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/ADT/DenseMap.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/CodeGen/LexicalScopes.h"
  20 #include "llvm/CodeGen/MachineBasicBlock.h"
  21 #include "llvm/CodeGen/MachineFunction.h"
  22 #include "llvm/CodeGen/MachineInstr.h"
  23 #include "llvm/IR/DebugInfoMetadata.h"
  24 #include "llvm/IR/Metadata.h"
  25 #include "llvm/Support/Casting.h"
  26 #include "llvm/Support/Compiler.h"
  27 #include "llvm/Support/Debug.h"
  28 #include "llvm/Support/raw_ostream.h"
  29 #include <cassert>
  30 #include <string>
  31 #include <tuple>
  32 #include <utility>
  33
  34 using namespace llvm;
  35
  36 #define DEBUG_TYPE "lexicalscopes"
  37
  38 /// reset - Reset the instance so that it's prepared for another function.
  39 void LexicalScopes::reset() {
  40   MF = nullptr;
  41   CurrentFnLexicalScope = nullptr;
  42   LexicalScopeMap.clear();
  43   AbstractScopeMap.clear();
  44   InlinedLexicalScopeMap.clear();
  45   AbstractScopesList.clear();
  46 }
  47
  48 /// initialize - Scan machine function and constuct lexical scope nest.
  49 void LexicalScopes::initialize(const MachineFunction &Fn) {
  50   // Don't attempt any lexical scope creation for a NoDebug compile unit.
  51   if (Fn.getFunction()->getSubprogram()->getUnit()->getEmissionKind() ==
  52       DICompileUnit::NoDebug)
  53     return;
  54   reset();
  55   MF = &Fn;
  56   SmallVector<InsnRange, 4> MIRanges;
  57   DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
  58   extractLexicalScopes(MIRanges, MI2ScopeMap);
  59   if (CurrentFnLexicalScope) {
  60     constructScopeNest(CurrentFnLexicalScope);
  61     assignInstructionRanges(MIRanges, MI2ScopeMap);
  62   }
  63 }
  64
  65 /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
  66 /// for the given machine function.
  67 void LexicalScopes::extractLexicalScopes(
  68     SmallVectorImpl<InsnRange> &MIRanges,
  69     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
  70   // Scan each instruction and create scopes. First build working set of scopes.
  71   for (const auto &MBB : *MF) {
  72     const MachineInstr *RangeBeginMI = nullptr;
  73     const MachineInstr *PrevMI = nullptr;
  74     const DILocation *PrevDL = nullptr;
  75     for (const auto &MInsn : MBB) {
  76       // Check if instruction has valid location information.
  77       const DILocation *MIDL = MInsn.getDebugLoc();
  78       if (!MIDL) {
  79         PrevMI = &MInsn;
  80         continue;
  81       }
  82
  83       // If scope has not changed then skip this instruction.
  84       if (MIDL == PrevDL) {
  85         PrevMI = &MInsn;
  86         continue;
  87       }
  88
  89       // Ignore DBG_VALUE. It does not contribute to any instruction in output.
  90       if (MInsn.isDebugValue())
  91         continue;
  92
  93       if (RangeBeginMI) {
  94         // If we have already seen a beginning of an instruction range and
  95         // current instruction scope does not match scope of first instruction
  96         // in this range then create a new instruction range.
  97         InsnRange R(RangeBeginMI, PrevMI);
  98         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
  99         MIRanges.push_back(R);
 100       }
 101
 102       // This is a beginning of a new instruction range.
 103       RangeBeginMI = &MInsn;
 104
 105       // Reset previous markers.
 106       PrevMI = &MInsn;
 107       PrevDL = MIDL;
 108     }
 109
 110     // Create last instruction range.
 111     if (RangeBeginMI && PrevMI && PrevDL) {
 112       InsnRange R(RangeBeginMI, PrevMI);
 113       MIRanges.push_back(R);
 114       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 115     }
 116   }
 117 }
 118
 119 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 120 /// given DebugLoc. Return NULL if not found.
 121 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
 122   DILocalScope *Scope = DL->getScope();
 123   if (!Scope)
 124     return nullptr;
 125
 126   // The scope that we were created with could have an extra file - which
 127   // isn't what we care about in this case.
 128   Scope = Scope->getNonLexicalBlockFileScope();
 129
 130   if (auto *IA = DL->getInlinedAt()) {
 131     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 132     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 133   }
 134   return findLexicalScope(Scope);
 135 }
 136
 137 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 138 /// not available then create new lexical scope.
 139 LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
 140                                                      const DILocation *IA) {
 141   if (IA) {
 142     // Skip scopes inlined from a NoDebug compile unit.
 143     if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
 144         DICompileUnit::NoDebug)
 145       return getOrCreateLexicalScope(IA);
 146     // Create an abstract scope for inlined function.
 147     getOrCreateAbstractScope(Scope);
 148     // Create an inlined scope for inlined function.
 149     return getOrCreateInlinedScope(Scope, IA);
 150   }
 151
 152   return getOrCreateRegularScope(Scope);
 153 }
 154
 155 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 156 LexicalScope *
 157 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 158   assert(Scope && "Invalid Scope encoding!");
 159   Scope = Scope->getNonLexicalBlockFileScope();
 160
 161   auto I = LexicalScopeMap.find(Scope);
 162   if (I != LexicalScopeMap.end())
 163     return &I->second;
 164
 165   // FIXME: Should the following dyn_cast be DILexicalBlock?
