llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp

   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->getDwarfFormParams(), Abbrevs,
  96                                       Offset);
  97 }
  98
  99 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
 100
 101 // Emit strings into a string section.
 102 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection,
 103                             bool UseRelativeOffsets) {
 104   StrPool.emit(*Asm, StrSection, OffsetSection, UseRelativeOffsets);
 105 }
 106
 107 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
 108   auto &ScopeVars = ScopeVariables[LS];
 109   const DILocalVariable *DV = Var->getVariable();
 110   if (unsigned ArgNum = DV->getArg()) {
 111     auto Cached = ScopeVars.Args.find(ArgNum);
 112     if (Cached == ScopeVars.Args.end())
 113       ScopeVars.Args[ArgNum] = Var;
 114     else {
 115       Cached->second->addMMIEntry(*Var);
 116       return false;
 117     }
 118   } else {
 119     ScopeVars.Locals.push_back(Var);
 120   }
 121   return true;
 122 }
 123
 124 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
 125   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
 126   Labels.push_back(Label);
 127 }
 128
 129 std::pair<uint32_t, RangeSpanList *>
 130 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
 131   CURangeLists.push_back(
 132       RangeSpanList{Asm->createTempSymbol("debug_ranges"), &CU, std::move(R)});
 133   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
 134 }