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 /// ~LexicalScopes - final cleanup after ourselves.
  30 LexicalScopes::~LexicalScopes() { reset(); }
  31
  32 /// reset - Reset the instance so that it's prepared for another function.
  33 void LexicalScopes::reset() {
  34   MF = nullptr;
  35   CurrentFnLexicalScope = nullptr;
  36   DeleteContainerSeconds(LexicalScopeMap);
  37   DeleteContainerSeconds(AbstractScopeMap);
  38   InlinedLexicalScopeMap.clear();
  39   AbstractScopesList.clear();
  40 }
  41
  42 /// initialize - Scan machine function and constuct lexical scope nest.
  43 void LexicalScopes::initialize(const MachineFunction &Fn) {
  44   reset();
  45   MF = &Fn;
  46   SmallVector<InsnRange, 4> MIRanges;
  47   DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
  48   extractLexicalScopes(MIRanges, MI2ScopeMap);
  49   if (CurrentFnLexicalScope) {
  50     constructScopeNest(CurrentFnLexicalScope);
  51     assignInstructionRanges(MIRanges, MI2ScopeMap);
  52   }
  53 }
  54
  55 /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
  56 /// for the given machine function.
  57 void LexicalScopes::extractLexicalScopes(
  58     SmallVectorImpl<InsnRange> &MIRanges,
  59     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
  60
  61   // Scan each instruction and create scopes. First build working set of scopes.
  62   for (const auto &MBB : *MF) {
  63     const MachineInstr *RangeBeginMI = nullptr;
  64     const MachineInstr *PrevMI = nullptr;
  65     DebugLoc PrevDL;
  66     for (MachineBasicBlock::const_iterator II = MBB.begin(), IE = MBB.end();
  67          II != IE; ++II) {
  68       const MachineInstr *MInsn = II;
  69
  70       // Check if instruction has valid location information.
  71       const DebugLoc MIDL = MInsn->getDebugLoc();
  72       if (MIDL.isUnknown()) {
  73         PrevMI = MInsn;
  74         continue;
  75       }
  76
  77       // If scope has not changed then skip this instruction.
  78       if (MIDL == PrevDL) {
  79         PrevMI = MInsn;
  80         continue;
  81       }
  82
  83       // Ignore DBG_VALUE. It does not contribute to any instruction in output.
  84       if (MInsn->isDebugValue())
  85         continue;
  86
  87       if (RangeBeginMI) {
  88         // If we have already seen a beginning of an instruction range and
  89         // current instruction scope does not match scope of first instruction
  90         // in this range then create a new instruction range.
  91         InsnRange R(RangeBeginMI, PrevMI);
  92         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
  93         MIRanges.push_back(R);
  94       }
  95
  96       // This is a beginning of a new instruction range.
  97       RangeBeginMI = MInsn;
  98
  99       // Reset previous markers.
 100       PrevMI = MInsn;
 101       PrevDL = MIDL;
 102     }
 103
 104     // Create last instruction range.
 105     if (RangeBeginMI && PrevMI && !PrevDL.isUnknown()) {
 106       InsnRange R(RangeBeginMI, PrevMI);
 107       MIRanges.push_back(R);
 108       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 109     }
 110   }
 111 }
 112
 113 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 114 /// given DebugLoc. Return NULL if not found.
 115 LexicalScope *LexicalScopes::findLexicalScope(DebugLoc DL) {
 116   MDNode *Scope = nullptr;
 117   MDNode *IA = nullptr;
 118   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
 119   if (!Scope)
 120     return nullptr;
 121
 122   // The scope that we were created with could have an extra file - which
 123   // isn't what we care about in this case.
 124   DIDescriptor D = DIDescriptor(Scope);
 125   if (D.isLexicalBlockFile())
 126     Scope = DILexicalBlockFile(Scope).getScope();
 127
 128   if (IA)
 129     return InlinedLexicalScopeMap.lookup(DebugLoc::getFromDILocation(IA));
 130   return LexicalScopeMap.lookup(Scope);
 131 }
 132
 133 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 134 /// not available then create new lexical scope.
 135 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
 136   MDNode *Scope = nullptr;
 137   MDNode *InlinedAt = nullptr;
 138   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
 139
 140   if (InlinedAt) {
 141     // Create an abstract scope for inlined function.
 142     getOrCreateAbstractScope(Scope);
 143     // Create an inlined scope for inlined function.
