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      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 #define DEBUG_TYPE "lexicalscopes"
     18 #include "llvm/CodeGen/LexicalScopes.h"
     19 #include "llvm/Function.h"
     20 #include "llvm/Analysis/DebugInfo.h"
     21 #include "llvm/CodeGen/MachineFunction.h"
     22 #include "llvm/CodeGen/MachineInstr.h"
     23 #include "llvm/Support/Debug.h"
     24 #include "llvm/Support/ErrorHandling.h"
     25 #include "llvm/Support/FormattedStream.h"
     26 using namespace llvm;
     27 
     28 LexicalScopes::~LexicalScopes() {
     29   releaseMemory();
     30 }
     31 
     32 /// releaseMemory - release memory.
     33 void LexicalScopes::releaseMemory() {
     34   MF = NULL;
     35   CurrentFnLexicalScope = NULL;
     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   releaseMemory();
     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::
     58 extractLexicalScopes(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();
     63        I != E; ++I) {
     64     const MachineInstr *RangeBeginMI = NULL;
     65     const MachineInstr *PrevMI = NULL;
     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 = NULL;
    118   MDNode *IA = NULL;
    119   DL.getScopeAndInlinedAt(Scope, IA, MF->getFunction()->getContext());
    120   if (!Scope) return NULL;
    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 = NULL;
    137   MDNode *InlinedAt = NULL;
    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 = NULL;
    163   if (D.isLexicalBlock())
    164     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
    165   WScope = new LexicalScope(Parent, DIDescriptor(Scope), NULL, 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 = NULL;
    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), NULL, 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 scop edominance 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 SmallVector<LexicalScope *, 4> &Children = WS->getChildren();
    222     bool visitedChildren = false;
    223     for (SmallVector<LexicalScope *, 4>::const_iterator SI = Children.begin(),
    224            SE = Children.end(); SI != SE; ++SI) {
    225       LexicalScope *ChildScope = *SI;
    226       if (!ChildScope->getDFSOut()) {
    227         WorkStack.push_back(ChildScope);
    228         visitedChildren = true;
    229         ChildScope->setDFSIn(++Counter);
    230         break;
    231       }
    232     }
    233     if (!visitedChildren) {
    234       WorkStack.pop_back();
    235       WS->setDFSOut(++Counter);
    236     }
    237   }
    238 }
    239 
    240 /// assignInstructionRanges - Find ranges of instructions covered by each
    241 /// lexical scope.
    242 void LexicalScopes::
    243 assignInstructionRanges(SmallVectorImpl<InsnRange> &MIRanges,
    244                     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap)
    245 {
    246 
    247   LexicalScope *PrevLexicalScope = NULL;
    248   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
    249          RE = MIRanges.end(); RI != RE; ++RI) {
    250     const InsnRange &R = *RI;
    251     LexicalScope *S = MI2ScopeMap.lookup(R.first);
    252     assert (S && "Lost LexicalScope for a machine instruction!");
    253     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
    254       PrevLexicalScope->closeInsnRange(S);
    255     S->openInsnRange(R.first);
    256     S->extendInsnRange(R.second);
    257     PrevLexicalScope = S;
    258   }
    259 
    260   if (PrevLexicalScope)
    261     PrevLexicalScope->closeInsnRange();
    262 }
    263 
    264 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
    265 /// have machine instructions that belong to lexical scope identified by
    266 /// DebugLoc.
    267 void LexicalScopes::
    268 getMachineBasicBlocks(DebugLoc DL,
    269                       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 (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
    277          I != E; ++I)
    278       MBBs.insert(I);
    279     return;
    280   }
    281 
    282   SmallVector<InsnRange, 4> &InsnRanges = Scope->getRanges();
    283   for (SmallVector<InsnRange, 4>::iterator I = InsnRanges.begin(),
    284          E = InsnRanges.end(); 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();
    303        I != E; ++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 void LexicalScope::anchor() { }
    315 
    316 /// dump - Print data structures.
    317 void LexicalScope::dump() const {
    318 #ifndef NDEBUG
    319   raw_ostream &err = dbgs();
    320   err.indent(IndentLevel);
    321   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
    322   const MDNode *N = Desc;
    323   N->dump();
    324   if (AbstractScope)
    325     err << "Abstract Scope\n";
    326 
    327   IndentLevel += 2;
    328   if (!Children.empty())
    329     err << "Children ...\n";
    330   for (unsigned i = 0, e = Children.size(); i != e; ++i)
    331     if (Children[i] != this)
    332       Children[i]->dump();
    333 
    334   IndentLevel -= 2;
    335 #endif
    336 }
    337 
    338