lib/CodeGen/LexicalScopes.cpp

   1 //===- LexicalScopes.cpp - Collecting lexical scope info ------------------===//
   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 // This file implements LexicalScopes analysis.
  11 //
  12 // This pass collects lexical scope information and maps machine instructions
  13 // to respective lexical scopes.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "llvm/CodeGen/LexicalScopes.h"
  18 #include "llvm/CodeGen/MachineFunction.h"
  19 #include "llvm/CodeGen/MachineInstr.h"
  20 #include "llvm/IR/DebugInfo.h"
  21 #include "llvm/IR/Function.h"
  22 #include "llvm/Support/Debug.h"
  23 #include "llvm/Support/ErrorHandling.h"
  24 #include "llvm/Support/FormattedStream.h"
  25 using namespace llvm;
  26
  27 #define DEBUG_TYPE "lexicalscopes"
  28
  29 /// reset - Reset the instance so that it's prepared for another function.
  30 void LexicalScopes::reset() {
  31   MF = nullptr;
  32   CurrentFnLexicalScope = nullptr;
  33   LexicalScopeMap.clear();
  34   AbstractScopeMap.clear();
  35   InlinedLexicalScopeMap.clear();
  36   AbstractScopesList.clear();
  37 }
  38
  39 /// initialize - Scan machine function and constuct lexical scope nest.
  40 void LexicalScopes::initialize(const MachineFunction &Fn) {
  41   reset();
  42   MF = &Fn;
  43   SmallVector<InsnRange, 4> MIRanges;
  44   DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
  45   extractLexicalScopes(MIRanges, MI2ScopeMap);
  46   if (CurrentFnLexicalScope) {
  47     constructScopeNest(CurrentFnLexicalScope);
  48     assignInstructionRanges(MIRanges, MI2ScopeMap);
  49   }
  50 }
  51
  52 /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
  53 /// for the given machine function.
  54 void LexicalScopes::extractLexicalScopes(
  55     SmallVectorImpl<InsnRange> &MIRanges,
  56     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
  57
  58   // Scan each instruction and create scopes. First build working set of scopes.
  59   for (const auto &MBB : *MF) {
  60     const MachineInstr *RangeBeginMI = nullptr;
  61     const MachineInstr *PrevMI = nullptr;
  62     const DILocation *PrevDL = nullptr;
  63     for (const auto &MInsn : MBB) {
  64       // Check if instruction has valid location information.
  65       const DILocation *MIDL = MInsn.getDebugLoc();
  66       if (!MIDL) {
  67         PrevMI = &MInsn;
  68         continue;
  69       }
  70
  71       // If scope has not changed then skip this instruction.
  72       if (MIDL == PrevDL) {
  73         PrevMI = &MInsn;
  74         continue;
  75       }
  76
  77       // Ignore DBG_VALUE. It does not contribute to any instruction in output.
  78       if (MInsn.isDebugValue())
  79         continue;
  80
  81       if (RangeBeginMI) {
  82         // If we have already seen a beginning of an instruction range and
  83         // current instruction scope does not match scope of first instruction
  84         // in this range then create a new instruction range.
  85         InsnRange R(RangeBeginMI, PrevMI);
  86         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
  87         MIRanges.push_back(R);
  88       }
  89
  90       // This is a beginning of a new instruction range.
  91       RangeBeginMI = &MInsn;
  92
  93       // Reset previous markers.
  94       PrevMI = &MInsn;
  95       PrevDL = MIDL;
  96     }
  97
  98     // Create last instruction range.
  99     if (RangeBeginMI && PrevMI && PrevDL) {
 100       InsnRange R(RangeBeginMI, PrevMI);
 101       MIRanges.push_back(R);
 102       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 103     }
 104   }
 105 }
 106
 107 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 108 /// given DebugLoc. Return NULL if not found.
 109 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
 110   DILocalScope *Scope = DL->getScope();
 111   if (!Scope)
 112     return nullptr;
 113
 114   // The scope that we were created with could have an extra file - which
 115   // isn't what we care about in this case.
 116   if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
 117     Scope = File->getScope();
 118
 119   if (auto *IA = DL->getInlinedAt()) {
 120     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 121     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 122   }
 123   return findLexicalScope(Scope);
 124 }
 125
 126 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 127 /// not available then create new lexical scope.
 128 LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
 129                                                      const DILocation *IA) {
 130   if (IA) {
 131     // Create an abstract scope for inlined function.
 132     getOrCreateAbstractScope(Scope);
 133     // Create an inlined scope for inlined function.
 134     return getOrCreateInlinedScope(Scope, IA);
 135   }
 136
 137   return getOrCreateRegularScope(Scope);
 138 }
 139
 140 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 141 LexicalScope *
 142 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 143   if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
 144     Scope = File->getScope();
 145
 146   auto I = LexicalScopeMap.find(Scope);
 147   if (I != LexicalScopeMap.end())
 148     return &I->second;
 149
 150   // FIXME: Should the following dyn_cast be DILexicalBlock?
