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   StringRef Prefix = "debug_addr_";
  29   MCSymbol *BeginLabel = Asm.createTempSymbol(Prefix + "start");
  30   MCSymbol *EndLabel = Asm.createTempSymbol(Prefix + "end");
  31
  32   Asm.OutStreamer->AddComment("Length of contribution");
  33   Asm.EmitLabelDifference(EndLabel, BeginLabel,
  34                           4); // TODO: Support DWARF64 format.
  35   Asm.OutStreamer->EmitLabel(BeginLabel);
  36   Asm.OutStreamer->AddComment("DWARF version number");
  37   Asm.emitInt16(Asm.getDwarfVersion());
  38   Asm.OutStreamer->AddComment("Address size");
  39   Asm.emitInt8(AddrSize);
  40   Asm.OutStreamer->AddComment("Segment selector size");
  41   Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
  42
  43   return EndLabel;
  44 }
  45
  46 // Emit addresses into the section given.
  47 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
  48   if (isEmpty())
  49     return;
  50
  51   // Start the dwarf addr section.
  52   Asm.OutStreamer->SwitchSection(AddrSection);
  53
  54   MCSymbol *EndLabel = nullptr;
  55
  56   if (Asm.getDwarfVersion() >= 5)
  57     EndLabel = emitHeader(Asm, AddrSection);
  58
  59   // Define the symbol that marks the start of the contribution.
  60   // It is referenced via DW_AT_addr_base.
  61   Asm.OutStreamer->EmitLabel(AddressTableBaseSym);
  62
  63   // Order the address pool entries by ID
  64   SmallVector<const MCExpr *, 64> Entries(Pool.size());
  65
  66   for (const auto &I : Pool)
  67     Entries[I.second.Number] =
  68         I.second.TLS
  69             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
  70             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
  71
  72   for (const MCExpr *Entry : Entries)
  73     Asm.OutStreamer->EmitValue(Entry, Asm.getDataLayout().getPointerSize());
  74
  75   if (EndLabel)
  76     Asm.OutStreamer->EmitLabel(EndLabel);
  77 }