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/MC/MCStreamer.h"
12 
13 using namespace llvm;
14 
15 static std::pair<MCSymbol *, unsigned> &
16 getEntry(AsmPrinter &Asm,
17          StringMap<std::pair<MCSymbol *, unsigned>, BumpPtrAllocator &> &Pool,
18          StringRef Prefix, StringRef Str) {
19   std::pair<MCSymbol *, unsigned> &Entry =
20       Pool.GetOrCreateValue(Str).getValue();
21   if (!Entry.first) {
22     Entry.second = Pool.size() - 1;
23     Entry.first = Asm.GetTempSymbol(Prefix, Entry.second);
24   }
25   return Entry;
26 }
27 
28 MCSymbol *DwarfStringPool::getSymbol(AsmPrinter &Asm, StringRef Str) {
29   return getEntry(Asm, Pool, Prefix, Str).first;
30 }
31 
32 unsigned DwarfStringPool::getIndex(AsmPrinter &Asm, StringRef Str) {
33   return getEntry(Asm, Pool, Prefix, Str).second;
34 }
35 
36 void DwarfStringPool::emit(AsmPrinter &Asm, const MCSection *StrSection,
37                            const MCSection *OffsetSection) {
38   if (Pool.empty())
39     return;
40 
41   // Start the dwarf str section.
42   Asm.OutStreamer.SwitchSection(StrSection);
43 
44   // Get all of the string pool entries and put them in an array by their ID so
45   // we can sort them.
46   SmallVector<const StringMapEntry<std::pair<MCSymbol *, unsigned>> *, 64>
47   Entries(Pool.size());
48 
49   for (const auto &E : Pool)
50     Entries[E.getValue().second] = &E;
51 
52   for (const auto &Entry : Entries) {
53     // Emit a label for reference from debug information entries.
54     Asm.OutStreamer.EmitLabel(Entry->getValue().first);
55 
56     // Emit the string itself with a terminating null byte.
57     Asm.OutStreamer.EmitBytes(
58         StringRef(Entry->getKeyData(), Entry->getKeyLength() + 1));
59   }
60 
61   // If we've got an offset section go ahead and emit that now as well.
62   if (OffsetSection) {
63     Asm.OutStreamer.SwitchSection(OffsetSection);
64     unsigned offset = 0;
65     unsigned size = 4; // FIXME: DWARF64 is 8.
66     for (const auto &Entry : Entries) {
67       Asm.OutStreamer.EmitIntValue(offset, size);
68       offset += Entry->getKeyLength() + 1;
69     }
70   }
71 }
72