[Bug c++/81476] New: severe slow-down with range-v3 library compared to clang

[h2+bugs at fsfe dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81476

            Bug ID: 81476
           Summary: severe slow-down with range-v3 library compared to
                    clang
           Product: gcc
           Version: 7.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: h2+bugs at fsfe dot org
  Target Milestone: ---

The small example posted on github illustrates severe slow-downs compared with
clang:
https://github.com/ericniebler/range-v3/issues/700#issuecomment-316050266
GCC is roughly
40x slower than Clang on -O3,
33x slower on -O1, and
10x slower on -O0

I have tested this on g++6 and current snapshots of 7 and 8.

Thanks for your help!