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 #include "DwarfCompileUnit.h"
12 #include "DwarfDebug.h"
13 #include "DwarfUnit.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/CodeGen/AsmPrinter.h"
16 #include "llvm/CodeGen/DIE.h"
17 #include "llvm/IR/DebugInfoMetadata.h"
18 #include "llvm/MC/MCStreamer.h"
19 #include <algorithm>
20 #include <cstdint>
21 
22 using namespace llvm;
23 
24 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
25     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
26 
27 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
28   CUs.push_back(std::move(U));
29 }
30 
31 // Emit the various dwarf units to the unit section USection with
32 // the abbreviations going into ASection.
33 void DwarfFile::emitUnits(bool UseOffsets) {
34   for (const auto &TheU : CUs)
35     emitUnit(TheU.get(), UseOffsets);
36 }
37 
38 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
39   if (TheU->getCUNode()->isDebugDirectivesOnly())
40     return;
41 
42   DIE &Die = TheU->getUnitDie();
43   MCSection *USection = TheU->getSection();
44   Asm->OutStreamer->SwitchSection(USection);
45 
46   TheU->emitHeader(UseOffsets);
47 
48   Asm->emitDwarfDIE(Die);
49 
50   Asm->OutStreamer->EmitLabel(TheU->getEndLabel());
51 }
52 
53 // Compute the size and offset for each DIE.
54 void DwarfFile::computeSizeAndOffsets() {
55   // Offset from the first CU in the debug info section is 0 initially.
56   unsigned SecOffset = 0;
57 
58   // Iterate over each compile unit and set the size and offsets for each
59   // DIE within each compile unit. All offsets are CU relative.
60   for (const auto &TheU : CUs) {
61     if (TheU->getCUNode()->isDebugDirectivesOnly())
62       continue;
63 
64     TheU->setDebugSectionOffset(SecOffset);
65     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
66   }
67 }
68 
69 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
70   // CU-relative offset is reset to 0 here.
71   unsigned Offset = sizeof(int32_t) +      // Length of Unit Info
72                     TheU->getHeaderSize(); // Unit-specific headers
73 
74   // The return value here is CU-relative, after laying out
75   // all of the CU DIE.
76   return computeSizeAndOffset(TheU->getUnitDie(), Offset);
77 }
78 
79 // Compute the size and offset of a DIE. The offset is relative to start of the
80 // CU. It returns the offset after laying out the DIE.
81 unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
82   return Die.computeOffsetsAndAbbrevs(Asm, Abbrevs, Offset);
83 }
84 
85 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
86 
87 // Emit strings into a string section.
88 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection,
89                             bool UseRelativeOffsets) {
90   StrPool.emit(*Asm, StrSection, OffsetSection, UseRelativeOffsets);
91 }
92 
93 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
94   auto &ScopeVars = ScopeVariables[LS];
95   const DILocalVariable *DV = Var->getVariable();
96   if (unsigned ArgNum = DV->getArg()) {
97     auto Cached = ScopeVars.Args.find(ArgNum);
98     if (Cached == ScopeVars.Args.end())
99       ScopeVars.Args[ArgNum] = Var;
100     else {
101       Cached->second->addMMIEntry(*Var);
102       return false;
103     }
104   } else {
105     ScopeVars.Locals.push_back(Var);
106   }
107   return true;
108 }
109 
110 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
111   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
112   Labels.push_back(Label);
113 }
114 
115 std::pair<uint32_t, RangeSpanList *>
116 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
117   CURangeLists.push_back(
118       RangeSpanList(Asm->createTempSymbol("debug_ranges"), CU, std::move(R)));
119   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
120 }
121