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