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