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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 "DebugHandlerBase.h"
16 #include "llvm/CodeGen/AsmPrinter.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/CodeGen/MachineModuleInfo.h"
20 #include "llvm/IR/DebugInfo.h"
21 #include "llvm/Target/TargetSubtargetInfo.h"
22 
23 using namespace llvm;
24 
DebugHandlerBase(AsmPrinter * A)25 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
26 
27 // Each LexicalScope has first instruction and last instruction to mark
28 // beginning and end of a scope respectively. Create an inverse map that list
29 // scopes starts (and ends) with an instruction. One instruction may start (or
30 // end) multiple scopes. Ignore scopes that are not reachable.
identifyScopeMarkers()31 void DebugHandlerBase::identifyScopeMarkers() {
32   SmallVector<LexicalScope *, 4> WorkList;
33   WorkList.push_back(LScopes.getCurrentFunctionScope());
34   while (!WorkList.empty()) {
35     LexicalScope *S = WorkList.pop_back_val();
36 
37     const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
38     if (!Children.empty())
39       WorkList.append(Children.begin(), Children.end());
40 
41     if (S->isAbstractScope())
42       continue;
43 
44     for (const InsnRange &R : S->getRanges()) {
45       assert(R.first && "InsnRange does not have first instruction!");
46       assert(R.second && "InsnRange does not have second instruction!");
47       requestLabelBeforeInsn(R.first);
48       requestLabelAfterInsn(R.second);
49     }
50   }
51 }
52 
53 // Return Label preceding the instruction.
getLabelBeforeInsn(const MachineInstr * MI)54 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
55   MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
56   assert(Label && "Didn't insert label before instruction");
57   return Label;
58 }
59 
60 // Return Label immediately following the instruction.
getLabelAfterInsn(const MachineInstr * MI)61 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
62   return LabelsAfterInsn.lookup(MI);
63 }
64 
65 // Determine the relative position of the pieces described by P1 and P2.
66 // Returns  -1 if P1 is entirely before P2, 0 if P1 and P2 overlap,
67 // 1 if P1 is entirely after P2.
pieceCmp(const DIExpression * P1,const DIExpression * P2)68 int DebugHandlerBase::pieceCmp(const DIExpression *P1, const DIExpression *P2) {
69   unsigned l1 = P1->getBitPieceOffset();
70   unsigned l2 = P2->getBitPieceOffset();
71   unsigned r1 = l1 + P1->getBitPieceSize();
72   unsigned r2 = l2 + P2->getBitPieceSize();
73   if (r1 <= l2)
74     return -1;
75   else if (r2 <= l1)
76     return 1;
77   else
78     return 0;
79 }
80 
81 /// Determine whether two variable pieces overlap.
piecesOverlap(const DIExpression * P1,const DIExpression * P2)82 bool DebugHandlerBase::piecesOverlap(const DIExpression *P1, const DIExpression *P2) {
83   if (!P1->isBitPiece() || !P2->isBitPiece())
84     return true;
85   return pieceCmp(P1, P2) == 0;
86 }
87 
88 /// If this type is derived from a base type then return base type size.
getBaseTypeSize(const DITypeRef TyRef)89 uint64_t DebugHandlerBase::getBaseTypeSize(const DITypeRef TyRef) {
90   DIType *Ty = TyRef.resolve();
91   assert(Ty);
92   DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
93   if (!DDTy)
94     return Ty->getSizeInBits();
95 
96   unsigned Tag = DDTy->getTag();
97 
98   if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
99       Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
100       Tag != dwarf::DW_TAG_restrict_type)
101     return DDTy->getSizeInBits();
102 
103   DIType *BaseType = DDTy->getBaseType().resolve();
104 
105   assert(BaseType && "Unexpected invalid base type");
106 
107   // If this is a derived type, go ahead and get the base type, unless it's a
108   // reference then it's just the size of the field. Pointer types have no need
109   // of this since they're a different type of qualification on the type.
110   if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
111       BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
112     return Ty->getSizeInBits();
113 
114   return getBaseTypeSize(BaseType);
115 }
116 
beginFunction(const MachineFunction * MF)117 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
118   // Grab the lexical scopes for the function, if we don't have any of those
119   // then we're not going to be able to do anything.
120   LScopes.initialize(*MF);
121   if (LScopes.empty())
122     return;
123 
124   // Make sure that each lexical scope will have a begin/end label.
125   identifyScopeMarkers();
126 
127   // Calculate history for local variables.
128   assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
129   calculateDbgValueHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
130                            DbgValues);
131 
132   // Request labels for the full history.
133   for (const auto &I : DbgValues) {
134     const auto &Ranges = I.second;
135     if (Ranges.empty())
136       continue;
137 
138     // The first mention of a function argument gets the CurrentFnBegin
139     // label, so arguments are visible when breaking at function entry.
140     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
141     if (DIVar->isParameter() &&
142         getDISubprogram(DIVar->getScope())->describes(MF->getFunction())) {
143       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
144       if (Ranges.front().first->getDebugExpression()->isBitPiece()) {
145         // Mark all non-overlapping initial pieces.
146         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
147           const DIExpression *Piece = I->first->getDebugExpression();
148           if (std::all_of(Ranges.begin(), I,
149                           [&](DbgValueHistoryMap::InstrRange Pred) {
150                 return !piecesOverlap(Piece, Pred.first->getDebugExpression());
151               }))
152             LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
153           else
154             break;
155         }
156       }
157     }
158 
159     for (const auto &Range : Ranges) {
160       requestLabelBeforeInsn(Range.first);
161       if (Range.second)
162         requestLabelAfterInsn(Range.second);
163     }
164   }
165 
166   PrevInstLoc = DebugLoc();
167   PrevLabel = Asm->getFunctionBegin();
168 }
169 
beginInstruction(const MachineInstr * MI)170 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
171   if (!MMI->hasDebugInfo())
172     return;
173 
174   assert(CurMI == nullptr);
175   CurMI = MI;
176 
177   // Insert labels where requested.
178   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
179       LabelsBeforeInsn.find(MI);
180 
181   // No label needed.
182   if (I == LabelsBeforeInsn.end())
183     return;
184 
185   // Label already assigned.
186   if (I->second)
187     return;
188 
189   if (!PrevLabel) {
190     PrevLabel = MMI->getContext().createTempSymbol();
191     Asm->OutStreamer->EmitLabel(PrevLabel);
192   }
193   I->second = PrevLabel;
194 }
195 
endInstruction()196 void DebugHandlerBase::endInstruction() {
197   if (!MMI->hasDebugInfo())
198     return;
199 
200   assert(CurMI != nullptr);
201   // Don't create a new label after DBG_VALUE instructions.
202   // They don't generate code.
203   if (!CurMI->isDebugValue())
204     PrevLabel = nullptr;
205 
206   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
207       LabelsAfterInsn.find(CurMI);
208   CurMI = nullptr;
209 
210   // No label needed.
211   if (I == LabelsAfterInsn.end())
212     return;
213 
214   // Label already assigned.
215   if (I->second)
216     return;
217 
218   // We need a label after this instruction.
219   if (!PrevLabel) {
220     PrevLabel = MMI->getContext().createTempSymbol();
221     Asm->OutStreamer->EmitLabel(PrevLabel);
222   }
223   I->second = PrevLabel;
224 }
225 
endFunction(const MachineFunction * MF)226 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
227   DbgValues.clear();
228   LabelsBeforeInsn.clear();
229   LabelsAfterInsn.clear();
230 }
231