[Bug middle-end/50770] New: limits-fndefn.c times out on ARM; runs 22 x faster with -fno-var-tracking

["michael.hope at linaro dot org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50770

             Bug #: 50770
           Summary: limits-fndefn.c times out on ARM; runs 22 x faster
                    with -fno-var-tracking
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: michael.hope@linaro.org


On a Cortex-A9 with recent trunk:

cbuild@tcpanda01:~$ time
./gcc-4.7~svn179959-armv7l-natty-cbuild199-tcpanda06-cortexa9r1/bin/gcc -O3 -g 
-c limits-fndefn.c 

real    17m44.543s
user    7m7.477s
sys    10m33.117s

Adding -fno-var-tracking gives:

cbuild@tcpanda01:~$ time
./gcc-4.7~svn179959-armv7l-natty-cbuild199-tcpanda06-cortexa9r1/bin/gcc -O3 -g
-fno-var-tracking -c limits-fndefn.c 

real    0m31.788s
user    0m30.398s
sys    0m0.937s

The times are similar on the 4.6 branch.

This isn't causing problems, but suggests that the var tracking code could be
improved.