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     DebugLoc PrevDL;
  63     for (const auto &MInsn : MBB) {
  64       // Check if instruction has valid location information.
  65       const DebugLoc MIDL = MInsn.getDebugLoc();
  66       if (MIDL.isUnknown()) {
  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.isUnknown()) {
 100       InsnRange R(RangeBeginMI, PrevMI);
 101       MIRanges.push_back(R);
 102       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 103     }
 104   }
 105 }
 106
 107 LexicalScope *LexicalScopes::findInlinedScope(DebugLoc DL) {
 108   MDNode *Scope = nullptr;
 109   MDNode *IA = nullptr;
 110   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
 111   auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 112   return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 113 }
 114
 115 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 116 /// given DebugLoc. Return NULL if not found.
 117 LexicalScope *LexicalScopes::findLexicalScope(DebugLoc DL) {
 118   MDNode *Scope = nullptr;
 119   MDNode *IA = nullptr;
 120   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
 121   if (!Scope)
 122     return nullptr;
 123
 124   // The scope that we were created with could have an extra file - which
 125   // isn't what we care about in this case.
 126   DIDescriptor D = DIDescriptor(Scope);
 127   if (D.isLexicalBlockFile())
 128     Scope = DILexicalBlockFile(Scope).getScope();
 129
 130   if (IA) {
 131     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 132     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 133   }
 134   return findLexicalScope(Scope);
 135 }
 136
 137 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 138 /// not available then create new lexical scope.
 139 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
 140   if (DL.isUnknown())
 141     return nullptr;
 142   MDNode *Scope = nullptr;
 143   MDNode *InlinedAt = nullptr;
 144   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
 145
 146   if (InlinedAt) {
 147     // Create an abstract scope for inlined function.
 148     getOrCreateAbstractScope(Scope);
 149     // Create an inlined scope for inlined function.
 150     return getOrCreateInlinedScope(Scope, InlinedAt);
 151   }
 152
 153   return getOrCreateRegularScope(Scope);
 154 }
 155
 156 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 157 LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
 158   DIDescriptor D = DIDescriptor(Scope);
 159   if (D.isLexicalBlockFile()) {
 160     Scope = DILexicalBlockFile(Scope).getScope();
 161     D = DIDescriptor(Scope);
 162   }
 163
 164   auto I = LexicalScopeMap.find(Scope);
 165   if (I != LexicalScopeMap.end())
 166     return &I->second;
 167
 168   LexicalScope *Parent = nullptr;
 169   if (D.isLexicalBlock())
 170     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
 171   I = LexicalScopeMap.emplace(std::piecewise_construct,
 172                               std::forward_as_tuple(Scope),
 173                               std::forward_as_tuple(Parent, DIDescriptor(Scope),
 174                                                     nullptr, false)).first;
 175
 176   if (!Parent) {
 177     assert(DIDescriptor(Scope).isSubprogram());
 178     assert(DISubprogram(Scope).describes(MF->getFunction()));
 179     assert(!CurrentFnLexicalScope);
 180     CurrentFnLexicalScope = &I->second;
 181   }
 182
 183   return &I->second;
 184 }
 185
 186 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 187 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *ScopeNode,
 188                                                      MDNode *InlinedAt) {
 189   std::pair<const MDNode*, const MDNode*> P(ScopeNode, InlinedAt);
 190   auto I = InlinedLexicalScopeMap.find(P);
 191   if (I != InlinedLexicalScopeMap.end())
 192     return &I->second;
 193
 194   LexicalScope *Parent;
 195   DILexicalBlock Scope(ScopeNode);
 196   if (Scope.isSubprogram())
 197     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILocation(InlinedAt));
 198   else
 199     Parent = getOrCreateInlinedScope(Scope.getContext(), InlinedAt);
 200
 201   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
 202                                      std::forward_as_tuple(P),
 203                                      std::forward_as_tuple(Parent, Scope,
 204                                                            InlinedAt, false))
 205           .first;
 206   return &I->second;
 207 }
 208
 209 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 210 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
 211   assert(N && "Invalid Scope encoding!");
 212
 213   DIDescriptor Scope(N);
 214   if (Scope.isLexicalBlockFile())
 215     Scope = DILexicalBlockFile(Scope).getScope();
 216   auto I = AbstractScopeMap.find(Scope);
 217   if (I != AbstractScopeMap.end())
 218     return &I->second;
 219
 220   LexicalScope *Parent = nullptr;
