1 //===-- llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp -------*- C++ -*--===//
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
7 //===----------------------------------------------------------------------===//
9 // Common functionality for different debug information format backends.
10 // LLVM currently supports DWARF and CodeView.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/DebugHandlerBase.h"
15 #include "llvm/ADT/Optional.h"
16 #include "llvm/ADT/Twine.h"
17 #include "llvm/CodeGen/AsmPrinter.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineInstr.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/CodeGen/TargetSubtargetInfo.h"
22 #include "llvm/IR/DebugInfo.h"
23 #include "llvm/MC/MCStreamer.h"
27 #define DEBUG_TYPE "dwarfdebug"
29 Optional<DbgVariableLocation>
30 DbgVariableLocation::extractFromMachineInstruction(
31 const MachineInstr &Instruction) {
32 DbgVariableLocation Location;
33 if (!Instruction.isDebugValue())
35 if (!Instruction.getDebugOperand(0).isReg())
37 Location.Register = Instruction.getDebugOperand(0).getReg();
38 Location.FragmentInfo.reset();
39 // We only handle expressions generated by DIExpression::appendOffset,
40 // which doesn't require a full stack machine.
42 const DIExpression *DIExpr = Instruction.getDebugExpression();
43 auto Op = DIExpr->expr_op_begin();
44 while (Op != DIExpr->expr_op_end()) {
45 switch (Op->getOp()) {
46 case dwarf::DW_OP_constu: {
47 int Value = Op->getArg(0);
49 if (Op != DIExpr->expr_op_end()) {
50 switch (Op->getOp()) {
51 case dwarf::DW_OP_minus:
54 case dwarf::DW_OP_plus:
62 case dwarf::DW_OP_plus_uconst:
63 Offset += Op->getArg(0);
65 case dwarf::DW_OP_LLVM_fragment:
66 Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};
68 case dwarf::DW_OP_deref:
69 Location.LoadChain.push_back(Offset);
78 // Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE
80 // FIXME: Replace these with DIExpression.
81 if (Instruction.isIndirectDebugValue())
82 Location.LoadChain.push_back(Offset);
87 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
89 // Each LexicalScope has first instruction and last instruction to mark
90 // beginning and end of a scope respectively. Create an inverse map that list
91 // scopes starts (and ends) with an instruction. One instruction may start (or
92 // end) multiple scopes. Ignore scopes that are not reachable.
93 void DebugHandlerBase::identifyScopeMarkers() {
94 SmallVector<LexicalScope *, 4> WorkList;
95 WorkList.push_back(LScopes.getCurrentFunctionScope());
96 while (!WorkList.empty()) {
97 LexicalScope *S = WorkList.pop_back_val();
99 const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
100 if (!Children.empty())
101 WorkList.append(Children.begin(), Children.end());
103 if (S->isAbstractScope())
106 for (const InsnRange &R : S->getRanges()) {
107 assert(R.first && "InsnRange does not have first instruction!");
108 assert(R.second && "InsnRange does not have second instruction!");
109 requestLabelBeforeInsn(R.first);
110 requestLabelAfterInsn(R.second);
115 // Return Label preceding the instruction.
116 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
117 MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
118 assert(Label && "Didn't insert label before instruction");
122 // Return Label immediately following the instruction.
123 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
124 return LabelsAfterInsn.lookup(MI);
127 /// If this type is derived from a base type then return base type size.
128 uint64_t DebugHandlerBase::getBaseTypeSize(const DIType *Ty) {
130 const DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
132 return Ty->getSizeInBits();
134 unsigned Tag = DDTy->getTag();
136 if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
137 Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
138 Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type)
139 return DDTy->getSizeInBits();
141 DIType *BaseType = DDTy->getBaseType();
146 // If this is a derived type, go ahead and get the base type, unless it's a
147 // reference then it's just the size of the field. Pointer types have no need
148 // of this since they're a different type of qualification on the type.
149 if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
150 BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
151 return Ty->getSizeInBits();
153 return getBaseTypeSize(BaseType);
156 static bool hasDebugInfo(const MachineModuleInfo *MMI,
157 const MachineFunction *MF) {
158 if (!MMI->hasDebugInfo())
160 auto *SP = MF->getFunction().getSubprogram();
163 assert(SP->getUnit());
164 auto EK = SP->getUnit()->getEmissionKind();
165 if (EK == DICompileUnit::NoDebug)
170 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
171 PrevInstBB = nullptr;
173 if (!Asm || !hasDebugInfo(MMI, MF)) {
174 skippedNonDebugFunction();
178 // Grab the lexical scopes for the function, if we don't have any of those
179 // then we're not going to be able to do anything.
