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   MDNode *Scope = nullptr;
 141   MDNode *InlinedAt = nullptr;
 142   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
 143
 144   if (InlinedAt) {
 145     // Create an abstract scope for inlined function.
 146     getOrCreateAbstractScope(Scope);
 147     // Create an inlined scope for inlined function.
 148     return getOrCreateInlinedScope(Scope, InlinedAt);
 149   }
 150
 151   return getOrCreateRegularScope(Scope);
 152 }
 153
 154 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 155 LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
 156   DIDescriptor D = DIDescriptor(Scope);
 157   if (D.isLexicalBlockFile()) {
 158     Scope = DILexicalBlockFile(Scope).getScope();
 159     D = DIDescriptor(Scope);
 160   }
 161
 162   auto I = LexicalScopeMap.find(Scope);
 163   if (I != LexicalScopeMap.end())
 164     return &I->second;
 165
 166   LexicalScope *Parent = nullptr;
 167   if (D.isLexicalBlock())
 168     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
 169   // FIXME: Use forward_as_tuple instead of make_tuple, once MSVC2012
 170   // compatibility is no longer required.
 171   I = LexicalScopeMap.emplace(std::piecewise_construct, std::make_tuple(Scope),
 172                               std::make_tuple(Parent, DIDescriptor(Scope),
 173                                               nullptr, false)).first;
 174
 175   if (!Parent && DIDescriptor(Scope).isSubprogram() &&
 176       DISubprogram(Scope).describes(MF->getFunction()))
 177     CurrentFnLexicalScope = &I->second;
 178
 179   return &I->second;
 180 }
 181
 182 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 183 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *ScopeNode,
 184                                                      MDNode *InlinedAt) {
 185   std::pair<const MDNode*, const MDNode*> P(ScopeNode, InlinedAt);
 186   auto I = InlinedLexicalScopeMap.find(P);
 187   if (I != InlinedLexicalScopeMap.end())
 188     return &I->second;
 189
 190   LexicalScope *Parent;
 191   DILexicalBlock Scope(ScopeNode);
 192   if (Scope.isLexicalBlock()) {
 193     DILexicalBlock PB(Scope.getContext());
 194     Parent = getOrCreateInlinedScope(PB, InlinedAt);
 195   } else
 196     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILocation(InlinedAt));
 197
 198   // FIXME: Use forward_as_tuple instead of make_tuple, once MSVC2012
 199   // compatibility is no longer required.
 200   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
 201                                      std::make_tuple(P),
 202                                      std::make_tuple(Parent, Scope, InlinedAt,
 203                                                      false)).first;
 204   return &I->second;
 205 }
 206
 207 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 208 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
 209   assert(N && "Invalid Scope encoding!");
 210
 211   DIDescriptor Scope(N);
 212   if (Scope.isLexicalBlockFile())
 213     Scope = DILexicalBlockFile(Scope).getScope();
 214   auto I = AbstractScopeMap.find(N);
 215   if (I != AbstractScopeMap.end())
 216     return &I->second;
 217
 218   LexicalScope *Parent = nullptr;
 219   if (Scope.isLexicalBlock()) {
 220     DILexicalBlock DB(N);
 221     DIDescriptor ParentDesc = DB.getContext();
 222     Parent = getOrCreateAbstractScope(ParentDesc);
 223   }
 224   I = AbstractScopeMap.emplace(std::piecewise_construct,
 225                                std::forward_as_tuple(N),
 226                                std::forward_as_tuple(Parent, DIDescriptor(N),
 227                                                      nullptr, true)).first;
 228   if (DIDescriptor(N).isSubprogram())
 229     AbstractScopesList.push_back(&I->second);
 230   return &I->second;
 231 }
 232
 233 /// constructScopeNest
 234 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 235   assert(Scope && "Unable to calculate scope dominance graph!");
 236   SmallVector<LexicalScope *, 4> WorkStack;
 237   WorkStack.push_back(Scope);
 238   unsigned Counter = 0;
 239   while (!WorkStack.empty()) {
 240     LexicalScope *WS = WorkStack.back();
 241     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 242     bool visitedChildren = false;
 243     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
 244                                                          SE = Children.end();
 245          SI != SE; ++SI) {
 246       LexicalScope *ChildScope = *SI;
 247       if (!ChildScope->getDFSOut()) {
 248         WorkStack.push_back(ChildScope);
 249         visitedChildren = true;
 250         ChildScope->setDFSIn(++Counter);
 251         break;
 252       }
 253     }
 254     if (!visitedChildren) {
 255       WorkStack.pop_back();
 256       WS->setDFSOut(++Counter);
 257     }
 258   }
 259 }
 260
 261 /// assignInstructionRanges - Find ranges of instructions covered by each
 262 /// lexical scope.
 263 void LexicalScopes::assignInstructionRanges(
 264     SmallVectorImpl<InsnRange> &MIRanges,
 265     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 266
 267   LexicalScope *PrevLexicalScope = nullptr;
 268   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 269                                                   RE = MIRanges.end();
 270        RI != RE; ++RI) {
 271     const InsnRange &R = *RI;
 272     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 273     assert(S && "Lost LexicalScope for a machine instruction!");
 274     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 275       PrevLexicalScope->closeInsnRange(S);
 276     S->openInsnRange(R.first);
 277     S->extendInsnRange(R.second);
 278     PrevLexicalScope = S;
 279   }
 280
 281   if (PrevLexicalScope)
 282     PrevLexicalScope->closeInsnRange();
 283 }
 284
 285 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 286 /// have machine instructions that belong to lexical scope identified by
 287 /// DebugLoc.
 288 void LexicalScopes::getMachineBasicBlocks(
 289     DebugLoc DL, SmallPtrSet<const MachineBasicBlock *, 4> &MBBs) {
 290   MBBs.clear();
 291   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 292   if (!Scope)
 293     return;
 294
 295   if (Scope == CurrentFnLexicalScope) {
 296     for (const auto &MBB : *MF)
 297       MBBs.insert(&MBB);
 298     return;
 299   }
 300
 301   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 302   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 303                                             E = InsnRanges.end();
 304        I != E; ++I) {
 305     InsnRange &R = *I;
 306     MBBs.insert(R.first->getParent());
 307   }
 308 }
 309
 310 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 311 /// machine instruction's lexical scope in a given machine basic block.
 312 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
 313   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 314   if (!Scope)
 315     return false;
 316
 317   // Current function scope covers all basic blocks in the function.
 318   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 319     return true;
 320
 321   bool Result = false;
 322   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 323        ++I) {
 324     DebugLoc IDL = I->getDebugLoc();
 325     if (IDL.isUnknown())
 326       continue;
 327     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 328       if (Scope->dominates(IScope))
 329         return true;
 330   }
 331   return Result;
 332 }
 333
 334 /// dump - Print data structures.
 335 void LexicalScope::dump(unsigned Indent) const {
 336 #ifndef NDEBUG
 337   raw_ostream &err = dbgs();
 338   err.indent(Indent);
 339   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 340   const MDNode *N = Desc;
 341   err.indent(Indent);
 342   N->dump();
 343   if (AbstractScope)
 344     err << std::string(Indent, ' ') << "Abstract Scope\n";
 345
 346   if (!Children.empty())
 347     err << std::string(Indent + 2, ' ') << "Children ...\n";
 348   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 349     if (Children[i] != this)
 350       Children[i]->dump(Indent + 2);
 351 #endif
 352 }