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 #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   if (IA)
 122     return InlinedLexicalScopeMap.lookup(DebugLoc::getFromDILocation(IA));
 123   return LexicalScopeMap.lookup(DL.getScope(Scope->getContext()));
 124 }
 125
 126 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 127 /// not available then create new lexical scope.
 128 LexicalScope *LexicalScopes::getOrCreateLexicalScope(DebugLoc DL) {
 129   MDNode *Scope = NULL;
 130   MDNode *InlinedAt = NULL;
 131   DL.getScopeAndInlinedAt(Scope, InlinedAt, MF->getFunction()->getContext());
 132   if (InlinedAt) {
 133     // Create an abstract scope for inlined function.
 134     getOrCreateAbstractScope(Scope);
 135     // Create an inlined scope for inlined function.
 136     return getOrCreateInlinedScope(Scope, InlinedAt);
 137   }
 138
 139   return getOrCreateRegularScope(Scope);
 140 }
 141
 142 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 143 LexicalScope *LexicalScopes::getOrCreateRegularScope(MDNode *Scope) {
 144   LexicalScope *WScope = LexicalScopeMap.lookup(Scope);
 145   if (WScope)
 146     return WScope;
 147
 148   LexicalScope *Parent = NULL;
 149   if (DIDescriptor(Scope).isLexicalBlock())
 150     Parent = getOrCreateLexicalScope(DebugLoc::getFromDILexicalBlock(Scope));
 151   WScope = new LexicalScope(Parent, DIDescriptor(Scope), NULL, false);
 152   LexicalScopeMap.insert(std::make_pair(Scope, WScope));
 153   if (!Parent && DIDescriptor(Scope).isSubprogram()
 154       && DISubprogram(Scope).describes(MF->getFunction()))
 155     CurrentFnLexicalScope = WScope;
 156
 157   return WScope;
 158 }
 159
 160 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 161 LexicalScope *LexicalScopes::getOrCreateInlinedScope(MDNode *Scope,
 162                                                      MDNode *InlinedAt) {
 163   LexicalScope *InlinedScope = LexicalScopeMap.lookup(InlinedAt);
 164   if (InlinedScope)
 165     return InlinedScope;
 166
 167   DebugLoc InlinedLoc = DebugLoc::getFromDILocation(InlinedAt);
 168   InlinedScope = new LexicalScope(getOrCreateLexicalScope(InlinedLoc),
 169                                   DIDescriptor(Scope), InlinedAt, false);
 170   InlinedLexicalScopeMap[InlinedLoc] = InlinedScope;
 171   LexicalScopeMap[InlinedAt] = InlinedScope;
 172   return InlinedScope;
 173 }
 174
 175 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 176 LexicalScope *LexicalScopes::getOrCreateAbstractScope(const MDNode *N) {
 177   assert(N && "Invalid Scope encoding!");
 178
 179   LexicalScope *AScope = AbstractScopeMap.lookup(N);
 180   if (AScope)
 181     return AScope;
 182
 183   LexicalScope *Parent = NULL;
 184   DIDescriptor Scope(N);
 185   if (Scope.isLexicalBlock()) {
 186     DILexicalBlock DB(N);
 187     DIDescriptor ParentDesc = DB.getContext();
 188     Parent = getOrCreateAbstractScope(ParentDesc);
 189   }
 190   AScope = new LexicalScope(Parent, DIDescriptor(N), NULL, true);
 191   AbstractScopeMap[N] = AScope;
 192   if (DIDescriptor(N).isSubprogram())
 193     AbstractScopesList.push_back(AScope);
 194   return AScope;
 195 }
 196
 197 /// constructScopeNest
 198 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 199   assert (Scope && "Unable to calculate scop edominance graph!");
 200   SmallVector<LexicalScope *, 4> WorkStack;
 201   WorkStack.push_back(Scope);
 202   unsigned Counter = 0;
 203   while (!WorkStack.empty()) {
 204     LexicalScope *WS = WorkStack.back();
 205     const SmallVector<LexicalScope *, 4> &Children = WS->getChildren();
 206     bool visitedChildren = false;
 207     for (SmallVector<LexicalScope *, 4>::const_iterator SI = Children.begin(),
 208            SE = Children.end(); SI != SE; ++SI) {
 209       LexicalScope *ChildScope = *SI;
 210       if (!ChildScope->getDFSOut()) {
 211         WorkStack.push_back(ChildScope);
 212         visitedChildren = true;
 213         ChildScope->setDFSIn(++Counter);
 214         break;
 215       }
 216     }
 217     if (!visitedChildren) {
 218       WorkStack.pop_back();
 219       WS->setDFSOut(++Counter);
 220     }
 221   }
 222 }
 223
 224 /// assignInstructionRanges - Find ranges of instructions covered by each lexical
 225 /// scope.
 226 void LexicalScopes::
 227 assignInstructionRanges(SmallVectorImpl<InsnRange> &MIRanges,
 228                     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 229
 230   LexicalScope *PrevLexicalScope = NULL;
 231   for (SmallVectorImpl<InsnRange>::const_iterator RI = MIRanges.begin(),
 232          RE = MIRanges.end(); RI != RE; ++RI) {
 233     const InsnRange &R = *RI;
 234     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 235     assert (S && "Lost LexicalScope for a machine instruction!");
 236     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 237       PrevLexicalScope->closeInsnRange(S);
 238     S->openInsnRange(R.first);
 239     S->extendInsnRange(R.second);
 240     PrevLexicalScope = S;
 241   }
 242
 243   if (PrevLexicalScope)
 244     PrevLexicalScope->closeInsnRange();
 245 }
 246
 247 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 248 /// have machine instructions that belong to lexical scope identified by
 249 /// DebugLoc.
 250 void LexicalScopes::
 251 getMachineBasicBlocks(DebugLoc DL, SmallPtrSet<const MachineBasicBlock*, 4> &MBBs) {
 252   MBBs.clear();
 253   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 254   if (!Scope)
 255     return;
 256
 257   SmallVector<InsnRange, 4> &InsnRanges = Scope->getRanges();
 258   for (SmallVector<InsnRange, 4>::iterator I = InsnRanges.begin(),
 259          E = InsnRanges.end(); I != E; ++I) {
 260     InsnRange &R = *I;
 261     MBBs.insert(R.first->getParent());
 262   }
 263 }
 264
 265 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 266 /// machine instruction's lexical scope in a given machine basic block.
 267 bool LexicalScopes::dominates(DebugLoc DL, MachineBasicBlock *MBB) {
 268   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 269   if (!Scope)
 270     return false;
 271   bool Result = false;
 272   for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
 273        I != E; ++I) {
 274     DebugLoc IDL = I->getDebugLoc();
 275     if (IDL.isUnknown())
 276       continue;
 277     if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 278       if (Scope->dominates(IScope))
 279         return true;
 280   }
 281   return Result;
 282 }
 283
 284 /// dump - Print data structures.
 285 void LexicalScope::dump() const {
 286 #ifndef NDEBUG
 287   raw_ostream &err = dbgs();
 288   err.indent(IndentLevel);
 289   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 290   const MDNode *N = Desc;
 291   N->dump();
 292   if (AbstractScope)
 293     err << "Abstract Scope\n";
 294
 295   IndentLevel += 2;
 296   if (!Children.empty())
 297     err << "Children ...\n";
 298   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 299     if (Children[i] != this)
 300       Children[i]->dump();
 301
 302   IndentLevel -= 2;
 303 #endif
 304 }
 305