lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp

   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/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/IR/DebugInfo.h"
  23 #include "llvm/MC/MCStreamer.h"
  24 #include "llvm/Target/TargetSubtargetInfo.h"
  25
  26 using namespace llvm;
  27
  28 Optional<DbgVariableLocation>
  29 DbgVariableLocation::extractFromMachineInstruction(
  30     const MachineInstr &Instruction) {
  31   DbgVariableLocation Location;
  32   if (!Instruction.isDebugValue())
  33     return None;
  34   if (!Instruction.getOperand(0).isReg())
  35     return None;
  36   Location.Register = Instruction.getOperand(0).getReg();
  37   Location.FragmentInfo.reset();
  38   // We only handle expressions generated by DIExpression::appendOffset,
  39   // which doesn't require a full stack machine.
  40   int64_t Offset = 0;
  41   const DIExpression *DIExpr = Instruction.getDebugExpression();
  42   auto Op = DIExpr->expr_op_begin();
  43   while (Op != DIExpr->expr_op_end()) {
  44     switch (Op->getOp()) {
  45     case dwarf::DW_OP_constu: {
  46       int Value = Op->getArg(0);
  47       ++Op;
  48       if (Op != DIExpr->expr_op_end()) {
  49         switch (Op->getOp()) {
  50         case dwarf::DW_OP_minus:
  51           Offset -= Value;
  52           break;
  53         case dwarf::DW_OP_plus:
  54           Offset += Value;
  55           break;
  56         default:
  57           continue;
  58         }
  59       }
  60     } break;
  61     case dwarf::DW_OP_plus_uconst:
  62       Offset += Op->getArg(0);
  63       break;
  64     case dwarf::DW_OP_LLVM_fragment:
  65       Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};
  66       break;
  67     case dwarf::DW_OP_deref:
  68       Location.LoadChain.push_back(Offset);
  69       Offset = 0;
  70       break;
  71     default:
  72       return None;
  73     }
  74     ++Op;
  75   }
  76
  77   // Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE
  78   // instruction.
  79   // FIXME: Replace these with DIExpression.
  80   if (Instruction.isIndirectDebugValue())
  81     Location.LoadChain.push_back(Offset);
  82
  83   return Location;
  84 }
  85
  86 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
  87
  88 // Each LexicalScope has first instruction and last instruction to mark
  89 // beginning and end of a scope respectively. Create an inverse map that list
  90 // scopes starts (and ends) with an instruction. One instruction may start (or
  91 // end) multiple scopes. Ignore scopes that are not reachable.
  92 void DebugHandlerBase::identifyScopeMarkers() {
  93   SmallVector<LexicalScope *, 4> WorkList;
  94   WorkList.push_back(LScopes.getCurrentFunctionScope());
  95   while (!WorkList.empty()) {
  96     LexicalScope *S = WorkList.pop_back_val();
  97
  98     const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
  99     if (!Children.empty())
 100       WorkList.append(Children.begin(), Children.end());
 101
 102     if (S->isAbstractScope())
 103       continue;
 104
 105     for (const InsnRange &R : S->getRanges()) {
 106       assert(R.first && "InsnRange does not have first instruction!");
 107       assert(R.second && "InsnRange does not have second instruction!");
 108       requestLabelBeforeInsn(R.first);
 109       requestLabelAfterInsn(R.second);
 110     }
 111   }
 112 }
 113
 114 // Return Label preceding the instruction.
 115 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
 116   MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
 117   assert(Label && "Didn't insert label before instruction");
 118   return Label;
 119 }
 120
 121 // Return Label immediately following the instruction.
 122 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
 123   return LabelsAfterInsn.lookup(MI);
 124 }
 125
 126 int DebugHandlerBase::fragmentCmp(const DIExpression *P1,
 127                                   const DIExpression *P2) {
 128   auto Fragment1 = *P1->getFragmentInfo();
 129   auto Fragment2 = *P2->getFragmentInfo();
 130   unsigned l1 = Fragment1.OffsetInBits;
 131   unsigned l2 = Fragment2.OffsetInBits;
 132   unsigned r1 = l1 + Fragment1.SizeInBits;
 133   unsigned r2 = l2 + Fragment2.SizeInBits;
 134   if (r1 <= l2)
 135     return -1;
 136   else if (r2 <= l1)
 137     return 1;
 138   else
 139     return 0;
 140 }
 141
 142 bool DebugHandlerBase::fragmentsOverlap(const DIExpression *P1,
 143                                         const DIExpression *P2) {
 144   if (!P1->isFragment() || !P2->isFragment())
 145     return true;
 146   return fragmentCmp(P1, P2) == 0;
 147 }
 148
 149 /// If this type is derived from a base type then return base type size.
 150 uint64_t DebugHandlerBase::getBaseTypeSize(const DITypeRef TyRef) {
 151   DIType *Ty = TyRef.resolve();
 152   assert(Ty);
 153   DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
 154   if (!DDTy)
 155     return Ty->getSizeInBits();
 156
 157   unsigned Tag = DDTy->getTag();
 158
 159   if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
 160       Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
 161       Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type)
 162     return DDTy->getSizeInBits();
 163
 164   DIType *BaseType = DDTy->getBaseType().resolve();
 165
 166   assert(BaseType && "Unexpected invalid base type");
 167
 168   // If this is a derived type, go ahead and get the base type, unless it's a
 169   // reference then it's just the size of the field. Pointer types have no need
 170   // of this since they're a different type of qualification on the type.
