Emit unwinding information for TurboFan code.

src/compiler/arm/unwinding-info-writer-arm.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_COMPILER_ARM_UNWINDING_INFO_WRITER_H_
+#define V8_COMPILER_ARM_UNWINDING_INFO_WRITER_H_
+
+#include <unordered_map>
+#include "src/eh-frame.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class InstructionBlock;
+
+class UnwindingInfoWriter {
+ public:
+  UnwindingInfoWriter() : saved_lr_(false), block_will_exit_(false) {}
+
+  void BeginInstructionBlock(int pc_offset, const InstructionBlock* block);
+  void EndInstructionBlock(const InstructionBlock* block);
+
+  void MarkLinkRegisterOnTopOfStack(int pc_offset);
+  void MarkPopLinkRegisterFromTopOfStack(int pc_offset);
+
+  void MarkFrameConstructed(int at_pc);
+  void MarkFrameDeconstructed(int at_pc);
+
+  void MarkBlockWillExit() { block_will_exit_ = true; }
+
+  void Finish(int code_size) { eh_frame_writer_.Finish(code_size); }
+
+  EhFrameWriter* eh_frame_writer() { return &eh_frame_writer_; }
+
+ private:
+  EhFrameWriter eh_frame_writer_;
+
+  struct BlockInitialState {
+    bool saved_lr_;
+  };
+
+  bool saved_lr_;
+  bool block_will_exit_;
+
+  std::unordered_map<int, BlockInitialState> block_initial_states_;

[Jarin, 2016/07/06 07:09:42]

Nit: Could not you use a zone vector here? It seems to me you have entries for
most BBs, so the vector would be pretty dense. Or am I missing something?

(Also, using naked STL hash table makes me slightly uneasy. We usually do not
allocate on C++ heap directly, we tend to use zones. This is partly to have
better memory accounting, but also because using an STL containers directly
relies on destructors being called, and I am not sure we always guarantee that.)

+  static_assert(kIntSize >= kInt32Size, "int too small to encode a RpoNumber");

[Jarin, 2016/07/06 07:09:42]

Normally, we use STATIC_ASSERT.

[Stefano Sanfilippo, 2016/07/06 13:25:10]

I followed the comment at line 216 of src/base/macros.h:

// TODO(all) Replace all uses of this macro with static_assert, remove macro.
#define STATIC_ASSERT(test) static_assert(test, #test)

[Jarin, 2016/07/07 07:31:40]

Ah, good to know. Thanks.

+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif