LLVM 20.0.0git
StringTableBuilder.cpp
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1//===- StringTableBuilder.cpp - String table building utility -------------===//
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
10#include "llvm/ADT/ArrayRef.h"
13#include "llvm/ADT/StringRef.h"
15#include "llvm/Support/Endian.h"
18#include <cassert>
19#include <cstddef>
20#include <cstdint>
21#include <cstring>
22#include <utility>
23#include <vector>
24
25using namespace llvm;
26
28
29void StringTableBuilder::initSize() {
30 // Account for leading bytes in table so that offsets returned from add are
31 // correct.
32 switch (K) {
33 case RAW:
34 case DWARF:
35 Size = 0;
36 break;
37 case MachOLinked:
38 case MachO64Linked:
39 Size = 2;
40 break;
41 case MachO:
42 case MachO64:
43 case ELF:
44 case DXContainer:
45 // Start the table with a NUL byte.
46 Size = 1;
47 break;
48 case XCOFF:
49 case WinCOFF:
50 // Make room to write the table size later.
51 Size = 4;
52 break;
53 }
54}
55
57 : K(K), Alignment(Alignment) {
58 initSize();
59}
60
64 Data.resize(getSize());
65 write((uint8_t *)Data.data());
66 OS << Data;
67}
68
69using StringPair = std::pair<CachedHashStringRef, size_t>;
70
71void StringTableBuilder::write(uint8_t *Buf) const {
73 for (const StringPair &P : StringIndexMap) {
74 StringRef Data = P.first.val();
75 if (!Data.empty())
76 memcpy(Buf + P.second, Data.data(), Data.size());
77 }
78 // The COFF formats store the size of the string table in the first 4 bytes.
79 // For Windows, the format is little-endian; for AIX, it is big-endian.
80 if (K == WinCOFF)
82 else if (K == XCOFF)
84}
85
86// Returns the character at Pos from end of a string.
87static int charTailAt(StringPair *P, size_t Pos) {
88 StringRef S = P->first.val();
89 if (Pos >= S.size())
90 return -1;
91 return (unsigned char)S[S.size() - Pos - 1];
92}
93
94// Three-way radix quicksort. This is much faster than std::sort with strcmp
95// because it does not compare characters that we already know the same.
97tailcall:
98 if (Vec.size() <= 1)
99 return;
100
101 // Partition items so that items in [0, I) are greater than the pivot,
102 // [I, J) are the same as the pivot, and [J, Vec.size()) are less than
103 // the pivot.
104 int Pivot = charTailAt(Vec[0], Pos);
105 size_t I = 0;
106 size_t J = Vec.size();
107 for (size_t K = 1; K < J;) {
108 int C = charTailAt(Vec[K], Pos);
109 if (C > Pivot)
110 std::swap(Vec[I++], Vec[K++]);
111 else if (C < Pivot)
112 std::swap(Vec[--J], Vec[K]);
113 else
114 K++;
115 }
116
117 multikeySort(Vec.slice(0, I), Pos);
118 multikeySort(Vec.slice(J), Pos);
119
120 // multikeySort(Vec.slice(I, J - I), Pos + 1), but with
121 // tail call optimization.
122 if (Pivot != -1) {
123 Vec = Vec.slice(I, J - I);
124 ++Pos;
125 goto tailcall;
126 }
127}
128
130 assert(K != DWARF);
131 finalizeStringTable(/*Optimize=*/true);
132}
133
135 finalizeStringTable(/*Optimize=*/false);
136}
137
138void StringTableBuilder::finalizeStringTable(bool Optimize) {
139 Finalized = true;
140
141 if (Optimize) {
142 std::vector<StringPair *> Strings;
143 Strings.reserve(StringIndexMap.size());
144 for (StringPair &P : StringIndexMap)
145 Strings.push_back(&P);
146
147 multikeySort(Strings, 0);
148 initSize();
149
150 StringRef Previous;
151 for (StringPair *P : Strings) {
152 StringRef S = P->first.val();
153 if (Previous.ends_with(S)) {
154 size_t Pos = Size - S.size() - (K != RAW);
155 if (isAligned(Alignment, Pos)) {
156 P->second = Pos;
157 continue;
158 }
159 }
160
161 Size = alignTo(Size, Alignment);
162 P->second = Size;
163
164 Size += S.size();
165 if (K != RAW)
166 ++Size;
167 Previous = S;
168 }
169 }
170
171 if (K == MachO || K == MachOLinked || K == DXContainer)
