1 //===-- llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp -------*- C++ -*--===//
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 //
10 // Common functionality for different debug information format backends.
11 // LLVM currently supports DWARF and CodeView.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/CodeGen/DebugHandlerBase.h"
16 #include "llvm/ADT/Optional.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineInstr.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/TargetSubtargetInfo.h"
23 #include "llvm/IR/DebugInfo.h"
24 #include "llvm/MC/MCStreamer.h"
25 
26 using namespace llvm;
27 
28 #define DEBUG_TYPE "dwarfdebug"
29 
30 Optional<DbgVariableLocation>
extractFromMachineInstruction(const MachineInstr & Instruction)31 DbgVariableLocation::extractFromMachineInstruction(
32     const MachineInstr &Instruction) {
33   DbgVariableLocation Location;
34   if (!Instruction.isDebugValue())
35     return None;
36   if (!Instruction.getOperand(0).isReg())
37     return None;
38   Location.Register = Instruction.getOperand(0).getReg();
39   Location.FragmentInfo.reset();
40   // We only handle expressions generated by DIExpression::appendOffset,
41   // which doesn't require a full stack machine.
42   int64_t Offset = 0;
43   const DIExpression *DIExpr = Instruction.getDebugExpression();
44   auto Op = DIExpr->expr_op_begin();
45   while (Op != DIExpr->expr_op_end()) {
46     switch (Op->getOp()) {
47     case dwarf::DW_OP_constu: {
48       int Value = Op->getArg(0);
49       ++Op;
50       if (Op != DIExpr->expr_op_end()) {
51         switch (Op->getOp()) {
52         case dwarf::DW_OP_minus:
53           Offset -= Value;
54           break;
55         case dwarf::DW_OP_plus:
56           Offset += Value;
57           break;
58         default:
59           continue;
60         }
61       }
62     } break;
63     case dwarf::DW_OP_plus_uconst:
64       Offset += Op->getArg(0);
65       break;
66     case dwarf::DW_OP_LLVM_fragment:
67       Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};
68       break;
69     case dwarf::DW_OP_deref:
70       Location.LoadChain.push_back(Offset);
71       Offset = 0;
72       break;
73     default:
74       return None;
75     }
76     ++Op;
77   }
78 
79   // Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE
80   // instruction.
81   // FIXME: Replace these with DIExpression.
82   if (Instruction.isIndirectDebugValue())
83     Location.LoadChain.push_back(Offset);
84 
85   return Location;
86 }
87 
DebugHandlerBase(AsmPrinter * A)88 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
89 
90 // Each LexicalScope has first instruction and last instruction to mark
91 // beginning and end of a scope respectively. Create an inverse map that list
92 // scopes starts (and ends) with an instruction. One instruction may start (or
93 // end) multiple scopes. Ignore scopes that are not reachable.
identifyScopeMarkers()94 void DebugHandlerBase::identifyScopeMarkers() {
95   SmallVector<LexicalScope *, 4> WorkList;
96   WorkList.push_back(LScopes.getCurrentFunctionScope());
97   while (!WorkList.empty()) {
98     LexicalScope *S = WorkList.pop_back_val();
99 
100     const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
101     if (!Children.empty())
102       WorkList.append(Children.begin(), Children.end());
103 
104     if (S->isAbstractScope())
105       continue;
106 
107     for (const InsnRange &R : S->getRanges()) {
108       assert(R.first && "InsnRange does not have first instruction!");
109       assert(R.second && "InsnRange does not have second instruction!");
110       requestLabelBeforeInsn(R.first);
111       requestLabelAfterInsn(R.second);
112     }
113   }
114 }
115 
116 // Return Label preceding the instruction.
getLabelBeforeInsn(const MachineInstr * MI)117 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
118   MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
119   assert(Label && "Didn't insert label before instruction");
120   return Label;
121 }
122 
123 // Return Label immediately following the instruction.
getLabelAfterInsn(const MachineInstr * MI)124 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
125   return LabelsAfterInsn.lookup(MI);
126 }
127 
128 // Return the function-local offset of an instruction.
129 const MCExpr *
getFunctionLocalOffsetAfterInsn(const MachineInstr * MI)130 DebugHandlerBase::getFunctionLocalOffsetAfterInsn(const MachineInstr *MI) {
131   MCContext &MC = Asm->OutContext;
132 
133   MCSymbol *Start = Asm->getFunctionBegin();
134   const auto *StartRef = MCSymbolRefExpr::create(Start, MC);
135 
136   MCSymbol *AfterInsn = getLabelAfterInsn(MI);
137   assert(AfterInsn && "Expected label after instruction");
138   const auto *AfterRef = MCSymbolRefExpr::create(AfterInsn, MC);
139 
140   return MCBinaryExpr::createSub(AfterRef, StartRef, MC);
141 }
142 
143 /// If this type is derived from a base type then return base type size.
getBaseTypeSize(const DITypeRef TyRef)144 uint64_t DebugHandlerBase::getBaseTypeSize(const DITypeRef TyRef) {
145   DIType *Ty = TyRef.resolve();
146   assert(Ty);
147   DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
148   if (!DDTy)
149     return Ty->getSizeInBits();
150 
151   unsigned Tag = DDTy->getTag();
152 
153   if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
154       Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
155       Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type)
156     return DDTy->getSizeInBits();
157 
158   DIType *BaseType = DDTy->getBaseType().resolve();
159 
160   if (!BaseType)
161     return 0;
162 
163   // If this is a derived type, go ahead and get the base type, unless it's a
164   // reference then it's just the size of the field. Pointer types have no need
165   // of this since they're a different type of qualification on the type.
