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 
27 void AddressPool::emitHeader(AsmPrinter &Asm, MCSection *Section) {
28   static const uint8_t AddrSize = Asm.getDataLayout().getPointerSize();
29   uint64_t Length = sizeof(uint16_t) // version
30                   + sizeof(uint8_t)  // address_size
31                   + sizeof(uint8_t)  // segment_selector_size
32                   + AddrSize * Pool.size(); // entries
33   Asm.OutStreamer->AddComment("Length of contribution");
34   Asm.emitInt32(Length); // TODO: Support DWARF64 format.
35   Asm.OutStreamer->AddComment("DWARF version number");
36   Asm.emitInt16(Asm.getDwarfVersion());
37   Asm.OutStreamer->AddComment("Address size");
38   Asm.emitInt8(AddrSize);
39   Asm.OutStreamer->AddComment("Segment selector size");
40   Asm.emitInt8(0); // TODO: Support non-zero segment_selector_size.
41 }
42 
43 // Emit addresses into the section given.
44 void AddressPool::emit(AsmPrinter &Asm, MCSection *AddrSection) {
45   if (isEmpty())
46     return;
47 
48   // Start the dwarf addr section.
49   Asm.OutStreamer->SwitchSection(AddrSection);
50 
51   if (Asm.getDwarfVersion() >= 5)
52     emitHeader(Asm, AddrSection);
53 
54   // Define the symbol that marks the start of the contribution.
55   // It is referenced via DW_AT_addr_base.
56   Asm.OutStreamer->EmitLabel(AddressTableBaseSym);
57 
58   // Order the address pool entries by ID
59   SmallVector<const MCExpr *, 64> Entries(Pool.size());
60 
61   for (const auto &I : Pool)
62     Entries[I.second.Number] =
63         I.second.TLS
64             ? Asm.getObjFileLowering().getDebugThreadLocalSymbol(I.first)
65             : MCSymbolRefExpr::create(I.first, Asm.OutContext);
66 
67   for (const MCExpr *Entry : Entries)
68     Asm.OutStreamer->EmitValue(Entry, Asm.getDataLayout().getPointerSize());
69 }
70