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//===- LexicalScopes.cpp - Collecting lexical scope info --------*- C++ -*-===//

//

// 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.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_LEXICALSCOPES_H

#define LLVM_CODEGEN_LEXICALSCOPES_H

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/IR/DebugInfoMetadata.h"

#include <cassert>

#include <unordered_map>

#include <utility>

namespace llvm {

class MachineBasicBlock;

class MachineFunction;

class MachineInstr;

class MDNode;

//===----------------------------------------------------------------------===//

/// InsnRange - This is used to track range of instructions with identical

/// lexical scope.

///

using InsnRange = std::pair<const MachineInstr *, const MachineInstr *>;

//===----------------------------------------------------------------------===//

/// LexicalScope - This class is used to track scope information.

///

class LexicalScope {

public:

  LexicalScope(LexicalScope *P, const DILocalScope *D, const DILocation *I,

               bool A)

      : Parent(P), Desc(D), InlinedAtLocation(I), AbstractScope(A) {

    assert(D);

    assert(D->getSubprogram()->getUnit()->getEmissionKind() !=

           DICompileUnit::NoDebug &&

           "Don't build lexical scopes for non-debug locations");

    assert(D->isResolved() && "Expected resolved node");

    assert((!I || I->isResolved()) && "Expected resolved node");

    if (Parent)

      Parent->addChild(this);

  }

  // Accessors.

  LexicalScope *getParent() const { return Parent; }

  const MDNode *getDesc() const { return Desc; }

  const DILocation *getInlinedAt() const { return InlinedAtLocation; }

  const DILocalScope *getScopeNode() const { return Desc; }

  bool isAbstractScope() const { return AbstractScope; }

  SmallVectorImpl<LexicalScope *> &getChildren() { return Children; }

  SmallVectorImpl<InsnRange> &getRanges() { return Ranges; }

  /// addChild - Add a child scope.

  void addChild(LexicalScope *S) { Children.push_back(S); }

  /// openInsnRange - This scope covers instruction range starting from MI.

  void openInsnRange(const MachineInstr *MI) {

    if (!FirstInsn)

      FirstInsn = MI;

    if (Parent)

      Parent->openInsnRange(MI);

  }

  /// extendInsnRange - Extend the current instruction range covered by

  /// this scope.

  void extendInsnRange(const MachineInstr *MI) {

    assert(FirstInsn && "MI Range is not open!");

    LastInsn = MI;

    if (Parent)

      Parent->extendInsnRange(MI);

  }

  /// closeInsnRange - Create a range based on FirstInsn and LastInsn collected

  /// until now. This is used when a new scope is encountered while walking

  /// machine instructions.

  void closeInsnRange(LexicalScope *NewScope = nullptr) {

    assert(LastInsn && "Last insn missing!");

    Ranges.push_back(InsnRange(FirstInsn, LastInsn));

    FirstInsn = nullptr;

    LastInsn = nullptr;

    // If Parent dominates NewScope then do not close Parent's instruction

    // range.

    if (Parent && (!NewScope || !Parent->dominates(NewScope)))

      Parent->closeInsnRange(NewScope);

  }

  /// dominates - Return true if current scope dominates given lexical scope.

  bool dominates(const LexicalScope *S) const {

    if (S == this)

      return true;

    if (DFSIn < S->getDFSIn() && DFSOut > S->getDFSOut())

      return true;

    return false;

  }

  // Depth First Search support to walk and manipulate LexicalScope hierarchy.

  unsigned getDFSOut() const { return DFSOut; }

  void setDFSOut(unsigned O) { DFSOut = O; }

  unsigned getDFSIn() const { return DFSIn; }

  void setDFSIn(unsigned I) { DFSIn = I; }

  /// dump - print lexical scope.

  void dump(unsigned Indent = 0) const;

private:

  LexicalScope *Parent;                        // Parent to this scope.

  const DILocalScope *Desc;                    // Debug info descriptor.

  const DILocation *InlinedAtLocation;         // Location at which this

                                               // scope is inlined.

  bool AbstractScope;                          // Abstract Scope

  SmallVector<LexicalScope *, 4> Children;     // Scopes defined in scope.

                                               // Contents not owned.

  SmallVector<InsnRange, 4> Ranges;

  const MachineInstr *LastInsn = nullptr;  // Last instruction of this scope.

  const MachineInstr *FirstInsn = nullptr; // First instruction of this scope.

  unsigned DFSIn = 0; // In & Out Depth use to determine scope nesting.

  unsigned DFSOut = 0;

};

//===----------------------------------------------------------------------===//

/// LexicalScopes -  This class provides interface to collect and use lexical

/// scoping information from machine instruction.

///

class LexicalScopes {

public:

  LexicalScopes() = default;

  /// initialize - Scan machine function and constuct lexical scope nest, resets

  /// the instance if necessary.

  void initialize(const MachineFunction &);

  /// releaseMemory - release memory.

  void reset();

  /// empty - Return true if there is any lexical scope information available.

  bool empty() { return CurrentFnLexicalScope == nullptr; }

  /// getCurrentFunctionScope - Return lexical scope for the current function.

