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/MC/MCStreamer.h"
22 #include "llvm/Target/TargetSubtargetInfo.h"
23 
24 using namespace llvm;
25 
26 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
27 
28 // Each LexicalScope has first instruction and last instruction to mark
29 // beginning and end of a scope respectively. Create an inverse map that list
30 // scopes starts (and ends) with an instruction. One instruction may start (or
31 // end) multiple scopes. Ignore scopes that are not reachable.
32 void DebugHandlerBase::identifyScopeMarkers() {
33   SmallVector<LexicalScope *, 4> WorkList;
34   WorkList.push_back(LScopes.getCurrentFunctionScope());
35   while (!WorkList.empty()) {
36     LexicalScope *S = WorkList.pop_back_val();
37 
38     const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
39     if (!Children.empty())
40       WorkList.append(Children.begin(), Children.end());
41 
42     if (S->isAbstractScope())
43       continue;
44 
45     for (const InsnRange &R : S->getRanges()) {
46       assert(R.first && "InsnRange does not have first instruction!");
47       assert(R.second && "InsnRange does not have second instruction!");
48       requestLabelBeforeInsn(R.first);
49       requestLabelAfterInsn(R.second);
50     }
51   }
52 }
53 
54 // Return Label preceding the instruction.
55 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
56   MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
57   assert(Label && "Didn't insert label before instruction");
58   return Label;
59 }
60 
61 // Return Label immediately following the instruction.
62 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
63   return LabelsAfterInsn.lookup(MI);
64 }
65 
66 int DebugHandlerBase::fragmentCmp(const DIExpression *P1,
67                                   const DIExpression *P2) {
68   auto Fragment1 = *P1->getFragmentInfo();
69   auto Fragment2 = *P2->getFragmentInfo();
70   unsigned l1 = Fragment1.OffsetInBits;
71   unsigned l2 = Fragment2.OffsetInBits;
72   unsigned r1 = l1 + Fragment1.SizeInBits;
73   unsigned r2 = l2 + Fragment2.SizeInBits;
74   if (r1 <= l2)
75     return -1;
76   else if (r2 <= l1)
77     return 1;
78   else
79     return 0;
80 }
81 
82 bool DebugHandlerBase::fragmentsOverlap(const DIExpression *P1,
83                                         const DIExpression *P2) {
84   if (!P1->isFragment() || !P2->isFragment())
85     return true;
86   return fragmentCmp(P1, P2) == 0;
87 }
88 
89 /// If this type is derived from a base type then return base type size.
90 uint64_t DebugHandlerBase::getBaseTypeSize(const DITypeRef TyRef) {
91   DIType *Ty = TyRef.resolve();
92   assert(Ty);
93   DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
94   if (!DDTy)
95     return Ty->getSizeInBits();
96 
97   unsigned Tag = DDTy->getTag();
98 
99   if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
100       Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
101       Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type)
102     return DDTy->getSizeInBits();
103 
104   DIType *BaseType = DDTy->getBaseType().resolve();
105 
106   assert(BaseType && "Unexpected invalid base type");
107 
108   // If this is a derived type, go ahead and get the base type, unless it's a
109   // reference then it's just the size of the field. Pointer types have no need
110   // of this since they're a different type of qualification on the type.
111   if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
112       BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
113     return Ty->getSizeInBits();
114 
115   return getBaseTypeSize(BaseType);
116 }
117 
118 bool hasDebugInfo(const MachineModuleInfo *MMI, const MachineFunction *MF) {
119   if (!MMI->hasDebugInfo())
120     return false;
121   auto *SP = MF->getFunction()->getSubprogram();
122   if (!SP)
123     return false;
124   assert(SP->getUnit());
125   auto EK = SP->getUnit()->getEmissionKind();
126   if (EK == DICompileUnit::NoDebug)
127     return false;
128   return true;
129 }
130 
131 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
132   assert(Asm);
133 
134   if (!hasDebugInfo(MMI, MF)) {
135     skippedNonDebugFunction();
136     return;
137   }
138 
139   // Grab the lexical scopes for the function, if we don't have any of those
140   // then we're not going to be able to do anything.
141   LScopes.initialize(*MF);
142   if (LScopes.empty()) {
143     beginFunctionImpl(MF);
144     return;
145   }
146 
147   // Make sure that each lexical scope will have a begin/end label.
148   identifyScopeMarkers();
149 
150   // Calculate history for local variables.
151   assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
152   calculateDbgValueHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
153                            DbgValues);
154 
155   // Request labels for the full history.
156   for (const auto &I : DbgValues) {
157     const auto &Ranges = I.second;
158     if (Ranges.empty())
159       continue;
160 
161     // The first mention of a function argument gets the CurrentFnBegin
162     // label, so arguments are visible when breaking at function entry.
163     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
164     if (DIVar->isParameter() &&
165         getDISubprogram(DIVar->getScope())->describes(MF->getFunction())) {
166       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
167       if (Ranges.front().first->getDebugExpression()->isFragment()) {
168         // Mark all non-overlapping initial fragments.
169         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
170           const DIExpression *Fragment = I->first->getDebugExpression();
171           if (std::all_of(Ranges.begin(), I,
172                           [&](DbgValueHistoryMap::InstrRange Pred) {
173                             return !fragmentsOverlap(
174                                 Fragment, Pred.first->getDebugExpression());
175                           }))
176             LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
177           else
178             break;
179         }
180       }
181     }
182 
183     for (const auto &Range : Ranges) {
184       requestLabelBeforeInsn(Range.first);
185       if (Range.second)
186         requestLabelAfterInsn(Range.second);
187     }
188   }
189 
190   PrevInstLoc = DebugLoc();
191   PrevLabel = Asm->getFunctionBegin();
192   beginFunctionImpl(MF);
193 }
194 
195 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
196   if (!MMI->hasDebugInfo())
197     return;
198 
199   assert(CurMI == nullptr);
200   CurMI = MI;
201 
202   // Insert labels where requested.
203   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
204       LabelsBeforeInsn.find(MI);
205 
206   // No label needed.
207   if (I == LabelsBeforeInsn.end())
208     return;
209 
210   // Label already assigned.
211   if (I->second)
212     return;
213 
214   if (!PrevLabel) {
215     PrevLabel = MMI->getContext().createTempSymbol();
216     Asm->OutStreamer->EmitLabel(PrevLabel);
217   }
218   I->second = PrevLabel;
219 }
220 
221 void DebugHandlerBase::endInstruction() {
222   if (!MMI->hasDebugInfo())
223     return;
224 
225   assert(CurMI != nullptr);
226   // Don't create a new label after DBG_VALUE instructions.
227   // They don't generate code.
228   if (!CurMI->isDebugValue()) {
229     PrevLabel = nullptr;
230     PrevInstBB = CurMI->getParent();
231   }
232 
233   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
234       LabelsAfterInsn.find(CurMI);
235   CurMI = nullptr;
236 
237   // No label needed.
238   if (I == LabelsAfterInsn.end())
239     return;
240 
241   // Label already assigned.
242   if (I->second)
243     return;
244 
245   // We need a label after this instruction.
246   if (!PrevLabel) {
247     PrevLabel = MMI->getContext().createTempSymbol();
248     Asm->OutStreamer->EmitLabel(PrevLabel);
249   }
250   I->second = PrevLabel;
251 }
252 
253 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
254   if (hasDebugInfo(MMI, MF))
255     endFunctionImpl(MF);
256   DbgValues.clear();
257   LabelsBeforeInsn.clear();
258   LabelsAfterInsn.clear();
259 }
260