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 
20 namespace llvm {
21 DwarfFile::DwarfFile(AsmPrinter *AP, DwarfDebug &DD, StringRef Pref,
22                      BumpPtrAllocator &DA)
23     : Asm(AP), DD(DD), StrPool(DA, *Asm, Pref) {}
24 
25 DwarfFile::~DwarfFile() {}
26 
27 // Define a unique number for the abbreviation.
28 //
29 void DwarfFile::assignAbbrevNumber(DIEAbbrev &Abbrev) {
30   // Check the set for priors.
31   DIEAbbrev *InSet = AbbreviationsSet.GetOrInsertNode(&Abbrev);
32 
33   // If it's newly added.
34   if (InSet == &Abbrev) {
35     // Add to abbreviation list.
36     Abbreviations.push_back(&Abbrev);
37 
38     // Assign the vector position + 1 as its number.
39     Abbrev.setNumber(Abbreviations.size());
40   } else {
41     // Assign existing abbreviation number.
42     Abbrev.setNumber(InSet->getNumber());
43   }
44 }
45 
46 void DwarfFile::addUnit(std::unique_ptr<DwarfUnit> U) {
47   CUs.push_back(std::move(U));
48 }
49 
50 // Emit the various dwarf units to the unit section USection with
51 // the abbreviations going into ASection.
52 void DwarfFile::emitUnits(const MCSymbol *ASectionSym) {
53   for (const auto &TheU : CUs) {
54     DIE &Die = TheU->getUnitDie();
55     const MCSection *USection = TheU->getSection();
56     Asm->OutStreamer.SwitchSection(USection);
57 
58     // Emit the compile units header.
59     Asm->OutStreamer.EmitLabel(TheU->getLabelBegin());
60 
61     // Emit size of content not including length itself
62     Asm->OutStreamer.AddComment("Length of Unit");
63     Asm->EmitInt32(TheU->getHeaderSize() + Die.getSize());
64 
65     TheU->emitHeader(ASectionSym);
66 
67     DD.emitDIE(Die);
68     Asm->OutStreamer.EmitLabel(TheU->getLabelEnd());
69   }
70 }
71 
72 // Compute the size and offset for each DIE.
73 void DwarfFile::computeSizeAndOffsets() {
74   // Offset from the first CU in the debug info section is 0 initially.
75   unsigned SecOffset = 0;
76 
77   // Iterate over each compile unit and set the size and offsets for each
78   // DIE within each compile unit. All offsets are CU relative.
79   for (const auto &TheU : CUs) {
80     TheU->setDebugInfoOffset(SecOffset);
81 
82     // CU-relative offset is reset to 0 here.
83     unsigned Offset = sizeof(int32_t) +      // Length of Unit Info
84                       TheU->getHeaderSize(); // Unit-specific headers
85 
86     // EndOffset here is CU-relative, after laying out
87     // all of the CU DIE.
88     unsigned EndOffset = computeSizeAndOffset(TheU->getUnitDie(), Offset);
89     SecOffset += EndOffset;
90   }
91 }
92 // Compute the size and offset of a DIE. The offset is relative to start of the
93 // CU. It returns the offset after laying out the DIE.
94 unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
95   // Record the abbreviation.
96   assignAbbrevNumber(Die.getAbbrev());
97 
98   // Get the abbreviation for this DIE.
99   const DIEAbbrev &Abbrev = Die.getAbbrev();
100 
101   // Set DIE offset
102   Die.setOffset(Offset);
103 
104   // Start the size with the size of abbreviation code.
105   Offset += getULEB128Size(Die.getAbbrevNumber());
106 
107   const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
108   const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
109 
110   // Size the DIE attribute values.
111   for (unsigned i = 0, N = Values.size(); i < N; ++i)
112     // Size attribute value.
113     Offset += Values[i]->SizeOf(Asm, AbbrevData[i].getForm());
114 
115   // Get the children.
116   const auto &Children = Die.getChildren();
117 
118   // Size the DIE children if any.
119   if (!Children.empty()) {
120     assert(Abbrev.hasChildren() && "Children flag not set");
121 
122     for (auto &Child : Children)
123       Offset = computeSizeAndOffset(*Child, Offset);
124 
125     // End of children marker.
126     Offset += sizeof(int8_t);
127   }
128 
129   Die.setSize(Offset - Die.getOffset());
130   return Offset;
131 }
132 void DwarfFile::emitAbbrevs(const MCSection *Section) {
133   // Check to see if it is worth the effort.
134   if (!Abbreviations.empty()) {
135     // Start the debug abbrev section.
136     Asm->OutStreamer.SwitchSection(Section);
137 
138     // For each abbrevation.
139     for (const DIEAbbrev *Abbrev : Abbreviations) {
140       // Emit the abbrevations code (base 1 index.)
141       Asm->EmitULEB128(Abbrev->getNumber(), "Abbreviation Code");
142 
143       // Emit the abbreviations data.
144       Abbrev->Emit(Asm);
145     }
146 
147     // Mark end of abbreviations.
148     Asm->EmitULEB128(0, "EOM(3)");
149   }
150 }
151 
152 // Emit strings into a string section.
153 void DwarfFile::emitStrings(const MCSection *StrSection,
154                             const MCSection *OffsetSection) {
155   StrPool.emit(*Asm, StrSection, OffsetSection);
156 }
157 
158 void DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
159   SmallVectorImpl<DbgVariable *> &Vars = ScopeVariables[LS];
160   DIVariable DV = Var->getVariable();
161   // Variables with positive arg numbers are parameters.
162   if (unsigned ArgNum = DV.getArgNumber()) {
163     // Keep all parameters in order at the start of the variable list to ensure
164     // function types are correct (no out-of-order parameters)
165     //
166     // This could be improved by only doing it for optimized builds (unoptimized
167     // builds have the right order to begin with), searching from the back (this
168     // would catch the unoptimized case quickly), or doing a binary search
169     // rather than linear search.
170     auto I = Vars.begin();
171     while (I != Vars.end()) {
172       unsigned CurNum = (*I)->getVariable().getArgNumber();
173       // A local (non-parameter) variable has been found, insert immediately
174       // before it.
175       if (CurNum == 0)
176         break;
177       // A later indexed parameter has been found, insert immediately before it.
178       if (CurNum > ArgNum)
179         break;
180       assert(CurNum != ArgNum);
181       ++I;
182     }
183     Vars.insert(I, Var);
184     return;
185   }
186 
187   Vars.push_back(Var);
188 }
189 }
190