lib/CodeGen/LexicalScopes.cpp

   1 //===- LexicalScopes.cpp - Collecting lexical scope info ------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements LexicalScopes analysis.
  10 //
  11 // This pass collects lexical scope information and maps machine instructions
  12 // to respective lexical scopes.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/CodeGen/LexicalScopes.h"
  17 #include "llvm/ADT/DenseMap.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/CodeGen/MachineBasicBlock.h"
  20 #include "llvm/CodeGen/MachineFunction.h"
  21 #include "llvm/CodeGen/MachineInstr.h"
  22 #include "llvm/Config/llvm-config.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   reset();
  51   // Don't attempt any lexical scope creation for a NoDebug compile unit.
  52   if (Fn.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
  53       DICompileUnit::NoDebug)
  54     return;
  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 and similar instruction that do not contribute to any
  90       // instruction in the output.
  91       if (MInsn.isMetaInstruction())
  92         continue;
  93
  94       if (RangeBeginMI) {
  95         // If we have already seen a beginning of an instruction range and
  96         // current instruction scope does not match scope of first instruction
  97         // in this range then create a new instruction range.
  98         InsnRange R(RangeBeginMI, PrevMI);
  99         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 100         MIRanges.push_back(R);
 101       }
 102
 103       // This is a beginning of a new instruction range.
 104       RangeBeginMI = &MInsn;
 105
 106       // Reset previous markers.
 107       PrevMI = &MInsn;
 108       PrevDL = MIDL;
 109     }
 110
 111     // Create last instruction range.
 112     if (RangeBeginMI && PrevMI && PrevDL) {
 113       InsnRange R(RangeBeginMI, PrevMI);
 114       MIRanges.push_back(R);
 115       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 116     }
 117   }
 118 }
 119
 120 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 121 /// given DebugLoc. Return NULL if not found.
 122 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
 123   DILocalScope *Scope = DL->getScope();
 124   if (!Scope)
 125     return nullptr;
 126
 127   // The scope that we were created with could have an extra file - which
 128   // isn't what we care about in this case.
 129   Scope = Scope->getNonLexicalBlockFileScope();
 130
 131   if (auto *IA = DL->getInlinedAt()) {
 132     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 133     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 134   }
 135   return findLexicalScope(Scope);
 136 }
 137
 138 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 139 /// not available then create new lexical scope.
 140 LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
 141                                                      const DILocation *IA) {
 142   if (IA) {
 143     // Skip scopes inlined from a NoDebug compile unit.
 144     if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
 145         DICompileUnit::NoDebug)
 146       return getOrCreateLexicalScope(IA);
 147     // Create an abstract scope for inlined function.
 148     getOrCreateAbstractScope(Scope);
 149     // Create an inlined scope for inlined function.
 150     return getOrCreateInlinedScope(Scope, IA);
 151   }
 152
 153   return getOrCreateRegularScope(Scope);
 154 }
 155
 156 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 157 LexicalScope *
 158 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 159   assert(Scope && "Invalid Scope encoding!");
 160   Scope = Scope->getNonLexicalBlockFileScope();
 161
 162   auto I = LexicalScopeMap.find(Scope);
 163   if (I != LexicalScopeMap.end())
 164     return &I->second;
 165
 166   // FIXME: Should the following dyn_cast be DILexicalBlock?
 167   LexicalScope *Parent = nullptr;
 168   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 169     Parent = getOrCreateLexicalScope(Block->getScope());
 170   I = LexicalScopeMap.emplace(std::piecewise_construct,
 171                               std::forward_as_tuple(Scope),
 172                               std::forward_as_tuple(Parent, Scope, nullptr,
 173                                                     false)).first;
 174
 175   if (!Parent) {
 176     assert(cast<DISubprogram>(Scope)->describes(&MF->getFunction()));
 177     assert(!CurrentFnLexicalScope);
 178     CurrentFnLexicalScope = &I->second;
 179   }
 180
 181   return &I->second;
 182 }
 183
 184 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 185 LexicalScope *
 186 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
 187                                        const DILocation *InlinedAt) {
 188   assert(Scope && "Invalid Scope encoding!");
 189   Scope = Scope->getNonLexicalBlockFileScope();
 190   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
 191   auto I = InlinedLexicalScopeMap.find(P);
 192   if (I != InlinedLexicalScopeMap.end())
 193     return &I->second;
 194
 195   LexicalScope *Parent;
 196   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 197     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 198   else
 199     Parent = getOrCreateLexicalScope(InlinedAt);
 200
 201   I = InlinedLexicalScopeMap
 202           .emplace(std::piecewise_construct, std::forward_as_tuple(P),
 203                    std::forward_as_tuple(Parent, Scope, InlinedAt, false))
 204           .first;
 205   return &I->second;
 206 }
 207
 208 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 209 LexicalScope *
 210 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
 211   assert(Scope && "Invalid Scope encoding!");
 212   Scope = Scope->getNonLexicalBlockFileScope();
 213   auto I = AbstractScopeMap.find(Scope);
 214   if (I != AbstractScopeMap.end())
 215     return &I->second;
 216
 217   // FIXME: Should the following isa be DILexicalBlock?
