DBC: Add single stepping check to fast Smi ops.

runtime/vm/simulator_dbc.cc

 // 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.
 
 #include <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_DBC)
 
@@ skipping 780 matching lines @@
 
 // Declare bytecode handler for a smi operation (e.g. AddTOS) with the
 // given result type and the given behavior specified as a function
 // that takes left and right operands and result slot and returns
 // true if fast-path succeeds.
 #define SMI_FASTPATH_TOS(ResultT, Func)                                        \
   {                                                                            \
     const intptr_t lhs = reinterpret_cast<intptr_t>(SP[-1]);                   \
     const intptr_t rhs = reinterpret_cast<intptr_t>(SP[-0]);                   \
     ResultT* slot = reinterpret_cast<ResultT*>(SP - 1);                        \
-    if (LIKELY(AreBothSmis(lhs, rhs) && !Func(lhs, rhs, slot))) {              \
+    if (LIKELY(!thread->isolate()->single_step()) &&                           \
+        LIKELY(AreBothSmis(lhs, rhs) &&                                        \
+        !Func(lhs, rhs, slot))) {                                              \
       SMI_FASTPATH_ICDATA_INC;                                                 \
       /* Fast path succeeded. Skip the generic call that follows. */           \
       pc++;                                                                    \
       /* We dropped 2 arguments and push result                   */           \
       SP--;                                                                    \
     }                                                                          \
   }
 
 // Skip the next instruction if there is no overflow.
 #define SMI_OP_CHECK(ResultT, Func)                                            \
@@ skipping 2214 matching lines @@
   pc_ = pc;
   special_[kExceptionSpecialIndex] = raw_exception;
   special_[kStacktraceSpecialIndex] = raw_stacktrace;
   buf->Longjmp();
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC