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diff --git a/llvm/lib/CodeGen/LexicalScopes.cpp b/llvm/lib/CodeGen/LexicalScopes.cpp
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+++ b/llvm/lib/CodeGen/LexicalScopes.cpp
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+//===- LexicalScopes.cpp - Collecting lexical scope info ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements LexicalScopes analysis.
+//
+// This pass collects lexical scope information and maps machine instructions
+// to respective lexical scopes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/LexicalScopes.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <string>
+#include <tuple>
+#include <utility>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lexicalscopes"
+
+/// reset - Reset the instance so that it's prepared for another function.
+void LexicalScopes::reset() {
+  MF = nullptr;
+  CurrentFnLexicalScope = nullptr;
+  LexicalScopeMap.clear();
+  AbstractScopeMap.clear();
+  InlinedLexicalScopeMap.clear();
+  AbstractScopesList.clear();
+}
+
+/// initialize - Scan machine function and constuct lexical scope nest.
+void LexicalScopes::initialize(const MachineFunction &Fn) {
+  reset();
+  // Don't attempt any lexical scope creation for a NoDebug compile unit.
+  if (Fn.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
+      DICompileUnit::NoDebug)
+    return;
+  MF = &Fn;
+  SmallVector<InsnRange, 4> MIRanges;
+  DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
+  extractLexicalScopes(MIRanges, MI2ScopeMap);
+  if (CurrentFnLexicalScope) {
+    constructScopeNest(CurrentFnLexicalScope);
+    assignInstructionRanges(MIRanges, MI2ScopeMap);
+  }
+}
+
+/// extractLexicalScopes - Extract instruction ranges for each lexical scopes
+/// for the given machine function.
+void LexicalScopes::extractLexicalScopes(
+    SmallVectorImpl<InsnRange> &MIRanges,
+    DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
+  // Scan each instruction and create scopes. First build working set of scopes.
+  for (const auto &MBB : *MF) {
+    const MachineInstr *RangeBeginMI = nullptr;
+    const MachineInstr *PrevMI = nullptr;
+    const DILocation *PrevDL = nullptr;
+    for (const auto &MInsn : MBB) {
+      // Check if instruction has valid location information.
+      const DILocation *MIDL = MInsn.getDebugLoc();
+      if (!MIDL) {
+        PrevMI = &MInsn;
+        continue;
+      }
+
+      // If scope has not changed then skip this instruction.
+      if (MIDL == PrevDL) {
+        PrevMI = &MInsn;
+        continue;
+      }
+
+      // Ignore DBG_VALUE and similar instruction that do not contribute to any
+      // instruction in the output.
+      if (MInsn.isMetaInstruction())
+        continue;
+
+      if (RangeBeginMI) {
+        // If we have already seen a beginning of an instruction range and
+        // current instruction scope does not match scope of first instruction
+        // in this range then create a new instruction range.
+        InsnRange R(RangeBeginMI, PrevMI);
+        MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
+        MIRanges.push_back(R);
+      }
+
+      // This is a beginning of a new instruction range.
+      RangeBeginMI = &MInsn;
+
+      // Reset previous markers.
+      PrevMI = &MInsn;
+      PrevDL = MIDL;
+    }
+
+    // Create last instruction range.
+    if (RangeBeginMI && PrevMI && PrevDL) {
+      InsnRange R(RangeBeginMI, PrevMI);
+      MIRanges.push_back(R);
+      MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
+    }
+  }
+}
+
+/// findLexicalScope - Find lexical scope, either regular or inlined, for the
+/// given DebugLoc. Return NULL if not found.
+LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
+  DILocalScope *Scope = DL->getScope();
+  if (!Scope)
+    return nullptr;
+
+  // The scope that we were created with could have an extra file - which
+  // isn't what we care about in this case.
+  Scope = Scope->getNonLexicalBlockFileScope();
+
+  if (auto *IA = DL->getInlinedAt()) {
+    auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
+    return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
+  }
+  return findLexicalScope(Scope);
+}
+
+/// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
+/// not available then create new lexical scope.
+LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
+                                                     const DILocation *IA) {
+  if (IA) {
+    // Skip scopes inlined from a NoDebug compile unit.
+    if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
+        DICompileUnit::NoDebug)
+      return getOrCreateLexicalScope(IA);
+    // Create an abstract scope for inlined function.
+    getOrCreateAbstractScope(Scope);
+    // Create an inlined scope for inlined function.
+    return getOrCreateInlinedScope(Scope, IA);
+  }
+
+  return getOrCreateRegularScope(Scope);
+}
+
+/// getOrCreateRegularScope - Find or create a regular lexical scope.
+LexicalScope *
+LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
+  assert(Scope && "Invalid Scope encoding!");
+  Scope = Scope->getNonLexicalBlockFileScope();
+
+  auto I = LexicalScopeMap.find(Scope);
+  if (I != LexicalScopeMap.end())
+    return &I->second;
+
+  // FIXME: Should the following dyn_cast be DILexicalBlock?
+  LexicalScope *Parent = nullptr;
+  if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
+    Parent = getOrCreateLexicalScope(Block->getScope());
+  I = LexicalScopeMap.emplace(std::piecewise_construct,
+                              std::forward_as_tuple(Scope),
+                              std::forward_as_tuple(Parent, Scope, nullptr,
+                                                    false)).first;
+
+  if (!Parent) {
+    assert(cast<DISubprogram>(Scope)->describes(&MF->getFunction()));
+    assert(!CurrentFnLexicalScope);
+    CurrentFnLexicalScope = &I->second;
+  }
+
+  return &I->second;
+}
+
+/// getOrCreateInlinedScope - Find or create an inlined lexical scope.