180 LScopes.initialize(*MF);
181 if (LScopes.empty()) {
182 beginFunctionImpl(MF);
186 // Make sure that each lexical scope will have a begin/end label.
187 identifyScopeMarkers();
189 // Calculate history for local variables.
190 assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
191 assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");
192 calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
193 DbgValues, DbgLabels);
194 LLVM_DEBUG(DbgValues.dump());
196 // Request labels for the full history.
197 for (const auto &I : DbgValues) {
198 const auto &Entries = I.second;
202 auto IsDescribedByReg = [](const MachineInstr *MI) {
203 return MI->getDebugOperand(0).isReg() && MI->getDebugOperand(0).getReg();
206 // The first mention of a function argument gets the CurrentFnBegin label,
207 // so arguments are visible when breaking at function entry.
209 // We do not change the label for values that are described by registers,
210 // as that could place them above their defining instructions. We should
211 // ideally not change the labels for constant debug values either, since
212 // doing that violates the ranges that are calculated in the history map.
213 // However, we currently do not emit debug values for constant arguments
214 // directly at the start of the function, so this code is still useful.
215 const DILocalVariable *DIVar =
216 Entries.front().getInstr()->getDebugVariable();
217 if (DIVar->isParameter() &&
218 getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {
219 if (!IsDescribedByReg(Entries.front().getInstr()))
220 LabelsBeforeInsn[Entries.front().getInstr()] = Asm->getFunctionBegin();
221 if (Entries.front().getInstr()->getDebugExpression()->isFragment()) {
222 // Mark all non-overlapping initial fragments.
223 for (auto I = Entries.begin(); I != Entries.end(); ++I) {
224 if (!I->isDbgValue())
226 const DIExpression *Fragment = I->getInstr()->getDebugExpression();
227 if (std::any_of(Entries.begin(), I,
228 [&](DbgValueHistoryMap::Entry Pred) {
229 return Pred.isDbgValue() &&
230 Fragment->fragmentsOverlap(
231 Pred.getInstr()->getDebugExpression());
234 // The code that generates location lists for DWARF assumes that the
235 // entries' start labels are monotonically increasing, and since we
236 // don't change the label for fragments that are described by
237 // registers, we must bail out when encountering such a fragment.
238 if (IsDescribedByReg(I->getInstr()))
240 LabelsBeforeInsn[I->getInstr()] = Asm->getFunctionBegin();
245 for (const auto &Entry : Entries) {
246 if (Entry.isDbgValue())
247 requestLabelBeforeInsn(Entry.getInstr());
249 requestLabelAfterInsn(Entry.getInstr());
253 // Ensure there is a symbol before DBG_LABEL.
254 for (const auto &I : DbgLabels) {
255 const MachineInstr *MI = I.second;
256 requestLabelBeforeInsn(MI);
259 PrevInstLoc = DebugLoc();
260 PrevLabel = Asm->getFunctionBegin();
261 beginFunctionImpl(MF);
264 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
265 if (!MMI->hasDebugInfo())
268 assert(CurMI == nullptr);
271 // Insert labels where requested.
272 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
273 LabelsBeforeInsn.find(MI);
276 if (I == LabelsBeforeInsn.end())
279 // Label already assigned.
284 PrevLabel = MMI->getContext().createTempSymbol();
285 Asm->OutStreamer->emitLabel(PrevLabel);
287 I->second = PrevLabel;
290 void DebugHandlerBase::endInstruction() {
291 if (!MMI->hasDebugInfo())
294 assert(CurMI != nullptr);
295 // Don't create a new label after DBG_VALUE and other instructions that don't
297 if (!CurMI->isMetaInstruction()) {
299 PrevInstBB = CurMI->getParent();
302 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
303 LabelsAfterInsn.find(CurMI);
307 if (I == LabelsAfterInsn.end())
310 // Label already assigned.
314 // We need a label after this instruction.
316 PrevLabel = MMI->getContext().createTempSymbol();
317 Asm->OutStreamer->emitLabel(PrevLabel);
319 I->second = PrevLabel;
322 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
323 if (hasDebugInfo(MMI, MF))
327 LabelsBeforeInsn.clear();
328 LabelsAfterInsn.clear();
331 void DebugHandlerBase::beginBasicBlock(const MachineBasicBlock &MBB) {
332 if (!MBB.isBeginSection())
335 PrevLabel = MBB.getSymbol();
338 void DebugHandlerBase::endBasicBlock(const MachineBasicBlock &MBB) {
339 if (!MBB.isEndSection())