//===- Scope.cpp - Lexical scope information --------------------*- 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 the Scope class, which is used for recording

// information about a lexical scope.

//

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

#include "clang/Sema/Scope.h"

#include "clang/AST/Decl.h"

#include "llvm/Support/raw_ostream.h"

using namespace clang;

void Scope::setFlags(Scope *parent, unsigned flags) {

  AnyParent = parent;

  Flags = flags;

  if (parent && !(flags & FnScope)) {

    BreakParent    = parent->BreakParent;

    ContinueParent = parent->ContinueParent;

  } else {

    // Control scopes do not contain the contents of nested function scopes for

    // control flow purposes.

    BreakParent = ContinueParent = nullptr;

  }

  if (parent) {

    Depth = parent->Depth + 1;

    PrototypeDepth = parent->PrototypeDepth;

    PrototypeIndex = 0;

    FnParent       = parent->FnParent;

    BlockParent    = parent->BlockParent;

    TemplateParamParent = parent->TemplateParamParent;

    MSLastManglingParent = parent->MSLastManglingParent;

    MSCurManglingNumber = getMSLastManglingNumber();

    if ((Flags & (FnScope | ClassScope | BlockScope | TemplateParamScope |

                  FunctionPrototypeScope | AtCatchScope | ObjCMethodScope)) ==

        0)

      Flags |= parent->getFlags() & OpenMPSimdDirectiveScope;

    // transmit the parent's 'order' flag, if exists

    if (parent->getFlags() & OpenMPOrderClauseScope)

      Flags |= OpenMPOrderClauseScope;

  } else {

    Depth = 0;

    PrototypeDepth = 0;

    PrototypeIndex = 0;

    MSLastManglingParent = FnParent = BlockParent = nullptr;

    TemplateParamParent = nullptr;

    MSLastManglingNumber = 1;

    MSCurManglingNumber = 1;

  }

  // If this scope is a function or contains breaks/continues, remember it.

  if (flags & FnScope)            FnParent = this;

  // The MS mangler uses the number of scopes that can hold declarations as

  // part of an external name.

  if (Flags & (ClassScope | FnScope)) {

    MSLastManglingNumber = getMSLastManglingNumber();

    MSLastManglingParent = this;

    MSCurManglingNumber = 1;

  }

  if (flags & BreakScope)         BreakParent = this;

  if (flags & ContinueScope)      ContinueParent = this;

  if (flags & BlockScope)         BlockParent = this;

  if (flags & TemplateParamScope) TemplateParamParent = this;

  // If this is a prototype scope, record that. Lambdas have an extra prototype

  // scope that doesn't add any depth.

  if (flags & FunctionPrototypeScope && !(flags & LambdaScope))

    PrototypeDepth++;

  if (flags & DeclScope) {

    if (flags & FunctionPrototypeScope)

      ; // Prototype scopes are uninteresting.

    else if ((flags & ClassScope) && getParent()->isClassScope())

      ; // Nested class scopes aren't ambiguous.

    else if ((flags & ClassScope) && getParent()->getFlags() == DeclScope)

      ; // Classes inside of namespaces aren't ambiguous.

    else if ((flags & EnumScope))

      ; // Don't increment for enum scopes.

    else

      incrementMSManglingNumber();

  }

}

void Scope::Init(Scope *parent, unsigned flags) {

  setFlags(parent, flags);

  DeclsInScope.clear();

  UsingDirectives.clear();

  Entity = nullptr;

  ErrorTrap.reset();

  NRVO = std::nullopt;

}

bool Scope::containedInPrototypeScope() const {

  const Scope *S = this;

  while (S) {

    if (S->isFunctionPrototypeScope())

      return true;

    S = S->getParent();

  }

  return false;

}

void Scope::AddFlags(unsigned FlagsToSet) {

  assert((FlagsToSet & ~(BreakScope | ContinueScope)) == 0 &&

         "Unsupported scope flags");

  if (FlagsToSet & BreakScope) {

    assert((Flags & BreakScope) == 0 && "Already set");

    BreakParent = this;

  }

  if (FlagsToSet & ContinueScope) {

    assert((Flags & ContinueScope) == 0 && "Already set");

    ContinueParent = this;

  }

  Flags |= FlagsToSet;

}

// The algorithm for updating NRVO candidate is as follows:

//   1. All previous candidates become invalid because a new NRVO candidate is

//      obtained. Therefore, we need to clear return slots for other

//      variables defined before the current return statement in the current

//      scope and in outer scopes.

