Magnetic core, the primary form of computer memory from the mid-fifties to the early seventies or thereabouts, had the slightly awkward property that reading it erased it, so every time the CPU performed a read, it had to spend an extra few microseconds writing back the word it just read.
It just occurred to me that you should be able to make such a computer more efficient by providing a variant instruction, read-and-erase, whose architectural specification would be 'read a word from memory into a register, and erase the memory location just read', and whose implementation would be 'read, and don't bother writing back'. It only occasionally happens in real code that you want to read a memory location and set it to zero, but it quite often happens that you don't care, you know the value in that memory location will only be used once, so it would be nice to save a few microseconds by skipping the writeback.
Did any computers of that era, provide such a variant instruction? If not, why not? Is there any disadvantage I am missing?