 221   if (Scope.isLexicalBlock()) {
 222     DILexicalBlock DB(Scope);
 223     DIDescriptor ParentDesc = DB.getContext();
 224     Parent = getOrCreateAbstractScope(ParentDesc);
 225   }
 226   I = AbstractScopeMap.emplace(std::piecewise_construct,
 227                                std::forward_as_tuple(Scope),
 228                                std::forward_as_tuple(Parent, Scope,
 229                                                      nullptr, true)).first;
 230   if (Scope.isSubprogram())
 231     AbstractScopesList.push_back(&I->second);
 232   return &I->second;
 233 }
 234
 235 /// constructScopeNest
 236 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 237   assert(Scope && "Unable to calculate scope dominance graph!");
 238   SmallVector<LexicalScope *, 4> WorkStack;
 239   WorkStack.push_back(Scope);
 240   unsigned Counter = 0;
 241   while (!WorkStack.empty()) {
 242     LexicalScope *WS = WorkStack.back();
 243     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 244     bool visitedChildren = false;
 245     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
 246                                                          SE = Children.end();
 247          SI != SE; ++SI) {
 248       LexicalScope *ChildScope = *SI;
 249       if (!ChildScope->getDFSOut()) {
 250         WorkStack.push_back(ChildScope);
 251         visitedChildren = true;
 252         ChildScope->setDFSIn(++Counter);
 253         break;
 254       }
 255     }
 256     if (!visitedChildren) {
 257       WorkStack.pop_back();
 258       WS->setDFSOut(++Counter);
 259     }
 260   }
 261 }
 262
 263 /// assignInstructionRanges - Find ranges of instructions covered by each
 264 /// lexical scope.
 265 void LexicalScopes::assignInstructionRanges(
 266     SmallVectorImpl<InsnRange> &MIRanges,
 267     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 268
 269   LexicalScope *PrevLexicalScope = nullptr;
 270   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 271                                                   RE = MIRanges.end();
 272        RI != RE; ++RI) {
 273     const InsnRange &R = *RI;
 274     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 275     assert(S && "Lost LexicalScope for a machine instruction!");
 276     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 277       PrevLexicalScope->closeInsnRange(S);
 278     S->openInsnRange(R.first);
 279     S->extendInsnRange(R.second);
 280     PrevLexicalScope = S;
 281   }
 282
 283   if (PrevLexicalScope)
 284     PrevLexicalScope->closeInsnRange();
 285 }
 286
 287 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 288 /// have machine instructions that belong to lexical scope identified by
 289 /// DebugLoc.
 290 void LexicalScopes::getMachineBasicBlocks(
 291     DebugLoc DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 292   MBBs.clear();
 293   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 294   if (!Scope)
 295     return;
 296
 297   if (Scope == CurrentFnLexicalScope) {
 298     for (const auto &MBB : *MF)
 299       MBBs.insert(&MBB);
 300     return;
 301   }
 302
 303   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 304   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 305                                             E = InsnRanges.end();
 306        I != E; ++I) {
 307     InsnRange &R = *I;
 308     MBBs.insert(R.first->getParent());
 309   }
 310 }
 311
 312 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 313 /// machine instruction's lexical scope in a given machine basic block.
 314 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
 315   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 316   if (!Scope)
 317     return false;
 318
 319   // Current function scope covers all basic blocks in the function.
 320   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 321     return true;
 322
 323   bool Result = false;
 324   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 325        ++I) {
 326     DebugLoc IDL = I->getDebugLoc();
 327     if (IDL.isUnknown())
 328       continue;
 329     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 330       if (Scope->dominates(IScope))
 331         return true;
 332   }
 333   return Result;
 334 }
 335
 336 /// dump - Print data structures.
 337 void LexicalScope::dump(unsigned Indent) const {
 338 #ifndef NDEBUG
 339   raw_ostream &err = dbgs();
 340   err.indent(Indent);
 341   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 342   const MDNode *N = Desc;
 343   err.indent(Indent);
 344   N->dump();
 345   if (AbstractScope)
 346     err << std::string(Indent, ' ') << "Abstract Scope\n";
 347
 348   if (!Children.empty())
 349     err << std::string(Indent + 2, ' ') << "Children ...\n";
 350   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 351     if (Children[i] != this)
 352       Children[i]->dump(Indent + 2);
 353 #endif
 354 }