1//===--- LayoutOverrideSource.cpp --Override Record Layouts ---------------===//
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#include "clang/Frontend/LayoutOverrideSource.h"
9#include "clang/AST/Decl.h"
10#include "clang/AST/DeclCXX.h"
11#include "clang/AST/Type.h"
12#include "clang/Basic/CharInfo.h"
13#include "llvm/Support/raw_ostream.h"
14#include <fstream>
15#include <string>
16
17using namespace clang;
18
19/// Parse a simple identifier.
20static std::string parseName(StringRef S) {
21 if (S.empty() || !isAsciiIdentifierStart(c: S[0]))
22 return "";
23
24 unsigned Offset = 1;
25 while (Offset < S.size() && isAsciiIdentifierContinue(c: S[Offset]))
26 ++Offset;
27
28 return S.substr(Start: 0, N: Offset).str();
29}
30
31/// Parse an unsigned integer and move S to the next non-digit character.
32static bool parseUnsigned(StringRef &S, unsigned long long &ULL) {
33 if (S.empty() || !isDigit(c: S[0]))
34 return false;
35 unsigned Idx = 1;
36 while (Idx < S.size() && isDigit(c: S[Idx]))
37 ++Idx;
38 (void)S.substr(Start: 0, N: Idx).getAsInteger(Radix: 10, Result&: ULL);
39 S = S.substr(Start: Idx);
40 return true;
41}
42
43LayoutOverrideSource::LayoutOverrideSource(StringRef Filename) {
44 std::ifstream Input(Filename.str().c_str());
45 if (!Input.is_open())
46 return;
47
48 // Parse the output of -fdump-record-layouts.
49 std::string CurrentType;
50 Layout CurrentLayout;
51 bool ExpectingType = false;
52
53 while (Input.good()) {
54 std::string Line;
55 getline(is&: Input, str&: Line);
56
57 StringRef LineStr(Line);
58
59 // Determine whether the following line will start a
60 if (LineStr.contains(Other: "*** Dumping AST Record Layout")) {
61 // Flush the last type/layout, if there is one.
62 if (!CurrentType.empty())
63 Layouts[CurrentType] = CurrentLayout;
64 CurrentLayout = Layout();
65
66 ExpectingType = true;
67 continue;
68 }
69
70 // If we're expecting a type, grab it.
71 if (ExpectingType) {
72 ExpectingType = false;
73
74 StringRef::size_type Pos;
75 if ((Pos = LineStr.find(Str: "struct ")) != StringRef::npos)
76 LineStr = LineStr.substr(Start: Pos + strlen(s: "struct "));
77 else if ((Pos = LineStr.find(Str: "class ")) != StringRef::npos)
78 LineStr = LineStr.substr(Start: Pos + strlen(s: "class "));
79 else if ((Pos = LineStr.find(Str: "union ")) != StringRef::npos)
80 LineStr = LineStr.substr(Start: Pos + strlen(s: "union "));
81 else
82 continue;
83
84 // Find the name of the type.
85 CurrentType = parseName(S: LineStr);
86 CurrentLayout = Layout();
87 continue;
88 }
89
90 // Check for the size of the type.
91 StringRef::size_type Pos = LineStr.find(Str: " Size:");
92 if (Pos != StringRef::npos) {
93 // Skip past the " Size:" prefix.
94 LineStr = LineStr.substr(Start: Pos + strlen(s: " Size:"));
95
96 unsigned long long Size = 0;
97 if (parseUnsigned(S&: LineStr, ULL&: Size))
98 CurrentLayout.Size = Size;
99 continue;
100 }
101
102 // Check for the alignment of the type.
103 Pos = LineStr.find(Str: "Alignment:");
104 if (Pos != StringRef::npos) {
105 // Skip past the "Alignment:" prefix.
106 LineStr = LineStr.substr(Start: Pos + strlen(s: "Alignment:"));
107
108 unsigned long long Alignment = 0;
109 if (parseUnsigned(S&: LineStr, ULL&: Alignment))
110 CurrentLayout.Align = Alignment;
111 continue;
112 }
113
114 // Check for the size/alignment of the type. The number follows "size=" or
115 // "align=" indicates number of bytes.
116 Pos = LineStr.find(Str: "sizeof=");
117 if (Pos != StringRef::npos) {
118 /* Skip past the sizeof= prefix. */
119 LineStr = LineStr.substr(Start: Pos + strlen(s: "sizeof="));
120
121 // Parse size.
122 unsigned long long Size = 0;
123 if (parseUnsigned(S&: LineStr, ULL&: Size))
124 CurrentLayout.Size = Size * 8;
125
126 Pos = LineStr.find(Str: "align=");
127 if (Pos != StringRef::npos) {
128 /* Skip past the align= prefix. */
129 LineStr = LineStr.substr(Start: Pos + strlen(s: "align="));
130
131 // Parse alignment.
132 unsigned long long Alignment = 0;
133 if (parseUnsigned(S&: LineStr, ULL&: Alignment))
134 CurrentLayout.Align = Alignment * 8;
135 }
136
137 continue;
138 }
139
140 // Check for the field offsets of the type.
