Initial support for emitting unwinding information in perf jitdump.

src/unwinding-info.h

+// Copyright 2016 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_UNWINDING_INFO_H_
+#define V8_UNWINDING_INFO_H_
+
+#include <cstdint>
+
+namespace v8 {
+namespace internal {
+
+class Code;
+
+class EhFrameHdr final {

[rmcilroy, 2016/06/21 13:47:44]

This file should be eh_frame_header (and the the class named similarly, i.e.,
EhFrameHeader).

[Stefano Sanfilippo, 2016/06/23 15:23:44]

.eh_frame_hdr is the name of the section and how it is referred to in all
documentation, so I'd rather not expand the Hdr bit in the name.

I agree on the first part, and I have renamed this file to eh-frame.h, instead
of eh-frame-hdr.h, because other things related to the eh-frame might end up
here. Same for the .cc file. 

+ public:
+  explicit EhFrameHdr(Code* code);
+  static const int kRecordSize = 20;
+
+ private:
+  uint8_t version_;
+  uint8_t eh_frame_ptr_encoding_;
+  uint8_t lut_size_encoding_;
+  uint8_t lut_entries_encoding_;
+  int32_t offset_to_eh_frame_;
+  uint32_t lut_entries_number_;
+  int32_t offset_to_procedure_;
+  int32_t offset_to_fde_;
+};
+
+void PatchProcedureBoundariesInEhFrame(Code* code);
+
+}  // namespace internal
+}  // namespace v8
+
+#endif