LLVM API Documentation

LexicalScopes.cpp
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00001 //===- LexicalScopes.cpp - Collecting lexical scope info ------------------===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements LexicalScopes analysis.
00011 //
00012 // This pass collects lexical scope information and maps machine instructions
00013 // to respective lexical scopes.
00014 //
00015 //===----------------------------------------------------------------------===//
00016 
00017 #include "llvm/CodeGen/LexicalScopes.h"
00018 #include "llvm/CodeGen/MachineFunction.h"
00019 #include "llvm/CodeGen/MachineInstr.h"
00020 #include "llvm/IR/DebugInfo.h"
00021 #include "llvm/IR/Function.h"
00022 #include "llvm/Support/Debug.h"
00023 #include "llvm/Support/ErrorHandling.h"
00024 #include "llvm/Support/FormattedStream.h"
00025 using namespace llvm;
00026 
00027 #define DEBUG_TYPE "lexicalscopes"
00028 
00029 /// reset - Reset the instance so that it's prepared for another function.
00030 void LexicalScopes::reset() {
00031   MF = nullptr;
00032   CurrentFnLexicalScope = nullptr;
00033   LexicalScopeMap.clear();
00034   AbstractScopeMap.clear();
00035   InlinedLexicalScopeMap.clear();
00036   AbstractScopesList.clear();
00037 }
00038 
00039 /// initialize - Scan machine function and constuct lexical scope nest.
00040 void LexicalScopes::initialize(const MachineFunction &Fn) {
00041   reset();
00042   MF = &Fn;
00043   SmallVector<InsnRange, 4> MIRanges;
00044   DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
00045   extractLexicalScopes(MIRanges, MI2ScopeMap);
00046   if (CurrentFnLexicalScope) {
00047     constructScopeNest(CurrentFnLexicalScope);
00048     assignInstructionRanges(MIRanges, MI2ScopeMap);
00049   }
00050 }
00051 
00052 /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
00053 /// for the given machine function.
00054 void LexicalScopes::extractLexicalScopes(
00055     SmallVectorImpl<InsnRange> &MIRanges,
00056     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
00057 
00058   // Scan each instruction and create scopes. First build working set of scopes.
00059   for (const auto &MBB : *MF) {
00060     const MachineInstr *RangeBeginMI = nullptr;
00061     const MachineInstr *PrevMI = nullptr;
00062     DebugLoc PrevDL;
00063     for (const auto &MInsn : MBB) {
00064       // Check if instruction has valid location information.
00065       const DebugLoc MIDL = MInsn.getDebugLoc();
00066       if (MIDL.isUnknown()) {
00067         PrevMI = &MInsn;
00068         continue;
00069       }
00070 
00071       // If scope has not changed then skip this instruction.
00072       if (MIDL == PrevDL) {
00073         PrevMI = &MInsn;
00074         continue;
00075       }
00076 
00077       // Ignore DBG_VALUE. It does not contribute to any instruction in output.
00078       if (MInsn.isDebugValue())
00079         continue;
00080 
00081       if (RangeBeginMI) {
00082         // If we have already seen a beginning of an instruction range and
00083         // current instruction scope does not match scope of first instruction
00084         // in this range then create a new instruction range.
00085         InsnRange R(RangeBeginMI, PrevMI);
00086         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
00087         MIRanges.push_back(R);
00088       }
00089 
00090       // This is a beginning of a new instruction range.
00091       RangeBeginMI = &MInsn;
00092 
00093       // Reset previous markers.
00094       PrevMI = &MInsn;
00095       PrevDL = MIDL;
00096     }
00097 
00098     // Create last instruction range.
00099     if (RangeBeginMI && PrevMI && !PrevDL.isUnknown()) {
00100       InsnRange R(RangeBeginMI, PrevMI);
00101       MIRanges.push_back(R);
00102       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
00103     }
00104   }
00105 }
00106 
00107 LexicalScope *LexicalScopes::findInlinedScope(DebugLoc DL) {
00108   MDNode *Scope = nullptr;
00109   MDNode *IA = nullptr;
00110   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
00111   auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
00112   return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
00113 }
00114 
00115 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
00116 /// given DebugLoc. Return NULL if not found.
