1//===- UDTLayout.cpp ------------------------------------------------------===//
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
9#include "llvm/DebugInfo/PDB/UDTLayout.h"
10#include "llvm/ADT/ArrayRef.h"
11#include "llvm/ADT/BitVector.h"
12#include "llvm/ADT/STLExtras.h"
13#include "llvm/DebugInfo/PDB/IPDBEnumChildren.h"
14#include "llvm/DebugInfo/PDB/IPDBLineNumber.h"
15#include "llvm/DebugInfo/PDB/IPDBRawSymbol.h"
16#include "llvm/DebugInfo/PDB/IPDBSession.h"
17#include "llvm/DebugInfo/PDB/PDBSymbol.h"
18#include "llvm/DebugInfo/PDB/PDBSymbolData.h"
19#include "llvm/DebugInfo/PDB/PDBSymbolFunc.h"
20#include "llvm/DebugInfo/PDB/PDBSymbolTypeBaseClass.h"
21#include "llvm/DebugInfo/PDB/PDBSymbolTypeBuiltin.h"
22#include "llvm/DebugInfo/PDB/PDBSymbolTypeFunctionSig.h"
23#include "llvm/DebugInfo/PDB/PDBSymbolTypePointer.h"
24#include "llvm/DebugInfo/PDB/PDBSymbolTypeUDT.h"
25#include "llvm/DebugInfo/PDB/PDBSymbolTypeVTable.h"
26#include "llvm/DebugInfo/PDB/PDBTypes.h"
27#include "llvm/Support/Casting.h"
28#include <algorithm>
29#include <cassert>
30#include <cstdint>
31#include <memory>
32
33using namespace llvm;
34using namespace llvm::pdb;
35
36static std::unique_ptr<PDBSymbol> getSymbolType(const PDBSymbol &Symbol) {
37 const IPDBSession &Session = Symbol.getSession();
38 const IPDBRawSymbol &RawSymbol = Symbol.getRawSymbol();
39 uint32_t TypeId = RawSymbol.getTypeId();
40 return Session.getSymbolById(SymbolId: TypeId);
41}
42
43static uint32_t getTypeLength(const PDBSymbol &Symbol) {
44 auto SymbolType = getSymbolType(Symbol);
45 const IPDBRawSymbol &RawType = SymbolType->getRawSymbol();
46
47 return RawType.getLength();
48}
49
50LayoutItemBase::LayoutItemBase(const UDTLayoutBase *Parent,
51 const PDBSymbol *Symbol, const std::string &Name,
52 uint32_t OffsetInParent, uint32_t Size,
53 bool IsElided)
54 : Symbol(Symbol), Parent(Parent), Name(Name),
55 OffsetInParent(OffsetInParent), SizeOf(Size), LayoutSize(Size),
56 IsElided(IsElided) {
57 UsedBytes.resize(N: SizeOf, t: true);
58}
59
60uint32_t LayoutItemBase::deepPaddingSize() const {
61 return UsedBytes.size() - UsedBytes.count();
62}
63
64uint32_t LayoutItemBase::tailPadding() const {
65 int Last = UsedBytes.find_last();
66
67 return UsedBytes.size() - (Last + 1);
68}
69
70DataMemberLayoutItem::DataMemberLayoutItem(
71 const UDTLayoutBase &Parent, std::unique_ptr<PDBSymbolData> Member)
72 : LayoutItemBase(&Parent, Member.get(), Member->getName(),
73 Member->getOffset(), getTypeLength(Symbol: *Member), false),
74 DataMember(std::move(Member)) {
75 auto Type = DataMember->getType();
76 if (auto UDT = unique_dyn_cast<PDBSymbolTypeUDT>(Val&: Type)) {
77 UdtLayout = std::make_unique<ClassLayout>(args: std::move(UDT));
78 UsedBytes = UdtLayout->usedBytes();
79 }
80}
81
82VBPtrLayoutItem::VBPtrLayoutItem(const UDTLayoutBase &Parent,
83 std::unique_ptr<PDBSymbolTypeBuiltin> Sym,
84 uint32_t Offset, uint32_t Size)
85 : LayoutItemBase(&Parent, Sym.get(), "<vbptr>", Offset, Size, false),
86 Type(std::move(Sym)) {
87}
88
89const PDBSymbolData &DataMemberLayoutItem::getDataMember() {
90 return *cast<PDBSymbolData>(Val: Symbol);
91}
92
93bool DataMemberLayoutItem::hasUDTLayout() const { return UdtLayout != nullptr; }
94
95const ClassLayout &DataMemberLayoutItem::getUDTLayout() const {
96 return *UdtLayout;
97}
98
99VTableLayoutItem::VTableLayoutItem(const UDTLayoutBase &Parent,
100 std::unique_ptr<PDBSymbolTypeVTable> VT)
101 : LayoutItemBase(&Parent, VT.get(), "<vtbl>", 0, getTypeLength(Symbol: *VT), false),
102 VTable(std::move(VT)) {
103 auto VTableType = cast<PDBSymbolTypePointer>(Val: VTable->getType());
104 ElementSize = VTableType->getLength();
105}
106
107UDTLayoutBase::UDTLayoutBase(const UDTLayoutBase *Parent, const PDBSymbol &Sym,
108 const std::string &Name, uint32_t OffsetInParent,
109 uint32_t Size, bool IsElided)
110 : LayoutItemBase(Parent, &Sym, Name, OffsetInParent, Size, IsElided) {
111 // UDT storage comes from a union of all the children's storage, so start out
112 // uninitialized.
