Method PushThenEntry

cpp/src/gandiva/expr_decomposer.cc:260–287

// Both of the above optimisations save CPU cycles during expression evaluation.

int ExprDecomposer::PushThenEntry(const IfNode& node, bool reuse_bitmap) {
  int local_bitmap_idx;

  if (reuse_bitmap) {
    // we also need stack in addition to reuse_bitmap flag since we
    // can also enter other if-else nodes when we visit the condition-node
    // (which themselves might be nested) before we visit then-node
    DCHECK_EQ(if_entries_stack_.empty(), false) << "PushThenEntry: stack is empty";
    DCHECK_EQ(if_entries_stack_.top()->entry_type_, kStackEntryElse)
        << "PushThenEntry: top of stack is not of type entry_else";
    auto top = if_entries_stack_.top().get();

    // inside a nested else statement (i.e if-else-if). use the parent's bitmap.
    local_bitmap_idx = top->local_bitmap_idx_;

    // clear the is_terminal bit in the current top entry (else).
    top->is_terminal_else_ = false;
  } else {
    // alloc a new bitmap.
    local_bitmap_idx = annotator_.AddLocalBitMap();
  }

  // push new entry to the stack.
  std::unique_ptr<IfStackEntry> entry(new IfStackEntry(
      node, kStackEntryThen, false /*is_terminal_else*/, local_bitmap_idx));
  if_entries_stack_.emplace(std::move(entry));
  return local_bitmap_idx;
}

void ExprDecomposer::PopThenEntry(const IfNode& node) {
  DCHECK_EQ(if_entries_stack_.empty(), false) << "PopThenEntry: found empty stack";