[Bug c++/56493] New: Performance regression in google dense hashmap

[andrewjcg at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56493

             Bug #: 56493
           Summary: Performance regression in google dense hashmap
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andrewjcg@gmail.com


When compared to gcc-4.6.2, gcc-4.7.1 shows about a 10-20% performance
regression when inserting into a google dense hashmap in a tight loop.  A small
sample program is attached and was compiled with '-O3' and on a linux x86_64
box (using -std=gnu++0x, as required by sparsehash).  Potentially related, the
generated binary under gcc-4.7 is also over 50% bigger.