1// Copyright 2016 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "src/compiler/x64/unwinding-info-writer-x64.h"
6#include "src/compiler/instruction.h"
7
8namespace v8 {
9namespace internal {
10namespace compiler {
11
12void UnwindingInfoWriter::BeginInstructionBlock(int pc_offset,
13                                                const InstructionBlock* block) {
14  if (!enabled()) return;
15
16  block_will_exit_ = false;
17
18  DCHECK_LT(block->rpo_number().ToInt(),
19            static_cast<int>(block_initial_states_.size()));
20  const BlockInitialState* initial_state =
21      block_initial_states_[block->rpo_number().ToInt()];
22  if (initial_state) {
23    if (!initial_state->register_.is(eh_frame_writer_.base_register()) &&
24        initial_state->offset_ != eh_frame_writer_.base_offset()) {
25      eh_frame_writer_.AdvanceLocation(pc_offset);
26      eh_frame_writer_.SetBaseAddressRegisterAndOffset(initial_state->register_,
27                                                       initial_state->offset_);
28    } else if (!initial_state->register_.is(eh_frame_writer_.base_register())) {
29      eh_frame_writer_.AdvanceLocation(pc_offset);
30      eh_frame_writer_.SetBaseAddressRegister(initial_state->register_);
31    } else if (initial_state->offset_ != eh_frame_writer_.base_offset()) {
32      eh_frame_writer_.AdvanceLocation(pc_offset);
33      eh_frame_writer_.SetBaseAddressOffset(initial_state->offset_);
34    }
35
36    tracking_fp_ = initial_state->tracking_fp_;
37  } else {
38    // The entry block always lacks an explicit initial state.
39    // The exit block may lack an explicit state, if it is only reached by
40    //   the block ending in a ret.
41    // All the other blocks must have an explicit initial state.
42    DCHECK(block->predecessors().empty() || block->successors().empty());
43  }
44}
45
46void UnwindingInfoWriter::EndInstructionBlock(const InstructionBlock* block) {
47  if (!enabled() || block_will_exit_) return;
48
49  for (const RpoNumber& successor : block->successors()) {
50    int successor_index = successor.ToInt();
51    DCHECK_LT(successor_index, static_cast<int>(block_initial_states_.size()));
52    const BlockInitialState* existing_state =
53        block_initial_states_[successor_index];
54    // If we already had an entry for this BB, check that the values are the
55    // same we are trying to insert.
56    if (existing_state) {
57      DCHECK(existing_state->register_.is(eh_frame_writer_.base_register()));
58      DCHECK_EQ(existing_state->offset_, eh_frame_writer_.base_offset());
59      DCHECK_EQ(existing_state->tracking_fp_, tracking_fp_);
60    } else {
61      block_initial_states_[successor_index] = new (zone_)
62          BlockInitialState(eh_frame_writer_.base_register(),
63                            eh_frame_writer_.base_offset(), tracking_fp_);
64    }
65  }
66}
67
68void UnwindingInfoWriter::MarkFrameConstructed(int pc_base) {
69  if (!enabled()) return;
70
71  // push rbp
72  eh_frame_writer_.AdvanceLocation(pc_base + 1);
73  eh_frame_writer_.IncreaseBaseAddressOffset(kInt64Size);
74  // <base address> points at the bottom of the current frame on x64 and
75  // <base register> is rsp, which points to the top of the frame by definition.
76  // Thus, the distance between <base address> and the top is -<base offset>.
77  int top_of_stack = -eh_frame_writer_.base_offset();
78  eh_frame_writer_.RecordRegisterSavedToStack(rbp, top_of_stack);
79
80  // mov rbp, rsp
81  eh_frame_writer_.AdvanceLocation(pc_base + 4);
82  eh_frame_writer_.SetBaseAddressRegister(rbp);
83
84  tracking_fp_ = true;
85}
86
87void UnwindingInfoWriter::MarkFrameDeconstructed(int pc_base) {
88  if (!enabled()) return;
89
90  // mov rsp, rbp
91  eh_frame_writer_.AdvanceLocation(pc_base + 3);
92  eh_frame_writer_.SetBaseAddressRegister(rsp);
93
94  // pop rbp
95  eh_frame_writer_.AdvanceLocation(pc_base + 4);
96  eh_frame_writer_.IncreaseBaseAddressOffset(-kInt64Size);
97
98  tracking_fp_ = false;
99}
100
101}  // namespace compiler
102}  // namespace internal
103}  // namespace v8
104