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