1//===-- llvm/CodeGen/DwarfStringPool.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 "DwarfStringPool.h"
11#include "llvm/CodeGen/AsmPrinter.h"
12#include "llvm/MC/MCAsmInfo.h"
13#include "llvm/MC/MCStreamer.h"
14
15using namespace llvm;
16
17DwarfStringPool::DwarfStringPool(BumpPtrAllocator &A, AsmPrinter &Asm,
18                                 StringRef Prefix)
19    : Pool(A), Prefix(Prefix),
20      ShouldCreateSymbols(Asm.MAI->doesDwarfUseRelocationsAcrossSections()) {}
21
22DwarfStringPool::EntryRef DwarfStringPool::getEntry(AsmPrinter &Asm,
23                                                    StringRef Str) {
24  auto I = Pool.insert(std::make_pair(Str, EntryTy()));
25  if (I.second) {
26    auto &Entry = I.first->second;
27    Entry.Index = Pool.size() - 1;
28    Entry.Offset = NumBytes;
29    Entry.Symbol = ShouldCreateSymbols ? Asm.createTempSymbol(Prefix) : nullptr;
30
31    NumBytes += Str.size() + 1;
32    assert(NumBytes > Entry.Offset && "Unexpected overflow");
33  }
34  return EntryRef(*I.first);
35}
36
37void DwarfStringPool::emit(AsmPrinter &Asm, MCSection *StrSection,
38                           MCSection *OffsetSection) {
39  if (Pool.empty())
40    return;
41
42  // Start the dwarf str section.
43  Asm.OutStreamer->SwitchSection(StrSection);
44
45  // Get all of the string pool entries and put them in an array by their ID so
46  // we can sort them.
47  SmallVector<const StringMapEntry<EntryTy> *, 64> Entries(Pool.size());
48
49  for (const auto &E : Pool)
50    Entries[E.getValue().Index] = &E;
51
52  for (const auto &Entry : Entries) {
53    assert(ShouldCreateSymbols == static_cast<bool>(Entry->getValue().Symbol) &&
54           "Mismatch between setting and entry");
55
56    // Emit a label for reference from debug information entries.
57    if (ShouldCreateSymbols)
58      Asm.OutStreamer->EmitLabel(Entry->getValue().Symbol);
59
60    // Emit the string itself with a terminating null byte.
61    Asm.OutStreamer->AddComment("string offset=" +
62                                Twine(Entry->getValue().Offset));
63    Asm.OutStreamer->EmitBytes(
64        StringRef(Entry->getKeyData(), Entry->getKeyLength() + 1));
65  }
66
67  // If we've got an offset section go ahead and emit that now as well.
68  if (OffsetSection) {
69    Asm.OutStreamer->SwitchSection(OffsetSection);
70    unsigned size = 4; // FIXME: DWARF64 is 8.
71    for (const auto &Entry : Entries)
72      Asm.OutStreamer->EmitIntValue(Entry->getValue().Offset, size);
73  }
74}
75