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