113 UsedBytes.reset(I: 0, E: Size);
114
115 initializeChildren(Sym);
116 if (LayoutSize < Size)
117 UsedBytes.resize(N: LayoutSize);
118}
119
120uint32_t UDTLayoutBase::tailPadding() const {
121 uint32_t Abs = LayoutItemBase::tailPadding();
122 if (!LayoutItems.empty()) {
123 const LayoutItemBase *Back = LayoutItems.back();
124 uint32_t ChildPadding = Back->LayoutItemBase::tailPadding();
125 if (Abs < ChildPadding)
126 Abs = 0;
127 else
128 Abs -= ChildPadding;
129 }
130 return Abs;
131}
132
133ClassLayout::ClassLayout(const PDBSymbolTypeUDT &UDT)
134 : UDTLayoutBase(nullptr, UDT, UDT.getName(), 0, UDT.getLength(), false),
135 UDT(UDT) {
136 ImmediateUsedBytes.resize(N: SizeOf, t: false);
137 for (auto &LI : LayoutItems) {
138 uint32_t Begin = LI->getOffsetInParent();
139 uint32_t End = Begin + LI->getLayoutSize();
140 End = std::min(a: SizeOf, b: End);
141 ImmediateUsedBytes.set(I: Begin, E: End);
142 }
143}
144
145ClassLayout::ClassLayout(std::unique_ptr<PDBSymbolTypeUDT> UDT)
146 : ClassLayout(*UDT) {
147 OwnedStorage = std::move(UDT);
148}
149
150uint32_t ClassLayout::immediatePadding() const {
151 return SizeOf - ImmediateUsedBytes.count();
152}
153
154BaseClassLayout::BaseClassLayout(const UDTLayoutBase &Parent,
155 uint32_t OffsetInParent, bool Elide,
156 std::unique_ptr<PDBSymbolTypeBaseClass> B)
157 : UDTLayoutBase(&Parent, *B, B->getName(), OffsetInParent, B->getLength(),
158 Elide),
159 Base(std::move(B)) {
160 if (isEmptyBase()) {
161 // Special case an empty base so that it doesn't get treated as padding.
162 UsedBytes.resize(N: 1);
163 UsedBytes.set(0);
164 }
165 IsVirtualBase = Base->isVirtualBaseClass();
166}
167
168void UDTLayoutBase::initializeChildren(const PDBSymbol &Sym) {
169 // Handled bases first, followed by VTables, followed by data members,
170 // followed by functions, followed by other. This ordering is necessary
171 // so that bases and vtables get initialized before any functions which
172 // may override them.
173 UniquePtrVector<PDBSymbolTypeBaseClass> Bases;
174 UniquePtrVector<PDBSymbolTypeVTable> VTables;
175 UniquePtrVector<PDBSymbolData> Members;
176 UniquePtrVector<PDBSymbolTypeBaseClass> VirtualBaseSyms;
177
178 auto Children = Sym.findAllChildren();
179 while (auto Child = Children->getNext()) {
180 if (auto Base = unique_dyn_cast<PDBSymbolTypeBaseClass>(Val&: Child)) {
181 if (Base->isVirtualBaseClass())
182 VirtualBaseSyms.push_back(x: std::move(Base));
183 else
184 Bases.push_back(x: std::move(Base));
185 }
186 else if (auto Data = unique_dyn_cast<PDBSymbolData>(Val&: Child)) {
187 if (Data->getDataKind() == PDB_DataKind::Member)
188 Members.push_back(x: std::move(Data));
189 else
190 Other.push_back(x: std::move(Data));
191 } else if (auto VT = unique_dyn_cast<PDBSymbolTypeVTable>(Val&: Child))
192 VTables.push_back(x: std::move(VT));
193 else if (auto Func = unique_dyn_cast<PDBSymbolFunc>(Val&: Child))
194 Funcs.push_back(x: std::move(Func));
195 else {
196 Other.push_back(x: std::move(Child));
197 }
198 }
199
200 // We don't want to have any re-allocations in the list of bases, so make
201 // sure to reserve enough space so that our ArrayRefs don't get invalidated.