 144     return getOrCreateInlinedScope(Scope, InlinedAt);
 145   }
 146
 147   return getOrCreateRegularScope(Scope);
 148 }
 149
 150 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 151 LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
 152   DIDescriptor D = DIDescriptor(Scope);
 153   if (D.isLexicalBlockFile()) {
 154     Scope = DILexicalBlockFile(Scope).getScope();
 155     D = DIDescriptor(Scope);
 156   }
 157
 158   LexicalScope *WScope = LexicalScopeMap.lookup(Scope);
 159   if (WScope)
 160     return WScope;
 161
 162   LexicalScope *Parent = nullptr;
 163   if (D.isLexicalBlock())
 164     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
 165   WScope = new LexicalScope(Parent, DIDescriptor(Scope), nullptr, false);
 166   LexicalScopeMap.insert(std::make_pair(Scope, WScope));
 167   if (!Parent && DIDescriptor(Scope).isSubprogram() &&
 168       DISubprogram(Scope).describes(MF->getFunction()))
 169     CurrentFnLexicalScope = WScope;
 170
 171   return WScope;
 172 }
 173
 174 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 175 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *Scope,
 176                                                      MDNode *InlinedAt) {
 177   LexicalScope *InlinedScope = LexicalScopeMap.lookup(InlinedAt);
 178   if (InlinedScope)
 179     return InlinedScope;
 180
 181   DebugLoc InlinedLoc = DebugLoc::getFromDILocation(InlinedAt);
 182   InlinedScope = new LexicalScope(getOrCreateLexicalScope(InlinedLoc),
 183                                   DIDescriptor(Scope), InlinedAt, false);
 184   InlinedLexicalScopeMap[InlinedLoc] = InlinedScope;
 185   LexicalScopeMap[InlinedAt] = InlinedScope;
 186   return InlinedScope;
 187 }
 188
 189 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 190 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
 191   assert(N && "Invalid Scope encoding!");
 192
 193   DIDescriptor Scope(N);
 194   if (Scope.isLexicalBlockFile())
 195     Scope = DILexicalBlockFile(Scope).getScope();
 196   LexicalScope *AScope = AbstractScopeMap.lookup(N);
 197   if (AScope)
 198     return AScope;
 199
 200   LexicalScope *Parent = nullptr;
 201   if (Scope.isLexicalBlock()) {
 202     DILexicalBlock DB(N);
 203     DIDescriptor ParentDesc = DB.getContext();
 204     Parent = getOrCreateAbstractScope(ParentDesc);
 205   }
 206   AScope = new LexicalScope(Parent, DIDescriptor(N), nullptr, true);
 207   AbstractScopeMap[N] = AScope;
 208   if (DIDescriptor(N).isSubprogram())
 209     AbstractScopesList.push_back(AScope);
 210   return AScope;
 211 }
 212
 213 /// constructScopeNest
 214 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 215   assert(Scope && "Unable to calculate scope dominance graph!");
 216   SmallVector<LexicalScope *, 4> WorkStack;
 217   WorkStack.push_back(Scope);
 218   unsigned Counter = 0;
 219   while (!WorkStack.empty()) {
 220     LexicalScope *WS = WorkStack.back();
 221     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 222     bool visitedChildren = false;
 223     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
 224                                                          SE = Children.end();
 225          SI != SE; ++SI) {
 226       LexicalScope *ChildScope = *SI;
 227       if (!ChildScope->getDFSOut()) {
 228         WorkStack.push_back(ChildScope);
 229         visitedChildren = true;
 230         ChildScope->setDFSIn(++Counter);
 231         break;
 232       }
 233     }
 234     if (!visitedChildren) {
 235       WorkStack.pop_back();
 236       WS->setDFSOut(++Counter);
 237     }
 238   }
 239 }
 240
 241 /// assignInstructionRanges - Find ranges of instructions covered by each
 242 /// lexical scope.
 243 void LexicalScopes::assignInstructionRanges(
 244     SmallVectorImpl<InsnRange> &MIRanges,
 245     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 246
 247   LexicalScope *PrevLexicalScope = nullptr;
 248   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 249                                                   RE = MIRanges.end();
 250        RI != RE; ++RI) {
 251     const InsnRange &R = *RI;
 252     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 253     assert(S && "Lost LexicalScope for a machine instruction!");
 254     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 255       PrevLexicalScope->closeInsnRange(S);
 256     S->openInsnRange(R.first);
 257     S->extendInsnRange(R.second);
 258     PrevLexicalScope = S;
 259   }
 260
 261   if (PrevLexicalScope)
 262     PrevLexicalScope->closeInsnRange();
 263 }
 264
 265 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 266 /// have machine instructions that belong to lexical scope identified by
 267 /// DebugLoc.
 268 void LexicalScopes::getMachineBasicBlocks(
 269     DebugLoc DL, SmallPtrSet<const MachineBasicBlock *, 4> &MBBs) {
 270   MBBs.clear();
 271   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 272   if (!Scope)
 273     return;
 274
 275   if (Scope == CurrentFnLexicalScope) {
 276     for (const auto &MBB : *MF)
 277       MBBs.insert(&MBB);
 278     return;
 279   }
 280
 281   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 282   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 283                                             E = InsnRanges.end();
 284        I != E; ++I) {
 285     InsnRange &R = *I;
 286     MBBs.insert(R.first->getParent());
 287   }
 288 }
 289
 290 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 291 /// machine instruction's lexical scope in a given machine basic block.
 292 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
 293   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 294   if (!Scope)
 295     return false;
 296
 297   // Current function scope covers all basic blocks in the function.
 298   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 299     return true;
 300
 301   bool Result = false;
 302   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 303        ++I) {
 304     DebugLoc IDL = I->getDebugLoc();
 305     if (IDL.isUnknown())
 306       continue;
 307     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 308       if (Scope->dominates(IScope))
 309         return true;
 310   }
 311   return Result;
 312 }
 313
 314 /// dump - Print data structures.
 315 void LexicalScope::dump(unsigned Indent) const {
 316 #ifndef NDEBUG
 317   raw_ostream &err = dbgs();
 318   err.indent(Indent);
 319   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 320   const MDNode *N = Desc;
 321   err.indent(Indent);
 322   N->dump();
 323   if (AbstractScope)
 324     err << std::string(Indent, ' ') << "Abstract Scope\n";
 325
 326   if (!Children.empty())
 327     err << std::string(Indent + 2, ' ') << "Children ...\n";
 328   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 329     if (Children[i] != this)
 330       Children[i]->dump(Indent + 2);
 331 #endif
 332 }