Re: linux-next: build failure while building Linus' tree

[Nick Desaulniers]

+ Rasmus

This was introduced in
commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add
fallback code")
which added division using the `/` operator, which is problematic when checking
for overflows of 64b operands on 32b targets.

We'll probably need helpers from linux/math64.h and some combination of
__builtin_choose_expr/__builtin_types_compatible_p.

That will help us fix another compiler bug for older clang releases, too.
https://github.com/ClangBuiltLinux/linux/issues/1438.