[Bug target/57907] New: warning: switch -mcpu=cortex-a15 conflicts with -march=armv7-a switch [enabled by default]

["christian dot helmuth at genode-labs dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57907

            Bug ID: 57907
           Summary: warning: switch -mcpu=cortex-a15 conflicts with
                    -march=armv7-a switch [enabled by default]
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: christian.helmuth@genode-labs.com

The manpage states that "This option [-march] can be used in conjunction with
or instead of the -mcpu= option." and this works for, e.g., -mcpu=cortex-a9. On
the other GCC complains for -mcpu=cortex-a15 and -mcpu=cortex-a7 in conjunction
with -march=armv7-a.

The following command line reproduces the issue:

> echo "int main() {}" | /usr/local/genode-gcc/bin/genode-arm-g++ -c -x c++ - -o /tmp/stdin.o -march=armv7-a -mcpu=cortex-a15
<stdin>:1:0: warning: switch -mcpu=cortex-a15 conflicts with -march=armv7-a
switch [enabled by default]

Examples in bugzilla never user both options for ARM but just -mcpu. Will the
combination be supported in the future or should I adapt the mcpu-only
approach? Does it have drawbacks?