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.emitDwarfUnitLength(EndLabel, BeginLabel, "Length of contribution");
33   Asm.OutStreamer->emitLabel(BeginLabel);
34   Asm.OutStreamer->AddComment("DWARF version number");
35   Asm.emitInt16(Asm.getDwarfVersion());
36   Asm.OutStreamer->AddComment("Address size");
37   Asm.emitInt8(AddrSize);
38   Asm.OutStreamer->AddComment("Segment selector size");
39   Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
40 
41   return EndLabel;
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   MCSymbol *EndLabel = nullptr;
53 
54   if (Asm.getDwarfVersion() >= 5)
55     EndLabel = emitHeader(Asm, AddrSection);
56 
57   // Define the symbol that marks the start of the contribution.
58   // It is referenced via DW_AT_addr_base.
59   Asm.OutStreamer->emitLabel(AddressTableBaseSym);
60 
61   // Order the address pool entries by ID
62   SmallVector<const MCExpr *, 64> Entries(Pool.size());
63 
64   for (const auto &I : Pool)
65     Entries[I.second.Number] =
66         I.second.TLS
67             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
68             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
69 
70   for (const MCExpr *Entry : Entries)
71     Asm.OutStreamer->emitValue(Entry, Asm.getDataLayout().getPointerSize());
72 
73   if (EndLabel)
74     Asm.OutStreamer->emitLabel(EndLabel);
75 }
76