[Bug gcov-profile/67992] GCOV takes an absurdly long time to process a file

[jan.stancek at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67992

Jan Stancek <jan.stancek at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.stancek at gmail dot com

--- Comment #3 from Jan Stancek <jan.stancek at gmail dot com> ---
Created attachment 36992
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36992&action=edit
reproducer based off linux kernel fs/xfs/libxfs/xfs_sb.c

I came across this problem while running lcov on gcov enabled kernel. gcov is
really struggling with xfs_sb.c - it takes up to _36 hours_ to complete on
Intel Xeon CPUs.

I narrowed it down to following condition:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/xfs/libxfs/xfs_sb.c?h=v4.4-rc4#n229

And based on that I made the attached reproducer. To reproduce run:

gcc -O2 -fprofile-arcs -ftest-coverage test1.c
./a.out
gcov -b -c -d -a test1.gcda