// Notice: This updates flags, unlike normal Push.
__ sub(backtrack_stackpointer(), Immediate(kPointerSize));
__ mov(Operand(backtrack_stackpointer(), 0), source);
// Notice: This updates flags, unlike normal Push.
__ sub(backtrack_stackpointer(), Immediate(kPointerSize));
__ mov(Operand(backtrack_stackpointer(), 0), source);