LLVM 17.0.0git
DwarfStringPool.cpp
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1//===- llvm/CodeGen/DwarfStringPool.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 "DwarfStringPool.h"
11#include "llvm/ADT/Twine.h"
13#include "llvm/MC/MCAsmInfo.h"
14#include "llvm/MC/MCStreamer.h"
15#include <cassert>
16#include <utility>
17
18using namespace llvm;
19
21 StringRef Prefix)
22 : Pool(A), Prefix(Prefix),
23 ShouldCreateSymbols(Asm.doesDwarfUseRelocationsAcrossSections()) {}
24
26DwarfStringPool::getEntryImpl(AsmPrinter &Asm, StringRef Str) {
27 auto I = Pool.insert(std::make_pair(Str, EntryTy()));
28 auto &Entry = I.first->second;
29 if (I.second) {
30 Entry.Index = EntryTy::NotIndexed;
31 Entry.Offset = NumBytes;
32 Entry.Symbol = ShouldCreateSymbols ? Asm.createTempSymbol(Prefix) : nullptr;
33
34 NumBytes += Str.size() + 1;
35 }
36 return *I.first;
37}
38
40 StringRef Str) {
41 auto &MapEntry = getEntryImpl(Asm, Str);
42 return EntryRef(MapEntry);
43}
44
46 StringRef Str) {
47 auto &MapEntry = getEntryImpl(Asm, Str);
48 if (!MapEntry.getValue().isIndexed())
49 MapEntry.getValue().Index = NumIndexedStrings++;
50 return EntryRef(MapEntry);
51}
52
54 MCSection *Section,
55 MCSymbol *StartSym) {
56 if (getNumIndexedStrings() == 0)
57 return;
58 Asm.OutStreamer->switchSection(Section);
59 unsigned EntrySize = Asm.getDwarfOffsetByteSize();
60 // We are emitting the header for a contribution to the string offsets
61 // table. The header consists of an entry with the contribution's
62 // size (not including the size of the length field), the DWARF version and
63 // 2 bytes of padding.
64 Asm.emitDwarfUnitLength(getNumIndexedStrings() * EntrySize + 4,
65 "Length of String Offsets Set");
66 Asm.emitInt16(Asm.getDwarfVersion());
67 Asm.emitInt16(0);
68 // Define the symbol that marks the start of the contribution. It is
69 // referenced by most unit headers via DW_AT_str_offsets_base.
70 // Split units do not use the attribute.
71 if (StartSym)
72 Asm.OutStreamer->emitLabel(StartSym);
73}
74
76 MCSection *OffsetSection, bool UseRelativeOffsets) {
77 if (Pool.empty())
78 return;
79
80 // Start the dwarf str section.
81 Asm.OutStreamer->switchSection(StrSection);
82
83 // Get all of the string pool entries and sort them by their offset.
85 Entries.reserve(Pool.size());
86
87 for (const auto &E : Pool)
88 Entries.push_back(&E);
89
90 llvm::sort(Entries, [](const StringMapEntry<EntryTy> *A,
92 return A->getValue().Offset < B->getValue().Offset;
93 });
94
95 for (const auto &Entry : Entries) {
96 assert(ShouldCreateSymbols == static_cast<bool>(Entry->getValue().Symbol) &&
97 "Mismatch between setting and entry");
98
99 // Emit a label for reference from debug information entries.
100 if (ShouldCreateSymbols)
101 Asm.OutStreamer->emitLabel(Entry->getValue().Symbol);
102
103 // Emit the string itself with a terminating null byte.
104 Asm.OutStreamer->AddComment("string offset=" +
105 Twine(Entry->getValue().Offset));
106 Asm.OutStreamer->emitBytes(
107 StringRef(Entry->getKeyData(), Entry->getKeyLength() + 1));
108 }
109
110 // If we've got an offset section go ahead and emit that now as well.
111 if (OffsetSection) {
112 // Now only take the indexed entries and put them in an array by their ID so
113 // we can emit them in order.
114 Entries.resize(NumIndexedStrings);
115 for (const auto &Entry : Pool) {
116 if (Entry.getValue().isIndexed())
117 Entries[Entry.getValue().Index] = &Entry;
118 }
119
120 Asm.OutStreamer->switchSection(OffsetSection);
121 unsigned size = Asm.getDwarfOffsetByteSize();
122 for (const auto &Entry : Entries)
123 if (UseRelativeOffsets)
124 Asm.emitDwarfStringOffset(Entry->getValue());
125 else
126 Asm.OutStreamer->emitIntValue(Entry->getValue().Offset, size);
127 }
128}
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
#define I(x, y, z)
Definition: MD5.cpp:58
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallVector class.
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:84
Allocate memory in an ever growing pool, as if by bump-pointer.
Definition: Allocator.h:66
DwarfStringPoolEntryRef: Dwarf string pool entry reference.
EntryRef getEntry(AsmPrinter &Asm, StringRef Str)
Get a reference to an entry in the string pool.
EntryRef getIndexedEntry(AsmPrinter &Asm, StringRef Str)
Same as getEntry, except that you can use EntryRef::getIndex to obtain a unique ID of this entry (e....
DwarfStringPoolEntryRef EntryRef
unsigned getNumIndexedStrings() const
void emitStringOffsetsTableHeader(AsmPrinter &Asm, MCSection *OffsetSection, MCSymbol *StartSym)
unsigned size() const
DwarfStringPool(BumpPtrAllocator &A, AsmPrinter &Asm, StringRef Prefix)
void emit(AsmPrinter &Asm, MCSection *StrSection, MCSection *OffsetSection=nullptr, bool UseRelativeOffsets=false)
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:39
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
StringMapEntry - This is used to represent one value that is inserted into a StringMap.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ Offset
Definition: DWP.cpp:406
void sort(IteratorTy Start, IteratorTy End)
Definition: STLExtras.h:1683
static constexpr unsigned NotIndexed