166   if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
167       BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
168     return Ty->getSizeInBits();
169 
170   return getBaseTypeSize(BaseType);
171 }
172 
hasDebugInfo(const MachineModuleInfo * MMI,const MachineFunction * MF)173 static bool hasDebugInfo(const MachineModuleInfo *MMI,
174                          const MachineFunction *MF) {
175   if (!MMI->hasDebugInfo())
176     return false;
177   auto *SP = MF->getFunction().getSubprogram();
178   if (!SP)
179     return false;
180   assert(SP->getUnit());
181   auto EK = SP->getUnit()->getEmissionKind();
182   if (EK == DICompileUnit::NoDebug)
183     return false;
184   return true;
185 }
186 
beginFunction(const MachineFunction * MF)187 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
188   PrevInstBB = nullptr;
189 
190   if (!Asm || !hasDebugInfo(MMI, MF)) {
191     skippedNonDebugFunction();
192     return;
193   }
194 
195   // Grab the lexical scopes for the function, if we don't have any of those
196   // then we're not going to be able to do anything.
197   LScopes.initialize(*MF);
198   if (LScopes.empty()) {
199     beginFunctionImpl(MF);
200     return;
201   }
202 
203   // Make sure that each lexical scope will have a begin/end label.
204   identifyScopeMarkers();
205 
206   // Calculate history for local variables.
207   assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
208   assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");
209   calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
210                             DbgValues, DbgLabels);
211   LLVM_DEBUG(DbgValues.dump());
212 
213   // Request labels for the full history.
214   for (const auto &I : DbgValues) {
215     const auto &Ranges = I.second;
216     if (Ranges.empty())
217       continue;
218 
219     // The first mention of a function argument gets the CurrentFnBegin
220     // label, so arguments are visible when breaking at function entry.
221     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
222     if (DIVar->isParameter() &&
223         getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {
224       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
225       if (Ranges.front().first->getDebugExpression()->isFragment()) {
226         // Mark all non-overlapping initial fragments.
227         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
228           const DIExpression *Fragment = I->first->getDebugExpression();
229           if (std::all_of(Ranges.begin(), I,
230                           [&](DbgValueHistoryMap::InstrRange Pred) {
231                             return !Fragment->fragmentsOverlap(
232                                 Pred.first->getDebugExpression());
233                           }))
234             LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
235           else
236             break;
237         }
238       }
239     }
240 
241     for (const auto &Range : Ranges) {
242       requestLabelBeforeInsn(Range.first);
243       if (Range.second)
244         requestLabelAfterInsn(Range.second);
245     }
246   }
247 
248   // Ensure there is a symbol before DBG_LABEL.
249   for (const auto &I : DbgLabels) {
250     const MachineInstr *MI = I.second;
251     requestLabelBeforeInsn(MI);
252   }
253 
254   PrevInstLoc = DebugLoc();
255   PrevLabel = Asm->getFunctionBegin();
256   beginFunctionImpl(MF);
257 }
258 
beginInstruction(const MachineInstr * MI)259 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
260   if (!MMI->hasDebugInfo())
261     return;
262 
263   assert(CurMI == nullptr);
264   CurMI = MI;
265 
266   // Insert labels where requested.
267   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
268       LabelsBeforeInsn.find(MI);
269 
270   // No label needed.
271   if (I == LabelsBeforeInsn.end())
272     return;
273 
274   // Label already assigned.
275   if (I->second)
276     return;
277 
278   if (!PrevLabel) {
279     PrevLabel = MMI->getContext().createTempSymbol();
280     Asm->OutStreamer->EmitLabel(PrevLabel);
281   }
282   I->second = PrevLabel;
283 }
284 
endInstruction()285 void DebugHandlerBase::endInstruction() {
286   if (!MMI->hasDebugInfo())
287     return;
288 
289   assert(CurMI != nullptr);
290   // Don't create a new label after DBG_VALUE and other instructions that don't
291   // generate code.
292   if (!CurMI->isMetaInstruction()) {
293     PrevLabel = nullptr;
294     PrevInstBB = CurMI->getParent();
295   }
296 
297   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
298       LabelsAfterInsn.find(CurMI);
299   CurMI = nullptr;
300 
301   // No label needed.
302   if (I == LabelsAfterInsn.end())
303     return;
304 
305   // Label already assigned.
306   if (I->second)
307     return;
308 
309   // We need a label after this instruction.
310   if (!PrevLabel) {
311     PrevLabel = MMI->getContext().createTempSymbol();
312     Asm->OutStreamer->EmitLabel(PrevLabel);
313   }
314   I->second = PrevLabel;
315 }
316 
endFunction(const MachineFunction * MF)317 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
318   if (hasDebugInfo(MMI, MF))
319     endFunctionImpl(MF);
320   DbgValues.clear();
321   DbgLabels.clear();
322   LabelsBeforeInsn.clear();
323   LabelsAfterInsn.clear();
324 }
325