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/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 void 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 Ret = ScopeVars.Args.insert({ArgNum, Var});
 110     assert(Ret.second);
 111     (void)Ret;
 112   } else {
 113     ScopeVars.Locals.push_back(Var);
 114   }
 115 }
 116
 117 void DwarfFile::addScopeLabel(LexicalScope *LS, DbgLabel *Label) {
 118   SmallVectorImpl<DbgLabel *> &Labels = ScopeLabels[LS];
 119   Labels.push_back(Label);
 120 }
 121
 122 std::pair<uint32_t, RangeSpanList *>
 123 DwarfFile::addRange(const DwarfCompileUnit &CU, SmallVector<RangeSpan, 2> R) {
 124   CURangeLists.push_back(
 125       RangeSpanList{Asm->createTempSymbol("debug_ranges"), &CU, std::move(R)});
 126   return std::make_pair(CURangeLists.size() - 1, &CURangeLists.back());
 127 }