInstanceCall2Opt:
       case Bytecode::kDebugBreak:
         return true;
 
       default:
         return false;
     }
   }
 
+  DART_FORCE_INLINE static bool IsFastSmiOpcode(Instr instr) {
+    switch (DecodeOpcode(instr)) {
+      case Bytecode::kAddTOS:
+      case Bytecode::kSubTOS:
+      case Bytecode::kMulTOS:
+      case Bytecode::kBitOrTOS:
+      case Bytecode::kBitAndTOS:
+      case Bytecode::kEqualTOS:
+      case Bytecode::kLessThanTOS:
+      case Bytecode::kGreaterThanTOS:
+        return true;
+
+      default:
+        return false;
+    }
+  }
+
   DART_FORCE_INLINE static uint8_t DecodeArgc(Instr call) {
     ASSERT(IsCallOpcode(call));
     return (call >> 8) & 0xFF;
   }
 
   static Instr At(uword pc) { return *reinterpret_cast<Instr*>(pc); }
 
  private:
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Bytecode);
@@ skipping 26 matching lines @@
 
 // After a comparison, the condition NEXT_IS_TRUE means the following
 // instruction is executed if the comparision is true and skipped over overwise.
 // Conidition NEXT_IS_FALSE means the following instruction is executed if the
 // comparison is false and skipped over otherwise.
 enum Condition { NEXT_IS_TRUE, NEXT_IS_FALSE };
 
 }  // namespace dart
 
 #endif  // VM_CONSTANTS_DBC_H_