//   2. Store the new candidate if its return slot is available. Otherwise,

//      there is no NRVO candidate so far.

void Scope::updateNRVOCandidate(VarDecl *VD) {

  auto UpdateReturnSlotsInScopeForVD = [VD](Scope *S) -> bool {

    bool IsReturnSlotFound = S->ReturnSlots.contains(VD);

    // We found a candidate variable that can be put into a return slot.

    // Clear the set, because other variables cannot occupy a return

    // slot in the same scope.

    S->ReturnSlots.clear();

    if (IsReturnSlotFound)

      S->ReturnSlots.insert(VD);

    return IsReturnSlotFound;

  };

  bool CanBePutInReturnSlot = false;

  for (auto *S = this; S; S = S->getParent()) {

    CanBePutInReturnSlot |= UpdateReturnSlotsInScopeForVD(S);

    if (S->getEntity())

      break;

  }

  // Consider the variable as NRVO candidate if the return slot is available

  // for it in the current scope, or if it can be available in outer scopes.

  NRVO = CanBePutInReturnSlot ? VD : nullptr;

}

void Scope::applyNRVO() {

  // There is no NRVO candidate in the current scope.

  if (!NRVO.has_value())

    return;

  if (*NRVO && isDeclScope(*NRVO))

    (*NRVO)->setNRVOVariable(true);

  // It's necessary to propagate NRVO candidate to the parent scope for cases

  // when the parent scope doesn't contain a return statement.

  // For example:

  //    X foo(bool b) {

  //      X x;

  //      if (b)

  //        return x;

  //      exit(0);

  //    }

  // Also, we need to propagate nullptr value that means NRVO is not

  // allowed in this scope.

  // For example:

  //    X foo(bool b) {

  //      X x;

  //      if (b)

  //        return x;

  //      else

  //        return X(); // NRVO is not allowed

  //    }

  if (!getEntity())

    getParent()->NRVO = *NRVO;

}

LLVM_DUMP_METHOD void Scope::dump() const { dumpImpl(llvm::errs()); }

void Scope::dumpImpl(raw_ostream &OS) const {

  unsigned Flags = getFlags();

  bool HasFlags = Flags != 0;

  if (HasFlags)

    OS << "Flags: ";

  std::pair<unsigned, const char *> FlagInfo[] = {

      {FnScope, "FnScope"},

      {BreakScope, "BreakScope"},

      {ContinueScope, "ContinueScope"},

      {DeclScope, "DeclScope"},

      {ControlScope, "ControlScope"},

      {ClassScope, "ClassScope"},

      {BlockScope, "BlockScope"},

      {TemplateParamScope, "TemplateParamScope"},

      {FunctionPrototypeScope, "FunctionPrototypeScope"},

      {FunctionDeclarationScope, "FunctionDeclarationScope"},

      {AtCatchScope, "AtCatchScope"},

      {ObjCMethodScope, "ObjCMethodScope"},

      {SwitchScope, "SwitchScope"},

      {TryScope, "TryScope"},

      {FnTryCatchScope, "FnTryCatchScope"},

      {OpenMPDirectiveScope, "OpenMPDirectiveScope"},

      {OpenMPLoopDirectiveScope, "OpenMPLoopDirectiveScope"},

      {OpenMPSimdDirectiveScope, "OpenMPSimdDirectiveScope"},

      {EnumScope, "EnumScope"},

      {SEHTryScope, "SEHTryScope"},

      {SEHExceptScope, "SEHExceptScope"},

      {SEHFilterScope, "SEHFilterScope"},

      {CompoundStmtScope, "CompoundStmtScope"},

      {ClassInheritanceScope, "ClassInheritanceScope"},

      {CatchScope, "CatchScope"},

  };

  for (auto Info : FlagInfo) {

    if (Flags & Info.first) {

      OS << Info.second;

      Flags &= ~Info.first;

      if (Flags)

        OS << " | ";

    }

  }

  assert(Flags == 0 && "Unknown scope flags");

  if (HasFlags)

    OS << '\n';

  if (const Scope *Parent = getParent())

    OS << "Parent: (clang::Scope*)" << Parent << '\n';

  OS << "Depth: " << Depth << '\n';

  OS << "MSLastManglingNumber: " << getMSLastManglingNumber() << '\n';

  OS << "MSCurManglingNumber: " << getMSCurManglingNumber() << '\n';

  if (const DeclContext *DC = getEntity())

    OS << "Entity : (clang::DeclContext*)" << DC << '\n';

  if (!NRVO)

    OS << "there is no NRVO candidate\n";

  else if (*NRVO)

    OS << "NRVO candidate : (clang::VarDecl*)" << *NRVO << '\n';

  else

    OS << "NRVO is not allowed\n";

}