1//===- llvm/CodeGen/AddressPool.cpp - Dwarf Debug Framework ---------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "AddressPool.h"
10#include "llvm/ADT/SmallVector.h"
11#include "llvm/CodeGen/AsmPrinter.h"
12#include "llvm/IR/DataLayout.h"
13#include "llvm/MC/MCStreamer.h"
14#include "llvm/Target/TargetLoweringObjectFile.h"
15#include <utility>
16
17using namespace llvm;
18
19unsigned AddressPool::getIndex(const MCSymbol *Sym, bool TLS) {
20  HasBeenUsed = true;
21  auto IterBool =
22      Pool.insert(std::make_pair(Sym, AddressPoolEntry(Pool.size(), TLS)));
23  return IterBool.first->second.Number;
24}
25
26MCSymbol *AddressPool::emitHeader(AsmPrinter &Asm, MCSection *Section) {
27  static const uint8_t AddrSize = Asm.getDataLayout().getPointerSize();
28  StringRef Prefix = "debug_addr_";
29  MCSymbol *BeginLabel = Asm.createTempSymbol(Prefix + "start");
30  MCSymbol *EndLabel = Asm.createTempSymbol(Prefix + "end");
31
32  Asm.OutStreamer->AddComment("Length of contribution");
33  Asm.emitLabelDifference(EndLabel, BeginLabel,
34                          4); // TODO: Support DWARF64 format.
35  Asm.OutStreamer->emitLabel(BeginLabel);
36  Asm.OutStreamer->AddComment("DWARF version number");
37  Asm.emitInt16(Asm.getDwarfVersion());
38  Asm.OutStreamer->AddComment("Address size");
39  Asm.emitInt8(AddrSize);
40  Asm.OutStreamer->AddComment("Segment selector size");
41  Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
42
43  return EndLabel;
44}
45
46// Emit addresses into the section given.
47void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
48  if (isEmpty())
49    return;
50
51  // Start the dwarf addr section.
52  Asm.OutStreamer->SwitchSection(AddrSection);
53
54  MCSymbol *EndLabel = nullptr;
55
56  if (Asm.getDwarfVersion() >= 5)
57    EndLabel = emitHeader(Asm, AddrSection);
58
59  // Define the symbol that marks the start of the contribution.
60  // It is referenced via DW_AT_addr_base.
61  Asm.OutStreamer->emitLabel(AddressTableBaseSym);
62
63  // Order the address pool entries by ID
64  SmallVector<const MCExpr *, 64> Entries(Pool.size());
65
66  for (const auto &I : Pool)
67    Entries[I.second.Number] =
68        I.second.TLS
69            ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
70            : MCSymbolRefExpr::create(I.first, Asm.OutContext);
71
72  for (const MCExpr *Entry : Entries)
73    Asm.OutStreamer->emitValue(Entry, Asm.getDataLayout().getPointerSize());
74
75  if (EndLabel)
76    Asm.OutStreamer->emitLabel(EndLabel);
77}
78