Insert debug step check at the beginning of a function.

runtime/vm/flow_graph_builder.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_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/class_finalizer.h"
@@ skipping 4180 matching lines @@
   LocalScope* scope = node->scope();
   const Function& function = owner()->function();
   const intptr_t num_context_variables =
       (scope != NULL) ? scope->num_context_variables() : 0;
   const bool is_top_level_sequence =
       node == owner()->parsed_function().node_sequence();
   // The outermost function sequence cannot contain a label.
   ASSERT((node->label() == NULL) || !is_top_level_sequence);
   NestedBlock nested_block(owner(), node);
 
+  if (FLAG_support_debugger && is_top_level_sequence) {
+    AddInstruction(new(Z) DebugStepCheckInstr(function.token_pos(),

[Cutch, 2015/07/14 19:54:36]

I wonder if you could insert this after the GraphcEntryInstr?

[rmacnak, 2015/07/14 22:28:29]

We don't seem to have the right things in scope to easily add it right where the
GraphEntry is constructed.

+                                              RawPcDescriptors::kRuntimeCall));
+  }
+
   if (num_context_variables > 0) {
     // The local scope declares variables that are captured.
     // Allocate and chain a new context (Except don't chain when at the function
     // entry if the function does not capture any variables from outer scopes).
     Value* allocated_context =
         Bind(new(Z) AllocateContextInstr(node->token_pos(),
                                          num_context_variables));
     { LocalVariable* tmp_var = EnterTempLocalScope(allocated_context);
       if (!is_top_level_sequence || HasContextScope()) {
         ASSERT(is_top_level_sequence ||
@@ skipping 591 matching lines @@
   Report::MessageF(Report::kBailout,
                    Script::Handle(function.script()),
                    function.token_pos(),
                    "FlowGraphBuilder Bailout: %s %s",
                    String::Handle(function.name()).ToCString(),
                    reason);
   UNREACHABLE();
 }
 
 }  // namespace dart