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/ADT/SmallVector.h"
  14 #include "llvm/CodeGen/AsmPrinter.h"
  15 #include "llvm/CodeGen/DIE.h"
  16 #include "llvm/IR/DebugInfoMetadata.h"
  17 #include "llvm/MC/MCStreamer.h"
  18 #include <algorithm>
  19 #include <cstdint>
  20
  21 using namespace llvm;
  22
  23 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
  24     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
  25
  26 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
  27   CUs.push_back(std::move(U));
  28 }
  29
  30 // Emit the various dwarf units to the unit section USection with
  31 // the abbreviations going into ASection.
  32 void DwarfFile::emitUnits(bool UseOffsets) {
  33   for (const auto &TheU : CUs)
  34     emitUnit(TheU.get(), UseOffsets);
  35 }
  36
  37 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
  38   if (TheU->getCUNode()->isDebugDirectivesOnly())
  39     return;
  40
  41   MCSection *S = TheU->getSection();
  42
  43   if (!S)
  44     return;
  45
  46   // Skip CUs that ended up not being needed (split CUs that were abandoned
  47   // because they added no information beyond the non-split CU)
  48   if (llvm::empty(TheU->getUnitDie().values()))
  49     return;
  50
  51   Asm->OutStreamer->SwitchSection(S);
  52   TheU->emitHeader(UseOffsets);
  53   Asm->emitDwarfDIE(TheU->getUnitDie());
  54
  55   if (MCSymbol *EndLabel = TheU->getEndLabel())
  56     Asm->OutStreamer->EmitLabel(EndLabel);
  57 }
  58
  59 // Compute the size and offset for each DIE.
  60 void DwarfFile::computeSizeAndOffsets() {
  61   // Offset from the first CU in the debug info section is 0 initially.
  62   unsigned SecOffset = 0;
  63
  64   // Iterate over each compile unit and set the size and offsets for each
  65   // DIE within each compile unit. All offsets are CU relative.
  66   for (const auto &TheU : CUs) {
  67     if (TheU->getCUNode()->isDebugDirectivesOnly())
  68       continue;
  69
  70     // Skip CUs that ended up not being needed (split CUs that were abandoned
  71     // because they added no information beyond the non-split CU)
  72     if (llvm::empty(TheU->getUnitDie().values()))
  73       return;
  74
  75     TheU->setDebugSectionOffset(SecOffset);
  76     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
  77   }
  78 }
  79
  80 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
  81   // CU-relative offset is reset to 0 here.
  82   unsigned Offset = sizeof(int32_t) +      // 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, Abbrevs, Offset);
  94 }
  95
  96 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
  97
  98 // Emit strings into a string section.
  99 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection,
 100                             bool UseRelativeOffsets) {
 101   StrPool.emit(*Asm, StrSection, OffsetSection, UseRelativeOffsets);
 102 }
 103
 104 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
 105   auto &ScopeVars = ScopeVariables[LS];
 106   const DILocalVariable *DV = Var->getVariable();
 107   if (unsigned ArgNum = DV->getArg()) {
 108     auto Cached = ScopeVars.Args.find(ArgNum);
 109     if (Cached == ScopeVars.Args.end())
 110       ScopeVars.Args[ArgNum] = Var;
 111     else {
 112       Cached->second->addMMIEntry(*Var);
 113       return false;
 114     }
 115   } else {
 116     ScopeVars.Locals.push_back(Var);
 117   }
 118   return true;
 119 }
 120
 121 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
 122   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
 123   Labels.push_back(Label);
 124 }
 125
 126 std::pair<uint32_t, RangeSpanList *>
 127 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
 128   CURangeLists.push_back(
 129       RangeSpanList(Asm->createTempSymbol("debug_ranges"), CU, std::move(R)));
 130   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
 131 }