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 MDLocation *DL) {
 138   if (!DL)
 139     return nullptr;
 140   MDLocalScope *Scope = DL->getScope();
 141   if (auto *InlinedAt = DL->getInlinedAt()) {
 142     // Create an abstract scope for inlined function.
 143     getOrCreateAbstractScope(Scope);
 144     // Create an inlined scope for inlined function.
 145     return getOrCreateInlinedScope(Scope, InlinedAt);
 146   }
 147
 148   return getOrCreateRegularScope(Scope);
 149 }
 150
 151 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 152 LexicalScope *
 153 LexicalScopes::getOrCreateRegularScope(const MDLocalScope *Scope) {
 154   if (auto *File = dyn_cast<MDLexicalBlockFile>(Scope))
 155     Scope = getScopeOfScope(File);
 156
 157   auto I = LexicalScopeMap.find(Scope);
 158   if (I != LexicalScopeMap.end())
 159     return &I->second;
 160
 161   LexicalScope *Parent = nullptr;
 162   if (isa<MDLexicalBlockBase>(Scope)) // FIXME: Should this be MDLexicalBlock?
 163     Parent =
 164         getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(
 165                                     const_cast<MDLocalScope *>(Scope)).get());
 166   I = LexicalScopeMap.emplace(std::piecewise_construct,
 167                               std::forward_as_tuple(Scope),
 168                               std::forward_as_tuple(Parent, Scope, nullptr,
 169                                                     false)).first;
 170
 171   if (!Parent) {
 172     assert(DIDescriptor(Scope).isSubprogram());
 173     assert(DISubprogram(Scope).describes(MF->getFunction()));
 174     assert(!CurrentFnLexicalScope);
 175     CurrentFnLexicalScope = &I->second;
 176   }
 177
 178   return &I->second;
 179 }
 180
 181 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 182 LexicalScope *
 183 LexicalScopes::getOrCreateInlinedScope(const MDLocalScope *Scope,
 184                                        const MDLocation *InlinedAt) {
 185   std::pair<const MDLocalScope *, const MDLocation *> P(Scope, InlinedAt);
 186   auto I = InlinedLexicalScopeMap.find(P);
 187   if (I != InlinedLexicalScopeMap.end())
 188     return &I->second;
 189
 190   LexicalScope *Parent;
 191   if (auto *Block = dyn_cast<MDLexicalBlockBase>(Scope))
 192     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 193   else
 194     Parent = getOrCreateLexicalScope(InlinedAt);
 195
 196   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
 197                                      std::forward_as_tuple(P),
 198                                      std::forward_as_tuple(Parent, Scope,
 199                                                            InlinedAt, false))
 200           .first;
 201   return &I->second;
 202 }
 203
 204 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 205 LexicalScope *
 206 LexicalScopes::getOrCreateAbstractScope(const MDLocalScope *Scope) {
 207   assert(Scope && "Invalid Scope encoding!");
 208
 209   if (auto *File = dyn_cast<MDLexicalBlockFile>(Scope))
 210     Scope = getScopeOfScope(File);
 211   auto I = AbstractScopeMap.find(Scope);
 212   if (I != AbstractScopeMap.end())
 213     return &I->second;
 214
 215   // FIXME: Should the following isa be MDLexicalBlock?
 216   LexicalScope *Parent = nullptr;
 217   if (auto *Block = dyn_cast<MDLexicalBlockBase>(Scope))
 218     Parent = getOrCreateAbstractScope(Block->getScope());
 219
 220   I = AbstractScopeMap.emplace(std::piecewise_construct,
 221                                std::forward_as_tuple(Scope),
 222                                std::forward_as_tuple(Parent, Scope,
 223                                                      nullptr, true)).first;
 224   if (isa<MDSubprogram>(Scope))
 225     AbstractScopesList.push_back(&I->second);
 226   return &I->second;
 227 }
 228
 229 /// constructScopeNest
 230 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 231   assert(Scope && "Unable to calculate scope dominance graph!");
 232   SmallVector<LexicalScope *, 4> WorkStack;
 233   WorkStack.push_back(Scope);
 234   unsigned Counter = 0;
 235   while (!WorkStack.empty()) {
 236     LexicalScope *WS = WorkStack.back();
 237     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 238     bool visitedChildren = false;
 239     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
 240                                                          SE = Children.end();
 241          SI != SE; ++SI) {
 242       LexicalScope *ChildScope = *SI;
 243       if (!ChildScope->getDFSOut()) {
 244         WorkStack.push_back(ChildScope);
 245         visitedChildren = true;
 246         ChildScope->setDFSIn(++Counter);
 247         break;
 248       }
 249     }
 250     if (!visitedChildren) {
 251       WorkStack.pop_back();
 252       WS->setDFSOut(++Counter);
 253     }
 254   }
 255 }
 256
 257 /// assignInstructionRanges - Find ranges of instructions covered by each
 258 /// lexical scope.
 259 void LexicalScopes::assignInstructionRanges(
 260     SmallVectorImpl<InsnRange> &MIRanges,
 261     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 262
 263   LexicalScope *PrevLexicalScope = nullptr;
 264   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 265                                                   RE = MIRanges.end();
 266        RI != RE; ++RI) {
 267     const InsnRange &R = *RI;
 268     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 269     assert(S && "Lost LexicalScope for a machine instruction!");
 270     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 271       PrevLexicalScope->closeInsnRange(S);
 272     S->openInsnRange(R.first);
 273     S->extendInsnRange(R.second);
 274     PrevLexicalScope = S;
 275   }
 276
 277   if (PrevLexicalScope)
 278     PrevLexicalScope->closeInsnRange();
 279 }
 280
 281 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 282 /// have machine instructions that belong to lexical scope identified by
 283 /// DebugLoc.
 284 void LexicalScopes::getMachineBasicBlocks(
 285     const MDLocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 286   MBBs.clear();
 287   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 288   if (!Scope)
 289     return;
 290
 291   if (Scope == CurrentFnLexicalScope) {
 292     for (const auto &MBB : *MF)
 293       MBBs.insert(&MBB);
 294     return;
 295   }
 296
 297   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 298   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 299                                             E = InsnRanges.end();
 300        I != E; ++I) {
 301     InsnRange &R = *I;
 302     MBBs.insert(R.first->getParent());
 303   }
 304 }
 305
 306 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 307 /// machine instruction's lexical scope in a given machine basic block.
 308 bool LexicalScopes::dominates(const MDLocation *DL, MachineBasicBlock *MBB) {
 309   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 310   if (!Scope)
 311     return false;
 312
 313   // Current function scope covers all basic blocks in the function.
 314   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 315     return true;
 316
 317   bool Result = false;
 318   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 319        ++I) {
 320     DebugLoc IDL = I->getDebugLoc();
 321     if (!IDL)
 322       continue;
 323     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 324       if (Scope->dominates(IScope))
 325         return true;
 326   }
 327   return Result;
 328 }
 329
 330 /// dump - Print data structures.
 331 void LexicalScope::dump(unsigned Indent) const {
 332 #ifndef NDEBUG
 333   raw_ostream &err = dbgs();
 334   err.indent(Indent);
 335   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 336   const MDNode *N = Desc;
 337   err.indent(Indent);
 338   N->dump();
 339   if (AbstractScope)
 340     err << std::string(Indent, ' ') << "Abstract Scope\n";
 341
 342   if (!Children.empty())
 343     err << std::string(Indent + 2, ' ') << "Children ...\n";
 344   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 345     if (Children[i] != this)
 346       Children[i]->dump(Indent + 2);
 347 #endif
 348 }