contrib/llvm/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     const DILocation *PrevDL = nullptr;
  63     for (const auto &MInsn : MBB) {
  64       // Check if instruction has valid location information.
  65       const DILocation *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 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 108 /// given DebugLoc. Return NULL if not found.
 109 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
 110   DILocalScope *Scope = DL->getScope();
 111   if (!Scope)
 112     return nullptr;
 113
 114   // The scope that we were created with could have an extra file - which
 115   // isn't what we care about in this case.
 116   Scope = Scope->getNonLexicalBlockFileScope();
 117
 118   if (auto *IA = DL->getInlinedAt()) {
 119     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 120     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 121   }
 122   return findLexicalScope(Scope);
 123 }
 124
 125 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 126 /// not available then create new lexical scope.
 127 LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
 128                                                      const DILocation *IA) {
 129   if (IA) {
 130     // Create an abstract scope for inlined function.
 131     getOrCreateAbstractScope(Scope);
 132     // Create an inlined scope for inlined function.
 133     return getOrCreateInlinedScope(Scope, IA);
 134   }
 135
 136   return getOrCreateRegularScope(Scope);
 137 }
 138
 139 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 140 LexicalScope *
 141 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 142   assert(Scope && "Invalid Scope encoding!");
 143   Scope = Scope->getNonLexicalBlockFileScope();
 144
 145   auto I = LexicalScopeMap.find(Scope);
 146   if (I != LexicalScopeMap.end())
 147     return &I->second;
 148
 149   // FIXME: Should the following dyn_cast be DILexicalBlock?
 150   LexicalScope *Parent = nullptr;
 151   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 152     Parent = getOrCreateLexicalScope(Block->getScope());
 153   I = LexicalScopeMap.emplace(std::piecewise_construct,
 154                               std::forward_as_tuple(Scope),
 155                               std::forward_as_tuple(Parent, Scope, nullptr,
 156                                                     false)).first;
 157
 158   if (!Parent) {
 159     assert(cast<DISubprogram>(Scope)->describes(MF->getFunction()));
 160     assert(!CurrentFnLexicalScope);
 161     CurrentFnLexicalScope = &I->second;
 162   }
 163
 164   return &I->second;
 165 }
 166
 167 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 168 LexicalScope *
 169 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
 170                                        const DILocation *InlinedAt) {
 171   assert(Scope && "Invalid Scope encoding!");
 172   Scope = Scope->getNonLexicalBlockFileScope();
 173   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
 174   auto I = InlinedLexicalScopeMap.find(P);
 175   if (I != InlinedLexicalScopeMap.end())
 176     return &I->second;
 177
 178   LexicalScope *Parent;
 179   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 180     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 181   else
 182     Parent = getOrCreateLexicalScope(InlinedAt);
 183
 184   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
 185                                      std::forward_as_tuple(P),
 186                                      std::forward_as_tuple(Parent, Scope,
 187                                                            InlinedAt, false))
 188           .first;
 189   return &I->second;
 190 }
 191
 192 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 193 LexicalScope *
 194 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
 195   assert(Scope && "Invalid Scope encoding!");
 196   Scope = Scope->getNonLexicalBlockFileScope();
 197   auto I = AbstractScopeMap.find(Scope);
 198   if (I != AbstractScopeMap.end())
 199     return &I->second;
 200
 201   // FIXME: Should the following isa be DILexicalBlock?
 202   LexicalScope *Parent = nullptr;
 203   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 204     Parent = getOrCreateAbstractScope(Block->getScope());
 205
 206   I = AbstractScopeMap.emplace(std::piecewise_construct,
 207                                std::forward_as_tuple(Scope),
 208                                std::forward_as_tuple(Parent, Scope,
 209                                                      nullptr, true)).first;
 210   if (isa<DISubprogram>(Scope))
 211     AbstractScopesList.push_back(&I->second);
 212   return &I->second;
 213 }
 214
 215 /// constructScopeNest
 216 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 217   assert(Scope && "Unable to calculate scope dominance graph!");
 218   SmallVector<LexicalScope *, 4> WorkStack;
 219   WorkStack.push_back(Scope);
 220   unsigned Counter = 0;
 221   while (!WorkStack.empty()) {
 222     LexicalScope *WS = WorkStack.back();
 223     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 224     bool visitedChildren = false;
 225     for (auto &ChildScope : Children)
 226       if (!ChildScope->getDFSOut()) {
 227         WorkStack.push_back(ChildScope);
 228         visitedChildren = true;
 229         ChildScope->setDFSIn(++Counter);
 230         break;
 231       }
 232     if (!visitedChildren) {
 233       WorkStack.pop_back();
 234       WS->setDFSOut(++Counter);
 235     }
 236   }
 237 }
 238
 239 /// assignInstructionRanges - Find ranges of instructions covered by each
 240 /// lexical scope.
 241 void LexicalScopes::assignInstructionRanges(
 242     SmallVectorImpl<InsnRange> &MIRanges,
 243     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 244
 245   LexicalScope *PrevLexicalScope = nullptr;
 246   for (const auto &R : MIRanges) {
 247     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 248     assert(S && "Lost LexicalScope for a machine instruction!");
 249     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 250       PrevLexicalScope->closeInsnRange(S);
 251     S->openInsnRange(R.first);
 252     S->extendInsnRange(R.second);
 253     PrevLexicalScope = S;
 254   }
 255
 256   if (PrevLexicalScope)
 257     PrevLexicalScope->closeInsnRange();
 258 }
 259
 260 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 261 /// have machine instructions that belong to lexical scope identified by
 262 /// DebugLoc.
 263 void LexicalScopes::getMachineBasicBlocks(
 264     const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 265   MBBs.clear();
 266   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 267   if (!Scope)
 268     return;
 269
 270   if (Scope == CurrentFnLexicalScope) {
 271     for (const auto &MBB : *MF)
 272       MBBs.insert(&MBB);
 273     return;
 274   }
 275
 276   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 277   for (auto &R : InsnRanges)
 278     MBBs.insert(R.first->getParent());
 279 }
 280
 281 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 282 /// machine instruction's lexical scope in a given machine basic block.
 283 bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
 284   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 285   if (!Scope)
 286     return false;
 287
 288   // Current function scope covers all basic blocks in the function.
 289   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 290     return true;
 291
 292   bool Result = false;
 293   for (auto &I : *MBB) {
 294     if (const DILocation *IDL = I.getDebugLoc())
 295       if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 296         if (Scope->dominates(IScope))
 297           return true;
 298   }
 299   return Result;
 300 }
 301
 302 /// dump - Print data structures.
 303 void LexicalScope::dump(unsigned Indent) const {
 304 #ifndef NDEBUG
 305   raw_ostream &err = dbgs();
 306   err.indent(Indent);
 307   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 308   const MDNode *N = Desc;
 309   err.indent(Indent);
 310   N->dump();
 311   if (AbstractScope)
 312     err << std::string(Indent, ' ') << "Abstract Scope\n";
 313
 314   if (!Children.empty())
 315     err << std::string(Indent + 2, ' ') << "Children ...\n";
 316   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 317     if (Children[i] != this)
 318       Children[i]->dump(Indent + 2);
 319 #endif
 320 }