00117 LexicalScope *LexicalScopes::findLexicalScope(DebugLoc DL) {
00118   MDNode *Scope = nullptr;
00119   MDNode *IA = nullptr;
00120   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
00121   if (!Scope)
00122     return nullptr;
00123 
00124   // The scope that we were created with could have an extra file - which
00125   // isn't what we care about in this case.
00126   DIDescriptor D = DIDescriptor(Scope);
00127   if (D.isLexicalBlockFile())
00128     Scope = DILexicalBlockFile(Scope).getScope();
00129 
00130   if (IA) {
00131     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
00132     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
00133   }
00134   return findLexicalScope(Scope);
00135 }
00136 
00137 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
00138 /// not available then create new lexical scope.
00139 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
00140   MDNode *Scope = nullptr;
00141   MDNode *InlinedAt = nullptr;
00142   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
00143 
00144   if (InlinedAt) {
00145     // Create an abstract scope for inlined function.
00146     getOrCreateAbstractScope(Scope);
00147     // Create an inlined scope for inlined function.
00148     return getOrCreateInlinedScope(Scope, InlinedAt);
00149   }
00150 
00151   return getOrCreateRegularScope(Scope);
00152 }
00153 
00154 /// getOrCreateRegularScope - Find or create a regular lexical scope.
00155 LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
00156   DIDescriptor D = DIDescriptor(Scope);
00157   if (D.isLexicalBlockFile()) {
00158     Scope = DILexicalBlockFile(Scope).getScope();
00159     D = DIDescriptor(Scope);
00160   }
00161 
00162   auto I = LexicalScopeMap.find(Scope);
00163   if (I != LexicalScopeMap.end())
00164     return &I->second;
00165 
00166   LexicalScope *Parent = nullptr;
00167   if (D.isLexicalBlock())
00168     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
00169   // FIXME: Use forward_as_tuple instead of make_tuple, once MSVC2012
00170   // compatibility is no longer required.
00171   I = LexicalScopeMap.emplace(std::piecewise_construct, std::make_tuple(Scope),
00172                               std::make_tuple(Parent, DIDescriptor(Scope),
00173                                               nullptr, false)).first;
00174 
00175   if (!Parent && DIDescriptor(Scope).isSubprogram() &&
00176       DISubprogram(Scope).describes(MF->getFunction()))
00177     CurrentFnLexicalScope = &I->second;
00178 
00179   return &I->second;
00180 }
00181 
00182 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
00183 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *ScopeNode,
00184                                                      MDNode *InlinedAt) {
00185   std::pair<const MDNode*, const MDNode*> P(ScopeNode, InlinedAt);
00186   auto I = InlinedLexicalScopeMap.find(P);
00187   if (I != InlinedLexicalScopeMap.end())
00188     return &I->second;
00189 
00190   LexicalScope *Parent;
00191   DILexicalBlock Scope(ScopeNode);
00192   if (Scope.isSubprogram())
00193     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILocation(InlinedAt));
00194   else
00195     Parent = getOrCreateInlinedScope(Scope.getContext(), InlinedAt);
00196 
00197   // FIXME: Use forward_as_tuple instead of make_tuple, once MSVC2012
00198   // compatibility is no longer required.
00199   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
00200                                      std::make_tuple(P),
00201                                      std::make_tuple(Parent, Scope, InlinedAt,
00202                                                      false)).first;
00203   return &I->second;
00204 }
00205 
00206 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
00207 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
00208   assert(N && "Invalid Scope encoding!");
00209 
00210   DIDescriptor Scope(N);
00211   if (Scope.isLexicalBlockFile())
00212     Scope = DILexicalBlockFile(Scope).getScope();
00213   auto I = AbstractScopeMap.find(Scope);
00214   if (I != AbstractScopeMap.end())
00215     return &I->second;
00216 
00217   LexicalScope *Parent = nullptr;
00218   if (Scope.isLexicalBlock()) {
00219     DILexicalBlock DB(Scope);
00220     DIDescriptor ParentDesc = DB.getContext();
00221     Parent = getOrCreateAbstractScope(ParentDesc);
00222   }
00223   I = AbstractScopeMap.emplace(std::piecewise_construct,
00224                                std::forward_as_tuple(Scope),
00225                                std::forward_as_tuple(Parent, Scope,
00226                                                      nullptr, true)).first;
00227   if (Scope.isSubprogram())
00228     AbstractScopesList.push_back(&I->second);
00229   return &I->second;
00230 }
00231 
00232 /// constructScopeNest
00233 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
00234   assert(Scope && "Unable to calculate scope dominance graph!");
00235   SmallVector<LexicalScope *, 4> WorkStack;
00236   WorkStack.push_back(Scope);
00237   unsigned Counter = 0;
00238   while (!WorkStack.empty()) {
00239     LexicalScope *WS = WorkStack.back();
00240     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
00241     bool visitedChildren = false;
00242     for (SmallVectorImpl<LexicalScope *>::const_iterator SI = Children.begin(),
00243                                                          SE = Children.end();
00244          SI != SE; ++SI) {
00245       LexicalScope *ChildScope = *SI;
00246       if (!ChildScope->getDFSOut()) {
00247         WorkStack.push_back(ChildScope);
00248         visitedChildren = true;
00249         ChildScope->setDFSIn(++Counter);
00250         break;
00251       }
00252     }
00253     if (!visitedChildren) {
00254       WorkStack.pop_back();
00255       WS->setDFSOut(++Counter);
00256     }
00257   }
00258 }
00259 
00260 /// assignInstructionRanges - Find ranges of instructions covered by each
00261 /// lexical scope.
