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