  LexicalScope *getCurrentFunctionScope() const {

    return CurrentFnLexicalScope;

  }

  /// getMachineBasicBlocks - Populate given set using machine basic blocks

  /// which have machine instructions that belong to lexical scope identified by

  /// DebugLoc.

  void getMachineBasicBlocks(const DILocation *DL,

                             SmallPtrSetImpl<const MachineBasicBlock *> &MBBs);

  /// Return true if DebugLoc's lexical scope dominates at least one machine

  /// instruction's lexical scope in a given machine basic block.

  bool dominates(const DILocation *DL, MachineBasicBlock *MBB);

  /// findLexicalScope - Find lexical scope, either regular or inlined, for the

  /// given DebugLoc. Return NULL if not found.

  LexicalScope *findLexicalScope(const DILocation *DL);

  /// getAbstractScopesList - Return a reference to list of abstract scopes.

  ArrayRef<LexicalScope *> getAbstractScopesList() const {

    return AbstractScopesList;

  }

  /// findAbstractScope - Find an abstract scope or return null.

  LexicalScope *findAbstractScope(const DILocalScope *N) {

    auto I = AbstractScopeMap.find(N);

    return I != AbstractScopeMap.end() ? &I->second : nullptr;

  }

  /// findInlinedScope - Find an inlined scope for the given scope/inlined-at.

  LexicalScope *findInlinedScope(const DILocalScope *N, const DILocation *IA) {

    auto I = InlinedLexicalScopeMap.find(std::make_pair(N, IA));

    return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;

  }

  /// findLexicalScope - Find regular lexical scope or return null.

  LexicalScope *findLexicalScope(const DILocalScope *N) {

    auto I = LexicalScopeMap.find(N);

    return I != LexicalScopeMap.end() ? &I->second : nullptr;

  }

  /// getOrCreateAbstractScope - Find or create an abstract lexical scope.

  LexicalScope *getOrCreateAbstractScope(const DILocalScope *Scope);

private:

  /// getOrCreateLexicalScope - Find lexical scope for the given Scope/IA. If

  /// not available then create new lexical scope.

  LexicalScope *getOrCreateLexicalScope(const DILocalScope *Scope,

                                        const DILocation *IA = nullptr);

  LexicalScope *getOrCreateLexicalScope(const DILocation *DL) {

    return DL ? getOrCreateLexicalScope(DL->getScope(), DL->getInlinedAt())

              : nullptr;

  }

  /// getOrCreateRegularScope - Find or create a regular lexical scope.

  LexicalScope *getOrCreateRegularScope(const DILocalScope *Scope);

  /// getOrCreateInlinedScope - Find or create an inlined lexical scope.

  LexicalScope *getOrCreateInlinedScope(const DILocalScope *Scope,

                                        const DILocation *InlinedAt);

  /// extractLexicalScopes - Extract instruction ranges for each lexical scopes

  /// for the given machine function.

  void extractLexicalScopes(SmallVectorImpl<InsnRange> &MIRanges,

                            DenseMap<const MachineInstr *, LexicalScope *> &M);

  void constructScopeNest(LexicalScope *Scope);

  void

  assignInstructionRanges(SmallVectorImpl<InsnRange> &MIRanges,

                          DenseMap<const MachineInstr *, LexicalScope *> &M);

  const MachineFunction *MF = nullptr;

  /// LexicalScopeMap - Tracks the scopes in the current function.

  // Use an unordered_map to ensure value pointer validity over insertion.

  std::unordered_map<const DILocalScope *, LexicalScope> LexicalScopeMap;

  /// InlinedLexicalScopeMap - Tracks inlined function scopes in current

  /// function.

  std::unordered_map<std::pair<const DILocalScope *, const DILocation *>,

                     LexicalScope,

                     pair_hash<const DILocalScope *, const DILocation *>>

      InlinedLexicalScopeMap;

  /// AbstractScopeMap - These scopes are  not included LexicalScopeMap.

  // Use an unordered_map to ensure value pointer validity over insertion.

  std::unordered_map<const DILocalScope *, LexicalScope> AbstractScopeMap;

  /// AbstractScopesList - Tracks abstract scopes constructed while processing

  /// a function.

  SmallVector<LexicalScope *, 4> AbstractScopesList;

  /// CurrentFnLexicalScope - Top level scope for the current function.

  ///

  LexicalScope *CurrentFnLexicalScope = nullptr;

  /// Map a location to the set of basic blocks it dominates. This is a cache

  /// for \ref LexicalScopes::getMachineBasicBlocks results.

  using BlockSetT = SmallPtrSet<const MachineBasicBlock *, 4>;

  DenseMap<const DILocation *, std::unique_ptr<BlockSetT>> DominatedBlocks;

};

} // end namespace llvm

#endif // LLVM_CODEGEN_LEXICALSCOPES_H