llvm/lib/CodeGen/AsmPrinter/AddressPool.cpp

   1 //===- llvm/CodeGen/AddressPool.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 "AddressPool.h"
  10 #include "llvm/ADT/SmallVector.h"
  11 #include "llvm/CodeGen/AsmPrinter.h"
  12 #include "llvm/IR/DataLayout.h"
  13 #include "llvm/MC/MCStreamer.h"
  14 #include "llvm/Target/TargetLoweringObjectFile.h"
  15 #include <utility>
  16
  17 using namespace llvm;
  18
  19 unsigned AddressPool::getIndex(const MCSymbol *Sym, bool TLS) {
  20   HasBeenUsed = true;
  21   auto IterBool =
  22       Pool.insert(std::make_pair(Sym, AddressPoolEntry(Pool.size(), TLS)));
  23   return IterBool.first->second.Number;
  24 }
  25
  26 MCSymbol *AddressPool::emitHeader(AsmPrinter &Asm, MCSection *Section) {
  27   static const uint8_t AddrSize = Asm.getDataLayout().getPointerSize();
  28
  29   MCSymbol *EndLabel =
  30       Asm.emitDwarfUnitLength("debug_addr", "Length of contribution");
  31   Asm.OutStreamer->AddComment("DWARF version number");
  32   Asm.emitInt16(Asm.getDwarfVersion());
  33   Asm.OutStreamer->AddComment("Address size");
  34   Asm.emitInt8(AddrSize);
  35   Asm.OutStreamer->AddComment("Segment selector size");
  36   Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
  37
  38   return EndLabel;
  39 }
  40
  41 // Emit addresses into the section given.
  42 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
  43   if (isEmpty())
  44     return;
  45
  46   // Start the dwarf addr section.
  47   Asm.OutStreamer->SwitchSection(AddrSection);
  48
  49   MCSymbol *EndLabel = nullptr;
  50
  51   if (Asm.getDwarfVersion() >= 5)
  52     EndLabel = emitHeader(Asm, AddrSection);
  53
  54   // Define the symbol that marks the start of the contribution.
  55   // It is referenced via DW_AT_addr_base.
  56   Asm.OutStreamer->emitLabel(AddressTableBaseSym);
  57
  58   // Order the address pool entries by ID
  59   SmallVector<const MCExpr *, 64> Entries(Pool.size());
  60
  61   for (const auto &I : Pool)
  62     Entries[I.second.Number] =
  63         I.second.TLS
  64             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
  65             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
  66
  67   for (const MCExpr *Entry : Entries)
  68     Asm.OutStreamer->emitValue(Entry, Asm.getDataLayout().getPointerSize());
  69
  70   if (EndLabel)
  71     Asm.OutStreamer->emitLabel(EndLabel);
  72 }