C++ stable_iterator::strictlyEncloses方法代码示例

/// Pops cleanup blocks until the given savepoint is reached.
void CodeGenFunction::PopCleanupBlocks(EHScopeStack::stable_iterator Old) {
  assert(Old.isValid());

  while (EHStack.stable_begin() != Old) {
    EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());

    // As long as Old strictly encloses the scope's enclosing normal
    // cleanup, we're going to emit another normal cleanup which
    // fallthrough can propagate through.
    bool FallThroughIsBranchThrough =
      Old.strictlyEncloses(Scope.getEnclosingNormalCleanup());

    PopCleanupBlock(FallThroughIsBranchThrough);
  }
}

static bool IsUsedAsNormalCleanup(EHScopeStack &EHStack,
                                  EHScopeStack::stable_iterator C) {
  // If we needed a normal block for any reason, that counts.
  if (cast<EHCleanupScope>(*EHStack.find(C)).getNormalBlock())
    return true;

  // Check whether any enclosed cleanups were needed.
  for (EHScopeStack::stable_iterator
         I = EHStack.getInnermostNormalCleanup();
         I != C; ) {
    assert(C.strictlyEncloses(I));
    EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
    if (S.getNormalBlock()) return true;
    I = S.getEnclosingNormalCleanup();
  }

  return false;
}

static bool IsUsedAsEHCleanup(EHScopeStack &EHStack,
                              EHScopeStack::stable_iterator cleanup) {
  // If we needed an EH block for any reason, that counts.
  if (EHStack.find(cleanup)->hasEHBranches())
    return true;

  // Check whether any enclosed cleanups were needed.
  for (EHScopeStack::stable_iterator
         i = EHStack.getInnermostEHScope(); i != cleanup; ) {
    assert(cleanup.strictlyEncloses(i));

    EHScope &scope = *EHStack.find(i);
    if (scope.hasEHBranches())
      return true;

    i = scope.getEnclosingEHScope();
  }

  return false;
}

/// Terminate the current block by emitting a branch which might leave
/// the current cleanup-protected scope.  The target scope may not yet
/// be known, in which case this will require a fixup.
///
/// As a side-effect, this method clears the insertion point.
void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) {
  assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
         && "stale jump destination");

  if (!HaveInsertPoint())
    return;

  // Create the branch.
  llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock());

  // Calculate the innermost active normal cleanup.
  EHScopeStack::stable_iterator
    TopCleanup = EHStack.getInnermostActiveNormalCleanup();

  // If we're not in an active normal cleanup scope, or if the
  // destination scope is within the innermost active normal cleanup
  // scope, we don't need to worry about fixups.
  if (TopCleanup == EHStack.stable_end() ||
      TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid
    Builder.ClearInsertionPoint();
    return;
  }

  // If we can't resolve the destination cleanup scope, just add this
  // to the current cleanup scope as a branch fixup.
  if (!Dest.getScopeDepth().isValid()) {
    BranchFixup &Fixup = EHStack.addBranchFixup();
    Fixup.Destination = Dest.getBlock();
    Fixup.DestinationIndex = Dest.getDestIndex();
    Fixup.InitialBranch = BI;
    Fixup.OptimisticBranchBlock = nullptr;

    Builder.ClearInsertionPoint();
    return;
  }

  // Otherwise, thread through all the normal cleanups in scope.

  // Store the index at the start.
  llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex());
  new llvm::StoreInst(Index, getNormalCleanupDestSlot(), BI);

  // Adjust BI to point to the first cleanup block.
  {
    EHCleanupScope &Scope =
      cast<EHCleanupScope>(*EHStack.find(TopCleanup));
    BI->setSuccessor(0, CreateNormalEntry(*this, Scope));
  }

  // Add this destination to all the scopes involved.
  EHScopeStack::stable_iterator I = TopCleanup;
  EHScopeStack::stable_iterator E = Dest.getScopeDepth();
  if (E.strictlyEncloses(I)) {
    while (true) {
      EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I));
      assert(Scope.isNormalCleanup());
      I = Scope.getEnclosingNormalCleanup();

      // If this is the last cleanup we're propagating through, tell it
      // that there's a resolved jump moving through it.
      if (!E.strictlyEncloses(I)) {
        Scope.addBranchAfter(Index, Dest.getBlock());
        break;
      }

      // Otherwise, tell the scope that there's a jump propoagating
      // through it.  If this isn't new information, all the rest of
      // the work has been done before.
      if (!Scope.addBranchThrough(Dest.getBlock()))
        break;
    }
  }
  
  Builder.ClearInsertionPoint();
}

/// Activate a cleanup that was created in an inactivated state.
void CodeGenFunction::ActivateCleanup(EHScopeStack::stable_iterator C) {
  assert(C != EHStack.stable_end() && "activating bottom of stack?");
  EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
  assert(!Scope.isActive() && "double activation");

  // Calculate whether the cleanup was used:
  bool Used = false;

  //   - as a normal cleanup
  if (Scope.isNormalCleanup()) {
    bool NormalUsed = false;
    if (Scope.getNormalBlock()) {
      NormalUsed = true;
    } else {
      // Check whether any enclosed cleanups were needed.
      for (EHScopeStack::stable_iterator
             I = EHStack.getInnermostNormalCleanup(); I != C; ) {
        assert(C.strictlyEncloses(I));
        EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
        if (S.getNormalBlock()) {
          NormalUsed = true;
          break;
        }
        I = S.getEnclosingNormalCleanup();
      }
    }

    if (NormalUsed)
      Used = true;
    else
      Scope.setActivatedBeforeNormalUse(true);
  }

  //  - as an EH cleanup
  if (Scope.isEHCleanup()) {
    bool EHUsed = false;
    if (Scope.getEHBlock()) {
      EHUsed = true;
    } else {
      // Check whether any enclosed cleanups were needed.
      for (EHScopeStack::stable_iterator
             I = EHStack.getInnermostEHCleanup(); I != C; ) {
        assert(C.strictlyEncloses(I));
        EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
        if (S.getEHBlock()) {
          EHUsed = true;
          break;
        }
        I = S.getEnclosingEHCleanup();
      }
    }

    if (EHUsed)
      Used = true;
    else
      Scope.setActivatedBeforeEHUse(true);
  }
  
  llvm::AllocaInst *Var = EHCleanupScope::activeSentinel();
  if (Used) {
    Var = CreateTempAlloca(Builder.getInt1Ty());
    InitTempAlloca(Var, Builder.getFalse());
  }
  Scope.setActiveVar(Var);
}