00262 void LexicalScopes::assignInstructionRanges(
00263     SmallVectorImpl<InsnRange> &MIRanges,
00264     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
00265 
00266   LexicalScope *PrevLexicalScope = nullptr;
00267   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
00268                                                   RE = MIRanges.end();
00269        RI != RE; ++RI) {
00270     const InsnRange &R = *RI;
00271     LexicalScope *S = MI2ScopeMap.lookup(R.first);
00272     assert(S && "Lost LexicalScope for a machine instruction!");
00273     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
00274       PrevLexicalScope->closeInsnRange(S);
00275     S->openInsnRange(R.first);
00276     S->extendInsnRange(R.second);
00277     PrevLexicalScope = S;
00278   }
00279 
00280   if (PrevLexicalScope)
00281     PrevLexicalScope->closeInsnRange();
00282 }
00283 
00284 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
00285 /// have machine instructions that belong to lexical scope identified by
00286 /// DebugLoc.
00287 void LexicalScopes::getMachineBasicBlocks(
00288     DebugLoc DL, SmallPtrSet<const MachineBasicBlock *, 4> &MBBs) {
00289   MBBs.clear();
00290   LexicalScope *Scope = getOrCreateLexicalScope(DL);
00291   if (!Scope)
00292     return;
00293 
00294   if (Scope == CurrentFnLexicalScope) {
00295     for (const auto &MBB : *MF)
00296       MBBs.insert(&MBB);
00297     return;
00298   }
00299 
00300   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
00301   for (SmallVectorImpl<InsnRange>::iterator I = InsnRanges.begin(),
00302                                             E = InsnRanges.end();
00303        I != E; ++I) {
00304     InsnRange &R = *I;
00305     MBBs.insert(R.first->getParent());
00306   }
00307 }
00308 
00309 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
00310 /// machine instruction's lexical scope in a given machine basic block.
00311 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
00312   LexicalScope *Scope = getOrCreateLexicalScope(DL);
00313   if (!Scope)
00314     return false;
00315 
00316   // Current function scope covers all basic blocks in the function.
00317   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
00318     return true;
00319 
00320   bool Result = false;
00321   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
00322        ++I) {
00323     DebugLoc IDL = I->getDebugLoc();
00324     if (IDL.isUnknown())
00325       continue;
00326     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
00327       if (Scope->dominates(IScope))
00328         return true;
00329   }
00330   return Result;
00331 }
00332 
00333 /// dump - Print data structures.
00334 void LexicalScope::dump(unsigned Indent) const {
00335 #ifndef NDEBUG
00336   raw_ostream &err = dbgs();
00337   err.indent(Indent);
00338   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
00339   const MDNode *N = Desc;
00340   err.indent(Indent);
00341   N->dump();
00342   if (AbstractScope)
00343     err << std::string(Indent, ' ') << "Abstract Scope\n";
00344 
00345   if (!Children.empty())
00346     err << std::string(Indent + 2, ' ') << "Children ...\n";
00347   for (unsigned i = 0, e = Children.size(); i != e; ++i)
00348     if (Children[i] != this)
00349       Children[i]->dump(Indent + 2);
00350 #endif
00351 }