[Bug tree-optimization/66948] New: Performance regression in bit manipulation code

[martin@mpa-garching.mpg.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66948

            Bug ID: 66948
           Summary: Performance regression in bit manipulation code
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: martin@mpa-garching.mpg.de
  Target Milestone: ---

Created attachment 36017
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36017&action=edit
Testcase

The attached test code requires significantly more CPU time when compiled with
current trunk, compared to gcc 4.8.4 and the gcc 5 branch.

gcc 4.8.4:
martin@marvin ~/lsnew $ gcc -std=c99 -O3 testcase.c
martin@marvin ~/lsnew $ time ./a.out

real    0m4.039s
user    0m4.041s
sys     0m0.000s


gcc 5 branch:
martin@marvin ~/lsnew $ gcc -std=c99 -O3 testcase.c
martin@marvin ~/lsnew $  time ./a.out

real    0m3.820s
user    0m3.822s
sys     0m0.000s

trunk:
martin@marvin ~/lsnew $  gcc -std=c99 -O3 testcase.c
martin@marvin ~/lsnew $ time ./a.out

real    0m4.492s
user    0m4.493s
sys     0m0.004s