Emit unwinding information for TurboFan code.

src/compiler/arm/unwinding-info-writer-arm.cc

+// 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.
+
+#include "src/compiler/arm/unwinding-info-writer-arm.h"
+#include "src/compiler/instruction.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+void UnwindingInfoWriter::BeginInstructionBlock(int pc_offset,
+                                                const InstructionBlock* block) {
+  block_will_exit_ = false;
+
+  auto lookup = block_initial_states_.find(block->rpo_number().ToInt());
+  if (lookup != block_initial_states_.end()) {
+    if (lookup->second.saved_lr_ != saved_lr_) {
+      eh_frame_writer_.AdvanceLocation(pc_offset);
+      if (lookup->second.saved_lr_) {
+        eh_frame_writer_.RecordRegisterSavedToStack(lr, -4);

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

-4 ==> -kPointerSize? (Here and below.)

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

Done.

+      } else {
+        eh_frame_writer_.RecordRegisterIsValid(lr);
+      }
+      saved_lr_ = lookup->second.saved_lr_;
+    }
+  } else {
+    // The entry block always lacks an explicit initial state.
+    // The exit block may lack an explicit state, if it is only reached by
+    //   the block ending in a bx lr.
+    // All the other blocks must have an explicit initial state.
+    DCHECK(block->predecessors().empty() || block->successors().empty());
+  }
+}
+
+void UnwindingInfoWriter::EndInstructionBlock(const InstructionBlock* block) {
+  if (block_will_exit_) return;
+
+  for (const RpoNumber& successor : block->successors()) {
+    BlockInitialState state = {saved_lr_};
+    auto inserted = block_initial_states_.insert({successor.ToInt(), state});
+    // If we already had an entry for this BB, check that the values are the
+    // same we were trying to insert.
+    if (!inserted.second) {
+      DCHECK_EQ(inserted.first->second.saved_lr_, state.saved_lr_);
+    }
+  }
+}
+
+void UnwindingInfoWriter::MarkFrameConstructed(int at_pc) {
+  // Regardless of the type of frame constructed, the relevant part of the
+  // layout is always the one in the diagram:
+  //
+  // |   ....   |         higher addresses
+  // +----------+               ^
+  // |    LR    |               |            |
+  // +----------+               |            |
+  // | saved FP |               |            |
+  // +----------+ <-- FP                     v
+  // |   ....   |                       stack growth
+  //
+  // The LR is pushed on the stack, and we can record this fact at the end of
+  // the construction, since the LR itself is not modified in the process.
+  eh_frame_writer_.AdvanceLocation(at_pc);
+  eh_frame_writer_.RecordRegisterSavedToStack(lr, -4);
+  saved_lr_ = true;
+}
+
+void UnwindingInfoWriter::MarkFrameDeconstructed(int at_pc) {
+  // The lr is restored by the last operation in LeaveFrame().
+  eh_frame_writer_.AdvanceLocation(at_pc);
+  eh_frame_writer_.RecordRegisterIsValid(lr);
+  saved_lr_ = false;
+}
+
+void UnwindingInfoWriter::MarkLinkRegisterOnTopOfStack(int pc_offset) {
+  eh_frame_writer_.AdvanceLocation(pc_offset);
+  eh_frame_writer_.SetBaseAddressRegisterAndOffset(sp, 0);
+  eh_frame_writer_.RecordRegisterSavedToStack(lr, 0);
+}
+
+void UnwindingInfoWriter::MarkPopLinkRegisterFromTopOfStack(int pc_offset) {
+  eh_frame_writer_.AdvanceLocation(pc_offset);
+  eh_frame_writer_.SetBaseAddressRegisterAndOffset(fp, 0);
+  eh_frame_writer_.RecordRegisterIsValid(lr);
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8