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/Basic/CharInfo.h"
11 #include "llvm/Support/raw_ostream.h"
12 #include <fstream>
13 #include <string>
14 
15 using namespace clang;
16 
17 /// Parse a simple identifier.
18 static std::string parseName(StringRef S) {
19   if (S.empty() || !isIdentifierHead(S[0]))
20     return "";
21 
22   unsigned Offset = 1;
23   while (Offset < S.size() && isIdentifierBody(S[Offset]))
24     ++Offset;
25 
26   return S.substr(0, Offset).str();
27 }
28 
29 LayoutOverrideSource::LayoutOverrideSource(StringRef Filename) {
30   std::ifstream Input(Filename.str().c_str());
31   if (!Input.is_open())
32     return;
33 
34   // Parse the output of -fdump-record-layouts.
35   std::string CurrentType;
36   Layout CurrentLayout;
37   bool ExpectingType = false;
38 
39   while (Input.good()) {
40     std::string Line;
41     getline(Input, Line);
42 
43     StringRef LineStr(Line);
44 
45     // Determine whether the following line will start a
46     if (LineStr.find("*** Dumping AST Record Layout") != StringRef::npos)  {
47       // Flush the last type/layout, if there is one.
48       if (!CurrentType.empty())
49         Layouts[CurrentType] = CurrentLayout;
50       CurrentLayout = Layout();
51 
52       ExpectingType = true;
53       continue;
54     }
55 
56     // If we're expecting a type, grab it.
57     if (ExpectingType) {
58       ExpectingType = false;
59 
60       StringRef::size_type Pos;
61       if ((Pos = LineStr.find("struct ")) != StringRef::npos)
62         LineStr = LineStr.substr(Pos + strlen("struct "));
63       else if ((Pos = LineStr.find("class ")) != StringRef::npos)
64         LineStr = LineStr.substr(Pos + strlen("class "));
65       else if ((Pos = LineStr.find("union ")) != StringRef::npos)
66         LineStr = LineStr.substr(Pos + strlen("union "));
67       else
68         continue;
69 
70       // Find the name of the type.
71       CurrentType = parseName(LineStr);
72       CurrentLayout = Layout();
73       continue;
74     }
75 
76     // Check for the size of the type.
77     StringRef::size_type Pos = LineStr.find(" Size:");
78     if (Pos != StringRef::npos) {
79       // Skip past the " Size:" prefix.
80       LineStr = LineStr.substr(Pos + strlen(" Size:"));
81 
82       unsigned long long Size = 0;
83       (void)LineStr.getAsInteger(10, Size);
84       CurrentLayout.Size = Size;
85       continue;
86     }
87 
88     // Check for the alignment of the type.
89     Pos = LineStr.find("Alignment:");
90     if (Pos != StringRef::npos) {
91       // Skip past the "Alignment:" prefix.
92       LineStr = LineStr.substr(Pos + strlen("Alignment:"));
93 
94       unsigned long long Alignment = 0;
95       (void)LineStr.getAsInteger(10, Alignment);
96       CurrentLayout.Align = Alignment;
97       continue;
98     }
99 
100     // Check for the size/alignment of the type.
101     Pos = LineStr.find("sizeof=");
102     if (Pos != StringRef::npos) {
103       /* Skip past the sizeof= prefix. */
104       LineStr = LineStr.substr(Pos + strlen("sizeof="));
105 
106       // Parse size.
107       unsigned long long Size = 0;
108       (void)LineStr.getAsInteger(10, Size);
109       CurrentLayout.Size = Size;
110 
111       Pos = LineStr.find("align=");
112       if (Pos != StringRef::npos) {
113         /* Skip past the align= prefix. */
114         LineStr = LineStr.substr(Pos + strlen("align="));
115 
116         // Parse alignment.
117         unsigned long long Alignment = 0;
118         (void)LineStr.getAsInteger(10, Alignment);
119         CurrentLayout.Align = Alignment;
120       }
121 
122       continue;
123     }
124 
125     // Check for the field offsets of the type.
126     Pos = LineStr.find("FieldOffsets: [");
127     if (Pos == StringRef::npos)
128       continue;
129 
130     LineStr = LineStr.substr(Pos + strlen("FieldOffsets: ["));
131     while (!LineStr.empty() && isDigit(LineStr[0])) {
132       // Parse this offset.
133       unsigned Idx = 1;
134       while (Idx < LineStr.size() && isDigit(LineStr[Idx]))
135         ++Idx;
136 
137       unsigned long long Offset = 0;
138       (void)LineStr.substr(0, Idx).getAsInteger(10, Offset);
139 
140       CurrentLayout.FieldOffsets.push_back(Offset);
141 
142       // Skip over this offset, the following comma, and any spaces.
143       LineStr = LineStr.substr(Idx + 1);
144       while (!LineStr.empty() && isWhitespace(LineStr[0]))
145         LineStr = LineStr.substr(1);
146     }
147   }
148 
149   // Flush the last type/layout, if there is one.
150   if (!CurrentType.empty())
151     Layouts[CurrentType] = CurrentLayout;
152 }
153 
154 bool
155 LayoutOverrideSource::layoutRecordType(const RecordDecl *Record,
156   uint64_t &Size, uint64_t &Alignment,
157   llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
158   llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
159   llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets)
160 {
161   // We can't override unnamed declarations.
162   if (!Record->getIdentifier())
163     return false;
164 
165   // Check whether we have a layout for this record.
166   llvm::StringMap<Layout>::iterator Known = Layouts.find(Record->getName());
167   if (Known == Layouts.end())
168     return false;
169 
170   // Provide field layouts.
171   unsigned NumFields = 0;
172   for (RecordDecl::field_iterator F = Record->field_begin(),
173                                FEnd = Record->field_end();
174        F != FEnd; ++F, ++NumFields) {
175     if (NumFields >= Known->second.FieldOffsets.size())
176       continue;
177 
178     FieldOffsets[*F] = Known->second.FieldOffsets[NumFields];
179   }
180 
181   // Wrong number of fields.
182   if (NumFields != Known->second.FieldOffsets.size())
183     return false;
184 
185   Size = Known->second.Size;
186   Alignment = Known->second.Align;
187   return true;
188 }
189 
190 LLVM_DUMP_METHOD void LayoutOverrideSource::dump() {
191   raw_ostream &OS = llvm::errs();
192   for (llvm::StringMap<Layout>::iterator L = Layouts.begin(),
193                                       LEnd = Layouts.end();
194        L != LEnd; ++L) {
195     OS << "Type: blah " << L->first() << '\n';
196     OS << "  Size:" << L->second.Size << '\n';
197     OS << "  Alignment:" << L->second.Align << '\n';
198     OS << "  FieldOffsets: [";
199     for (unsigned I = 0, N = L->second.FieldOffsets.size(); I != N; ++I) {
200       if (I)
201         OS << ", ";
202       OS << L->second.FieldOffsets[I];
203     }
204     OS << "]\n";
205   }
206 }
207 
208