[turbofan] Implement OSR for outer loops.

src/compiler/osr.h

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_COMPILER_OSR_H_
+#define V8_COMPILER_OSR_H_
+
+#include "src/zone.h"
+
+namespace v8 {
+namespace internal {
+
+class CompilationInfo;
+
+namespace compiler {
+
+class Graph;
+class CommonOperatorBuilder;
+class Frame;
+class Linkage;
+
+// Encapsulates logic relating to OSR compilations as well has handles some
+// details of the frame layout.
+class OsrHelper {
+ public:
+  explicit OsrHelper(CompilationInfo* info);
+
+  // Deconstructs the artificial {OsrNormalEntry} and rewrites the graph so
+  // that only the path corresponding to {OsrLoopEntry} remains.
+  void Deconstruct(Graph* graph, CommonOperatorBuilder* common, Zone* tmp_zone);
+
+  // Prepares the frame w.r.t. OSR.
+  void SetupFrame(Frame* frame);
+
+  // Returns the number of unoptimized frame slots for this OSR.
+  size_t UnoptimizedFrameSlots() { return stack_slot_count_; }
+
+  // Returns the environment index of the first stack slot.
+  static int FirstStackSlotIndex(int parameter_count) {
+    // n.b. unlike Crankshaft, TurboFan environments do not contain the context.
+    return 1 + parameter_count;  // receiver + params
+  }
+
+ private:
+  size_t parameter_count_;
+  size_t stack_slot_count_;
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_OSR_H_