 218   LexicalScope *Parent = nullptr;
 219   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 220     Parent = getOrCreateAbstractScope(Block->getScope());
 221
 222   I = AbstractScopeMap.emplace(std::piecewise_construct,
 223                                std::forward_as_tuple(Scope),
 224                                std::forward_as_tuple(Parent, Scope,
 225                                                      nullptr, true)).first;
 226   if (isa<DISubprogram>(Scope))
 227     AbstractScopesList.push_back(&I->second);
 228   return &I->second;
 229 }
 230
 231 /// constructScopeNest
 232 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 233   assert(Scope && "Unable to calculate scope dominance graph!");
 234   SmallVector<LexicalScope *, 4> WorkStack;
 235   WorkStack.push_back(Scope);
 236   unsigned Counter = 0;
 237   while (!WorkStack.empty()) {
 238     LexicalScope *WS = WorkStack.back();
 239     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 240     bool visitedChildren = false;
 241     for (auto &ChildScope : Children)
 242       if (!ChildScope->getDFSOut()) {
 243         WorkStack.push_back(ChildScope);
 244         visitedChildren = true;
 245         ChildScope->setDFSIn(++Counter);
 246         break;
 247       }
 248     if (!visitedChildren) {
 249       WorkStack.pop_back();
 250       WS->setDFSOut(++Counter);
 251     }
 252   }
 253 }
 254
 255 /// assignInstructionRanges - Find ranges of instructions covered by each
 256 /// lexical scope.
 257 void LexicalScopes::assignInstructionRanges(
 258     SmallVectorImpl<InsnRange> &MIRanges,
 259     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 260   LexicalScope *PrevLexicalScope = nullptr;
 261   for (const auto &R : MIRanges) {
 262     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 263     assert(S && "Lost LexicalScope for a machine instruction!");
 264     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 265       PrevLexicalScope->closeInsnRange(S);
 266     S->openInsnRange(R.first);
 267     S->extendInsnRange(R.second);
 268     PrevLexicalScope = S;
 269   }
 270
 271   if (PrevLexicalScope)
 272     PrevLexicalScope->closeInsnRange();
 273 }
 274
 275 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 276 /// have machine instructions that belong to lexical scope identified by
 277 /// DebugLoc.
 278 void LexicalScopes::getMachineBasicBlocks(
 279     const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 280   assert(MF && "Method called on a uninitialized LexicalScopes object!");
 281   MBBs.clear();
 282
 283   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 284   if (!Scope)
 285     return;
 286
 287   if (Scope == CurrentFnLexicalScope) {
 288     for (const auto &MBB : *MF)
 289       MBBs.insert(&MBB);
 290     return;
 291   }
 292
 293   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 294   for (auto &R : InsnRanges)
 295     MBBs.insert(R.first->getParent());
 296 }
 297
 298 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 299 /// machine instruction's lexical scope in a given machine basic block.
 300 bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
 301   assert(MF && "Unexpected uninitialized LexicalScopes object!");
 302   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 303   if (!Scope)
 304     return false;
 305
 306   // Current function scope covers all basic blocks in the function.
 307   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 308     return true;
 309
 310   bool Result = false;
 311   for (auto &I : *MBB) {
 312     if (const DILocation *IDL = I.getDebugLoc())
 313       if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 314         if (Scope->dominates(IScope))
 315           return true;
 316   }
 317   return Result;
 318 }
 319
 320 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 321 LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
 322   raw_ostream &err = dbgs();
 323   err.indent(Indent);
 324   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 325   const MDNode *N = Desc;
 326   err.indent(Indent);
 327   N->dump();
 328   if (AbstractScope)
 329     err << std::string(Indent, ' ') << "Abstract Scope\n";
 330
 331   if (!Children.empty())
 332     err << std::string(Indent + 2, ' ') << "Children ...\n";
 333   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 334     if (Children[i] != this)
 335       Children[i]->dump(Indent + 2);
 336 }
 337 #endif