[llvm-dev] Potentially unsafe loop optimization

[Richard Kenner via llvm-dev]

> Nikita's patch, 835104a1141a06ae7821fe2b642b9603e00aa17b removes the
> nuw from the add on trunk. I didn't look at why llvm 10 works.

Note that when I apply just that patch to LLVM 11.0.1, it doesn't seem
to do anything with this test.  Is that expected?