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/Function.h"
  25 #include "llvm/IR/Metadata.h"
  26 #include "llvm/Support/Casting.h"
  27 #include "llvm/Support/Compiler.h"
  28 #include "llvm/Support/Debug.h"
  29 #include "llvm/Support/raw_ostream.h"
  30 #include <cassert>
  31 #include <string>
  32 #include <tuple>
  33 #include <utility>
  34
  35 using namespace llvm;
  36
  37 #define DEBUG_TYPE "lexicalscopes"
  38
  39 /// reset - Reset the instance so that it's prepared for another function.
  40 void LexicalScopes::reset() {
  41   MF = nullptr;
  42   CurrentFnLexicalScope = nullptr;
  43   LexicalScopeMap.clear();
  44   AbstractScopeMap.clear();
  45   InlinedLexicalScopeMap.clear();
  46   AbstractScopesList.clear();
  47 }
  48
  49 /// initialize - Scan machine function and constuct lexical scope nest.
  50 void LexicalScopes::initialize(const MachineFunction &Fn) {
  51   reset();
  52   // Don't attempt any lexical scope creation for a NoDebug compile unit.
  53   if (Fn.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
  54       DICompileUnit::NoDebug)
  55     return;
  56   MF = &Fn;
  57   SmallVector<InsnRange, 4> MIRanges;
  58   DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
  59   extractLexicalScopes(MIRanges, MI2ScopeMap);
  60   if (CurrentFnLexicalScope) {
  61     constructScopeNest(CurrentFnLexicalScope);
  62     assignInstructionRanges(MIRanges, MI2ScopeMap);
  63   }
  64 }
  65
  66 /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
  67 /// for the given machine function.
  68 void LexicalScopes::extractLexicalScopes(
  69     SmallVectorImpl<InsnRange> &MIRanges,
  70     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
  71   // Scan each instruction and create scopes. First build working set of scopes.
  72   for (const auto &MBB : *MF) {
  73     const MachineInstr *RangeBeginMI = nullptr;
  74     const MachineInstr *PrevMI = nullptr;
  75     const DILocation *PrevDL = nullptr;
  76     for (const auto &MInsn : MBB) {
  77       // Check if instruction has valid location information.
  78       const DILocation *MIDL = MInsn.getDebugLoc();
  79       if (!MIDL) {
  80         PrevMI = &MInsn;
  81         continue;
  82       }
  83
  84       // If scope has not changed then skip this instruction.
  85       if (MIDL == PrevDL) {
  86         PrevMI = &MInsn;
  87         continue;
  88       }
  89
  90       // Ignore DBG_VALUE and similar instruction that do not contribute to any
  91       // instruction in the output.
  92       if (MInsn.isMetaInstruction())
  93         continue;
  94
  95       if (RangeBeginMI) {
  96         // If we have already seen a beginning of an instruction range and
  97         // current instruction scope does not match scope of first instruction
  98         // in this range then create a new instruction range.
  99         InsnRange R(RangeBeginMI, PrevMI);
 100         MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 101         MIRanges.push_back(R);
 102       }
 103
 104       // This is a beginning of a new instruction range.
 105       RangeBeginMI = &MInsn;
 106
 107       // Reset previous markers.
 108       PrevMI = &MInsn;
 109       PrevDL = MIDL;
 110     }
 111
 112     // Create last instruction range.
 113     if (RangeBeginMI && PrevMI && PrevDL) {
 114       InsnRange R(RangeBeginMI, PrevMI);
 115       MIRanges.push_back(R);
 116       MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
 117     }
 118   }
 119 }
 120
 121 /// findLexicalScope - Find lexical scope, either regular or inlined, for the
 122 /// given DebugLoc. Return NULL if not found.
 123 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
 124   DILocalScope *Scope = DL->getScope();
 125   if (!Scope)
 126     return nullptr;
 127
 128   // The scope that we were created with could have an extra file - which
 129   // isn't what we care about in this case.
 130   Scope = Scope->getNonLexicalBlockFileScope();
 131
 132   if (auto *IA = DL->getInlinedAt()) {
 133     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
 134     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
 135   }
 136   return findLexicalScope(Scope);
 137 }
 138
 139 /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
 140 /// not available then create new lexical scope.
 141 LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
 142                                                      const DILocation *IA) {
 143   if (IA) {
 144     // Skip scopes inlined from a NoDebug compile unit.
 145     if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
 146         DICompileUnit::NoDebug)
 147       return getOrCreateLexicalScope(IA);
 148     // Create an abstract scope for inlined function.
 149     getOrCreateAbstractScope(Scope);
 150     // Create an inlined scope for inlined function.
 151     return getOrCreateInlinedScope(Scope, IA);
 152   }
 153
 154   return getOrCreateRegularScope(Scope);
 155 }
 156
 157 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 158 LexicalScope *
 159 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 160   assert(Scope && "Invalid Scope encoding!");
 161   Scope = Scope->getNonLexicalBlockFileScope();
 162
 163   auto I = LexicalScopeMap.find(Scope);
 164   if (I != LexicalScopeMap.end())
 165     return &I->second;
 166
 167   // FIXME: Should the following dyn_cast be DILexicalBlock?
