Scale the OSR optimization threshold by loop nesting depth.

runtime/vm/intermediate_language.h

 // 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.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 5902 matching lines @@
 
  private:
   const Token::Kind op_kind_;
 
   DISALLOW_COPY_AND_ASSIGN(UnarySmiOpInstr);
 };
 
 
 class CheckStackOverflowInstr : public TemplateInstruction<0> {
  public:
-  CheckStackOverflowInstr(intptr_t token_pos, bool in_loop)
-      : token_pos_(token_pos), in_loop_(in_loop) {}
+  CheckStackOverflowInstr(intptr_t token_pos, intptr_t loop_depth)
+      : token_pos_(token_pos), loop_depth_(loop_depth) {}
 
   intptr_t token_pos() const { return token_pos_; }
-  bool in_loop() const { return in_loop_; }
+  bool in_loop() const { return loop_depth_ > 0; }
+  intptr_t loop_depth() const { return loop_depth_; }
 
   DECLARE_INSTRUCTION(CheckStackOverflow)
 
   virtual intptr_t ArgumentCount() const { return 0; }
 
   virtual bool CanDeoptimize() const { return true; }
 
   virtual EffectSet Effects() const { return EffectSet::None(); }
 
   virtual bool MayThrow() const { return false; }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
  private:
   const intptr_t token_pos_;
-  const bool in_loop_;
+  const intptr_t loop_depth_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckStackOverflowInstr);
 };
 
 
 class SmiToDoubleInstr : public TemplateDefinition<1> {
  public:
   explicit SmiToDoubleInstr(Value* value) {
     SetInputAt(0, value);
   }
@@ skipping 534 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_