202 AllBases.reserve(n: Bases.size() + VirtualBaseSyms.size());
203
204 // Only add non-virtual bases to the class first. Only at the end of the
205 // class, after all non-virtual bases and data members have been added do we
206 // add virtual bases. This way the offsets are correctly aligned when we go
207 // to lay out virtual bases.
208 for (auto &Base : Bases) {
209 uint32_t Offset = Base->getOffset();
210 // Non-virtual bases never get elided.
211 auto BL = std::make_unique<BaseClassLayout>(args&: *this, args&: Offset, args: false,
212 args: std::move(Base));
213
214 AllBases.push_back(x: BL.get());
215 addChildToLayout(Child: std::move(BL));
216 }
217 NonVirtualBases = AllBases;
218
219 assert(VTables.size() <= 1);
220 if (!VTables.empty()) {
221 auto VTLayout =
222 std::make_unique<VTableLayoutItem>(args&: *this, args: std::move(VTables[0]));
223
224 VTable = VTLayout.get();
225
226 addChildToLayout(Child: std::move(VTLayout));
227 }
228
229 for (auto &Data : Members) {
230 auto DM = std::make_unique<DataMemberLayoutItem>(args&: *this, args: std::move(Data));
231
232 addChildToLayout(Child: std::move(DM));
233 }
234
235 // Make sure add virtual bases before adding functions, since functions may be
236 // overrides of virtual functions declared in a virtual base, so the VTables
237 // and virtual intros need to be correctly initialized.
238 for (auto &VB : VirtualBaseSyms) {
239 int VBPO = VB->getVirtualBasePointerOffset();
240 if (!hasVBPtrAtOffset(Off: VBPO)) {
241 if (auto VBP = VB->getRawSymbol().getVirtualBaseTableType()) {
242 auto VBPL = std::make_unique<VBPtrLayoutItem>(args&: *this, args: std::move(VBP),
243 args&: VBPO, args: VBP->getLength());
244 VBPtr = VBPL.get();
245 addChildToLayout(Child: std::move(VBPL));
246 }
247 }
248
249 // Virtual bases always go at the end. So just look for the last place we
250 // ended when writing something, and put our virtual base there.
251 // Note that virtual bases get elided unless this is a top-most derived
252 // class.
253 uint32_t Offset = UsedBytes.find_last() + 1;
254 bool Elide = (Parent != nullptr);
255 auto BL =
256 std::make_unique<BaseClassLayout>(args&: *this, args&: Offset, args&: Elide, args: std::move(VB));
257 AllBases.push_back(x: BL.get());
258
259 // Only lay this virtual base out directly inside of *this* class if this
260 // is a top-most derived class. Keep track of it regardless, but only
261 // physically lay it out if it's a topmost derived class.
262 addChildToLayout(Child: std::move(BL));
263 }
264 VirtualBases = ArrayRef(AllBases).drop_front(N: NonVirtualBases.size());
265
266 if (Parent != nullptr)
267 LayoutSize = UsedBytes.find_last() + 1;
268}
269
270bool UDTLayoutBase::hasVBPtrAtOffset(uint32_t Off) const {
271 if (VBPtr && VBPtr->getOffsetInParent() == Off)
272 return true;
273 for (BaseClassLayout *BL : AllBases) {
274 if (BL->hasVBPtrAtOffset(Off: Off - BL->getOffsetInParent()))
275 return true;
276 }
277 return false;
278}
279
280void UDTLayoutBase::addChildToLayout(std::unique_ptr<LayoutItemBase> Child) {
281 uint32_t Begin = Child->getOffsetInParent();
282
283 if (!Child->isElided()) {
284 BitVector ChildBytes = Child->usedBytes();
285
286 // Suppose the child occupies 4 bytes starting at offset 12 in a 32 byte
287 // class. When we call ChildBytes.resize(32), the Child's storage will
288 // still begin at offset 0, so we need to shift it left by offset bytes
289 // to get it into the right position.
290 ChildBytes.resize(N: UsedBytes.size());
291 ChildBytes <<= Child->getOffsetInParent();
292 UsedBytes |= ChildBytes;
293
294 if (ChildBytes.count() > 0) {
295 auto Loc = llvm::upper_bound(
296 Range&: LayoutItems, Value&: Begin, C: [](uint32_t Off, const LayoutItemBase *Item) {
297 return (Off < Item->getOffsetInParent());
298 });
299
300 LayoutItems.insert(position: Loc, x: Child.get());
301 }
302 }
303
304 ChildStorage.push_back(x: std::move(Child));
305}
306

source code of llvm/lib/DebugInfo/PDB/UDTLayout.cpp