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 16 using namespace clang; 17 18 /// Parse a simple identifier. 19 static std::string parseName(StringRef S) { 20 if (S.empty() || !isAsciiIdentifierStart(S[0])) 21 return ""; 22 23 unsigned Offset = 1; 24 while (Offset < S.size() && isAsciiIdentifierContinue(S[Offset])) 25 ++Offset; 26 27 return S.substr(0, Offset).str(); 28 } 29 30 /// Parse an unsigned integer and move S to the next non-digit character. 31 static bool parseUnsigned(StringRef &S, unsigned long long &ULL) { 32 if (S.empty() || !isDigit(S[0])) 33 return false; 34 unsigned Idx = 1; 35 while (Idx < S.size() && isDigit(S[Idx])) 36 ++Idx; 37 (void)S.substr(0, Idx).getAsInteger(10, ULL); 38 S = S.substr(Idx); 39 return true; 40 } 41 42 LayoutOverrideSource::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(Input, Line); 55 56 StringRef LineStr(Line); 57 58 // Determine whether the following line will start a 59 if (LineStr.contains("*** 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("struct ")) != StringRef::npos) 75 LineStr = LineStr.substr(Pos + strlen("struct ")); 76 else if ((Pos = LineStr.find("class ")) != StringRef::npos) 77 LineStr = LineStr.substr(Pos + strlen("class ")); 78 else if ((Pos = LineStr.find("union ")) != StringRef::npos) 79 LineStr = LineStr.substr(Pos + strlen("union ")); 80 else 81 continue; 82 83 // Find the name of the type. 84 CurrentType = parseName(LineStr); 85 CurrentLayout = Layout(); 86 continue; 87 } 88 89 // Check for the size of the type. 90 StringRef::size_type Pos = LineStr.find(" Size:"); 91 if (Pos != StringRef::npos) { 92 // Skip past the " Size:" prefix. 93 LineStr = LineStr.substr(Pos + strlen(" Size:")); 94 95 unsigned long long Size = 0; 96 if (parseUnsigned(LineStr, Size)) 97 CurrentLayout.Size = Size; 98 continue; 99 } 100 101 // Check for the alignment of the type. 102 Pos = LineStr.find("Alignment:"); 103 if (Pos != StringRef::npos) { 104 // Skip past the "Alignment:" prefix. 105 LineStr = LineStr.substr(Pos + strlen("Alignment:")); 106 107 unsigned long long Alignment = 0; 108 if (parseUnsigned(LineStr, 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("sizeof="); 116 if (Pos != StringRef::npos) { 117 /* Skip past the sizeof= prefix. */ 118 LineStr = LineStr.substr(Pos + strlen("sizeof=")); 119 120 // Parse size. 121 unsigned long long Size = 0; 122 if (parseUnsigned(LineStr, Size)) 123 CurrentLayout.Size = Size * 8; 124 125 Pos = LineStr.find("align="); 126 if (Pos != StringRef::npos) { 127 /* Skip past the align= prefix. */ 128 LineStr = LineStr.substr(Pos + strlen("align=")); 129 130 // Parse alignment. 131 unsigned long long Alignment = 0; 132 if (parseUnsigned(LineStr, 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("FieldOffsets: ["); 141 if (Pos != StringRef::npos) { 142 LineStr = LineStr.substr(Pos + strlen("FieldOffsets: [")); 143 while (!LineStr.empty() && isDigit(LineStr[0])) { 144 unsigned long long Offset = 0; 145 if (parseUnsigned(LineStr, Offset)) 146 CurrentLayout.FieldOffsets.push_back(Offset); 147 148 // Skip over this offset, the following comma, and any spaces. 149 LineStr = LineStr.substr(1); 150 while (!LineStr.empty() && isWhitespace(LineStr[0])) 151 LineStr = LineStr.substr(1); 152 } 153 } 154 155 // Check for the virtual base offsets. 