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