[Bug c++/53958] New: set_slot_part and canon_value_cmp using 90% of compile time

["ncahill_alt at yahoo dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53958

             Bug #: 53958
           Summary: set_slot_part and canon_value_cmp using 90% of compile
                    time
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ncahill_alt@yahoo.com


Created attachment 27786
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27786
Source code showing problem.

I've got a situation here where the compile basically stalls, and a profiling
sample from a late enough stage shows 92% of time going to set_slot_part and
canon_value_cmp (from var-tracking.c).  So I guess the assumptions about the
size of some data structure are being invalidated.

I am unable to give a small testcase, but I've attached the preprocessed code
that causes this condition.  The flag that seems to give the trouble is
-fno-omit-frame-pointer.  Without this flag, it completes in reasonable time.

This is with gcc 4.7.1, i686-pc-linux-gnu, 32 bit.  

Commands:

cc1plus -v b.c -dumpbase b.c -march=athlon -mtune=pentium2 -auxbase-strip b.o
-g2 -O2 -std=gnu++98 -fno-inline -funroll-loops -funswitch-loops
-fno-strict-aliasing -fno-omit-frame-pointer


gcc -pipe -g2 -fno-omit-frame-pointer -O2 -Werror -fno-strict-aliasing
-march=athlon -mtune=pentium2 e -funroll-loops -funswitch-loops -Wall
-Wcast-align -Wundef -Wformat-security -Wwrite-strings -Wno-se -Wno-conversion
-Wno-narrowing -pthread -pthread -x c++ -std=gnu++98 -Woverloaded-virtual -c
b.c -o b.o


Thank you.
Neil.