[Bug c++/58437] New: Sorting value in reverse order is much slower compare to gcc44

[tammy at Cadence dot COM]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58437

            Bug ID: 58437
           Summary: Sorting value in reverse order is much slower compare
                    to gcc44
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tammy at Cadence dot COM

For the following testcase:

=======================================================
#include <algorithm>
#include <vector>

using namespace std;

int main()
{
    const size_t num = 10000000;
    vector<int> v(num);

    generate(v.begin(), v.end(), &rand);
    sort(v.begin(), v.end());
    sort(v.rbegin(), v.rend());
}
======================================================

If we compile it with "g++ -O3", it takes 1 sec to sort random
values with either gcc445 or gcc481. Gcc445 takes 0.33 sec to sort
value in reverse order, but gcc 4.7/4.8 takes 2 secs.

Is there any way to improve the run-time performance?