1 //===- llvm/CodeGen/DwarfFile.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 "DwarfFile.h"
10 #include "DwarfCompileUnit.h"
11 #include "DwarfDebug.h"
12 #include "DwarfUnit.h"
13 #include "llvm/CodeGen/AsmPrinter.h"
14 #include "llvm/IR/DebugInfoMetadata.h"
15 #include "llvm/IR/Metadata.h"
16 #include "llvm/MC/MCStreamer.h"
17 #include <algorithm>
18 #include <cstdint>
19 
20 using namespace llvm;
21 
22 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
23     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
24 
25 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
26   CUs.push_back(std::move(U));
27 }
28 
29 // Emit the various dwarf units to the unit section USection with
30 // the abbreviations going into ASection.
31 void DwarfFile::emitUnits(bool UseOffsets) {
32   for (const auto &TheU : CUs)
33     emitUnit(TheU.get(), UseOffsets);
34 }
35 
36 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
37   if (TheU->getCUNode()->isDebugDirectivesOnly())
38     return;
39 
40   MCSection *S = TheU->getSection();
41 
42   if (!S)
43     return;
44 
45   // Skip CUs that ended up not being needed (split CUs that were abandoned
46   // because they added no information beyond the non-split CU)
47   if (llvm::empty(TheU->getUnitDie().values()))
48     return;
49 
50   Asm->OutStreamer->SwitchSection(S);
51   TheU->emitHeader(UseOffsets);
52   Asm->emitDwarfDIE(TheU->getUnitDie());
53 
54   if (MCSymbol *EndLabel = TheU->getEndLabel())
55     Asm->OutStreamer->emitLabel(EndLabel);
56 }
57 
58 // Compute the size and offset for each DIE.
59 void DwarfFile::computeSizeAndOffsets() {
60   // Offset from the first CU in the debug info section is 0 initially.
61   uint64_t SecOffset = 0;
62 
63   // Iterate over each compile unit and set the size and offsets for each
64   // DIE within each compile unit. All offsets are CU relative.
65   for (const auto &TheU : CUs) {
66     if (TheU->getCUNode()->isDebugDirectivesOnly())
67       continue;
68 
69     // Skip CUs that ended up not being needed (split CUs that were abandoned
70     // because they added no information beyond the non-split CU)
71     if (llvm::empty(TheU->getUnitDie().values()))
72       return;
73 
74     TheU->setDebugSectionOffset(SecOffset);
75     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
76   }
77   if (SecOffset > UINT32_MAX && !Asm->isDwarf64())
78     report_fatal_error("The generated debug information is too large "
79                        "for the 32-bit DWARF format.");
80 }
81 
82 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
83   // CU-relative offset is reset to 0 here.
84   unsigned Offset = Asm->getUnitLengthFieldByteSize() + // Length of Unit Info
85                     TheU->getHeaderSize();              // Unit-specific headers
86 
87   // The return value here is CU-relative, after laying out
88   // all of the CU DIE.
89   return computeSizeAndOffset(TheU->getUnitDie(), Offset);
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   return Die.computeOffsetsAndAbbrevs(Asm, Abbrevs, Offset);
96 }
97 
98 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
99 
100 // Emit strings into a string section.
101 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection,
102                             bool UseRelativeOffsets) {
103   StrPool.emit(*Asm, StrSection, OffsetSection, UseRelativeOffsets);
104 }
105 
106 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
107   auto &ScopeVars = ScopeVariables[LS];
108   const DILocalVariable *DV = Var->getVariable();
109   if (unsigned ArgNum = DV->getArg()) {
110     auto Cached = ScopeVars.Args.find(ArgNum);
111     if (Cached == ScopeVars.Args.end())
112       ScopeVars.Args[ArgNum] = Var;
113     else {
114       Cached->second->addMMIEntry(*Var);
115       return false;
116     }
117   } else {
118     ScopeVars.Locals.push_back(Var);
119   }
120   return true;
121 }
122 
123 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
124   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
125   Labels.push_back(Label);
126 }
127 
128 std::pair<uint32_t, RangeSpanList *>
129 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
130   CURangeLists.push_back(
131       RangeSpanList{Asm->createTempSymbol("debug_ranges"), &CU, std::move(R)});
132   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
133 }
134