172 Size = alignTo(Size, 4); // Pad to multiple of 4.
173 if (K == MachO64 || K == MachO64Linked)
174 Size = alignTo(Size, 8); // Pad to multiple of 8.
175
176 // According to ld64 the string table of a final linked Mach-O binary starts
177 // with " ", i.e. the first byte is ' ' and the second byte is zero. In
178 // 'initSize()' we reserved the first two bytes for holding this string.
179 if (K == MachOLinked || K == MachO64Linked)
180 StringIndexMap[CachedHashStringRef(" ")] = 0;
181
182 // The first byte in an ELF string table must be null, according to the ELF
183 // specification. In 'initSize()' we reserved the first byte to hold null for
184 // this purpose and here we actually add the string to allow 'getOffset()' to
185 // be called on an empty string.
186 if (K == ELF)
187 StringIndexMap[CachedHashStringRef("")] = 0;
188}
189
191 Finalized = false;
192 StringIndexMap.clear();
193}
194
197 auto I = StringIndexMap.find(S);
198 assert(I != StringIndexMap.end() && "String is not in table!");
199 return I->second;
200}
201
203 if (K == WinCOFF)
204 assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
205
207 auto P = StringIndexMap.insert(std::make_pair(S, 0));
208 if (P.second) {
209 size_t Start = alignTo(Size, Alignment);
210 P.first->second = Start;
211 Size = Start + S.size() + (K != RAW);
212 }
213 return P.first->second;
214}
This file defines CachedHashString and CachedHashStringRef.
#define I(x, y, z)
Definition: MD5.cpp:58
#define P(N)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
This file defines the SmallString class.
static int charTailAt(StringPair *P, size_t Pos)
std::pair< CachedHashStringRef, size_t > StringPair
static void multikeySort(MutableArrayRef< StringPair * > Vec, int Pos)
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:165
A container which contains a StringRef plus a precomputed hash.
MutableArrayRef - Represent a mutable reference to an array (0 or more elements consecutively in memo...
Definition: ArrayRef.h:307
MutableArrayRef< T > slice(size_t N, size_t M) const
slice(n, m) - Chop off the first N elements of the array, and keep M elements in the array.
Definition: ArrayRef.h:376
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition: SmallString.h:26
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
constexpr size_t size() const
size - Get the string size.
Definition: StringRef.h:137
bool ends_with(StringRef Suffix) const
Check if this string ends with the given Suffix.
Definition: StringRef.h:262
void finalizeInOrder()
Finalize the string table without reording it.
size_t getOffset(CachedHashStringRef S) const
Get the offest of a string in the string table.
void write(raw_ostream &OS) const
size_t add(CachedHashStringRef S)
Add a string to the builder.
void finalize()
Analyze the strings and build the final table.
StringTableBuilder(Kind K, Align Alignment=Align(1))
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
@ NameSize
Definition: COFF.h:57
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
void write32le(void *P, uint32_t V)
Definition: Endian.h:468
void write32be(void *P, uint32_t V)
Definition: Endian.h:477
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
bool isAligned(Align Lhs, uint64_t SizeInBytes)
Checks that SizeInBytes is a multiple of the alignment.
Definition: Alignment.h:145
uint64_t alignTo(uint64_t Size, Align A)
Returns a multiple of A needed to store Size bytes.
Definition: Alignment.h:155
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:860
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39