 166   LexicalScope *Parent = nullptr;
 167   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 168     Parent = getOrCreateLexicalScope(Block->getScope());
 169   I = LexicalScopeMap.emplace(std::piecewise_construct,
 170                               std::forward_as_tuple(Scope),
 171                               std::forward_as_tuple(Parent, Scope, nullptr,
 172                                                     false)).first;
 173
 174   if (!Parent) {
 175     assert(cast<DISubprogram>(Scope)->describes(MF->getFunction()));
 176     assert(!CurrentFnLexicalScope);
 177     CurrentFnLexicalScope = &I->second;
 178   }
 179
 180   return &I->second;
 181 }
 182
 183 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 184 LexicalScope *
 185 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
 186                                        const DILocation *InlinedAt) {
 187   assert(Scope && "Invalid Scope encoding!");
 188   Scope = Scope->getNonLexicalBlockFileScope();
 189   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
 190   auto I = InlinedLexicalScopeMap.find(P);
 191   if (I != InlinedLexicalScopeMap.end())
 192     return &I->second;
 193
 194   LexicalScope *Parent;
 195   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 196     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 197   else
 198     Parent = getOrCreateLexicalScope(InlinedAt);
 199
 200   I = InlinedLexicalScopeMap
 201           .emplace(std::piecewise_construct, std::forward_as_tuple(P),
 202                    std::forward_as_tuple(Parent, Scope, InlinedAt, false))
 203           .first;
 204   return &I->second;
 205 }
 206
 207 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 208 LexicalScope *
 209 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
 210   assert(Scope && "Invalid Scope encoding!");
 211   Scope = Scope->getNonLexicalBlockFileScope();
 212   auto I = AbstractScopeMap.find(Scope);
 213   if (I != AbstractScopeMap.end())
 214     return &I->second;
 215
 216   // FIXME: Should the following isa be DILexicalBlock?
 217   LexicalScope *Parent = nullptr;
 218   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 219     Parent = getOrCreateAbstractScope(Block->getScope());
 220
 221   I = AbstractScopeMap.emplace(std::piecewise_construct,
 222                                std::forward_as_tuple(Scope),
 223                                std::forward_as_tuple(Parent, Scope,
 224                                                      nullptr, true)).first;
 225   if (isa<DISubprogram>(Scope))
 226     AbstractScopesList.push_back(&I->second);
 227   return &I->second;
 228 }
 229
 230 /// constructScopeNest
 231 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 232   assert(Scope && "Unable to calculate scope dominance graph!");
 233   SmallVector<LexicalScope *, 4> WorkStack;
 234   WorkStack.push_back(Scope);
 235   unsigned Counter = 0;
 236   while (!WorkStack.empty()) {
 237     LexicalScope *WS = WorkStack.back();
 238     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 239     bool visitedChildren = false;
 240     for (auto &ChildScope : Children)
 241       if (!ChildScope->getDFSOut()) {
 242         WorkStack.push_back(ChildScope);
 243         visitedChildren = true;
 244         ChildScope->setDFSIn(++Counter);
 245         break;
 246       }
 247     if (!visitedChildren) {
 248       WorkStack.pop_back();
 249       WS->setDFSOut(++Counter);
 250     }
 251   }
 252 }
 253
 254 /// assignInstructionRanges - Find ranges of instructions covered by each
 255 /// lexical scope.
 256 void LexicalScopes::assignInstructionRanges(
 257     SmallVectorImpl<InsnRange> &MIRanges,
 258     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 259   LexicalScope *PrevLexicalScope = nullptr;
 260   for (const auto &R : MIRanges) {
 261     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 262     assert(S && "Lost LexicalScope for a machine instruction!");
 263     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 264       PrevLexicalScope->closeInsnRange(S);
 265     S->openInsnRange(R.first);
 266     S->extendInsnRange(R.second);
 267     PrevLexicalScope = S;
 268   }
 269
 270   if (PrevLexicalScope)
 271     PrevLexicalScope->closeInsnRange();
 272 }
 273
 274 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 275 /// have machine instructions that belong to lexical scope identified by
 276 /// DebugLoc.
 277 void LexicalScopes::getMachineBasicBlocks(
 278     const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 279   MBBs.clear();
 280   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 281   if (!Scope)
 282     return;
 283
 284   if (Scope == CurrentFnLexicalScope) {
 285     for (const auto &MBB : *MF)
 286       MBBs.insert(&MBB);
 287     return;
 288   }
 289
 290   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 291   for (auto &R : InsnRanges)
 292     MBBs.insert(R.first->getParent());
 293 }
 294
 295 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 296 /// machine instruction's lexical scope in a given machine basic block.
 297 bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
 298   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 299   if (!Scope)
 300     return false;
 301
 302   // Current function scope covers all basic blocks in the function.
 303   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 304     return true;
 305
 306   bool Result = false;
 307   for (auto &I : *MBB) {
 308     if (const DILocation *IDL = I.getDebugLoc())
 309       if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 310         if (Scope->dominates(IScope))
 311           return true;
 312   }
 313   return Result;
 314 }
 315
 316 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 317 LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
 318   raw_ostream &err = dbgs();
 319   err.indent(Indent);
 320   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 321   const MDNode *N = Desc;
 322   err.indent(Indent);
 323   N->dump();
 324   if (AbstractScope)
 325     err << std::string(Indent, ' ') << "Abstract Scope\n";
 326
 327   if (!Children.empty())
 328     err << std::string(Indent + 2, ' ') << "Children ...\n";
 329   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 330     if (Children[i] != this)
 331       Children[i]->dump(Indent + 2);
 332 }
 333 #endif