156 Pos = LineStr.find("VBaseOffsets: ["); 157 if (Pos != StringRef::npos) { 158 LineStr = LineStr.substr(Pos + strlen("VBaseOffsets: [")); 159 while (!LineStr.empty() && isDigit(LineStr[0])) { 160 unsigned long long Offset = 0; 161 if (parseUnsigned(LineStr, Offset)) 162 CurrentLayout.VBaseOffsets.push_back(CharUnits::fromQuantity(Offset)); 163 164 // Skip over this offset, the following comma, and any spaces. 165 LineStr = LineStr.substr(1); 166 while (!LineStr.empty() && isWhitespace(LineStr[0])) 167 LineStr = LineStr.substr(1); 168 } 169 continue; 170 } 171 172 // Check for the base offsets. 173 Pos = LineStr.find("BaseOffsets: ["); 174 if (Pos != StringRef::npos) { 175 LineStr = LineStr.substr(Pos + strlen("BaseOffsets: [")); 176 while (!LineStr.empty() && isDigit(LineStr[0])) { 177 unsigned long long Offset = 0; 178 if (parseUnsigned(LineStr, Offset)) 179 CurrentLayout.BaseOffsets.push_back(CharUnits::fromQuantity(Offset)); 180 181 // Skip over this offset, the following comma, and any spaces. 182 LineStr = LineStr.substr(1); 183 while (!LineStr.empty() && isWhitespace(LineStr[0])) 184 LineStr = LineStr.substr(1); 185 } 186 } 187 } 188 189 // Flush the last type/layout, if there is one. 190 if (!CurrentType.empty()) 191 Layouts[CurrentType] = CurrentLayout; 192 } 193 194 bool 195 LayoutOverrideSource::layoutRecordType(const RecordDecl *Record, 196 uint64_t &Size, uint64_t &Alignment, 197 llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets, 198 llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets, 199 llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets) 200 { 201 // We can't override unnamed declarations. 202 if (!Record->getIdentifier()) 203 return false; 204 205 // Check whether we have a layout for this record. 206 llvm::StringMap<Layout>::iterator Known = Layouts.find(Record->getName()); 207 if (Known == Layouts.end()) 208 return false; 209 210 // Provide field layouts. 211 unsigned NumFields = 0; 212 for (RecordDecl::field_iterator F = Record->field_begin(), 213 FEnd = Record->field_end(); 214 F != FEnd; ++F, ++NumFields) { 215 if (NumFields >= Known->second.FieldOffsets.size()) 216 continue; 217 218 FieldOffsets[*F] = Known->second.FieldOffsets[NumFields]; 219 } 220 221 // Wrong number of fields. 222 if (NumFields != Known->second.FieldOffsets.size()) 223 return false; 224 225 // Provide base offsets. 226 if (const auto *RD = dyn_cast<CXXRecordDecl>(Record)) { 227 unsigned NumNB = 0; 228 unsigned NumVB = 0; 229 for (const auto &I : RD->vbases()) { 230 if (NumVB >= Known->second.VBaseOffsets.size()) 231 continue; 232 const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl(); 233 VirtualBaseOffsets[VBase] = Known->second.VBaseOffsets[NumVB++]; 234 } 235 for (const auto &I : RD->bases()) { 236 if (I.isVirtual() || NumNB >= Known->second.BaseOffsets.size()) 237 continue; 238 const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl(); 239 BaseOffsets[Base] = Known->second.BaseOffsets[NumNB++]; 240 } 241 } 242 243 Size = Known->second.Size; 244 Alignment = Known->second.Align; 245 return true; 246 } 247 248 LLVM_DUMP_METHOD void LayoutOverrideSource::dump() { 249 raw_ostream &OS = llvm::errs(); 250 for (llvm::StringMap<Layout>::iterator L = Layouts.begin(), 251 LEnd = Layouts.end(); 252 L != LEnd; ++L) { 253 OS << "Type: blah " << L->first() << '\n'; 254 OS << " Size:" << L->second.Size << '\n'; 255 OS << " Alignment:" << L->second.Align << '\n'; 256 OS << " FieldOffsets: ["; 257 for (unsigned I = 0, N = L->second.FieldOffsets.size(); I != N; ++I) { 258 if (I) 259 OS << ", "; 260 OS << L->second.FieldOffsets[I]; 261 } 262 OS << "]\n"; 263 } 264 } 265 266