141 Pos = LineStr.find(Str: "FieldOffsets: [");
142 if (Pos != StringRef::npos) {
143 LineStr = LineStr.substr(Start: Pos + strlen(s: "FieldOffsets: ["));
144 while (!LineStr.empty() && isDigit(c: LineStr[0])) {
145 unsigned long long Offset = 0;
146 if (parseUnsigned(S&: LineStr, ULL&: Offset))
147 CurrentLayout.FieldOffsets.push_back(Elt: Offset);
148
149 // Skip over this offset, the following comma, and any spaces.
150 LineStr = LineStr.substr(Start: 1);
151 LineStr = LineStr.drop_while(F: isWhitespace);
152 }
153 }
154
155 // Check for the virtual base offsets.
156 Pos = LineStr.find(Str: "VBaseOffsets: [");
157 if (Pos != StringRef::npos) {
158 LineStr = LineStr.substr(Start: Pos + strlen(s: "VBaseOffsets: ["));
159 while (!LineStr.empty() && isDigit(c: LineStr[0])) {
160 unsigned long long Offset = 0;
161 if (parseUnsigned(S&: LineStr, ULL&: Offset))
162 CurrentLayout.VBaseOffsets.push_back(Elt: CharUnits::fromQuantity(Quantity: Offset));
163
164 // Skip over this offset, the following comma, and any spaces.
165 LineStr = LineStr.substr(Start: 1);
166 LineStr = LineStr.drop_while(F: isWhitespace);
167 }
168 continue;
169 }
170
171 // Check for the base offsets.
172 Pos = LineStr.find(Str: "BaseOffsets: [");
173 if (Pos != StringRef::npos) {
174 LineStr = LineStr.substr(Start: Pos + strlen(s: "BaseOffsets: ["));
175 while (!LineStr.empty() && isDigit(c: LineStr[0])) {
176 unsigned long long Offset = 0;
177 if (parseUnsigned(S&: LineStr, ULL&: Offset))
178 CurrentLayout.BaseOffsets.push_back(Elt: CharUnits::fromQuantity(Quantity: Offset));
179
180 // Skip over this offset, the following comma, and any spaces.
181 LineStr = LineStr.substr(Start: 1);
182 LineStr = LineStr.drop_while(F: isWhitespace);
183 }
184 }
185 }
186
187 // Flush the last type/layout, if there is one.
188 if (!CurrentType.empty())
189 Layouts[CurrentType] = CurrentLayout;
190}
191
192bool
193LayoutOverrideSource::layoutRecordType(const RecordDecl *Record,
194 uint64_t &Size, uint64_t &Alignment,
195 llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
196 llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
197 llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets)
198{
199 // We can't override unnamed declarations.
200 if (!Record->getIdentifier())
201 return false;
202
203 // Check whether we have a layout for this record.
204 llvm::StringMap<Layout>::iterator Known = Layouts.find(Key: Record->getName());
205 if (Known == Layouts.end())
206 return false;
207
208 // Provide field layouts.
209 unsigned NumFields = 0;
210 for (RecordDecl::field_iterator F = Record->field_begin(),
211 FEnd = Record->field_end();
212 F != FEnd; ++F, ++NumFields) {
213 if (NumFields >= Known->second.FieldOffsets.size())
214 continue;
215
216 FieldOffsets[*F] = Known->second.FieldOffsets[NumFields];
217 }
218
219 // Wrong number of fields.
220 if (NumFields != Known->second.FieldOffsets.size())
221 return false;
222
223 // Provide base offsets.
224 if (const auto *RD = dyn_cast<CXXRecordDecl>(Val: Record)) {
225 unsigned NumNB = 0;
226 unsigned NumVB = 0;
227 for (const auto &I : RD->vbases()) {
228 if (NumVB >= Known->second.VBaseOffsets.size())
229 continue;
230 const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl();
231 VirtualBaseOffsets[VBase] = Known->second.VBaseOffsets[NumVB++];
232 }
233 for (const auto &I : RD->bases()) {
234 if (I.isVirtual() || NumNB >= Known->second.BaseOffsets.size())
235 continue;
236 const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl();
237 BaseOffsets[Base] = Known->second.BaseOffsets[NumNB++];
238 }
239 }
240
241 Size = Known->second.Size;
242 Alignment = Known->second.Align;
243 return true;
244}
245
246LLVM_DUMP_METHOD void LayoutOverrideSource::dump() {
247 raw_ostream &OS = llvm::errs();
248 for (llvm::StringMap<Layout>::iterator L = Layouts.begin(),
249 LEnd = Layouts.end();
250 L != LEnd; ++L) {
251 OS << "Type: blah " << L->first() << '\n';
252 OS << " Size:" << L->second.Size << '\n';
253 OS << " Alignment:" << L->second.Align << '\n';
254 OS << " FieldOffsets: [";
255 for (unsigned I = 0, N = L->second.FieldOffsets.size(); I != N; ++I) {
256 if (I)
257 OS << ", ";
258 OS << L->second.FieldOffsets[I];
259 }
260 OS << "]\n";
261 }
262}
263
264