Add flow graph printing into a .cfg file with flag --print-flow-graph-file.

vm/intermediate_language.cc

Index: vm/intermediate_language.cc
===================================================================
--- vm/intermediate_language.cc	(revision 8145)
+++ vm/intermediate_language.cc	(working copy)
@@ -171,6 +171,9 @@
       (variable_count == 0) ? NULL : new BitVector(variable_count);
   assigned_vars->Add(vars);
 
+  // The graph entry consists of only one instruction.
+  set_last_instruction(this);
+
   // Iteratively traverse all successors.  In the unoptimized code, we will
   // enter the function at the first successor in reverse postorder, so we
   // must visit the normal entry last.
@@ -269,6 +272,44 @@
 }
 
 
+intptr_t Instruction::SuccessorCount() const {
+  ASSERT(!IsBranch());
+  ASSERT(!IsGraphEntry());
+  ASSERT(StraightLineSuccessor() == NULL ||
+         StraightLineSuccessor()->IsBlockEntry());
+  return StraightLineSuccessor() != NULL ? 1 : 0;
+}
+
+
+BlockEntryInstr* Instruction::SuccessorAt(intptr_t index) const {
+  return StraightLineSuccessor()->AsBlockEntry();
+}
+
+
+intptr_t GraphEntryInstr::SuccessorCount() const {
+  return 1 + catch_entries_.length();
+}
+
+
+BlockEntryInstr* GraphEntryInstr::SuccessorAt(intptr_t index) const {
+  if (index == 0) return normal_entry_;
+  return catch_entries_[index - 1];
+}
+
+
+intptr_t BranchInstr::SuccessorCount() const {
+  return 2;
+}
+
+
+BlockEntryInstr* BranchInstr::SuccessorAt(intptr_t index) const {
+  if (index == 0) return true_successor_;
+  if (index == 1) return false_successor_;
+  UNREACHABLE();
+  return NULL;
+}
+
+
 // ==== Support for propagating static type.
 RawAbstractType* ConstantVal::StaticType() const {
   if (value().IsInstance()) {