1//===-- llvm/CodeGen/DwarfFile.cpp - Dwarf Debug Framework ----------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "DwarfFile.h"
11
12#include "DwarfDebug.h"
13#include "DwarfUnit.h"
14#include "llvm/MC/MCStreamer.h"
15#include "llvm/Support/LEB128.h"
16#include "llvm/IR/DataLayout.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/Target/TargetLoweringObjectFile.h"
19
20namespace llvm {
21DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
22    : Asm(AP), StrPool(DA, *Asm, Pref) {}
23
24DwarfFile::~DwarfFile() {}
25
26// Define a unique number for the abbreviation.
27//
28void DwarfFile::assignAbbrevNumber(DIEAbbrev &Abbrev) {
29  // Check the set for priors.
30  DIEAbbrev *InSet = AbbreviationsSet.GetOrInsertNode(&Abbrev);
31
32  // If it's newly added.
33  if (InSet == &Abbrev) {
34    // Add to abbreviation list.
35    Abbreviations.push_back(&Abbrev);
36
37    // Assign the vector position + 1 as its number.
38    Abbrev.setNumber(Abbreviations.size());
39  } else {
40    // Assign existing abbreviation number.
41    Abbrev.setNumber(InSet->getNumber());
42  }
43}
44
45void DwarfFile::addUnit(std::unique_ptr<DwarfUnit> U) {
46  CUs.push_back(std::move(U));
47}
48
49// Emit the various dwarf units to the unit section USection with
50// the abbreviations going into ASection.
51void DwarfFile::emitUnits(DwarfDebug *DD, const MCSymbol *ASectionSym) {
52  for (const auto &TheU : CUs) {
53    DIE &Die = TheU->getUnitDie();
54    const MCSection *USection = TheU->getSection();
55    Asm->OutStreamer.SwitchSection(USection);
56
57    // Emit the compile units header.
58    Asm->OutStreamer.EmitLabel(TheU->getLabelBegin());
59
60    // Emit size of content not including length itself
61    Asm->OutStreamer.AddComment("Length of Unit");
62    Asm->EmitInt32(TheU->getHeaderSize() + Die.getSize());
63
64    TheU->emitHeader(ASectionSym);
65
66    DD->emitDIE(Die);
67    Asm->OutStreamer.EmitLabel(TheU->getLabelEnd());
68  }
69}
70// Compute the size and offset for each DIE.
71void DwarfFile::computeSizeAndOffsets() {
72  // Offset from the first CU in the debug info section is 0 initially.
73  unsigned SecOffset = 0;
74
75  // Iterate over each compile unit and set the size and offsets for each
76  // DIE within each compile unit. All offsets are CU relative.
77  for (const auto &TheU : CUs) {
78    TheU->setDebugInfoOffset(SecOffset);
79
80    // CU-relative offset is reset to 0 here.
81    unsigned Offset = sizeof(int32_t) +      // Length of Unit Info
82                      TheU->getHeaderSize(); // Unit-specific headers
83
84    // EndOffset here is CU-relative, after laying out
85    // all of the CU DIE.
86    unsigned EndOffset = computeSizeAndOffset(TheU->getUnitDie(), Offset);
87    SecOffset += EndOffset;
88  }
89}
90// Compute the size and offset of a DIE. The offset is relative to start of the
91// CU. It returns the offset after laying out the DIE.
92unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
93  // Record the abbreviation.
94  assignAbbrevNumber(Die.getAbbrev());
95
96  // Get the abbreviation for this DIE.
97  const DIEAbbrev &Abbrev = Die.getAbbrev();
98
99  // Set DIE offset
100  Die.setOffset(Offset);
101
102  // Start the size with the size of abbreviation code.
103  Offset += getULEB128Size(Die.getAbbrevNumber());
104
105  const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
106  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
107
108  // Size the DIE attribute values.
109  for (unsigned i = 0, N = Values.size(); i < N; ++i)
110    // Size attribute value.
111    Offset += Values[i]->SizeOf(Asm, AbbrevData[i].getForm());
112
113  // Get the children.
114  const auto &Children = Die.getChildren();
115
116  // Size the DIE children if any.
117  if (!Children.empty()) {
118    assert(Abbrev.hasChildren() && "Children flag not set");
119
120    for (auto &Child : Children)
121      Offset = computeSizeAndOffset(*Child, Offset);
122
123    // End of children marker.
124    Offset += sizeof(int8_t);
125  }
126
127  Die.setSize(Offset - Die.getOffset());
128  return Offset;
129}
130void DwarfFile::emitAbbrevs(const MCSection *Section) {
131  // Check to see if it is worth the effort.
132  if (!Abbreviations.empty()) {
133    // Start the debug abbrev section.
134    Asm->OutStreamer.SwitchSection(Section);
135
136    // For each abbrevation.
137    for (const DIEAbbrev *Abbrev : Abbreviations) {
138      // Emit the abbrevations code (base 1 index.)
139      Asm->EmitULEB128(Abbrev->getNumber(), "Abbreviation Code");
140
141      // Emit the abbreviations data.
142      Abbrev->Emit(Asm);
143    }
144
145    // Mark end of abbreviations.
146    Asm->EmitULEB128(0, "EOM(3)");
147  }
148}
149
150// Emit strings into a string section.
151void DwarfFile::emitStrings(const MCSection *StrSection,
152                            const MCSection *OffsetSection,
153                            const MCSymbol *StrSecSym) {
154  StrPool.emit(*Asm, StrSection, OffsetSection, StrSecSym);
155}
156}
157