 171   if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
 172       BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
 173     return Ty->getSizeInBits();
 174
 175   return getBaseTypeSize(BaseType);
 176 }
 177
 178 static bool hasDebugInfo(const MachineModuleInfo *MMI,
 179                          const MachineFunction *MF) {
 180   if (!MMI->hasDebugInfo())
 181     return false;
 182   auto *SP = MF->getFunction()->getSubprogram();
 183   if (!SP)
 184     return false;
 185   assert(SP->getUnit());
 186   auto EK = SP->getUnit()->getEmissionKind();
 187   if (EK == DICompileUnit::NoDebug)
 188     return false;
 189   return true;
 190 }
 191
 192 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
 193   PrevInstBB = nullptr;
 194
 195   if (!Asm || !hasDebugInfo(MMI, MF)) {
 196     skippedNonDebugFunction();
 197     return;
 198   }
 199
 200   // Grab the lexical scopes for the function, if we don't have any of those
 201   // then we're not going to be able to do anything.
 202   LScopes.initialize(*MF);
 203   if (LScopes.empty()) {
 204     beginFunctionImpl(MF);
 205     return;
 206   }
 207
 208   // Make sure that each lexical scope will have a begin/end label.
 209   identifyScopeMarkers();
 210
 211   // Calculate history for local variables.
 212   assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
 213   calculateDbgValueHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
 214                            DbgValues);
 215
 216   // Request labels for the full history.
 217   for (const auto &I : DbgValues) {
 218     const auto &Ranges = I.second;
 219     if (Ranges.empty())
 220       continue;
 221
 222     // The first mention of a function argument gets the CurrentFnBegin
 223     // label, so arguments are visible when breaking at function entry.
 224     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
 225     if (DIVar->isParameter() &&
 226         getDISubprogram(DIVar->getScope())->describes(MF->getFunction())) {
 227       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
 228       if (Ranges.front().first->getDebugExpression()->isFragment()) {
 229         // Mark all non-overlapping initial fragments.
 230         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
 231           const DIExpression *Fragment = I->first->getDebugExpression();
 232           if (std::all_of(Ranges.begin(), I,
 233                           [&](DbgValueHistoryMap::InstrRange Pred) {
 234                             return !fragmentsOverlap(
 235                                 Fragment, Pred.first->getDebugExpression());
 236                           }))
 237             LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
 238           else
 239             break;
 240         }
 241       }
 242     }
 243
 244     for (const auto &Range : Ranges) {
 245       requestLabelBeforeInsn(Range.first);
 246       if (Range.second)
 247         requestLabelAfterInsn(Range.second);
 248     }
 249   }
 250
 251   PrevInstLoc = DebugLoc();
 252   PrevLabel = Asm->getFunctionBegin();
 253   beginFunctionImpl(MF);
 254 }
 255
 256 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
 257   if (!MMI->hasDebugInfo())
 258     return;
 259
 260   assert(CurMI == nullptr);
 261   CurMI = MI;
 262
 263   // Insert labels where requested.
 264   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
 265       LabelsBeforeInsn.find(MI);
 266
 267   // No label needed.
 268   if (I == LabelsBeforeInsn.end())
 269     return;
 270
 271   // Label already assigned.
 272   if (I->second)
 273     return;
 274
 275   if (!PrevLabel) {
 276     PrevLabel = MMI->getContext().createTempSymbol();
 277     Asm->OutStreamer->EmitLabel(PrevLabel);
 278   }
 279   I->second = PrevLabel;
 280 }
 281
 282 void DebugHandlerBase::endInstruction() {
 283   if (!MMI->hasDebugInfo())
 284     return;
 285
 286   assert(CurMI != nullptr);
 287   // Don't create a new label after DBG_VALUE and other instructions that don't
 288   // generate code.
 289   if (!CurMI->isMetaInstruction()) {
 290     PrevLabel = nullptr;
 291     PrevInstBB = CurMI->getParent();
 292   }
 293
 294   DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
 295       LabelsAfterInsn.find(CurMI);
 296   CurMI = nullptr;
 297
 298   // No label needed.
 299   if (I == LabelsAfterInsn.end())
 300     return;
 301
 302   // Label already assigned.
 303   if (I->second)
 304     return;
 305
 306   // We need a label after this instruction.
 307   if (!PrevLabel) {
 308     PrevLabel = MMI->getContext().createTempSymbol();
 309     Asm->OutStreamer->EmitLabel(PrevLabel);
 310   }
 311   I->second = PrevLabel;
 312 }
 313
 314 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
 315   if (hasDebugInfo(MMI, MF))
 316     endFunctionImpl(MF);
 317   DbgValues.clear();
 318   LabelsBeforeInsn.clear();
 319   LabelsAfterInsn.clear();
 320 }