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
15using namespace clang;
16
17/// Parse a simple identifier.
18static 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
29LayoutOverrideSource::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
154bool
155LayoutOverrideSource::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
190LLVM_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