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/MC/MCStreamer.h"
16 #include <cstdint>
17 
18 using namespace llvm;
19 
20 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
21     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
22 
23 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
24   CUs.push_back(std::move(U));
25 }
26 
27 // Emit the various dwarf units to the unit section USection with
28 // the abbreviations going into ASection.
29 void DwarfFile::emitUnits(bool UseOffsets) {
30   for (const auto &TheU : CUs)
31     emitUnit(TheU.get(), UseOffsets);
32 }
33 
34 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
35   if (TheU->getCUNode()->isDebugDirectivesOnly())
36     return;
37 
38   MCSection *S = TheU->getSection();
39 
40   if (!S)
41     return;
42 
43   // Skip CUs that ended up not being needed (split CUs that were abandoned
44   // because they added no information beyond the non-split CU)
45   if (TheU->getUnitDie().values().empty())
46     return;
47 
48   Asm->OutStreamer->switchSection(S);
49   TheU->emitHeader(UseOffsets);
50   Asm->emitDwarfDIE(TheU->getUnitDie());
51 
52   if (MCSymbol *EndLabel = TheU->getEndLabel())
53     Asm->OutStreamer->emitLabel(EndLabel);
54 }
55 
56 // Compute the size and offset for each DIE.
57 void DwarfFile::computeSizeAndOffsets() {
58   // Offset from the first CU in the debug info section is 0 initially.
59   uint64_t SecOffset = 0;
60 
61   // Iterate over each compile unit and set the size and offsets for each
62   // DIE within each compile unit. All offsets are CU relative.
63   for (const auto &TheU : CUs) {
64     if (TheU->getCUNode()->isDebugDirectivesOnly())
65       continue;
66 
67     // Skip CUs that ended up not being needed (split CUs that were abandoned
68     // because they added no information beyond the non-split CU)
69     if (TheU->getUnitDie().values().empty())
70       return;
71 
72     TheU->setDebugSectionOffset(SecOffset);
73     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
74   }
75   if (SecOffset > UINT32_MAX && !Asm->isDwarf64())
76     report_fatal_error("The generated debug information is too large "
77                        "for the 32-bit DWARF format.");
78 }
79 
80 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
81   // CU-relative offset is reset to 0 here.
82   unsigned Offset = Asm->getUnitLengthFieldByteSize() + // Length of Unit Info
83                     TheU->getHeaderSize();              // Unit-specific headers
84 
85   // The return value here is CU-relative, after laying out
86   // all of the CU DIE.
87   return computeSizeAndOffset(TheU->getUnitDie(), Offset);
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.
92 unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
93   return Die.computeOffsetsAndAbbrevs(Asm->getDwarfFormParams(), Abbrevs,
94                                       Offset);
95 }
96 
97 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
98 
99 // Emit strings into a string section.
100 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection,
101                             bool UseRelativeOffsets) {
102   StrPool.emit(*Asm, StrSection, OffsetSection, UseRelativeOffsets);
103 }
104 
105 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
106   auto &ScopeVars = ScopeVariables[LS];
107   const DILocalVariable *DV = Var->getVariable();
108   if (unsigned ArgNum = DV->getArg()) {
109     auto Cached = ScopeVars.Args.find(ArgNum);
110     if (Cached == ScopeVars.Args.end())
111       ScopeVars.Args[ArgNum] = Var;
112     else {
113       Cached->second->addMMIEntry(*Var);
114       return false;
115     }
116   } else {
117     ScopeVars.Locals.push_back(Var);
118   }
119   return true;
120 }
121 
122 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
123   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
124   Labels.push_back(Label);
125 }
126 
127 std::pair<uint32_t, RangeSpanList *>
128 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
129   CURangeLists.push_back(
130       RangeSpanList{Asm->createTempSymbol("debug_ranges"), &CU, std::move(R)});
131   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
132 }
133