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1 //===--- LayoutOverrideSource.cpp --Override Record Layouts ---------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 #include "clang/Frontend/LayoutOverrideSource.h"
10 #include "clang/AST/Decl.h"
11 #include "clang/Basic/CharInfo.h"
12 #include "llvm/Support/raw_ostream.h"
13 #include <fstream>
14 #include <string>
15 
16 using namespace clang;
17 
18 /// \brief Parse a simple identifier.
parseName(StringRef S)19 static std::string parseName(StringRef S) {
20   if (S.empty() || !isIdentifierHead(S[0]))
21     return "";
22 
23   unsigned Offset = 1;
24   while (Offset < S.size() && isIdentifierBody(S[Offset]))
25     ++Offset;
26 
27   return S.substr(0, Offset).str();
28 }
29 
LayoutOverrideSource(StringRef Filename)30 LayoutOverrideSource::LayoutOverrideSource(StringRef Filename) {
31   std::ifstream Input(Filename.str().c_str());
32   if (!Input.is_open())
33     return;
34 
35   // Parse the output of -fdump-record-layouts.
36   std::string CurrentType;
37   Layout CurrentLayout;
38   bool ExpectingType = false;
39 
40   while (Input.good()) {
41     std::string Line;
42     getline(Input, Line);
43 
44     StringRef LineStr(Line);
45 
46     // Determine whether the following line will start a
47     if (LineStr.find("*** Dumping AST Record Layout") != StringRef::npos)  {
48       // Flush the last type/layout, if there is one.
49       if (!CurrentType.empty())
50         Layouts[CurrentType] = CurrentLayout;
51       CurrentLayout = Layout();
52 
53       ExpectingType = true;
54       continue;
55     }
56 
57     // If we're expecting a type, grab it.
58     if (ExpectingType) {
59       ExpectingType = false;
60 
61       StringRef::size_type Pos;
62       if ((Pos = LineStr.find("struct ")) != StringRef::npos)
63         LineStr = LineStr.substr(Pos + strlen("struct "));
64       else if ((Pos = LineStr.find("class ")) != StringRef::npos)
65         LineStr = LineStr.substr(Pos + strlen("class "));
66       else if ((Pos = LineStr.find("union ")) != StringRef::npos)
67         LineStr = LineStr.substr(Pos + strlen("union "));
68       else
69         continue;
70 
71       // Find the name of the type.
72       CurrentType = parseName(LineStr);
73       CurrentLayout = Layout();
74       continue;
75     }
76 
77     // Check for the size of the type.
78     StringRef::size_type Pos = LineStr.find(" Size:");
79     if (Pos != StringRef::npos) {
80       // Skip past the " Size:" prefix.
81       LineStr = LineStr.substr(Pos + strlen(" Size:"));
82 
83       unsigned long long Size = 0;
84       (void)LineStr.getAsInteger(10, Size);
85       CurrentLayout.Size = Size;
86       continue;
87     }
88 
89     // Check for the alignment of the type.
90     Pos = LineStr.find("Alignment:");
91     if (Pos != StringRef::npos) {
92       // Skip past the "Alignment:" prefix.
93       LineStr = LineStr.substr(Pos + strlen("Alignment:"));
94 
95       unsigned long long Alignment = 0;
96       (void)LineStr.getAsInteger(10, Alignment);
97       CurrentLayout.Align = Alignment;
98       continue;
99     }
100 
101     // Check for the size/alignment of the type.
102     Pos = LineStr.find("sizeof=");
103     if (Pos != StringRef::npos) {
104       /* Skip past the sizeof= prefix. */
105       LineStr = LineStr.substr(Pos + strlen("sizeof="));
106 
107       // Parse size.
108       unsigned long long Size = 0;
109       (void)LineStr.getAsInteger(10, Size);
110       CurrentLayout.Size = Size;
111 
112       Pos = LineStr.find("align=");
113       if (Pos != StringRef::npos) {
114         /* Skip past the align= prefix. */
115         LineStr = LineStr.substr(Pos + strlen("align="));
116 
117         // Parse alignment.
118         unsigned long long Alignment = 0;
119         (void)LineStr.getAsInteger(10, Alignment);
120         CurrentLayout.Align = Alignment;
121       }
122 
123       continue;
124     }
125 
126     // Check for the field offsets of the type.
127     Pos = LineStr.find("FieldOffsets: [");
128     if (Pos == StringRef::npos)
129       continue;
130 
131     LineStr = LineStr.substr(Pos + strlen("FieldOffsets: ["));
132     while (!LineStr.empty() && isDigit(LineStr[0])) {
133       // Parse this offset.
134       unsigned Idx = 1;
135       while (Idx < LineStr.size() && isDigit(LineStr[Idx]))
136         ++Idx;
137 
138       unsigned long long Offset = 0;
139       (void)LineStr.substr(0, Idx).getAsInteger(10, Offset);
140 
141       CurrentLayout.FieldOffsets.push_back(Offset);
142 
143       // Skip over this offset, the following comma, and any spaces.
144       LineStr = LineStr.substr(Idx + 1);
145       while (!LineStr.empty() && isWhitespace(LineStr[0]))
146         LineStr = LineStr.substr(1);
147     }
148   }
149 
150   // Flush the last type/layout, if there is one.
151   if (!CurrentType.empty())
152     Layouts[CurrentType] = CurrentLayout;
153 }
154 
155 bool
layoutRecordType(const RecordDecl * Record,uint64_t & Size,uint64_t & Alignment,llvm::DenseMap<const FieldDecl *,uint64_t> & FieldOffsets,llvm::DenseMap<const CXXRecordDecl *,CharUnits> & BaseOffsets,llvm::DenseMap<const CXXRecordDecl *,CharUnits> & VirtualBaseOffsets)156 LayoutOverrideSource::layoutRecordType(const RecordDecl *Record,
157   uint64_t &Size, uint64_t &Alignment,
158   llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
159   llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
160   llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets)
161 {
162   // We can't override unnamed declarations.
163   if (!Record->getIdentifier())
164     return false;
165 
166   // Check whether we have a layout for this record.
167   llvm::StringMap<Layout>::iterator Known = Layouts.find(Record->getName());
168   if (Known == Layouts.end())
169     return false;
170 
171   // Provide field layouts.
172   unsigned NumFields = 0;
173   for (RecordDecl::field_iterator F = Record->field_begin(),
174                                FEnd = Record->field_end();
175        F != FEnd; ++F, ++NumFields) {
176     if (NumFields >= Known->second.FieldOffsets.size())
177       continue;
178 
179     FieldOffsets[*F] = Known->second.FieldOffsets[NumFields];
180   }
181 
182   // Wrong number of fields.
183   if (NumFields != Known->second.FieldOffsets.size())
184     return false;
185 
186   Size = Known->second.Size;
187   Alignment = Known->second.Align;
188   return true;
189 }
190 
dump()191 LLVM_DUMP_METHOD void LayoutOverrideSource::dump() {
192   raw_ostream &OS = llvm::errs();
193   for (llvm::StringMap<Layout>::iterator L = Layouts.begin(),
194                                       LEnd = Layouts.end();
195        L != LEnd; ++L) {
196     OS << "Type: blah " << L->first() << '\n';
197     OS << "  Size:" << L->second.Size << '\n';
198     OS << "  Alignment:" << L->second.Align << '\n';
199     OS << "  FieldOffsets: [";
200     for (unsigned I = 0, N = L->second.FieldOffsets.size(); I != N; ++I) {
201       if (I)
202         OS << ", ";
203       OS << L->second.FieldOffsets[I];
204     }
205     OS << "]\n";
206   }
207 }
208 
209