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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 
     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.
     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.
     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.
     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.
     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.
     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.
     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 
    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 
    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 
    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 
    226 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
    227   DbgValues.clear();
    228   LabelsBeforeInsn.clear();
    229   LabelsAfterInsn.clear();
    230 }
    231