 168   LexicalScope *Parent = nullptr;
 169   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 170     Parent = getOrCreateLexicalScope(Block->getScope());
 171   I = LexicalScopeMap.emplace(std::piecewise_construct,
 172                               std::forward_as_tuple(Scope),
 173                               std::forward_as_tuple(Parent, Scope, nullptr,
 174                                                     false)).first;
 175
 176   if (!Parent) {
 177     assert(cast<DISubprogram>(Scope)->describes(&MF->getFunction()));
 178     assert(!CurrentFnLexicalScope);
 179     CurrentFnLexicalScope = &I->second;
 180   }
 181
 182   return &I->second;
 183 }
 184
 185 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 186 LexicalScope *
 187 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
 188                                        const DILocation *InlinedAt) {
 189   assert(Scope && "Invalid Scope encoding!");
 190   Scope = Scope->getNonLexicalBlockFileScope();
 191   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
 192   auto I = InlinedLexicalScopeMap.find(P);
 193   if (I != InlinedLexicalScopeMap.end())
 194     return &I->second;
 195
 196   LexicalScope *Parent;
 197   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 198     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
 199   else
 200     Parent = getOrCreateLexicalScope(InlinedAt);
 201
 202   I = InlinedLexicalScopeMap
 203           .emplace(std::piecewise_construct, std::forward_as_tuple(P),
 204                    std::forward_as_tuple(Parent, Scope, InlinedAt, false))
 205           .first;
 206   return &I->second;
 207 }
 208
 209 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 210 LexicalScope *
 211 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
 212   assert(Scope && "Invalid Scope encoding!");
 213   Scope = Scope->getNonLexicalBlockFileScope();
 214   auto I = AbstractScopeMap.find(Scope);
 215   if (I != AbstractScopeMap.end())
 216     return &I->second;
 217
 218   // FIXME: Should the following isa be DILexicalBlock?
 219   LexicalScope *Parent = nullptr;
 220   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
 221     Parent = getOrCreateAbstractScope(Block->getScope());
 222
 223   I = AbstractScopeMap.emplace(std::piecewise_construct,
 224                                std::forward_as_tuple(Scope),
 225                                std::forward_as_tuple(Parent, Scope,
 226                                                      nullptr, true)).first;
 227   if (isa<DISubprogram>(Scope))
 228     AbstractScopesList.push_back(&I->second);
 229   return &I->second;
 230 }
 231
 232 /// constructScopeNest
 233 void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
 234   assert(Scope && "Unable to calculate scope dominance graph!");
 235   SmallVector<LexicalScope *, 4> WorkStack;
 236   WorkStack.push_back(Scope);
 237   unsigned Counter = 0;
 238   while (!WorkStack.empty()) {
 239     LexicalScope *WS = WorkStack.back();
 240     const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
 241     bool visitedChildren = false;
 242     for (auto &ChildScope : Children)
 243       if (!ChildScope->getDFSOut()) {
 244         WorkStack.push_back(ChildScope);
 245         visitedChildren = true;
 246         ChildScope->setDFSIn(++Counter);
 247         break;
 248       }
 249     if (!visitedChildren) {
 250       WorkStack.pop_back();
 251       WS->setDFSOut(++Counter);
 252     }
 253   }
 254 }
 255
 256 /// assignInstructionRanges - Find ranges of instructions covered by each
 257 /// lexical scope.
 258 void LexicalScopes::assignInstructionRanges(
 259     SmallVectorImpl<InsnRange> &MIRanges,
 260     DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
 261   LexicalScope *PrevLexicalScope = nullptr;
 262   for (const auto &R : MIRanges) {
 263     LexicalScope *S = MI2ScopeMap.lookup(R.first);
 264     assert(S && "Lost LexicalScope for a machine instruction!");
 265     if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
 266       PrevLexicalScope->closeInsnRange(S);
 267     S->openInsnRange(R.first);
 268     S->extendInsnRange(R.second);
 269     PrevLexicalScope = S;
 270   }
 271
 272   if (PrevLexicalScope)
 273     PrevLexicalScope->closeInsnRange();
 274 }
 275
 276 /// getMachineBasicBlocks - Populate given set using machine basic blocks which
 277 /// have machine instructions that belong to lexical scope identified by
 278 /// DebugLoc.
 279 void LexicalScopes::getMachineBasicBlocks(
 280     const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
 281   assert(MF && "Method called on a uninitialized LexicalScopes object!");
 282   MBBs.clear();
 283
 284   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 285   if (!Scope)
 286     return;
 287
 288   if (Scope == CurrentFnLexicalScope) {
 289     for (const auto &MBB : *MF)
 290       MBBs.insert(&MBB);
 291     return;
 292   }
 293
 294   SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
 295   for (auto &R : InsnRanges)
 296     MBBs.insert(R.first->getParent());
 297 }
 298
 299 /// dominates - Return true if DebugLoc's lexical scope dominates at least one
 300 /// machine instruction's lexical scope in a given machine basic block.
 301 bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
 302   assert(MF && "Unexpected uninitialized LexicalScopes object!");
 303   LexicalScope *Scope = getOrCreateLexicalScope(DL);
 304   if (!Scope)
 305     return false;
 306
 307   // Current function scope covers all basic blocks in the function.
 308   if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
 309     return true;
 310
 311   bool Result = false;
 312   for (auto &I : *MBB) {
 313     if (const DILocation *IDL = I.getDebugLoc())
 314       if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
 315         if (Scope->dominates(IScope))
 316           return true;
 317   }
 318   return Result;
 319 }
 320
 321 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 322 LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
 323   raw_ostream &err = dbgs();
 324   err.indent(Indent);
 325   err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
 326   const MDNode *N = Desc;
 327   err.indent(Indent);
 328   N->dump();
 329   if (AbstractScope)
 330     err << std::string(Indent, ' ') << "Abstract Scope\n";
 331
 332   if (!Children.empty())
 333     err << std::string(Indent + 2, ' ') << "Children ...\n";
 334   for (unsigned i = 0, e = Children.size(); i != e; ++i)
 335     if (Children[i] != this)
 336       Children[i]->dump(Indent + 2);
 337 }
 338 #endif