[Bug middle-end/83653] [6/7/8 Regression] GCC fails to remove a can't-happen call on ia64

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83653

--- Comment #12 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Matthew Wilcox from comment #9)
> Maybe I'm a little slow, but I don't see what the path is that sets 'nr' to
> 0.  It's 1UL << compound_order.  Typically, compound_order is 0, although it
> may be anything up to log2(number of pages in the machine).  Are you saying

Sorry, yes 1<<0 will be 1, which is handled.  Let me dig into the threading.