[Bug gcov-profile/64123] [5 Regression] Instrumented Firefox segfaults on start

["hubicka at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64123

--- Comment #9 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Looking at the backtrace, all functions are 0x00007ffff07
until the __gcov_merge_add which is 0x00007ffff7fe so apparently coming from a
different DSO. This seems to be because the pointer come from gcov_info
desciptor that bids to different hidden instance. How this is supposed to work?

#2  0x00007ffff7fe1d1e in __gcov_read_counter () at
../../../libgcc/../gcc/gcov-io.c:555
#3  0x00007ffff7fe144d in gcov_get_counter () at ../../../libgcc/libgcov.h:316
#4  __gcov_merge_add (counters=0x7ffff7fe66f8
<__gcov0._Z30mozalloc_set_oom_abort_handlerPFvmE>, n_counters=<optimized out>)
at ../../../libgcc/libgcov-merge.c:56
#5  0x00007ffff0758f28 in merge_one_data (crc32=3347144653,
eof_pos_p=<synthetic pointer>, summary_pos_p=<synthetic pointer>,
this_prg=0x7fffffff8d60, prg_p=0x7fffffffa530,
    gi_ptr=0x7ffff7fe6340, filename=0x7ffff6f41920
"/aux/hubicka/firefox6-50-lto-fdo3/memory/mozalloc/Unified_cpp_memory_mozalloc0.gcda")
at ../../../libgcc/libgcov-driver.c:472
#6  dump_one_gcov (all_prg=<synthetic pointer>, this_prg=0x7fffffff8d60,
crc32=3347144653, run_counted=0, gf=<synthetic pointer>, gi_ptr=0x7ffff7fe6340)
    at ../../../libgcc/libgcov-driver.c:787
#7  gcov_do_dump (list=<optimized out>, run_counted=0) at
../../../libgcc/libgcov-driver.c:846
#8  0x00007ffff0759242 in __gcov_dump_one (root=root@entry=0x7ffff7fe7760
<__gcov_root>) at ../../../libgcc/libgcov-driver.c:858
#9  0x00007ffff0714fe8 in __gcov_dump_int () at
../../../libgcc/libgcov-interface.c:164
#