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