1 //===- llvm/CodeGen/AddressPool.cpp - Dwarf Debug Framework ---------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "AddressPool.h"
11 #include "llvm/ADT/SmallVector.h"
12 #include "llvm/CodeGen/AsmPrinter.h"
13 #include "llvm/IR/DataLayout.h"
14 #include "llvm/MC/MCStreamer.h"
15 #include "llvm/Target/TargetLoweringObjectFile.h"
16 #include <utility>
17 
18 using namespace llvm;
19 
20 unsigned AddressPool::getIndex(const MCSymbol *Sym, bool TLS) {
21   HasBeenUsed = true;
22   auto IterBool =
23       Pool.insert(std::make_pair(Sym, AddressPoolEntry(Pool.size(), TLS)));
24   return IterBool.first->second.Number;
25 }
26 
27 
28 void AddressPool::emitHeader(AsmPrinter &Asm, MCSection *Section) {
29   static const uint8_t AddrSize = Asm.getDataLayout().getPointerSize();
30   uint64_t Length = sizeof(uint16_t) // version
31                   + sizeof(uint8_t)  // address_size
32                   + sizeof(uint8_t)  // segment_selector_size
33                   + AddrSize * Pool.size(); // entries
34   Asm.emitInt32(Length); // TODO: Support DWARF64 format.
35   Asm.emitInt16(Asm.getDwarfVersion());
36   Asm.emitInt8(AddrSize);
37   Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
38 }
39 
40 // Emit addresses into the section given.
41 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
42   if (isEmpty())
43     return;
44 
45   // Start the dwarf addr section.
46   Asm.OutStreamer->SwitchSection(AddrSection);
47 
48   if (Asm.getDwarfVersion() >= 5)
49     emitHeader(Asm, AddrSection);
50 
51   // Define the symbol that marks the start of the contribution.
52   // It is referenced via DW_AT_addr_base.
53   Asm.OutStreamer->EmitLabel(AddressTableBaseSym);
54 
55   // Order the address pool entries by ID
56   SmallVector<const MCExpr *, 64> Entries(Pool.size());
57 
58   for (const auto &I : Pool)
59     Entries[I.second.Number] =
60         I.second.TLS
61             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
62             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
63 
64   for (const MCExpr *Entry : Entries)
65     Asm.OutStreamer->EmitValue(Entry, Asm.getDataLayout().getPointerSize());
66 }
67