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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.
     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 
     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
    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 
    191 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