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 (MachineFunction::const_iterator I = MF->begin(), E = MF->end(); I != E;
  63        ++I) {
  64     const MachineInstr *RangeBeginMI = nullptr;
  65     const MachineInstr *PrevMI = nullptr;
  66     DebugLoc PrevDL;
  67     for (MachineBasicBlock::const_iterator II = I->begin(), IE = I->end();
  68          II != IE; ++II) {
  69       const MachineInstr *MInsn = II;
  70
  71       // Check if instruction has valid location information.
  72       const DebugLoc MIDL = MInsn->getDebugLoc();
  73       if (MIDL.isUnknown()) {
  74         PrevMI = MInsn;
  75         continue;
  76       }
  77
  78       // If scope has not changed then skip this instruction.
  79       if (MIDL == PrevDL) {
  80         PrevMI = MInsn;
  81         continue;
  82       }
  83
  84       // Ignore DBG_VALUE. It does not contribute to any instruction in output.
  85       if (MInsn->isDebugValue())
  86         continue;
  87
  88       if (RangeBeginMI) {
  89         // If we have already seen a beginning of an instruction range and
  90         // current instruction scope does not match scope of first instruction
  91         // in this range then create a new instruction range.
  92         InsnRange R(RangeBeginMI, PrevMI);
  93         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
  94         MIRanges.push_back(R);
  95       }
  96
  97       // This is a beginning of a new instruction range.
  98       RangeBeginMI = MInsn;
  99
 100       // Reset previous markers.
 101       PrevMI = MInsn;
 102       PrevDL = MIDL;
 103     }
 104
 105     // Create last instruction range.
 106     if (RangeBeginMI && PrevMI && !PrevDL.isUnknown()) {
 107       InsnRange R(RangeBeginMI, PrevMI);
 108       MIRanges.push_back(R);
 109       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 110     }
 111   }
 112 }
 113
 114 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 115 /// given DebugLoc. Return NULL if not found.
 116 LexicalScope *LexicalScopes::findLexicalScope(DebugLoc DL) {
 117   MDNode *Scope = nullptr;
 118   MDNode *IA = nullptr;
 119   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
 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   DIDescriptor D = DIDescriptor(Scope);
 126   if (D.isLexicalBlockFile())
 127     Scope = DILexicalBlockFile(Scope).getScope();
 128
 129   if (IA)
 130     return InlinedLexicalScopeMap.lookup(DebugLoc::getFromDILocation(IA));
 131   return LexicalScopeMap.lookup(Scope);
 132 }
 133
 134 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 135 /// not available then create new lexical scope.
 136 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
 137   MDNode *Scope = nullptr;
 138   MDNode *InlinedAt = nullptr;
 139   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
 140
 141   if (InlinedAt) {
 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 *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
 153   DIDescriptor D = DIDescriptor(Scope);
 154   if (D.isLexicalBlockFile()) {
 155     Scope = DILexicalBlockFile(Scope).getScope();
 156     D = DIDescriptor(Scope);
 157   }
 158
 159   LexicalScope *WScope = LexicalScopeMap.lookup(Scope);
 160   if (WScope)
 161     return WScope;
 162
 163   LexicalScope *Parent = nullptr;
 164   if (D.isLexicalBlock())
 165     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
 166   WScope = new LexicalScope(Parent, DIDescriptor(Scope), nullptr, false);
 167   LexicalScopeMap.insert(std::make_pair(Scope, WScope));
 168   if (!Parent && DIDescriptor(Scope).isSubprogram() &&
 169       DISubprogram(Scope).describes(MF->getFunction()))
 170     CurrentFnLexicalScope = WScope;
 171
 172   return WScope;
 173 }
 174
 175 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 176 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *Scope,
 177                                                      MDNode *InlinedAt) {
 178   LexicalScope *InlinedScope = LexicalScopeMap.lookup(InlinedAt);
 179   if (InlinedScope)
 180     return InlinedScope;
 181
 182   DebugLoc InlinedLoc = DebugLoc::getFromDILocation(InlinedAt);
 183   InlinedScope = new LexicalScope(getOrCreateLexicalScope(InlinedLoc),
 184                                   DIDescriptor(Scope), InlinedAt, false);
 185   InlinedLexicalScopeMap[InlinedLoc] = InlinedScope;
 186   LexicalScopeMap[InlinedAt] = InlinedScope;
 187   return InlinedScope;
 188 }
 189
 190 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 191 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
 192   assert(N && "Invalid Scope encoding!");
 193
 194   DIDescriptor Scope(N);
 195   if (Scope.isLexicalBlockFile())
 196     Scope = DILexicalBlockFile(Scope).getScope();
 197   LexicalScope *AScope = AbstractScopeMap.lookup(N);
 198   if (AScope)
 199     return AScope;
 200
 201   LexicalScope *Parent = nullptr;
 202   if (Scope.isLexicalBlock()) {
 203     DILexicalBlock DB(N);
 204     DIDescriptor ParentDesc = DB.getContext();
 205     Parent = getOrCreateAbstractScope(ParentDesc);
 206   }
 207   AScope = new LexicalScope(Parent, DIDescriptor(N), nullptr, true);
 208   AbstractScopeMap[N] = AScope;
 209   if (DIDescriptor(N).isSubprogram())
 210     AbstractScopesList.push_back(AScope);
 211   return AScope;
 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 (MachineFunction::const_iterator I = MF->begin(), E = MF->end(); I != E;
 278          ++I)
 279       MBBs.insert(I);
 280     return;
 281   }
 282
 283   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 284   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
 285                                             E = InsnRanges.end();
 286        I != E; ++I) {
 287     InsnRange &R = *I;
 288     MBBs.insert(R.first->getParent());
 289   }
 290 }
 291
 292 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 293 /// machine instruction's lexical scope in a given machine basic block.
 294 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
 295   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 296   if (!Scope)
 297     return false;
 298
 299   // Current function scope covers all basic blocks in the function.
 300   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 301     return true;
 302
 303   bool Result = false;
 304   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
 305        ++I) {
 306     DebugLoc IDL = I->getDebugLoc();
 307     if (IDL.isUnknown())
 308       continue;
 309     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 310       if (Scope->dominates(IScope))
 311         return true;
 312   }
 313   return Result;
 314 }
 315
 316 /// dump - Print data structures.
 317 void LexicalScope::dump(unsigned Indent) const {
 318 #ifndef NDEBUG
 319   raw_ostream &err = dbgs();
 320   err.indent(Indent);
 321   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 322   const MDNode *N = Desc;
 323   err.indent(Indent);
 324   N->dump();
 325   if (AbstractScope)
 326     err << std::string(Indent, ' ') << "Abstract Scope\n";
 327
 328   if (!Children.empty())
 329     err << std::string(Indent + 2, ' ') << "Children ...\n";
 330   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 331     if (Children[i] != this)
 332       Children[i]->dump(Indent + 2);
 333 #endif
 334 }