+LexicalScope *
+LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
+                                       const DILocation *InlinedAt) {
+  assert(Scope && "Invalid Scope encoding!");
+  Scope = Scope->getNonLexicalBlockFileScope();
+  std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
+  auto I = InlinedLexicalScopeMap.find(P);
+  if (I != InlinedLexicalScopeMap.end())
+    return &I->second;
+
+  LexicalScope *Parent;
+  if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
+    Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
+  else
+    Parent = getOrCreateLexicalScope(InlinedAt);
+
+  I = InlinedLexicalScopeMap
+          .emplace(std::piecewise_construct, std::forward_as_tuple(P),
+                   std::forward_as_tuple(Parent, Scope, InlinedAt, false))
+          .first;
+  return &I->second;
+}
+
+/// getOrCreateAbstractScope - Find or create an abstract lexical scope.
+LexicalScope *
+LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
+  assert(Scope && "Invalid Scope encoding!");
+  Scope = Scope->getNonLexicalBlockFileScope();
+  auto I = AbstractScopeMap.find(Scope);
+  if (I != AbstractScopeMap.end())
+    return &I->second;
+
+  // FIXME: Should the following isa be DILexicalBlock?
+  LexicalScope *Parent = nullptr;
+  if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
+    Parent = getOrCreateAbstractScope(Block->getScope());
+
+  I = AbstractScopeMap.emplace(std::piecewise_construct,
+                               std::forward_as_tuple(Scope),
+                               std::forward_as_tuple(Parent, Scope,
+                                                     nullptr, true)).first;
+  if (isa<DISubprogram>(Scope))
+    AbstractScopesList.push_back(&I->second);
+  return &I->second;
+}
+
+/// constructScopeNest
+void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
+  assert(Scope && "Unable to calculate scope dominance graph!");
+  SmallVector<LexicalScope *, 4> WorkStack;
+  WorkStack.push_back(Scope);
+  unsigned Counter = 0;
+  while (!WorkStack.empty()) {
+    LexicalScope *WS = WorkStack.back();
+    const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
+    bool visitedChildren = false;
+    for (auto &ChildScope : Children)
+      if (!ChildScope->getDFSOut()) {
+        WorkStack.push_back(ChildScope);
+        visitedChildren = true;
+        ChildScope->setDFSIn(++Counter);
+        break;
+      }
+    if (!visitedChildren) {
+      WorkStack.pop_back();
+      WS->setDFSOut(++Counter);
+    }
+  }
+}
+
+/// assignInstructionRanges - Find ranges of instructions covered by each
+/// lexical scope.
+void LexicalScopes::assignInstructionRanges(
+    SmallVectorImpl<InsnRange> &MIRanges,
+    DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
+  LexicalScope *PrevLexicalScope = nullptr;
+  for (const auto &R : MIRanges) {
+    LexicalScope *S = MI2ScopeMap.lookup(R.first);
+    assert(S && "Lost LexicalScope for a machine instruction!");
+    if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
+      PrevLexicalScope->closeInsnRange(S);
+    S->openInsnRange(R.first);
+    S->extendInsnRange(R.second);
+    PrevLexicalScope = S;
+  }
+
+  if (PrevLexicalScope)
+    PrevLexicalScope->closeInsnRange();
+}
+
+/// getMachineBasicBlocks - Populate given set using machine basic blocks which
+/// have machine instructions that belong to lexical scope identified by
+/// DebugLoc.
+void LexicalScopes::getMachineBasicBlocks(
+    const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
+  assert(MF && "Method called on a uninitialized LexicalScopes object!");
+  MBBs.clear();
+
+  LexicalScope *Scope = getOrCreateLexicalScope(DL);
+  if (!Scope)
+    return;
+
+  if (Scope == CurrentFnLexicalScope) {
+    for (const auto &MBB : *MF)
+      MBBs.insert(&MBB);
+    return;
+  }
+
+  SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
+  for (auto &R : InsnRanges)
+    MBBs.insert(R.first->getParent());
+}
+
+/// dominates - Return true if DebugLoc's lexical scope dominates at least one
+/// machine instruction's lexical scope in a given machine basic block.
+bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
+  assert(MF && "Unexpected uninitialized LexicalScopes object!");
+  LexicalScope *Scope = getOrCreateLexicalScope(DL);
+  if (!Scope)
+    return false;
+
+  // Current function scope covers all basic blocks in the function.
+  if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
+    return true;
+
+  bool Result = false;
+  for (auto &I : *MBB) {
+    if (const DILocation *IDL = I.getDebugLoc())
+      if (LexicalScope *IScope = getOrCreateLexicalScope(IDL))
+        if (Scope->dominates(IScope))
+          return true;
+  }
+  return Result;
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
+  raw_ostream &err = dbgs();
+  err.indent(Indent);
+  err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
+  const MDNode *N = Desc;
+  err.indent(Indent);
+  N->dump();
+  if (AbstractScope)
+    err << std::string(Indent, ' ') << "Abstract Scope\n";
+
+  if (!Children.empty())
+    err << std::string(Indent + 2, ' ') << "Children ...\n";
+  for (unsigned i = 0, e = Children.size(); i != e; ++i)
+    if (Children[i] != this)
+      Children[i]->dump(Indent + 2);
+}
+#endif