[Bug other/57668] New: Regression in vectorizing memcpy pattern.

["neleai at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57668

            Bug ID: 57668
           Summary: Regression in vectorizing memcpy pattern.
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: neleai at seznam dot cz

Hi,
When I ran atached benchmark that test how gcc can optimize byte by byte
memcpy(attached memcpy_byte.c) I got a regression on nehalem and ivy_bridge
architectures.
I ran it by commands ./run machine 2> machine_result

For ivy bridge results between 4.7 and 4.9 are:

memcpyO3-4.7.s
0.66
0.65
0.64
0.64
0.64
memcpyO3-4.9.s
0.74
0.74
0.73
0.74
0.74

Also when I look at assemblies and 4.9 version is excessively large compared to
4.7 one.