 151   LexicalScope *Parent = nullptr;
 152   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 153     Parent = getOrCreateLexicalScope(Block->getScope());
 154   I = LexicalScopeMap.emplace(std::piecewise_construct,
 155                               std::forward_as_tuple(Scope),
 156                               std::forward_as_tuple(Parent, Scope, nullptr,
 157                                                     false)).first;
 158
 159   if (!Parent) {
 160     assert(cast<DISubprogram>(Scope)->describes(MF->getFunction()));
 161     assert(!CurrentFnLexicalScope);
 162     CurrentFnLexicalScope = &I->second;
 163   }
 164
 165   return &I->second;
 166 }
 167
 168 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 169 LexicalScope *
 170 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
 171                                        const DILocation *InlinedAt) {
 172   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
 173   auto I = InlinedLexicalScopeMap.find(P);
 174   if (I != InlinedLexicalScopeMap.end())
 175     return &I->second;
 176
 177   LexicalScope *Parent;
 178   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 179     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 180   else
 181     Parent = getOrCreateLexicalScope(InlinedAt);
 182
 183   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
 184                                      std::forward_as_tuple(P),
 185                                      std::forward_as_tuple(Parent, Scope,
 186                                                            InlinedAt, false))
 187           .first;
 188   return &I->second;
 189 }
 190
 191 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 192 LexicalScope *
 193 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
 194   assert(Scope && "Invalid Scope encoding!");
 195
 196   if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
 197     Scope = File->getScope();
 198   auto I = AbstractScopeMap.find(Scope);
 199   if (I != AbstractScopeMap.end())
 200     return &I->second;
 201
 202   // FIXME: Should the following isa be DILexicalBlock?
 203   LexicalScope *Parent = nullptr;
 204   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 205     Parent = getOrCreateAbstractScope(Block->getScope());
 206
 207   I = AbstractScopeMap.emplace(std::piecewise_construct,
 208                                std::forward_as_tuple(Scope),
 209                                std::forward_as_tuple(Parent, Scope,
 210                                                      nullptr, true)).first;
 211   if (isa<DISubprogram>(Scope))
 212     AbstractScopesList.push_back(&I->second);
 213   return &I->second;
 214 }
 215
 216 /// constructScopeNest
 217 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 218   assert(Scope && "Unable to calculate scope dominance graph!");
 219   SmallVector<LexicalScope *, 4> WorkStack;
 220   WorkStack.push_back(Scope);
 221   unsigned Counter = 0;
 222   while (!WorkStack.empty()) {
 223     LexicalScope *WS = WorkStack.back();
 224     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 225     bool visitedChildren = false;
 226     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
 227                                                          SE = Children.end();
 228          SI != SE; ++SI) {
 229       LexicalScope *ChildScope = *SI;
 230       if (!ChildScope->getDFSOut()) {
 231         WorkStack.push_back(ChildScope);
 232         visitedChildren = true;
 233         ChildScope->setDFSIn(++Counter);
 234         break;
 235       }
 236     }
 237     if (!visitedChildren) {
 238       WorkStack.pop_back();
 239       WS->setDFSOut(++Counter);
 240     }
 241   }
 242 }
 243
 244 /// assignInstructionRanges - Find ranges of instructions covered by each
 245 /// lexical scope.
 246 void LexicalScopes::assignInstructionRanges(
 247     SmallVectorImpl<InsnRange> &MIRanges,
 248     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 249
 250   LexicalScope *PrevLexicalScope = nullptr;
 251   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 252                                                   RE = MIRanges.end();
 253        RI != RE; ++RI) {
 254     const InsnRange &R = *RI;
 255     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 256     assert(S && "Lost LexicalScope for a machine instruction!");
 257     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 258       PrevLexicalScope->closeInsnRange(S);
 259     S->openInsnRange(R.first);
 260     S->extendInsnRange(R.second);
 261     PrevLexicalScope = S;
 262   }
 263
 264   if (PrevLexicalScope)
 265     PrevLexicalScope->closeInsnRange();
 266 }
 267
 268 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 269 /// have machine instructions that belong to lexical scope identified by
 270 /// DebugLoc.
 271 void LexicalScopes::getMachineBasicBlocks(
 272     const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 273   MBBs.clear();
 274   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 275   if (!Scope)
 276     return;
 277
 278   if (Scope == CurrentFnLexicalScope) {
 279     for (const auto &MBB : *MF)
 280       MBBs.insert(&MBB);
 281     return;
 282   }
 283
 284   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 285   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 286                                             E = InsnRanges.end();
 287        I != E; ++I) {
 288     InsnRange &R = *I;
 289     MBBs.insert(R.first->getParent());
 290   }
 291 }
 292
 293 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 294 /// machine instruction's lexical scope in a given machine basic block.
 295 bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
 296   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 297   if (!Scope)
 298     return false;
 299
 300   // Current function scope covers all basic blocks in the function.
 301   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 302     return true;
 303
 304   bool Result = false;
 305   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 306        ++I) {
 307     if (const DILocation *IDL = I->getDebugLoc())
 308       if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 309         if (Scope->dominates(IScope))
 310           return true;
 311   }
 312   return Result;
 313 }
 314
 315 /// dump - Print data structures.
 316 void LexicalScope::dump(unsigned Indent) const {
 317 #ifndef NDEBUG
 318   raw_ostream &err = dbgs();
 319   err.indent(Indent);
 320   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 321   const MDNode *N = Desc;
 322   err.indent(Indent);
 323   N->dump();
 324   if (AbstractScope)
 325     err << std::string(Indent, ' ') << "Abstract Scope\n";
 326
 327   if (!Children.empty())
 328     err << std::string(Indent + 2, ' ') << "Children ...\n";
 329   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 330     if (Children[i] != this)
 331       Children[i]->dump(Indent + 2);
 332 #endif
 333 }