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