[Bug target/86677] New: popcount builtin detection is breaking some kernel build

[kugan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86677

            Bug ID: 86677
           Summary: popcount builtin detection is breaking some kernel
                    build
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kugan at gcc dot gnu.org
  Target Milestone: ---

Linux kernel build for arm/aarch64 (and possibly other targets) which does not
provide appropriate patterns in the backend will break the kernel build. 

As for aarch64 this happens because kernel is built with -mgeneral-regs-only

Also discussed in:
https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00489.html