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.OutStreamer->AddComment("Length of contribution");
35   Asm.emitInt32(Length); // TODO: Support DWARF64 format.
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 
44 // Emit addresses into the section given.
45 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
46   if (isEmpty())
47     return;
48 
49   // Start the dwarf addr section.
50   Asm.OutStreamer->SwitchSection(AddrSection);
51 
52   if (Asm.getDwarfVersion() >= 5)
53     emitHeader(Asm, AddrSection);
54 
55   // Define the symbol that marks the start of the contribution.
56   // It is referenced via DW_AT_addr_base.
57   Asm.OutStreamer->EmitLabel(AddressTableBaseSym);
58 
59   // Order the address pool entries by ID
60   SmallVector<const MCExpr *, 64> Entries(Pool.size());
61 
62   for (const auto &I : Pool)
63     Entries[I.second.Number] =
64         I.second.TLS
65             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
66             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
67 
68   for (const MCExpr *Entry : Entries)
69     Asm.OutStreamer->EmitValue(Entry, Asm.getDataLayout().getPointerSize());
70 }
71