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